Lightspeed who are rebuilding my engine are concerned about the amount of sideways movement on the Cunningham rods I have on the 2.4 engine.

The width of the big end of the rod is 22mm. Ideally they would like to fit a 26mm wide rod. However Cunningham have a 12 week backlog of work. The alternative, which they they say is a valid solution, is to put high tech washers on the piston pin either side of the small end to centre the conrod.


The previous engine builders also commented on the amount of slop the rods had. I spoke to Barbz about this issue and he said that the rod design was the same as the original Fiat ones and the amount of movement was expected and was part of the design of the engine.

Any thoughts.

John

22mm is OE width at big end and small end of the rod. Crank is just over 26.5mm. The piston boss is 26mm. I can't see why this would be a problem? This clearance has been designed in by Fiat for a reason and it hasn’t caused a problem in the past I would leave it well alone.

John if it bothers you please send an email to Guy Croft and he'll explain what you need to know, its a floating pin and I'm darn sure my set up is the same.

it's nothing to worry about, tbh I can't think of any engine I have worked on that runs much less of a clearence gap either side if the small end, the big end is much more important and will stop the rod from sliding up and down the journal, they are worrying about nothing

The 20vt engine is "piston guided" (in German language)- means the rod is guided / centered by the piston. Therefore there is almost no gap between an original piston boss and the end of the rod.
There are other engines which are "crank guided" (not the 20VT) - these engines then will need more gap for the piston boss. The 20VT gap between piston/rod should not be more than 1mm. The original piston can be measured with about 23mm in the area of the rod. Therefore I assume that your piston is not correctly designed?!
Juergen

Lightspeed have never seen an engine designed like this before!

What they are seeing is roughly a 3mm valley either side of a 19mm bearing surface. The shell for the big end is 19mm wide. However the rod can float either side thus loosing roughly 20% of it's contact surface. There is evidence on the inside of the old pistons that the small end has worn grooves into the piston at either end of it's lateral travel.

what pistons do you use? the original ones have a gap of max 1mm to "hold" the rod in the middle...

What information is needed is, the width of the rod at the small end and big end, plus the width of the big end journal

Then the measurement of the inside of the piston between the piston pin boss's if you know what i mean

Stichl, There are examples of piston led engines that run much larger gaps either side of the small end for example the RB26 or even BDA's and BDG's that in some cases run large clearence gaps at the small end and the big end of the rod

edited to say the RB26 is in fact crank led, my mistake

Yesterday I checked the piston boss of my "old" 2,4l conversion pistons from CP.
It was not nice, what I had to realize...
The piston boss has a dimension of about 26mm as well...
The original one has about 22,3mm (measured)!!!
Means that the CP pistons allows the rod to move about 4mm (!!!)towards the original one (0,3mm!!!)
Maybe that this tolerance killed your shells?!
Sh... I installed the same pistons in my 2,4l conversion.
I hope that I won't get similar problems because of this "design problem".
But I think that Johns has the same pistons and rods in his car - and this already for a significant sum of miles.
I think, we would have realized already, if there would be a "2,4l conv. series problem"?!
Sh...
Juergen

The engine has thrust washers so there is no worry here as that is the most important factor. Engines with thrush washers are usually crank lead. I can't see any serious movement despite the clearance as the rotational force in an engine will keep the rod central anyway. Seriously John you have nothing to worry about.

Ah John I just re-read your message, I'll ask Guy for you.

rich

trevor are you reading this?

Yes! Give me a call some time

I've sent Guy and Barbz an email to try and clear this up as there seems to be conflicting comments regarding whether this engine is piston or crank lead.

Given the width of the big end is only 22mm compared to the gap of 26mm it sits in suggests it is piston lead. However the width of the boss on these pistons compared to the width of the small end would allow too much movement. It also appears that the width of the boss on the aftermarket pistons is wider than the OE pistons.

I had a look through the workshop manual and the only specification that looked relevant was "Gudgeon pin Small end bush" which is a width between 0.006 - 0.016. This is on page 87 (Page 10 of the technical data fot the 20V and 20V Turbo engines).

John

Guy says

"no way can you pack up the rods to reduce the lateral movement, any loose object there will knock the crankpin to bits. You need new rods that fit"

John

That's not nice...
I think even a shrank special washer becomes loose after some 1000 cycles and then will saw through the piston pin :-(
Sh... there are only 2 solutions
- dismantle the engine and change to another piston / rod - this is very expensive and needs a lot of time / work
- or to drive with this faulty design...

