Connecting rods

Juan AR155Q4 · 30-07-07, 20:36

I open this topic to ask the ones who have big modyfied engines.
What about the OEM connecting rods? How many HPs can they hold?
Has anybody fitted forged ones?

Does anybody know the dimensions of the OEM connectin rods?
I have this but don´t know if it´s true:
Length: 145mm
Big End Dia.: 54mm
Piston Pin: 22mm
Weight: 600grs (not sure)

Juan AR155Q4 · 03-08-07, 18:19

Nobody?
Serge? Somebody rebuilding engine?

axaQ4 · 03-08-07, 19:57

I have only polished conrods(but i thought about forged ones too...)

Brul(tm) · 04-08-07, 05:56

Originally Posted by Juan AR155Q4

What about the OEM connecting rods? How many HPs can they hold?

I have read somewhere that the OEM one's go up to 350 HP's.
Only can't remember where or what exectly, so I am not sure.

Greetings,
Marc

Stuntz · 04-08-07, 06:48

wolf ran stock i think it was 330 hp but he will verifie it when he gets home

K.Kotkas · 04-08-07, 08:12

in the www.fccuk.org/forum/ faq section they indicate that the conrods are good up to 300 HP, crank is good for 500.

On the other hand, that might be pushing it.
Personally I'd go with H beams, and forged pistons. See some other tech threads, there are some links to vendors. be ready to pay up to 2K eur for conrods and 1.5K eur for pistons... and still have problems with pistonrings.

Kristjan

http://www.lahe.net/gallery/disassembly some rebuilding pics.

Juan AR155Q4 · 06-08-07, 03:39

I have forged pistons for U$s350 from a local dealer and custom made. Pistonrings are std NPR rings and have no problem.

I have seen on ebay H beam conrods for about U$s600. Don't know about it's quality.

**Steve Webb** · 06-08-07, 16:27

As a halfway step couldn't you get some standard ones shot-peened (sp) as this relieves the internal stresses and helps the conrods handle bigger loads. Get them balanced at the same time.

Just a thought,

Steve

**Juan AR155Q4** · 08-08-07, 19:27

Sure could be a midterm solution.

I just was curious about this thing, but no planning to do this mod.... now.

**j1v** · 09-08-07, 00:15

Originally Posted by Steve Webb

As a halfway step couldn't you get some standard ones shot-peened (sp) as this relieves the internal stresses and helps the conrods handle bigger loads. Get them balanced at the same time.

Just a thought,

Steve

shot-peening does not strengthen the connrods ... just prevents from fatigue failures.
I bought these for 600 euros.

**K.Kotkas** · 09-08-07, 05:37

http://www.thsperformance.co.uk/acat...Integrale.html

?360.00

Not bad ?

**K.Kotkas** · 09-08-07, 13:51

umm then again, Made in China ...

**Steve Webb** · 09-08-07, 14:17

Originally Posted by THS Website

THS Performance is a UK based Company supplying performance parts by mail order.

We only take orders over the internet with paypal which means our overheads are reduced so we can spend more time developing new products.

Not sure I would be too happy using this company, no address or contact number.

**Juan AR155Q4** · 09-08-07, 14:28

Here are a couple from ebay.
I wouldn?t care about procendence, just look what material are made from and how well machined are they.

Ebay ?279 (without procendece)

Ebay ?340 (not chinesse)

Take a look that both are 4340 and forged.

**mindus** · 14-08-07, 18:39

Hi,

There was an alfa 155 Q4 in Lithuania with the engine boosted over 500HP (with NOS). It had standard connecting rods. This car was constantly running in a dragrace for a several years and had no failure in terms of connecting rods.
We've just finished rebuilding my engine and used standard conrods (my expectations are well below 500bhp... , besides std.conrods are forged). See if that'll be fine

Cheers,
M.

**K.Kotkas** · 14-08-07, 19:51

Originally Posted by mindus

Hi,

my engine and used standard conrods (my expectations are well below 500bhp... , besides std.conrods are forged). See if that'll be fine

Cheers,
M.

eee... keep your shorts up. "hardened and tempered steel alloy" is not forged.

**djsly** · 17-08-07, 12:57

High,

it's not the power that kills rods. It's the torque and rpm.

OEM rods are very very strong, and can handle alot of torque. My friend's q4 had more than OEMx2 torque and rods were doing just fine. If you'r planning on rev the engine above 8k rpm or run more than 500Nm torque then change them. If not, I think OEM ones will do the job perfectly.

**Xti** · 18-08-07, 20:32

OEM meens stock conrods? Where from does it comes? Sorry but i have a patient wating and I have to do my homeworks quicly. I haven't managed to read the hole workshop manual yet. Oups ! Thank you very much.

**Juan AR155Q4** · 18-08-07, 21:10

OEM = Original Equipment Manufacturer

**Xti** · 19-08-07, 16:28

Juan, thanks for understanding/ help. Agradecimiento !

**Wolf66** · 21-08-07, 13:45

As i was assured by italian tuner, who prepares rally integrales
OEM connecting rods are not HP dependant, but RPM dependant.
If the engine will stay under 7500 RPM, connecting rods will not fail.
I ran my car to 8000 RPM and over 500 hp without problems.

**cuore_sportivo_155** · 22-08-07, 20:28

true, RPM is what kills rods, or more to the point, the kinetic energy involved in moving the pistons up and down with average speeds over 21m/s. A balanced engine will do better here, and obviously forged pistons make matters worse (heavier thus the forces are greater at same piston speeds)

**Xti** · 20-09-07, 22:09

If I want to replace the OEM pistons with forged ones do I have to change the stock conrods too?
I believe forged pistons are are much heavier...could this affect also the conrod's properly work ?

Thanks a lot, Cristian.

**arjunior45** · 22-09-07, 05:30

Originally Posted by XTI

If I want to replace the OEM pistons with forged ones do I have to change the stock conrods too?
I believe forged pistons are are much heavier...could this affect also the conrod's properly work ?

Thanks a lot, Cristian.

no, it is not neccessary to replace the stock conrods too if you stay under the 270bhp and 7500 rpm.
And I do not think that forged pistons are much heavier than the OEM {stock} ones. Not that much to affect the conrod's properly work. Just balance them at 10 mgr {not the 2 - 3 gr, from the manufacturer} and you won't have problems.

cheers

Nick

**Xti** · 27-09-07, 21:47

Thanks for the help Nick.

I have in mind something around 300-350 bhp but this I'll have to see first if it's possible with a Garrett T3/ T4 Hybrid TBcharger. You know there are a lot of modifications that must be made and this is my concern for now. This means a lot of knowledge, time and money. I have very little of each but the 1st is more important to me. I'm now learning from the books, others experience but I must say that your help guys is much more important to me. Thanks to all that have allready shared experiences and to all that will.

Nick, what means balancing the conrods at 10 mgr? I had no idea neither that the stock ones are balanced at 2-3 gr . Hope I'm not persevering too much with the questions but it seems that passion has no limits. " La passione ha sempre raggione" . Thank Nick, thanks to you all.