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[Webby the Bear]

Hi ya,

Quick question.

I have two cylinder heads from my 2.5v6. I've removed valves as want them refurbed with new guides and stem seals (ALL guides are cracked from where the cambelt snapped).

Anyway, whilst having this done should I have them skimmed? Some say not to cos of the alteration to compression ratio.

Your thoughts welcome 

Oh and am I right in thinking that I can put 3L cam shafts in and not have to upgrade anything else???

 

[minifreek]

Get the heads skimmed to bring them true again, no problem in having them skimmed and don't worry about the compression ratio....

Fit the G cams, Iv done the same to my 2.5 V6 but you will lose some bottom end torque (as I have), it's not much of a problem unless - like me - you tow a big caravan around the country and you need the bottom end grunt to get you moving better...

[Webby the Bear]

Thanks MF...

Forgive my stupidity; what are G cams? 

[Nick W]

Skimming heads is worth doing if it's necessary. Check with a decent straight edge, and if they're not warped(which they almost certainly aren't) leave well alone. V engines can be problematic if heavily skimmed, as the inlet manifold might not fit afterwards. A clean-up skim isn't going to make any worthwhile difference to the compression ratio.

Fitting new valve guides will require recutting the valve seats; with 24 of the things that's going to be expensive, and in my opinion, hard to justify.

[Webby the Bear]

Skimming heads is worth doing if it's necessary. Check with a decent straight edge, and if they're not warped(which they almost certainly aren't) leave well alone. V engines can be problematic if heavily skimmed, as the inlet manifold might not fit afterwards. A clean-up skim isn't going to make any worthwhile difference to the compression ratio.

Fitting new valve guides will require recutting the valve seats; with 24 of the things that's going to be expensive, and in my opinion, hard to justify.

Thanks for the info Nick.

On that basis I may scrap them then. And if I decide to put the3L cams in do it on the current heads that are fine 

[minifreek]

The G cams are the 3 litre cams, fit 4 G cams for noticeable gains

OR

Fit 2 A cams on the exhausts and 2 G cams on the inlets as thats what they are anyway you will get gains and torque won't suffer...

[cem_devecioglu]

Skimming heads is worth doing if it's necessary. Check with a decent straight edge, and if they're not warped(which they almost certainly aren't) leave well alone. V engines can be problematic if heavily skimmed, as the inlet manifold might not fit afterwards. A clean-up skim isn't going to make any worthwhile difference to the compression ratio.

Fitting new valve guides will require recutting the valve seats; with 24 of the things that's going to be expensive, and in my opinion, hard to justify.

agreed..


and install 3.0 cams and a 3.0 ecu

[minifreek]

Does the 3 litre ECU make a difference...?

Are they mapped differently to the 3.5's..?

[cem_devecioglu]

Does the 3 litre ECU make a difference...?

Are they mapped differently to the 3.5's..?

I'm using a vauxhall 3.0 ecu.. before was an opel 2.5.. maps are definitely different which is also shown on the same dyno..

[Webby the Bear]

So upgrade to 3L cams and i'm going to need a 3.0L ECU too?

[05omegav6]

So upgrade to 3L cams and i'm going to need a 3.0L ECU too?

Not necessarily... The cams will improve things on there own

The full list would be...

4 G cams
3.0 long plenum
2.6/3.2 exhaust manifolds
3.0 Ecu
Ecu can be chipped to good effect as well.

 

[cem_devecioglu]

So upgrade to 3L cams and i'm going to need a 3.0L ECU too?

nope..  only if you want a better pull

[Webby the Bear]

So upgrade to 3L cams and i'm going to need a 3.0L ECU too?

Not necessarily... The cams will improve things on there own

The full list would be...

4 G cams
3.0 long plenum
2.6/3.2 exhaust manifolds
3.0 Ecu

 

Thanks Al,

i'll hunt for these G cams. When i want them (in the not too distant future) is an add on here the best way to get them?

[05omegav6]

Zirk is/was flogging some

[Webby the Bear]

Zirk is/was flogging some

Cheers mate