It seems to work well, when looking to Johns etc...
I haven't heard of any problems so far - and there should be more 2,4 Barbz engines on this planet...

What could happen when driving with such a gap?! Does somebody know possible consequences?

Juergen

Umm, so it looks like the rod is the same width as the OE item and it's the piston design that has changed. The boss on the new pistons (2.4 design) allows too much movement in the rod. The boss is 26mm wide compared to about 22mm in the OE pistons.

I'll get Lightspeed to comment on the wear on the piston boss and big end bearings but they've never seen it so bad. No wonder I had terminal oil pressure failure after only 1000 miles.

Lightspeed are recommending fitting some 2mm thick teflon washers to reduce the boss size back down to 22mm and have it piston lead. Either that or order some new rods with a 26mm big end and have it crank lead. Left as it is I'll be looking at another rebuild.

My problem is if I wait 3 months for the new rods the car won't be ready for the summer :-(

John

This is what Guy said in a further email:

My view - which is law at GCRE - if nowhere else, is that the rod must not be constrained by the piston, because to be so, the face of the small end would have to bear against the piston almost continually and it would rub it to bits. It would also generate a side load in the pin that would probably knock out the wrist pin clips too. I have never encountered such a setup. Every racing piston I have ever seen has a generous clearance in the span, albeit that it varies engine to engine according to speed and allowable bending load.

My design criterion with rods is that the clearance of small end in the piston span must always be greater than the clearance of the big end in the crank. What others do is often a mystery to me.

we need to know the side clearence on the big end as i'm sure it's lot less than what is at the small end and as such will not let the rod move to the extremes of the gap at the small end, does that make sense?

The crankpin gap is abut 26mm (roughly 19mm bearing surface with roughly 3mm valley at either end) which is the same as the boss gap on the 2.4 pistons. The rod is 22mm thick at both ends. Therefore it's possible for the small end to rub against the inside surface of the boss.

If this happens then the big end bearing is only sitting on about 80% of it's contact area.

As said earlier the engine is crank lead due to the thrust washers. All forged pistons fitted run a bigger clearance, the Accralites I have have a 26mm pin boss, they use a very similar forging in the Honda race engines. I have excellent oil pressure all the time. Even done a good 10,000 miles since the rebuild. CP pistons also have the 26mm boss. I don't see Flea, Nigel plus all the other users on here with forged internals having a problem. The piston end is not a problem and the crank end is still OE spec there is no concern here. I even spoke to Accralite this morning regarding this matter and he is in agreement.

Where do the thrust washers fit? Are there two pairs for each crankpin (one pair either side of the rod)?

Doh - found this out after posting above:

The engine had only one pair of thrust washers. These fit on the crankshaft to prevent the crankshaft moving too much.

No, no there are no thrust washers on crank pins, the 26.5mm gap is correct. There are two half cut washers in total that reduce the end float, they sit either side of the middle (ish 5 pot ) main journal. This is what I mean by being crank lead. John reread what GC said in your further e-mail, it’s correct. I think lightspeed are used to V8’s.

Have a look here:
http://img21.imageshack.us/img21/8023/dsc00532fg3.jpg
http://img21.imageshack.us/img21/5968/dsc00533iy8.jpg

Lets just read this and take it as gospel

"My design criterion with rods is that the clearance of small end in the piston span must always be greater than the clearance of the big end in the crank. What others do is often a mystery to me."

GC knows what he is talking about and what he is saying is the same as what i have seen in practice

To put your mind at rest there are a lot of cosworth BDA's and BDG's running a narrow journel setup that is very similer to yours without any problems, these are 15-25K race engines and so if they are good enough for cosworth/ford plus Acralite and GC then i think that pretty much covers it

Not to mention that loads of people on here that are running the same or similer setup are having no problems at all

