Just did a cam swap in my buddies truck. Its a 2003 1500 Z71 with the 5.3 in it. Threw the cam in, no problems on the install. Tried to fire it up, and nothin. Sounds like its not building compression. Threw the compression tester on it, only about 60 pounds of compression per cylinder. Car will not fire at all. WTF? The cam is a Lunati QB7H(TH001)(originally designed for an LS1). The other markings are RRS1-221-221-112. I assume this is a 221 221 duration with a 112 lope seperation, not sure on lift. Any reason why this wouldn't work on this truck? The valvetrain consists of stock lifters, stock pushrods, springs good to 550 lift, stock rockers, stock heads. Mail order tuned it. Got spark, got fuel, got air, just seems like the timing in the valvetrain is way off. Any input will help, thanks.

 

Ummmmm. Did you line up the dots on the timing chain?

 

Yep, their lined up, #1, TDC, cam gear dot down, crank gear dot up.

 

Your cam gear should be at 6 o'clock and the crank should be at 12 o'clock.

 

Maybe a larger base circle on the new cam?

 

By saying that, obviously air is leaking out by the valves being open so the timing is either off, or you adjusted the rockers wrong, or the pushrods are too long IMO.

 

take the valve cover off and rotate the engine untill one of your intake valves are closed. then loosen off the rocker arm and see if it closes more while your unscrewing the rocker. repeat on the exhaust valve. if they close more then thats your problem. good luck

 

Sounds like the crank and cam gear is a tooth off...I wonder if the cam was incorrectly ground?

 

whats the oil pressure gauge read ? what size push rods did you use ?

1. to me it sounds like you could be a tooth off
2. push rods are to long

 

I thought of that too, but he mentioned stock heads and pushrods, so if anything I'd think the pushrods would be a tad short (aren't the stockers like 7.38 and most aftermarkets 7.4?)