Changing conrods with engine in car!

[Efini]

Just did this today, and I must say it was a lot easier than expected.
Dropped the subframe a little by removing the two front main bolts, and removed the oilsump. Then it was just a matter of releasing the rodbolts and pushing the piston up and out (the head was ofcourse removed ).
Removed the rods from the piston, put the new rods and bearings in and chucked the piston back in the hole. On went the lower caps and the bolts were torqed to specification.
My first time ever doing a job on the car that turned out to be easier than expected!

Isn't it beautiful:


Next job is to put the head back on. Guess I'm gonna have to call a mate, doesn't look like a one-man job :

[Chris M]

Don't you need to balance the engine if you change the rods??

Cheers,

[Jon441cc]

Don't you need to balance the engine if you change the rods??

Cheers,

I was gonna say the samething

[caterpillar]

no! he has not need for that: if he dont race 24 t le mans race. for some race in the every day the engine are better then the org conrod : have you weighted the org conrods nice peace the head and intake

[Jon441cc]

Caterpiller, i remember you saying about Audi flywheels
What weight tolerance + or - did audi go down to when they balanced the I5 20v in the factory ?

[prosty]

I haven't balanced my engine and I have 3% overall leakdown test, and my engine is running really nice. But I'll do it the next time though, I had a time issue for my last build.

Not that the leakdown has that much to do with the balancing, but I just like to brag

[caterpillar]

you havent to rebalanc the engine if you dont use it for long dist runs... thats for sure. low cost.....

[Ross]

I think that as long as the rods have been balanced as a set it's OK. At least when my engine was balanced, the rods + pistons were done relative to each other so they were inter-changeable. For the reason that, if i ever lost a rod or piston, i could have one balanced to the same tolerance and could be used as a direct replacement without upsetting it...

Of course it's best to have the full engine balanced if it's never been done before, for the relatively small cost I thought it was well worth it. My engine was alot smoother and had a little quicker response after. It's safer to take it to high RPMs too, where the small weight differences really matter.

Cheers
Ross

[Jon441cc]

I think that as long as the rods have been balanced as a set it's OK. At least when my engine was balanced, the rods + pistons were done relative to each other so they were inter-changeable. For the reason that, if i ever lost a rod or piston, i could have one balanced to the same tolerance and could be used as a direct replacement without upsetting it...

Of course it's best to have the full engine balanced if it's never been done before, for the relatively small cost I thought it was well worth it. My engine was alot smoother and had a little quicker response after. It's safer to take it to high RPMs too, where the small weight differences really matter.

Cheers
Ross

I remember after we fitted your GT3071 kit and went for a shake down around my local track :mischeif: Me & Dave couldn't believe the throttle response. Its a pity your budget didn't a allow for the crank & flywheel to be lightened The thought makes me weak @ the knees.

[Billman]

According to Lehmann (the man who make the S1 and the other Audi Race engines) the crankshaft should not be touched. the Cost-Benefit is too low. Even on 500+ Lehman engines the crankshaft balancing is the original Audi.

That what i dont know is if he makes changes on the oil Channels or something else.

[Jamo]

Is this an acceptable practice or does it have to be balanced?

[Ross]

I think that really depends on who you ask Jamo.

You're race engineer or hardcore engine builder is gonna say balance it all the way. Obviously others out there have just fitted rods without balancing and their engines run fine. I don't think you'd have any problems if you got hold of a balanced set and swapped them, will probably be a bit of an improvement on factory tolerances anyway.

Now if you want a really smooth engine, probably a tiny power increase due to less vibration, and safe revving at 8,000rpm+ etc. then balance - but it'll be engine-out and in pieces.

In short, if you have it all in bits, get it balanced. If you don't want or can't afford a rebuild but want to safe torque, drop the sump and stick a balanced set in with the engine in-situ as per efini's post.

[Jamo]

Hmm considering changing the rods as well with the head off. If the rods can be changed I can run more than 1.5 bar of boost to probably 1.8-1.9 bar.

8k rpm is unrealistic for me, I never hit 7rpm nevermind 8rpm it's an Audi not a VTEC

The whole idea of buying the Avant was to avoid having to rebuild the engine as planned on the Coupe oh well.

I'm going to have to sit down and really work out the cost of everything and if it's worth it all.

[merlin's S4]

I'm going to have to sit down and really work out the cost of everything and if it's worth it all.

Well when you've worked out an idea of cost can you give me a heads up?? I've got to take the head off mine to do the gasket but I'm planning on having my spare 7A head overhauled and modified to fit. This would obviously be the time to fit some uprated rods but as I was hoping to do the clutch as well, I think the cost is going to get out of hand! Even though I'm hoping to do a lot of the work myself, I really have no idea how much the head overhaul will cost, let alone the rest!!

[Jamo]

Speak to MRC or Corey about 7A head machining. Put it this way Ross cost at least 4k on his old 3B but then he had to have the block rebored and new oversized pistons.

Time is money, money is time I have neither!