The rod has galled the side of the pin boss on both sides and has worn the bearing in a very unique way. Usually a bearing is worn in a parralel manner but these bearings have wear grooves at a 30 degree angle. Which means the rod is walking on and off the oil wedge. It is my op that one end or the other needs to have minimal movement. I have no problem with a narrow big end or a floating top end just pick one or the other. I am glad GC knows what he is doing but "it is a mystery to Me- cunningham-JE and Wisco" why this combination has been designed this way. I understand now it is not GC who engineered this combination so I retract my previous statements. The wear patterns indicate that this is not a proper solution though. Lightspeed builds 20 to 1 imports to domestic V-8's. The actual engine builder has years of Superbike motor assembly and a solid reputation. This is a poor design and needs to be rethought the small end of the rod should not rub on the pin boss end of story. It is a new solution is needed. I think a thicker rod end is ultimately the best design however that has major time constraints on it. Teflon pin buttons have been used in HP engines for years the idea is to make a teflon washer for the small end. So if anyone has data that could explain why this is a bad idea I am all ears. Either way I need a solution because this motor is not going to be assembled with the previously engineered combination.

I have talked with my former F1-engine builder Hartmut Lohman...
He confirmed what Lightspd said:
This is no correct design...
The Italian forged CPP- pistons have a correct gap between piston and rod - they are correctly designed. This problem seem to have not all aftermarket pistons - so far we know this problem from CP and Accralite.
Hartmut has a similar problem with his rods / piston combination from a 2,4l Fiat Coupe engine and he will install High End washers made from a special Aluminium to center the rod.
It is not acceptable to have any gap between this washer and the piston pin - therefore he will shrink these washers.
He has talked to various other race engine buliders - they confirmed that often test engines (also in F1) use such washers to center the rod - therefore this is practicable solution...
But not for me - I won't dismantle my engine any more...
My 2,4l has seen about 10000km - without any problems. A check of the shells 3 months before showed that the crank and the shells theirselves are in great condition...
I hope that this will remain for the future, too...
Juergen

Didn't Nigel have problems with his rods not so long ago? I can't remember if they were standard (lightened and shot-penned) or forged ones though. Plus I can't remember what the problem was, bearings or a bent rod etc..

Anyone else remember? Nigel!

I think Hartmut has machined a flat face on the piston for those washers.

But they are generally a floating design not a guided design.

If you want to change something I suppose it is the piston not the rod that would change. The Mariani rods and pistons were the same btw.
For me I am not bothered because when my engine was apart for inspection during the 2.4 tests there was no wear there

Can we have some pics of this specific engine and its problems

Also why would you be suffering from this problem but there seems to be no other documented cases of this problems

Might this be the first time a professional ENGINE builder has worked on one of these engines rather than (with the greatest of respect) a more general mechanic or even home builder?

Delivered my 2.4 bottom end to a professional engine shop on Monday along with the head and cams so they could measure exactly how much freedom we have to adjust the cam timing once on the rolling road. I alerted them to this thread last night (as it goes over my head technically). They have come back today telling me they cannot condone this engine for race use. Maybe they will be OK in road use, occasional track day, but I need a race engine that is ragged 100% ALL of the time. I have asked the engine shop to suggest an appropriate solution, at the moment it looks like I'll be having a new set of rods made up that don't have this free movement

I bent a standard rod due to running too much torque - they were balanced, but not shot-peened

Had no problems with thew forged rods (so far)

OK I have just spoke with Farndon who are making me up 35 rods for the group buy. He doesn’t know this engine but is working from the data I have supplied. He said that the Piston end clearance doesn’t matter as much its crank lead. However the crank end clearance is very concerning. To have a 22mm rod on a 26.5mm journal is a worry. His clearance is to usually run 3thou either side, he has not seen a clearance this wide from factory before. The mystery is that this clearance is OE spec???? Since the rods are at drawing stage I have told him not to go ahead with production just yet. His suggestion would be to widen the rod however he doesn’t want to take responsibility in case the engine was designed this way for a specific reason. I was totally unaware that a total gap of 4.5mm+ from factory would be a concern so now I’m concerned. It’s easy to say widen the rods but the real question is why have Fiat done this is there a genuine reason? Would a wider rod cause a problem? Let’s get hold of the boys from Brazil and see what they have done?

For the rod to be walking on and off the oil wedge as described would suggest that there was insufficient oil pressure in the first place. Given the pistons have forced gudgeon pin oiling and we have the benefit of oil jets I cannot see how you should ever not be on oil film, and in any case if there is that scenario regardless of design the little end will last about 5 minutes. I actually have a piston which was swapped after 20k miles on mine, there is no wear on it there whatsoever. There is a really minor scuff on the skirt from a foreign object but thats it.

J i've not seen an engine without thrust washers somewhere on the crank - I don't think its for the conclusion you made, as the washers have to take up the pressure of the clutch release bearing pusing or pulling against the crank.

