Whitch head for my turbo setup?

[280~Master]

So I got 2 choices of L28 heads to choose from. I will be turbo-ing this car with after market turbo setup.

I could use the P79

flat top pistons 8.71:1

dished with 7.52:1

I could use the N42

flat top 10.08:1

dished 8.47

Opinions please..

[EuroDat]

Im not much of an expert on turbo Z's, but if you not using "high" octane fuel the N42 with flat tops is out of the question.

The heads: The N42 is considered the better head because it doesnt have the exhaust port inserts. The P90 & P90A are considered the best flowing heads from all the Z's.

I would go for the N42 with dished pistons, but we can still get 98 octane fuel. With 91 octane it might not be the right choice.

Chas

[madkaw]

I'd stay away from the 42 with flattops.

Anything else will work- and there is no downside with the 79 liners

[LeonV]

[...] but we can still get 98 octane fuel. With 91 octane it might not be the right choice.

Chas

FWIW, your 98 octane (RON) is equivalent to our 93 octane (AKI).

[EuroDat]

Leon, Thanks for clearing the up. I knew there was a differance, but didnt know it was that big. 5%.

With pounds it even worse if you get it mixed up. 1 English pound to 1.6 US lbs.

[carrott]

The only head to use is the P90 for turbo . Best shape chamber , plenty of development has gone into it . Use the dished pistons to promote better flame path , basically set it up as per factory as the P90 head is what was used as the factory head on turbo installs ,but go for forged pistons if using higher boost and put money into good turbo , injectors , management and intercooler . Keep it simple for years of reliable , fun motoring.

[conedodger]

I agree with Carrott. The only acceptable CR choice you have is P79/dished. Anything higher than that will bring you detonation without much boost. P90 or P90a would be your best choices.

Watch the classifieds, I will be selling a turbo intake, exhaust, P90 in very good shape, and maybe a turbo oil pan if I can find another non-turbo pan in good shape...

[LeonV]

The only head to use is the P90 for turbo . Best shape chamber , plenty of development has gone into it . Use the dished pistons to promote better flame path , basically set it up as per factory as the P90 head is what was used as the factory head on turbo installs ,but go for forged pistons if using higher boost and put money into good turbo , injectors , management and intercooler . Keep it simple for years of reliable , fun motoring.

Forged pistons are unnecessary, they have nothing to do with "higher boost". Forged pistons allow for higher piston speeds, so unless you plan to rev to 7500rpm+ there is no point.

Just about every block/head combo has been turbo'd with success. It's not so much what individual parts you use, but how you use them . Knowledge of engine management and engine dynamics is a requirement for anything but a stock turbo setup.

[280~Master]

The P79 has the exact same combustion chamber as the P90, shape and all. The only difference is the exhaust ports. P79-Diamond/roundish shape Vs. P90 has square ports. Thanks for the input.

The only head to use is the P90 for turbo . Best shape chamber , plenty of development has gone into it . Use the dished pistons to promote better flame path

@conedodger - I will be using an extremely rare aftermarket kit made by BAE from the 80's. It comes with all the hardware necessary to complete the build. Will watch as I have other people I know of looking for turbo items here in Savannah.

After calling Rebello Racing I am going to go with F54/P79 turbo pistons .040 over sized (due to block wear). Having head rebuilt as well.

Thanks all,

John