03CobraMike

iTrader: (1)

alright, so i've got my motor all torn apart, and started putting it back together and am worried about my piston to valve clearance. originally my parts were all spec'd out assuming using stock rocker arms, but i went and bought harland sharp 1.7 non-adjustable roller rockers instead. can anyone tell me if they've run a similar setup or if they know how close my ptv clearance is going to be? here are all my specs:

2005 ls2 corvette

.617"/.610" 236/242 111+2lsa
stock lifters
stock pistons
stock valves
stock ported heads, no milling
patriot gold extreme .650" valve springs
harland sharp 1.7 non-adj. roller rockers
cometic .041" head gaskets
comp 7.425" pushrods

i really want to use the roller rockers, but i also don't want to destroy the motor and my guy that spec'd the parts thinks that it might be too close. please help me! i really want to get the car running again since it's finally getting nice outside.

thanks in advance.

05gto60

iTrader: (3)

I dont know who is doing the math on your motor, but you should let them know that those harland sharps are the same 1.7 ratio as the stock rockers.

that being said, you are using a .020 smaller head gasket and also a larger cam. an easy thing to do would be to put the motor together with the old headgasket and some clay in 1 or 2 cylinders and turn the motor by hand. after that, take it apart and measure the clay at the thinnest point the valves made. then you would know exactly how much PTV clearance you have

03CobraMike

iTrader: (1)

problem with that is i already torqued everything down. i called harland sharp about the rockers, and they said that under load, the stock ls2 rockers spec out about 1.69:1, where there's are usually about 1.71:1. doing the math on this, having a 1.71 as compared to a 1.69 rocker is .0123" extra intake valve lift on and .0122" extra exhaust valve lift. from what i was originally told, i was going to be at about .050 or .060 ptv, but when i asked the other day, he didn't seem to want to give me a number, hence me wanting to figure it out myself so there's no guess work. my friend actually just got his procharged c5 z06 back together, and what he did was to set the motor at tdc, bottom out the intake and exhaust lifter (problem is mine were soaked before install, so full of oil unlike his) so that the pushrods were at the farthest that they could ever go into the lifter, then put feeler gauges in between the valve stem and rocker tip. he then added another .080 of feeler gauges on top of that (because he wanted to make sure he had at least .080 of ptv clearance) and then very slowly and carefully turned the motor so that it went through it's full cycle, making sure it didn't bind up. this is what i was going to attempt to do, but since my lifters are full of oil and the heads are already on, i can't push hard enough on them to compress them fully. any ideas?

01FbTaWs6

iTrader: (12)

i did the exact same thing as your buddy. I loosed the rocker arm, tossed.110 worth on each side and cranked it over slowly to make sure i had atleast that much clearance. Only other way I know is to clay it

03CobraMike

iTrader: (1)

quick question, but would the lifter bottom out if i got the pushrods in, torqued down the rocker arms to spec, and then rotated the motor? or will that not create enough force to actually move the cup in the lifter? how much will a lifter actually depress? i guess if i knew how far a lifter for our cars depresses, then i could add that much more to the feeler gauges if spinning the motor doesn't in fact depress the lifter. any idea?