I checked 16v OE - BE bearing width 19 ish mm, rod big end width circa 26mm, piston pin to boss clearance 1mm+ each side.

Here is a pic of that used piston I mentioned 2.4 piston after 20k miles You cannot see any wear on the piston to rod interface because there is not any...

Yes my mistake Rich, I meant floating pin not thrust washers (what was I thinking ).

Due to further thinking it has to be lead by something. With the OE piston small end being 0.3mm clearance (going by Stichl measurements) and the big end being 4.6mm clearance it would seem this engine is piston lead as standard, I can’t see why as it has a floating pin, not pressed, then piston will become damaged as standard??? Its gotta be crank lead. I still think this engine is crank lead despite the 26.6mm big end width. I’m gonna go a measure a standard piston 2morrow as I think the 0.3mm (measured by Stichl) sounds too tight. I may be inclined to increased the rods width at the big end only as 4.6mm is sloppy however I still think there must be a reason for Fiat doing this.

Whether the pin is fixed/pressed or floating doesn't have a lot of bearing on the lateral clearance between the rod and the piston to be honest. In the CP Piston design usually there is forced gudgeon pin oiling through oil relief holes unless this option wasn't chosen in addition to the oiling from the jet. The rod should centre anyway which is why even on OE setups that are rod-guided there is a reasonable gap, much more than would be designed in if there were any sort of substantial lateral forces operating on the rod. Otherwise there would be a full bearing face and a suitable bearing material would be utilised.

anyone with some influence in motorsport world who can send email directly to Torino to ask this?

just a thought..

I am still on the side that there is a reason Fiat have done this. It hasn’t caused a problem in the past and looking at JohnS pistons after 20K I don't think it will be a problem for the future either otherwise we would have blown engines all over the place, so I think I’m gonna stick with the OE design at 22mm all the way.

Some of us have - five! Three of those include 2 snapped rods and one big end failure. Keith's machine shop identified an issue relating to the way the rods sit on the crank (remember, I don't do technical) a while back. Whether my failures are related in any way to this, who knows....

But my current preparer has a professional race engine builder looking over the 2.4 and he's not happy to have his name associated with it. So I await his proposal for a solution

And Fiat Italy will care because?????

What about the 16VT engine does that run a similar setup?

16vt bears no relation to the 20vt and many more people with race experience have been working on them. I know someone currently making some really trick bits for 16vt engines but this problem has not been mentioned

Just commissioned a set of Arrow rods to my engine builder's dimensions to fit my 2.4 without this issue. A long way from cheap but they reckon they can turn them round in 10 days

Funnily enough I'll have a set of 2.4 rods for sale in a couple of weeks, assembled, then taken straight back out again ;-)

So what big end width have you gone with then?

Why ask FIAT?
every engine manufacturer all over the world has to decide either to lead the rod by piston or lead it by crank.

FIAT decided to lead it by piston. That's all.

If someone has forgotten to tell CP or other manufacturers about the fact, FIAT is using piston lead rods, the above mentioned st happens.
C.P.S. is a piston manufacturer from Italy and that's the reason why my pistons got the right design, they know the rods are piston lead!

For my CP-piston/Cunningham-rod combination I will use aluminum spacer washers as Stichl said already.

But, and this is very important for everybody who is concerned, there will be no problem at all as JohnS told you. Nobody needs to dismantle his engine to insert those washers. But building up a new engine, it would'n be a good idea to forget this discussion. I will sleep better with the washers inserted.

Hartmut Lohmann

I have no idea! On the basis that I don't get a dog and then bark myself, I have engaged a race engine builder to resolve this and in the first instance getting his resolution organised was more important than worrying about what it is!!

But sometime over the next couple of weeks I will ask the question. Obviously I will be able to supply similar rods to anyone who wants them but it seems the existing ones are working OK for road engines (that seems to be the consensus amongst those already running 2.4) but the Arrows rods are REALLY dear. Farndon would have been able to do some cheaper, but not if I want to race this season - slight exaggeration - as with the existing group buy, would probably be looking at 10-12 weeks lead time. I don't have that

Forgive me if this sounds uber stupid.....

But would large side to side movement in the crank (i.e clutch pushing it) not create the exact same problem that is occuring - regardless of whether there is a large gap at either little or big ends (ofcourse the crank would have to move a certain amount in order to move the rod, which then grazes inside of the piston.

