whats goin on everyone? ive got a 2001 silverado with a pretty healthy 4.8,soon ill be ordering new heads which are 58cc combustion chambers and im trying to figure out what my CR will be. the plan is to make a decent amount of compression out of this little 4.8, id like to get the new heads milled .30 and run a cometic .40 HG so i was wondering a rough estimate of what the CR would be around? my other question is will i run into any PTV clearance issues with the shortened deck height due to milling and increased rocker arm ratio? if anyone could point me in the right direction itd be gladly appreciated!

thanks

tj

 

It should put you around 10.1 if im not mistaken on a 4.8. as dar as ptv what are cam specs?

 

Forgot the milling! milling will put it up around 10.7 i think

 

cam specs are a tsp228r .588/.588 on a 112 lsa n pac 1218s(.600) i think ill be going with the prc .675's since ill be going to the highest ratio yella tella rocker arm, i think its an 1.8 if i remember correctly? i figure ill probably also have to go with a shorter pushrod too with the milling also? and 10.7 isnt bad but im definitley looking for more lol. sorry for the dumb question here too but what is the furthest they can be milled without having intake mani fitment issues?

 

ive been 45 thou with no issues. some say it isnt possible but i did it

it wouldnt hurt to check, but i think you would be fine. and a push rod length checker is cheap yet a very good tool to have in the box!

 

tempting lol, mabey ill give that a shot too then if youve had no issues. id really like to get this thing around 11:1 as possible if not higher. and that is for sure, i think ill be investing in one soon! i could be wrong but i think ls7 lifters are a little shallower than the normal ones so a pushrod checker is definitley gonna be in my best interest to make sure everythings precise before the initial first start up. thanks for all the help and advice man, its much appreciated!

 

The CR does not matter, with the truck in your SIG that 4.8 is still going to be under powered/torqued.

 

out of curiousity how is it going to be underpowered? not to sound cocky or anything but its proved itself pretty well out on the streets. i know the big tires/lift slows it down but the final drive is near a 4.10 with the tire size/gears and its got a pretty loose converter in it that compliments the cam pretty well. im not trying to start a war here im just trying to hear out your example of why its underpowered

 

Don't matter, long as your happy with it that's all that counts.

 

Damn thats a big *** cam in a 4.8! Must idle pretty wild. How high do you rev it?