whats the maximum skim on a blacktop 20v 4ag

[waynemodz]

hi guys, i recently bought a blacktop engine like 3 days ago, which i want to boost but the guy who sold it to me told me he skimmed the head to the maximum, so the compression is way ato high for turbo, can someone advise me how many mm's is the max for blacktop? so i can decide if i should shave the piston or make a spacer or thicker gasket

[Donmik]

Hey mate,

I'm not too sure what minimum thickness of the head is, usually they have thickness indicators on the face of the head... I will try find Out today at work, I may have a specification sheet there...

However, for that engine I'm pretty sure you can buy different thickness metal gaskets!!! You will have to do a compression ratio check before deciding which is your best avenue!!!

[waynemodz]

Hi sir,

Actually I have not stripped the head from the block yet, but I've been advised its on the max. I would really appreciate some info, I wanna get it down to 8.0 but I have the 8.9 pistons. Unless I run meth injection 24/7... Hectic! But I'm building a street car thou it will not be used daily.

[Xauterus]

you can get pretty thick gaskets. I got a 2.0 mm HKS one.

[Donmik]

Sorry mate, couldn't find any "minimum thickness" info for that head...
Could only find 4A-C....

[Sam_Q]

I didn't think there was a minimum thickness? you could always change the pistons but I know that would be expensive

[Donmik]

Every cylinder head has a minimum thickness, although its really more Like a guide line, but don't for get every time you surface the head, your actually thinning out the deck getting closer and closer to the water jacket....

Waynemodz: 8.9 is not ridiculous for compression.... My celica is running 8.7:1 and I'm about to pour 20psi into her...