Chris

Your correct but its only minor amounts something like 0.3mm

There are a few things that need to be clarified here

For all the engines that i have worked on and examined in depth, all the Piston led engines have always had pressed pins, with this i mean the piston pin is pushed through the piston then through the rod then back in to the piston, the pin will be held in place by a friction fit in the small end of the rod and the bush part is then in the piston rather than the small end

This is a non floating small end

The reason for this is no doubt many fold but one i know for sure is to locate the rod and stop it from walking up and down the journal, and to stop the small end from wearing on the inside of the piston boss, hence being called piston led

Now we know for a fact that the standard setup is a fully floating setup and that would suggest that it is in fact crank led

But in the same breath, the clearence either side of the big end is massive and that would suggest a piston led setup, especially as the small end clearence seems to be smaller than that of the big end

Now obviously this is only my view and understanding of the Fiat 5 pot setup and is by no means gospal


So i put forward that this engine is somewhat of an odd-ball and seems not to follow convention, there a couple of things i do know for sure though

1, many people are running with forged pistons/rods with large equal clearence at the small and the big end for many many miles and no problems at all

2, and this is just my opinion but im sure many people from a engineering back ground would agree, and that is that its seems bad practice to use the inside of the piston as a bush for the rod to run against no matter how breif it may be

Now i have not worked on every kind of engine out there so if someone knows of another engine that is piston led and still fully floating at the small end i would be interested to know and it may be able to shed some light on the Fiat setup here and why they have done it like this

I just found an offer of the 20 years old titanium rods used by Mercedes in the German DTM

They are piston led

ebay no. 260362270042

Yes these are exactly as you discribe, and they are fully floating

here is a link of the above to save other people putting it into ebay

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?V...ries%26_fvi%3D1

But one point i must raise is that these rods have bushes either side of the small end, these are steps taken to stop the rod wearing on the inside of the piston boss.

Fiat have not done this, why? well it would normally suggest its a crank led engine but that seems odd especially with the large clearences at the big end


I take it these are from the old Cosworth 190E DTM cars, do you know if the standard engine run the same setup or was that a pressed fit pin?

the only thing i can confirm is that the 190e cosworth engine as standard had oil feed up the rod to the small end and these titanium ones do not, so im not sure what they have done about lubricating the small end

I cant find any other details on it myself

ok i have found a workshop manual for the 190e engine, its quite clear its piston led but this manual states that the pistons have thrust surfaces cast into the piston boss for the rod to run up against, I cant remember seeing a 20vt piston haveing anything like this but we need a picture of the inside of the piston to be sure, can anyone help with that?

There are partial surfaces but not a complete thrust surface because it isn't designed to be a load point

GC sent me this.

“I've read that whole thread. Generally very constructive and interesting insofar a thing called a piston-lead rod is interesting to me at all, because whilst it appears to exist (and I freely admit I had not heard of it before esp on a full-floating setup) it is utterly loony, risky, expecting an aluminium piston to restrain a steel rod. I cannot think of a single good engineering reason to do that. That said I don't get much time to think these days.

The fairest thing to say is this:
If you bring me a bare clean block with caps and bolts, crank, main brgs set, one big end brg pair (good used will do) and one complete conrod (std) and a sample new piston of the type your rods will be for (forged I assume) I will evaluate this and tell you what I would do.

I have to look at the grind width and radii on the crank, bore to crank relative positions, offsets blah blah. This is commonplace for me and it involves dummy building the crank into the block and setting up a rod piston set to see what lies where.

When I see the layout I will know but I cannot second guess this because, as is so often here, I have no prior exp of that bottom end albeit I have plenty with engines generally.”

GC

I guess the only way to get to the bottom of this is going to get a professionl engine builder design the rods/pistons.

My thoughts entirely. I've gone halfway house on this due to issues with both time and money. I'm having a set of rods made with appropriately wide big end, but even then it was suggested to me that a 19mm gudgeon pin is rather small for a turbo engine - at least in a race application. If I was to build another (please, NO!) it might be better to have the pistons done at least with larger gudgeon pin and rods made to suit

if you were going to through so much effort as to practically redesign the piston and rod you may as well get a custom crank done at the same time, especially in the case of the 2.4 setup as the rod to stroke ratio is far from ideal, but that's a whole new set of discussions and problems

Today i had a discussion with an expert of rally's engine at my job. We talk about rods and big-end bearings...

