I'm not a math genius sooo I'm asking people in the know...

basically heres my situation. I'm doing a full 85mmx89mm LsVtec build. And I'm trying to figure out what compression will the motor ultimately be at...

Heres build plan.

Head:
-B18C1
-MaxFlow Ported w/ 1mm Oversize Intake Valves from CCCylinderHeads.com
-Supertech Springs
-Supertech Valves
-Supertech Retainers
-Supertech Bronze Valve guides
-Skunk 2 Pro 2's
-Combustion Chambers up to 85mm
-Victor X Manifold
-68mm Throttle body
-3mm RS 85mm Layer Head gasket
-ARP head studs
-High End header ( for now )

Block:
-B18A sleeved by JG punched out to 85mm bore
-Not milled just cleaned
-85mm 12.5:1 Mahle Piston
-Eagle ESP 137mm LS/B20 rods
-GSR Girdle
-89mm Crank knife edge and micro-polish
-Morso Oil pan

sooo I was told by CCCylinderHeads.com that by opening up the combustion chambers I should effectively lower compression by 0.5:1 compression. So will I be at 12:1 compression ??? PLease let me know, thanx

 

Not necessarily.

You will be ordering a 12.5:1 piston from Mahle, but you need to remember that the advertised compression ratio is calculated with a certain stroke, piston to deck height and CC's. If they have a "12.5:1" piston with .030" piston to deck, and you put it in your block that has .020" piston to deck, you're gonna be staring at more than 12.5:1 compression.

I can open the chambers to match the bore, and depending on additional chamber work you can lose up to a full point in compression. The only way to be sure what compression you have is to CC a cylinder with the piston installed, and CC a combustion chamber and then do the math. Thats the only way to be 100% sure.

p.s. I just replied to your email.

 

Steve your the ish man... Thats why I want you to be the only one to touch my head...

Problem is I already ordered the Mahle pistons and I cant just return them... I paid up the *** for them $510.00 because they dont make them in a 85mm size anymore...

Problem is I dont know where to go for to CC my motor ....

 

You probably dont need to return them. Do you have a part number for the piston that you have? We can start by finding out exactly how they are calculating it as a 12.5:1 piston.

 

part number# is ACR181346D06

 

Got some bad news for ya.

That compression is measured with a 87.2mm stroke, so with a 89mm crank, you're looking at something in the 13:1 neighborhood, without any chamber mods. BUT again, the only way to really tell is to have everything CC'ed.

 

but we are planning on doing chamber work though. by opening them up to 85mm right ...

 

Right. But since I havent done the math, the compression could be higher than 13:1 before chamber work, thats why I said "13:1 neighborhood". Everything needs to be CC'ed, thats the reality, unless you want to get new pistons for some more breathing room.

 

DAmm it!!! I talked to a tech guy at Mahle and he said it should be fine because I'm using a 137mm rod vs 137.9mm rod... I was using the zealwerks.com compression calculator. And it look like it would fall into 12.06:1 compression....


heres the numbers I imputted in:

bore: 85mm
stroke:89mm
deck height:211.84
combustion chamber:46cc ( I figured that since the B20 head has 45cc and I plan on having you open up my combustion chambers to 85mm sooo it should be 46cc right ???)
Dome: 6cc
comp height:30
rod lenght: 137mm
gasket layer:0.026

 

The only way to be sure is to CC it, I'm sorry but I can't say it any other way.

 

What/where is the best place to get this done and approx cost?