924NA block vs 924Turbo block - HELP

JimN · 05-21-2010, 12:08 PM

I am a LeMons racer that is looking for a quick fix. My turbo block and pistons are shot but I have a 924N/A block and pistons. I know the crank and the head gaskets are the same and the N/A CR is a little higher, but will the turbo head fit and will it clear the N/A pistons?
Jim

krystar · 05-21-2010, 12:11 PM

head might....but will the valves clear the NA pistons.....i'm not holding my breath for that

emoore924 · 10:51 AM

Could be done I guess, but not without some serious mods.

Stock cams for turbo and n/a are the same part, so assuming the slight difference in exhaust valve diameter on the turbo head is compensated for by the fact that the piston on the n/a block stops 4mm further down in the bore, I think you'd probably be ok clearance-wise. The head will bolt up to the block, but the exhaust manny is different and your CR will be too low.

In a nutshell, the n/a has the combustion chamber in the top of the piston and uses a flathead. The turbo uses a combustion chamber in the head with a dished piston. If you put the turbo head with its combustion chamber with the n/a bottom end with its combustion chamber, you get a really low CR.

This is not an easy call. You could go over on 924.org and see if someone has a n/a head f/s. But then I think you'd have to change over to a complete n/a setup. And depending on your electrics, tranny, clutch, ignition, etc., that could be a project. Or, you could try to find a turbo engine or block and swap bottom ends. That might be a better way to go but turbo bottom ends are not growing on trees these days. There's aud nauseum discussion about the various turbo-n/a head/bottom end combinations over there. Better to go there and read up than try to relate it here...

Or you could just put an LT1 V8 in there and be done with it

ideola · ideola's Garage

If the turbo head is OK, all you need are the turbo pistons. Just use the turbo head, the NA block, crank and rods, and add some turbo pistons, and you'll be back in business. I have a complete set of S2 (8.5:1) 931 pistons available. PM me if interested. I presume this is the same car that I posted a response to over on Rennlist?

If not, strange that two LeMons cars would have similar problems...

Anyway, I have pistons if you need them. I know there are some budget constraints...would prefer to sell, but we can discuss trade bait if you have anything of use to me.

ideola · ideola's Garage

Here is a more detailed discussion of the various permutations possible by mixing and matching NA & 931 head & piston combinations
924Board.org :: View topic - measured 931 head volume!

JimN · 12:55 PM

Sounds like I need Turbo pistons.
I am checking out the 924 site too - thanks
So, does anyone have some 924 turbo pistons in the shed?
Thanks.

Yes, another team mate has posted on Rennlist.
Jim

emoore924 · 05-25-2010, 01:01 PM

Ja, there ya go, turbo pistons would make more sense. That's why we pay ideola the big bux

Rasta Monsta · Rasta Monsta's Garage

I have three sets. Do you know what size you removed?

Davie Boy · Davie Boy's Garage

What's that on the hood of your car? Fartini? Awesome!

JimN · 05-25-2010, 04:07 PM

Our 24hour of LeMons team is the OLD Fast Auto Race Team & Sons. OLD FARTS for short. We have a 924S and a 924 Turbo.

ideola · ideola's Garage

Quote:

Originally Posted by JimN

So, does anyone have some 924 turbo pistons in the shed?

YES:

Quote:

Originally Posted by ideola

I have pistons if you need them. I know there are some budget constraints...would prefer to sell, but we can discuss trade bait if you have anything of use to me.

Mine are from an S2 931, so 8.5:1 compression ratio.