J you told me yesterday that fitting 26mm rods (not original width) with 22mm big-end bearings (original width) won't be a problem... but the "expert" at my job said it's not possible

He said if we ask Farndon to make 26mm rods we will have to find big-end bearings that are specially made for the new sized rods. (larger bearings)

Personally, i think it's a coherent explication.

So where is the truth guys?

Can someone which have widened rods told us if widened big-end bearings are needed?

The rod can be made to wider but still use O/E bearings but there are other problems that guy croft has raised, the main one is wether or not the crank journal for the rod is in the centre of the bore or of set, TBH I think they should be left alone at 22mm, there are many coupes running with this setup and no problems

hmm, I've been following this thread with some real interest.

I am also baffled at the idea that there is that much clearance on the big ends & that the rod is being centralised on what looks like both ends ( crank & gudgeon, are you not sure that the gudgeon pin holds the small end in position with some internal circlips ? normally the piston is a loose fit on the gudgeon & the pin / rod is the interference fit )

unless the crank endfloat was to suddenly change ( eg main shells failing etc ), it does seem daft.

@ John / Tipo, did you use a new oil pump when the 2.4 was built ? ( silly question I know ).

My coop when it get VERY VERY hot, drops to about 1.75bar at idle, but it's now set to about 700 rpm, so it will be quite low, however as you rev it, it's spot on.

I can only assume that there must be some mechanism that prevents the rods from walking across the crank journal ?

usually, the rods are just smaller in width than the crank & the big ends are usually shaped to use the radii of the crank as its centraliser when oil pressure builds up.

Must admit, I've had no probs ( yet ). I know Trev has some interesting views, but alas, a my coop won't be tracked, it'll prob be ok ( fingers crossed ).

Ha! I have no views, I don't understand! Its all gone over my head - had to get Rich to translate for me ;-) But having entrusted the kappa to a motorsport outfit, I have to go on what they recommend or there is no point using them

Thing is, until someone breaks a 2.4 and can put the issue down to this, then I don't see any reason why anyone already with one would strip down their engine

that is true pal!, just hope I'm not the one to encounter this. I'd either scrap my coop, or just go back to a boggo 2.0 with all the forged bits.

As you said Trev, your engine builder has more experience that most of us on here, so his advice & guidance should be noted

Lightspeed have just let me know that the engine is all ready for me to collect. $7500 CAD in parts and labour to strip down, rebuild and repair head, new crank, pistons, valves, rebore and rebuild.

However I've decided I'm not happy with the use of washers on the piston pin and want to use different conrods instead. They are going to get some custom made ones from Carrillo in USA. $400 USD a rod but only a 4 week turnaround. These will use the existing bearings and will be 22mm at the small end and 26mm at the big end.

Now I need to order a new set of shells, head gasket and head bolts

John

I've been in contact with Arrow Precision Engineering who are making Trevor's rods. They asked would it not be better for them to leave the big end width as standard, so you don’t need to have the crank machined, and then make the small end width to suit your pistons so that the rod is then piston guided again?

I've received an email back from G&G Motorsport saying the crank will not need machining in any way. They will be a direct fit to the CP Pistons. Regarding crank or piston guided, as the pistons are of a slipper design with very little skirt to absorb thrust forces and side loading it will make much more sense to guide the rod from the crank end.

John

Just make sure before you get any machining work done that the rod journals are central to the bore, its quite possible that they are offset in which case you will need to offset the width of the big end on the rod to one side

In your setup you have no choice but to convert your engine to a crank led setup, the forged pistons and rods will not have any kind of bush where the small end touches the piston pin boss so you cant do that.

also have you got a quote for a after market crank?

if you go this route you could have the journals made to the width of the rod, not to mention an after market crank will be much stronger and you can get some parts of the design improved, for example having proper radii at the edge of the journal rather than the sort of channels that are on the O/E crank, this will improve the reliability of the crank led design aswell in my eyes

And it May be cheaper to go for a crank rather than the rods

have a look here

http://www.scatcrankshafts.com/

click on the custom billet crank button on the left

I have worked with one of there cranks before and the quality was very impressive for the money, not as good as Farndon or Arrow but not far off and quite a bit cheaper, and it will be multible times stronger than the O/E item and much better finished

this is the way i would do it but you need to make sure the journals are central to the bore before you do anything

