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Posted

The guy has come back to me with exact measurements of the rods -146.05mmx51.34mmx22.15mmx22.78mmx21.6mm - anyone know if these are likely to cause problems?

 

He states that the 2 litre and 2.5 litre rods are the same - I can't remember whether this is correct - anyone know?

 

Finally, the price for 6 rods is GBP350 including shipping fee which seems very good value (so long as they fit and they're not made of chocolate!)

 

Merry Christmas :)

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Posted

You NEED the dimension between bolt centres and the external width across the big end beyond the bolt centres.

Ie outer material dimension.

 

If it's bigger than 75mm on a STD engine it WON'T fit. (and that's a tough task for any engineer!).

 

If it's no bigger than 77mm, then you have to bore your engine right out, and fit forged pistons, so cheap it is NOT.

Posted

If they are as small as 74mm across they must be paper thin and weak as f........k!  ::)

 

I don't think I ever saw a conrod that thin!

Posted

GT, you said:

 

You NEED the dimension between bolt centres and the external width across the big end beyond the bolt centres.

Ie outer material dimension.

 

If it's bigger than 75mm on a STD engine it WON'T fit. (and that's a tough task for any engineer!).

 

What's the problem with them being 74mm?

Posted

yeap i dont understand either.

 

if we found out the dimension of the thinnest point round the big end would that help?

 

btw the pauter rods are 74mm aswell according to the dimensions they sent me whilst i was enquiring with them a while back before they told me the price.

Posted

I think there's a lot of confusion.

The minimum bore size for a strong rod with that bearing size is about 78mm, which again shows the preference for Lotus-Ford and proper performance engines to bore sizes of AT LEAST 83mm and up.

 

Under that, serious compromises have to be made, as the big end pin itself is 47.625mm.

(Triumphs use narrow bearings with relatively large ID)

 

If you check the wall thickness EXCLUDING even the bearing thickness (about 2mm) this leaves 26.375/2 or 13.1875mm in order to bore a hole for a 10mm fastener & make the thread area strong;-

Clearly impossible without leaving paper thin metal in all sorts of places and a weak thread.

 

Of course you can always use a cheaper fastener....... :o

 

Such a requirement does NOT exist for the Mk111 Spitfire which has a pin size of 41.27mm and a min bore size (overbored) of 74-75mm.

That gives an extra 3mm on each wall which is why cooper S/Spitfire 111 can/do use BIG strong bolts.

 

I would NEVER use a H section rod with those margins, remembering a rod/rod bolt failure is going to TOTAL your engine and block.

 

I've seen and have addresses of a whole load of crankshaft and conrod makers from China.

Caveat emptor.  :X

Posted

so you mean the area of metal half way up the threaded hole will be too thin and weak?

 

im just confused (as usual) pauter and carrillo are able to make these rods to fit and you praised them in the past how do they bypass this problem as it seems to be an impossible problem.

Posted

It's simple maths worked backwards.

If you use a 10mm fastener* you will get a wall thickness of about 0.020" between the bearing and the fastener (using a Spitfire bore), smack in the middle of the rod.

So you rely on the outer 2/3 of the rod to give rigidity to the centre 1/3, which has a whopping great H section above it.

 

The only other solution is to use a 7mm or 8mm fastener, but in a H section rod you are ending up in the air with the end of the thread.

You might like that.  :X

 

Although this end blade is really thick and wide it's suprisingly not very strong, because it's faced with reciprocal accelerations across the TDC and BDC. It's this change of direction that breaks them.

 

Genuine H section rods from Carillo have been known to fail spectacularly on BDH engines at 10-11000rpm, (a very short stroke 1300) leaving you holding a 20 grand mound of scrap metal.

 

Pauter rods of course are NOT H section, they use a totally different design which is much stronger and has far lower windage losses (a major problem with H section for oil control)

 

The problem with a lot of chinese stuff, if the price is too good to be true it probably is!

Chinese don't have the first clue about racing engines they just carry on churning out stuff copied from other people.

 

Those rods might work in a 100bhp Spitfire but would any lunatic in their right mind stick them in a Ferrari 308/328??

Nope! you would have to be clean out of your 'ed, when just 4 valves would set you back 200 quid!  ;D

 

It's all horses for courses, the only advantage you would get on a Spitfire 1500 would be to reduce centre main wear.

