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[frostbite]

Not to hijack but could you use 3.0l heads on a 2.5 if you were to supercharge?

[Kevin Wood]

Not to hijack but could you use 3.0l heads on a 2.5 if you were to supercharge?

It would reduce the compression. You'd have to do the sums to work out exactly what you'd end up with. The problem is, folklore has it that these engines start to get bottom end problems if forced induction is used. I think I'd be looking at what SAAB did to the V6s they turbocharged first.

[Diamond Black Geezer]

Supercharging has been done, and it's suggested super vs turbo is the was to go re: forced induction. However, for out and out powerrrr these engines aren't the best starting point. They are large, lazy motorway cruisers, that can idle smoothly and slowly, that's what they were designed for. From your 2500cc you get 167bhp... from your old 'redtop XE' of 2000cc you get 150+bhp, and 200bhp in turbocharged form, standard. That's before tuning.

If you wander over at Billing and say all snooty and self-satisfied to some Astra/Cavalier/Nova boys 'Hey guys, My 3-litre V6 has just over two-hundred bhp, year, you heard, two-hundred brake" you'd get laughed at. Scarily, the current Corsa VXR produces that, and that's a 1.6!!  With very little fettle turbo'd little 2-litres are pushing over 300bhp happily. I know that's comparing natural with forced induction, which is never fair, but realistically you might be looking at about 300 bhp from the 3-litre with a supercharger, before serious bottom-end work is required. And that's not really that impressive power for the cc's, as above.

Or, as a comparison, Lotus/GM managed a healthy 377bhp from the old straight-6 lump in the LC/LO... and many owners claim theirs produced more from the factory engine mods, and they have been tuned to even more. Strong engine.


And as Kevin says above - Saab did good things, and had good engine, some GM-derived. To be honest this always surprised me that GM didn't simply whack a Saab unit in the Omega. A new Sports model, all for free.

[Doctor Gollum]

If I had the inclination, which I don't, then it would be to fit a blown 2.2 into a manual 2.2 Sport.

That would be a hoot to drive 

[Nick W]

If I had the inclination, which I don't, then it would be to fit a blown 2.2 into a manual 2.2 Sport.

That would be a hoot to drive 

I've considered that too. Turbo Astras aren't worth much, and a 2.2 Omega even less. I wouldn't bother with a Sport, as some Bilsteins and some slightly stiffer springs would be on the list. A completely stock looking CD or CDX, still on the 16"wheels but with 300hp under the bonnet should be doable with some scrounging for about £2k.

[Diamond Black Geezer]

That would work so well.. and with the added advantage of an engine bay you can get to things to work on!

[Kevin Wood]

Indeed. The V6 is great for its' refinement and flat torque output, which you'd lose with a blown 4 pot.

Quite apart from anything else, packaging issues make forced induction on a V6 a non-starter. That and the fact that someone has already made all the expensive mistakes with various other engines.

A blown oxymoron would be a fun sleeper, that's for sure.

[Diamond Black Geezer]

Have a feeling the cooling needs addressing, as well, on the V6s? As you say, expensive mistakes; go for something that a large-scale manufacturer has already done for you.

[Keith ABS]

  Finally had some time to look into this one again. It has come back as X30SE heads. These came from a mechanic who said he always kept a spare set on his shelf for quick changes so he didnt have a headless car on his drive while looking for a pair. he just could not remember if they were 2.5 or 3.0. So, I have a spare set of 3,0 heads

Keith ABS

[Diamond Black Geezer]

Happy days!