Ricky

IMHO, you cannot say something is stronger just because it looks nice. Unless you have material spec for both items you are only guessing. Now I'm prepared to guess the std crank is forged steel then nitrided if it is similar to the 16v 2.0 crank. Now someone let me know if I'm wrong but I'll assume the 5 cylinder crank to have all of the crank throws at a different angles to the adjacent one, somewhat more complex then a single plane 4 cylinder crank, as it would have to be machined in phase or twisted to be in phase. Add to that the CAD work to come up with this one off design then I cannot see how it would be possible for such an item to be at comparable let alone cheaper cost then the rods. I've not heard of cranks breaking in well maintained 5 cylinder Fiats thus I would say the std is probably suitible up to all but the highest end lowest weight projects (yet to see anything like that). Incidentally another guess without looking but these grooves next to the journals I imagine are recessed rolled fillets on a radius thus not a stress raiser like a corner would be. This method perhaps also assists in production costs campared to an 'in line' fillet radius (?).

rich

scat stick to a set price with custom cranks and it may not be cheaper than the rods but there will not be much in it

As you have said I would think the standard crank is forged steel but it's unlikly to be EN40 or 4340 chromolly, it will be cheaper material and thus less sturdy

The main reason I suggested the after Market crank option was mainly to be able to narrow the journals but also for the proper rolled fillets rather than the recessesed items found on the O/E crank, it just seems wrong to me in a performance application

It just seems better than trying to run potentially a piston led setup converted to a crank led setup, especially as the pistons and rods that are being used have been designed for a crank led setup, why not get a crank made for a crank led setup as well?

It's all my opinion of course but one thing is for sure and that is that before any decisions are made every option should be checked out prior to any maching work being carried out

Are you talking about a Ferrari engine modification or is it still a FIAT engine?
The sky is the only limit!

Ricky, please email them and I'm prepared to bet that they will not honour any current pricing structure based on an even number of cylinders. Oh if it's (20v crank) like the 16v crank then it will be EN40b; and 'sturdy' isn't an engineering term I know of

Ok so we have come to the conclusion that it may or may not be made from a good strong material like en40b!

By design though it's not in my opinion the best way to go as the rods and pistons being used are not to O/E spec and changing the crank design would cure the problems here

As for cost, well he is going to be paying $1600 (can) for the rods you can get custom made cranks from around £1100, so let's say he is going to be paying roughly $2000, so for about $400 more he will have a setup that is superior, it doesn't sound to bad to me but of course it's upto the owner

I'm just trying to put another possibly better option ahead

The rods are a lot more than that! $400 USD each x5 = $2000 USD or 1400 of your UK pounds

Sorry I rushed through that in my mind and thought it was a 4 pot, but it backs up my theory on a new crank as a possible option

its worth getting a quote at least, there are plenty of other crank manufacturers that may be more competative on price as well but Scat seem to be very good value for money

Ricky you are still guessing they would even entertain a one off 5 cylinder crank. Which maybe they would be for not anywhere near the guesstimates you're making based on items they are tooled up to make. Its not a viable alternative based on a guess, and it would take a bit of ground work to get a decent estimate, look at DKE's estimation form for example.

I agree its a bit of a guestimation but its definetly worth getting a quote, they do mention on there site that they can make any kind of crank and to quote there web site

"specialized race, prototype and industrial engines
Available in a variety of materials and styles "

and

"SCAT can manufacture cranks for any application up to 40" length and 10" diameter "


As i said its worth getting a quote

I agree with Rich re the idea of making a custom 5 pot crank. I looked into it seriously because with a 2.4 abarth block you can make a 2.6 which will still rev to 7800rpm.

I believe that the piston-to-rod interface is unlikelyto be the cause of the problem but an effect of a problem which is related to a lack of oil or oil pressure. The oil pumps are not bulletproof, and a bottom end failure that causes an oil pressure frop may also have the same effect

When I had the engine assembled they stripped the oil pump down and checked it was all within the allowed tollerances.

Having said that this time I've fitted a brand new FIAT pump to be absolutely sure.

John

All im saying is if the crank can be made for a reasonable price then its seems a very good way to solve the problem of the rod walking, although im not specifically saying that the crank was the cause of the original problem

What is quite clear is that Tipoboy wants to stop the chances of the rod walking, the crank option that i have suggested is a viable option if the costs are not to high

Ok, sorry to bring this up, but I'm going to be closing the engine soon so I would like to know.