On a GT6 you can bore them out a lot, and I heard Steve has never had problems on his GT6, even with Pauter's miniaturised fasteners (for the above reasons again*).

 

Carillo, I believe put a lot of extra work into their rods, especially into using non recyled steels, forging techniques and post manufacture heat treatment.

 

What do the chinese know about any of that?

 

However it would be nice to sacrifice an engine just to see how much you can get it to rev before they break  :D

Posted

You can't reduce the size of big end bearing without seriously compromising the strength of the crank, so you would have to redesign it....

Of course if you do that and make it lighter it's also a different matter........

 

I heard Pauter's stuff is pretty strong!

Posted

I have been promised a sample rod in the new year, I will get it measured, trial fit it in a block and get the material checked.

 

They do seem very cheap but if they are lighter, fully balanced, shot penned and have decent fastners, they are likely to be superior to a standard rod.

 

Anybody whose lightened and balanced a set of rods will know the effort / time required to do it properly, you've then got another £50 to £75 to get them shot penned, and another £50 to £100 depending on the fixings you use (cosworth / ARP).

 

£300 for a set of six rods starts to look like good value.

Posted

My whole idea is to reduce the main center wear, anything that helps i will give a bash, when i spoke to pauter i was almost drueling then they told the price and i had a heart attack. These look like a good compromise, but only if they are better than std rods.

Posted

 

Anybody whose lightened and balanced a set of rods will know the effort / time required to do it properly, you've then got another £50 to £75 to get them shot penned, and another £50 to £100 depending on the fixings you use (cosworth / ARP).

 

Yes but why would you ever bother?

 

Best way is to get a knacked early set out of a TR5 that has shed a rod (they're usually within 3-5g), and use them in a 4 cyl.

 

Putting ARP/COS bolts in standard rods is totally pointless.

Really a total waste of money because it's not the bolts that let go, it's the threads in the rods!!

 

Lightening, balancing, polishing them makes no difference whatsoever to a STD rod apart from making them look prettier.

Being as they're made of cast iron I wouldn't bother, they stretch like mad at full revs!

Rubber crank, rubber rods.  ::)

Posted

NO but the stuff they made in 1967-69 was usually properly put together, so usually a doddle to balance.

Ditto Jaguar.

Even the enemy in Abingdon made some semi-decent cars in that period

Posted

I suppose the discussion has been going on long enough.

Of course 100g off the piston/conrod weight would help quite a bit, but TBH my old NOS motors seemed to last pretty OK.

 

If I were to have a chinky product to evaluate it would involve chopping one into bits, and another eg to tear apart on a machine measuring stretch.

 

If you're thinking high revs on a 1500, you're not going to get them anyway unless you can get the head to flow over 85-90cfm inlet and 60cfm exhaust.

I'd like to see that.

 

I've not seen A single one so far that actually gets anywhere close!

 

ALL max at 120bhp theoretic, that's you're lot ALL THEORETIC, so it's the thing I would worry about, not the rods.

The HEAD.

Posted

not sure i would agree with that, the head can be messed with but if the bottom end gives way all the time then you'll never know how it performs, id rather have a rock solid bottom end then play with the head.

Posted

Well, this may come as a suprise but I've NEVER blown a properly built 1500 EVER!

 

Not a single one of the NOS ones has come back apart from a regular precautionary bearing change (after it had been thrashed for 5 years/60 000kms), - actually one has just been thru a rebuild because of the cam/followers wearing out.

 

The majority of the bad reputations of British engines, always came from the fact they never hardened the cranks (with a few exceptions) whereas in Germany they invariably did.

 

Tufftriding is a German patent.

Posted

I think as GT says, if you do the job right, it'll hold out, plus most modded engines make penile power, so the stock stuff is fine. As he says, the power is in the head, the bottom-end won't make you anything much, unless it's superlight.

 

Right bearings, hardened crank, correct tolerances, right parts...

 

My bottom-end on the 1300 was good as gold, that was TOTALLY stock bar deck heights and "end to end" balanced rods and crank, flywheel done and fly lightened.

 

Really @ 110-115HP the stock stuff is fine.

 

Honestly show me your average port job/cam'ed 1500 doing over 115HP I'll eat my hat.

 

Most "tuned" engines barely break 100HP.

 

Lets say getting 119HP out of mine was no EASY game.

 

No idea what the head flowed, shame I sold it, could have tested it eh?


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