I'm finishing my motor and figure the compression is gonna be about 10.7 to 1. I'm not running any supercharger and aint planning to so that's not an issue. Might go with N2O later but I understand it doesn't effect compression. Taking my heads in the end of the week and was wondering if I should have them decked also. If so what s the extra charge for that?

 

you want your heads decked no matter what...doing this gives the gasket a smoorth surface to mate with...now the real question is, how much do you want shaved off the heads?...if i recall correctly .001 off the head is about .1 CR increase...stock is 10.5:1...i am planning on about 11:1, which i dont know if that can be done by decking, becuase if you shave too much, you start messing with intake to head mateing angles and stuff like that...but deffinatly get them decked, unless of course they are aftermarket or ported heads, then they will already have the smooth mateing surface...hope that helped some

 

i would recomend 11:1 - 11.5:1 with a decent cam


i run 12.5:1 and it works great but only on sunoco ultra 94 in a some what cool canadian climate.

 

every .010 taken off the head is +.25 so if you start out at 10.5 and take off .010 thats 10.75 CR so if you took off .030 that would be 11.25 to 1 but you can take off .020 and get the lt4 gasket which is .010 thinner than lt1 and that makes .030.

what that does is takes .020 of the head and if you ever over heated and they had to take off .010 to flatten the surface agian then you could go back with stock gaskets and be back at .030. this way you have a saftey cushion. and if something happens you havent lost anything, except time and alittle money and saved your heads.

unless you want to do the 30+ hours of porting again

hope this helps.

 

hahahaha. No kiddin Vince. Forget that crap. Did you get the finished pics i sent ya? But anyway what compression ya think I should run then 11:1?

 

i think you should hit about 11.1 to 1 or 11.5 to one. somewhere in that neighborhood.

ill check my email for the pics now.

 

Mine is 10.8:1......I didnt want to go more than 11:1.

 

I came in at 11.3:1 with good results thus far. Absolutely no detonation issues whatsoever. I wouldn't get too stressed about the static compression ratio anyways, since it's the dynamic compression that really matters.

 

Just CC them (one chamber is sufficient if your work was consistent), and figure .006 per CC. Sticking with the hotcam? I'd probably have it anywhere from 11-11.2 or so. I'd be more concerned with keeping your quench in the .040-.045 area if at all possible .

 

Hey Phil you lost me from the start. What the heck is CC them? What about the quench thing.....040-.045???

 

The god thing about the conversion is that I will always have the original OBDII laying around. (unless I sell it on EBAY ). So I can always change it back.

 

He's referring to measuring the combustion chamber volume, which you'll need to determine the compression ratio.