I have Accralite/Farndon combination (2.0 20vt). I bought new oil pump (even though mine is ok) and will be using a SA ecu.

So basicly if the oil pressure is good, the rod will be centered without possibility to "walk"?

What is the other option? Teflon washers? Who should I search to make me those? Machine shop doing the block boring or? ...

dearon, don't waste anytime or energy on this, you don't need to do anything, your setup is tested and proven to work perfectly as it is

my thoughts exactly, but had this topic in mind.. especially someone wrote: no need to strip down a running engine, but if building new one add telfon/aluminium washers..

thanks

Just seen this interesting thread. I had a custon crank made for my 16v engine, the company had a firm price on custom cranks and certainly came up with the goods. Catered for my every whim, delivered on time, changed at no extra cost details near the end, finest vacuum remelted E-4340 and nitrided twice, once before final polishing and again after. To my knowledge there's only one other company to better them and they are a closed shop.
http://i3.photobucket.com/albums/y85/1NRO/Eightweightassembly014.jpg
http://i3.photobucket.com/albums/y85/1NRO/Eightweightassembly015.jpg
It cost me nearly $3000 this time last year when it was a goood exchange rate, they didn't seem bothered what kind of crank it was. The price could of been bettered by other custom crank manufacturers but I wasn't in the market to be taking risks though some of the other places were very nearly chosen.

who was the manufacturer? Farndon and arrow are regarded as the best crank manufacters in the world although there are quite a few that are almost as good but quite a bit cheaper

They are good manufacturers both Arrow and Farndon but they are not the best in this world, not even in this country,MCT would be better for instance. There are quite a number of places who wouldn't let you through the door unless you were waving big development budgets under their noses,if at all. Others who wouldn't do you a custom one off unless you were very well connected who do production of mainstream cranks which are of exceptional quality, Bryant for instance. Scat might well be cheaper but thats due to most of the manufacturing of their product taking place in china with only the final finishing done in the States, they produce a reasonably stable level of quality due to this. Eagle on the other hand don't do any crank work in house, it's a finished item from China and consistancy doesn't come into it. It gets worse still, recently there was an ebay seller offering a "billet crank" which just shrieked China, an amateur who's gone to China to source a product was my opinion, the crank didn't even have oil drillings! It was only a cool grand so it must of been good

My crank came from the manufacturers, I met the man who designed it ready for production for me and the guy who stood on the shop floor who would be responsible for actually making it. They aren't the best in the world but IMO they are the best company in this world to make something like this for me, Joe public. The accuracy is correct to ten thou at any point I've checked. It's a little spooky, a finger nail draged across one of the weight makes it ring long after it's been removed. My only regret is not having the courage to tamper with the stroke, it did my head in specifying what I have without taking further risks, something for the future, I would like to build something with a lesser stroke. One thing you do need to do when this route is chosen is come up with the specification that YOU want, I've not come across anyone who would just make a crank with no detailed instruction. I had the same company make the rods as these are unique to the crank, this helped the risk factor as I had the piston specs by that stage. It all fit thankfully but the adrenalin was pumping when it all arrived and I tried it all in a block, a less polite version of phewww was clearly heard

I get your point but I was referring more towards the run of the mill stuff if it was a f1 engine or something of that ilk then pankle would be first on the list for me, I have been told that most f1 engines use pankle rods and cranks but I have never seen one to see what they do better than any of the other manufacturers

A couple of pics from my collection of F1 bits, both made by Pankle

http://i3.photobucket.com/albums/y85/1NRO/panklecrank.jpg
http://i3.photobucket.com/albums/y85/1NRO/pankle.jpg

anything jumping out at you?

Sure the DKE stuff must be well made, couldn't help thinking the capricorn item hadnicer fillets. Who makes the best - depends who's paying the bill for sure.

Nik have you run your crank design yet, or is it all part of the larger project you are working on? Just interested to see your opinions on your own work when the time arrives.

Hi Rich,

Not yet I haven't, still buying / making parts with quite some funds to find yet. For sure I'll tell the story as and when I run this engine, maybe a disaster looming but that'll not deter me having a go. Maybe I'll run all the bearings inside of an hour or maybe it'll go some. Either way I'm unlikely to stop at the initial build, I've lots I'd like to try.

Nik