Cometics and Compression Q's

[TT/Ameasap]

Got a .020 over 109. going from .120 gaskets to .060
piston sits .005 in the hole.
My compression from Weber is 8.54:1 with the .120 gaskets
Deck is 9.511

What part number Cometic do I go with for .060?
What will this bump my compression to?

 

[turbo89]

Got a .020 over 109. going from .120 gaskets to .060
piston sits .005 in the hole.
My compression from Weber is 8.54:1 with the .120 gaskets
Deck is 9.511

What part number Cometic do I go with for .060?
What will this bump my compression to?

What cylinder head volume ?

I'm gonna take a guess with the new gaskets you will be about 9.7:1

 

[pacecarta]

http://www.summitracing.com/expertadviceandnews/calcsandtools/compression-calculator

changing gasket from .120 to .60 with an old cr of 8.54:1 and not changing anything else should bump you one point to 9.5

you need for 3.86 bore x .060 ...not much choice on which one that will be unless you want custom which they can do

 

[pacecarta]

why the .120 gasket with only .015 off the deck , and are you sure it was8.54 or is that the advertised cr of the piston in a std application
were the heads heavily cut ..what was the head volume ?

 

[TT/Ameasap]

All i am going off of is the build sheet. The TTA heads with GN pistons will raise the compression a little. The heads are CC'd from Weber, so I will have to call because I dont have the numbers.

 

[chasmat2316]

you should cc the heads, you may have more cr than you think! TTA heads have a very small chamber!

 

[TT/Ameasap]

That is exactly what Weber said. Heads are sold tho. TA Aluminums going on now. Gonna get those CC'd to figure out what thickness gasket I need.

 

[turbo89]

That is exactly what Weber said. Heads are sold tho. TA Aluminums going on now. Gonna get those CC'd to figure out what thickness gasket I need.

Just curious .. what compression are you shooting for ?

 

[TT/Ameasap]

With E85 I want a little more CR. So Im hoping to get 9.5:1

 

[pacecarta]

not goin to happen with those pistons that far in the hole stock stoke
im at 9.24 ... stock stroke , 27-8 cc piston dish (je .030) , 43 cc head (gn1 8bolt) , .003 over the deck with .045 cometics

 

[TT/Ameasap]

I dont know the CC of the Wiseco Pro True pistons, but the crank is stroked.

 

[pacecarta]

stroked a .040-.045 gasket should put you at 9.5x with 43cc heads and .020 piston that should have .28 cc (calculated the dish volume working back from your old numbers and 41cc heads )

 

[TT/Ameasap]

Well, The only thing that has changed is the heads. I will be running ported TA heads. Talked to Nick today and he is going to CC them this week along with a few other things.

 

[TT/Ameasap]

New heads Combustion Chamber 46cc
Im thinking .030 to get about 9.5 for the new setup.

 

[pacecarta]

you can think that but with less than .040 to the piston you better check things close

 

[Ttype6]

I received my TA SI heads last October and the combustion chambers were 48.8 cc.

 

[BARRACUDA1968]

I received my TA SI heads last October and the combustion chambers were 48.8 cc.

Ditto