hey, I am new here and have been looking at some of the posts. I am going to be pulling the heads on my 03 sierra 5.3 lm7 and was considering putting on some 243 heads with a .040 cometic gasket to bring the compression to 9.8.
my concern was with torque, I use this truck as a dd and tow with it. so will I loose some bottom end running a 210 runner with a 2" valve??

also thought about just putting a 212/218 cam in with 918 springs and rods but am unsure about what needs to be tuned??never done it?? timing?? idle??

is ther a good cam that i can put in without a tune or springs etc.?? thanks

 

You will need to mill the heads to bring the compression up, they have larger combustion chambers than the stock LM7 heads. I had WCCH mill mine 0.022" to bring it back to the stock 9.5:1 SCR with stock thickness gaskets.

 

ok that makes sense to mill them and use the stock .051 gasket, I was going to keep them at 64cc's and use a thinner head gasket of .040. is that right..you can do it ether way? makes sense to me?? compression wopuld be about 9.7-9.8.

how is your low end throttle response, did you notice a gain in hp and tq?

 

Mill the heads .020 for stock cr and another .010-.015 for 9.8-9.9 cr and u should tho that cam in to at that time

 

what about a tune for that cam? is it needed?

 

yes to achieve the best performance out of it, especially if u are putting on ls6 heads

 

U need to have it tuned fir the heads or both heads and cam

 

ok thanks, do I need a new cam gear to degree the cam or can I just run it strait up and slap it in. also stock converter ok or should I be looking at a less duration cam, dont want to smoke the converter if the tuning job puts the rpm up to high..
anyone have this cam?? what is your rpm at idle??

 

212/218 is a very small cam, its not that much bigger than the stock cam. you dont need a new cam gear or need to degree it, just line up the cam gear dot to the crank gear dot perfectly and you will be good. tuning takes care of the rest. as far as RPMs go, tuning is just gonna change ur idle a lil bit if ur truck runs like crap when u do the cam swap. when i did my swap my truck was running at 5-600 RPMs and ran decently with a nice lope to it. I t now runs 7-800 RPMs after the tune...can still hear the lope a little bit.

 

Degreeing the cam on these engines is really just done to make sure the cam specs are what they say they are. Rarely are they not. Put it in dot-to-dot, spin the motor over by hand a few times to make sure the valve timing isn't horribly incorrect, and you're good to go. With my 212/212 114 I idle at 700 RPM with some noticeable lope. But it will do 600 easily, but I have it turned up since it's a manual trans.