Valve Adjustment on 5.7L Vortec

[76SeaRay]

Ok, so read all the threads about 3/4 versus 1 turn past zero lash. However, from what I found from Comp Cams, they say to 1/8 to 1/4 if the engine spends its time at high RPM and 1/4 to 1/2 turn for average "street driving". I am guessing their reference to the street would be applicable for boats. My machine shop was asked me if I was going to use 1/4 turn (he builds race engines) and I told him I would likely use 1/2 turn. I am using the Xtreme Marine 264 cam with .488 and .495 lift. The engine is going in a cruiser in large lakes so running low speed, medium cruise, and for long runs across the lake at high RPM. What is everyone's thought these days on 1/2 turn? Is there a technical reason to go tighter than recommended by Comp Cams?

Thanks...

 

[Scott Danforth]

If you have stock non-adjustable valve train, you tighten up to 30 lb-ft

If you converted your heads to adjustable valve train, then 3/4 turn past zero lash

So......what mods were done to your heads?

 

[76SeaRay]

Stock heads but improved valve springs, Comp Cams hydraulic roller cam, and Comp Cams 1.50 roller tip rockers on 3/8 rocker studs.

 

[Scott Danforth]

so you converted the heads to adjustable valve train then.

did you go with thread in studs, or do you still have the press-in studs that are stock? if you are running the press-in, you will need to monitor for the studs pulling out with the different springs

 

[76SeaRay]

No, they never were non-adjustable. Stock 1996 vortec uses non-roller tip stamped steel rockers on studs. