I have an tc 88. Stock compression,have mackie 510 cams stage1 ac se exhaust. I going to bore to 95 put cast se flat top pistons and street port the heads. I want 9.8.1 compression.Tell me what i have to do to get there please.Such as decking the heads,size of head gasket etc. thanks much.

 

I got my heads street ported, chambers cc'd at 82, heads milled slightly (don't know exactly how much), 0.030 gaskets, adjustable pushrods. I'm at just about 9.8:1.

 

Sounds like you are planning to do the work yourself? You need to figure this one out and become familiar with the math. Open the link to the BigBoyz compression calculator and work with it to answer your questio; you will see all the variables that go into the compression calculation.

A couple of points about compression for future reference. There is static compression, corrected or dynamic compression and cranking compression and all should be considered. Corrected and cranking CR will vary depending on the timing of the intake valve closing but static CR will remain the same as it is not affected by valve timing.

There is room for debate about what a reasonable level of corrected and cranking CR for a street build is; some like 9.3 corrected as the limit an some think 9.6 is the limit. When cranking compression approaches 190psi, you are in compression releas territory; maybe not a must but nice to have if/when needed. Compression releases will also extend battery and starter life if used.

A .030" head gasket does drop the static CR by about .25 points less than with the OEM head gasket but the more important reason for the .030" head gasket is to tighten up the squish, also referred to as the quench, area in the combustion chamber for a more complete and efficient burn of the air/fuel charge.

In your application, you will need to deck your heads to reduce chamber volume to about 80cc, with a .030" head gasket to hit 9.8 static CR assuming your deck height is 0.00 which it most likely is not. Typically OEM pistons are down in the hole .003"-.005" which will affect the CR calculation a bit. At 9.8CR, your corrected CR should be about 9.1 and cranking between 185-190psi. Not a bad place for a street build; should be a good runner.

Check out the BigBoyz calculator; it is a handy tool.

 

You can "assume" for every .007" you remove from the gasket surface, it'll decrease chamber volume by 1 cc.
Abitrarily doing so will not insure all is right, nor will it take into account variances from one chamber to the other.
Scott

 

Take it to an expert and get him to do it! This is hardly DIY stuff.

 

i agree,just the fact your asking the question,tells me you shouldnt DIY

 

thanks for your info. Iam sending the heads and cylinders in . Just had some questions. Bean will be doing the work i will be installing them.dyno will be done by fuel moto thanks alot

 

Bean will get it right. You should take the time to learn this stuff anyway but Bean will get it right while you learn.

 

djl. Thanks for your input and your right I will figure the numbers out. I just keep learning and doing. By the way your numbers you gave me were right on. Thanks jurgie

 

I have a 2001 95ci with 204 cams chain drive, I'm switching to carbs from magneti marelli efi . What is my compression ratio? should I go Super E or G ?
I was told, under 10 E, Over 10 G. Is this true ?