Using the c-speed racing site, gsr head, gsr block, ls crank and rods, 81.5mm usdm itr pistons, gasket thickness .036" but heads been milled 0.015" and block decked .006" and pistons 0.008" out of the hole, I got 12.9:1 I also have supertec flat faced valves so I will be more like 13.2:1. Does that sound right?

 

Numbers sound about right but the gasket is to thin. You will only have .028 or so of piston to head clearance. Normally you want .035-.040 so it could give you detonation problems. Not from overall compression, just from the quench.

 

Is it true that flat part of gsr head sticks above block deck 0.04" or are the stock gsr pistons around 0.04" below block deck?


Modified by all-mtr-teg at 9:45 AM 8/29/2007

 

Not sure what cam you are going to use, I would get the motor clayed to check clearances. 0.028 is below spec. With a big cam, you could potentially get some valve to piston action.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jay_Sensing &raquo;</TD></TR><TR><TD CLASS="quote">Numbers sound about right but the gasket is to thin. You will only have .028 or so of piston to head clearance. Normally you want .035-.040 so it could give you detonation problems. Not from overall compression, just from the quench.</TD></TR></TABLE>

why would having the piston close to the cylinder head promote detonation??

 

I got bc3 cams. I check v2v clearances and i should be okay till +4IN, -4EX Thats where i only got 0.04" clearance. But is there any other way to lower compression down to around 12.1-12.5:1 besides a 0.06" headgasket. Should I machine the flat faced of the pistons or can i adjust cam gears so lower compression some how. This is a d.d. and only have access to 91 octane


Modified by all-mtr-teg at 4:36 PM 8/30/2007

 

you could so a little combustion chamber work and maybe unshroud the intake and exhaust valves slightly but since you arent running 84mm+ bore i dont know if you will get many CC's out of the chamber

 

haha dont wanna jack you but i have question about my head gasket as well, i have a ls/vtec gsr head(milled .010) with 12.4:1 pistons with a 8.25 and my question is that i will have my cometic gasket tomorrow and its .045 and since the head was milled .010 it would be more of a .035 gasket is that to thin? i have some blueprint cams they are stage3's (more like a skunk2 stage 2 1/2 haha) i did a 3 angle valve job oem sized skunk valves. ill check back here for answer but dont wanna jack this guy so can some one pm with kinda of an idea WENT TO A .052 REALLY A .042 WITH HEAD MILLED .010


Modified by DSRacing at 3:27 PM 8/30/2007

 

if your pistons aren't coming out of the block like mine are, and they are flush with the block deck then you might be okay with 0.035" piston to head clearance, if your pistons sit below the block deck by .01" then your like 0.045" P2H clearance which is what endyn reccomends for stock steel rods. Check here

http://www.theoldone.com/artic...s.htm

 

what's the maximum P2H clearance you can run before puddling and detonation occur from exessive P2H clearance ?

 

Endyne reccomends 0.045" minimum P2H clearance for stock steel rods, and im thinking i'll have around 0.001-0.003" piston rock, so im thinking 0.048" P2H clearance will be safe?

 

yah that would be plenty safe