Engine Rebuild and Balancing?

[Jim Bowen 1]

Another question..

 

Got my bottom end bits all now, so ready to have it built. I just rang up Vince at stealth and he tells me its not worth balancing anything, says he stopped doing that years ago.

 

Other people i've spoke to have said its a must, but they don't know the VR6 engine.

Is it something worth doing?

 

A guy on vr6 owners club says he built an engine from same block as me (ebay 2.8) and after about 30miles he is taking it apart and having it balanced (he also forget to install the oil injectors so not sure if that has affected the engine.

[g0ldf1ng3r 13]

Jim - it could be to do with the gains versus costs

 

i believe gas flowing, lightening, balancing etc can be all very costly tasks but realistically do not produce gains that are worth the expense.

 

i to asked about if i should have my VR head gas flowed when i had my work done at stealth & vince said there was no point as i wouldnt see the benefit

 

plus, i guess its all in perspective too - IE if someone is rebuilding to produce as much power as possible (with turbo, over sized pistons, uprated injectors, straight through exhaust with decat blah de blah de blah) then maybe having everything lightened, balanced & flowed could help achieve 'slightly' higher figures but if its a standard rebuild the associated costs outwiegh the advantages

[DriverVR6 11]

Jim,

 

I used to build "race spec" engines many years ago and used to have them fully lightened and balanced. I used a place in Brierley Hill called Aldon Automotive.

 

Lightening and Balancing does nothing for engine power. All it does is improve the smoothness and reliability of the engine at very high revs.

 

All engines are balanced in OE form. Aftermarket balancing just does it to a finer tolerance.

 

Lightening just takes away any excess metal from the moving parts like the pistons, conrods, etc to lower the stress put on the crankshaft due to the inertia effect.

 

I would never recommend having an engine balanced and lightened unless you are going to use it for serious track/racing purposes.

 

Also, if in the future you install a new clutch kit (pressure plate and clutch plate) your engine will be back to it's OE "unbalanced" condition.

 

If you do have the engine lightened and balanced, then you need to take along the crankshaft and everything that attaches to the crankshaft....pistons, pins, conrods, flywheel, clutch pressure plate, clutch plate, front pulley, etc.

Edited July 2, 2014 by DriverVR6

[GrahamU 5]

I'm no expert so please dont take this as arguing with you DriverVR6, but I thought that lightening the fly, crank etc would give some gains in rpm, the less weight there is to turn, then the faster it will spin up meaning it would also rev higher.

 

Does that also mean things like knife edging the crank would not be done anymore either

[Jim Bowen 1]

Excellent, great replies, makes it a lot clearer for me. I won't bother.

 

Engine is going to be standard 2.8 with corrado inlet, throttle body and probably the schimmel 263's, exhaust and air filter, already bought the ARP head studs so may as well use them.

[g0ldf1ng3r 13]

glad to be of assistance jim, am please we helped

 

i had 263's fitted by vince during my head rebuild & can happily say that those coupled with a BMC & a 'vince special map' my VR now feels super smooth & responsive & grunty throughout the rev range :D

[Jim Bowen 1]

Am considering using that evans waterless coolant as well. Not sure if anyone has tried that on here yet though?

[seanl82 23]

Lightening will improve the rate at which revs climb due to lowering the point of inertia. This can have a detrimental effect on torque though. In all honesty, you wouldn't really notice much if any loss on a standard vr. Balancing as said is just for smoothness at high revs. Again, unless something is amiss from the manufacturing process, you wouldn't really notice any difference. It all sounds good on paper, but in reality, unless you have a super high revving high speed car, it's a bit pointless and a waste of money just to impress your mates down the pub.......

 

 

Ohhh, be interested to hear about the waterless coolant actually. Don't think anyone on here has actually tried it have they?

[Dox 22]

I've got a hotgolf lightened flywheel waiting on the shelf for when my engine comes out.

 

 

 

[davidwort 0]

blueprinting is what you want, each manifold, port, combustion chamber etc perfectly matched, it's time consuming and expensive to do but I've seen a race prepped totally standard 16v develop significantly higher power from this. The VR6 developing peak power at lower revs benefits less and of course non of this is cost effective for power gains on a road car.

The old 4cylinder engines can be really improved by balancing fully, makes them so much smoother, but the VR is a different beast to start with.

[DriverVR6 11]

I'm no expert so please dont take this as arguing with you DriverVR6, but I thought that lightening the fly, crank etc would give some gains in rpm, the less weight there is to turn, then the faster it will spin up meaning it would also rev higher.

 

Does that also mean things like knife edging the crank would not be done anymore either

 

The purpose of lightening and balancing is, as you say, to increase the rpm that the standard crank will cope with whilst maintaining reliability. Lightening and balancing will add about 250 to 400 rpm to what a standard crank can handle safely. It will do precisely jack to increase the power as bhp tails off at high rpm as other limitations in the engine become a factor.

 

Increase the rpm and have a gas flowed head and a cam that will feed the fuel (larger carburettors or performance injection system) and extract the exhaust (tubular manifolds and straight through exhaust systems) at higher rpm's, then yes you will get more power. However, you will lose low end tractability and idle will suffer. Ask anyone that has fitted OTT cams to any engine.

 

It's the same theory for every normally aspirated engine, be it a VW VR6 or a Ford OHC Pinto.

 

The questions to ask yourself is firstly, do you drive you VR6 at max rpms, and secondly is your name Ayrton Senna or Alain Prost or Gilles Villeneuve?

 

If you answer NO to both these questions then what I would do is build a reliable engine which starts perfectly, pulls strongly and will cope with the miles without any problems, but then I'm "old school".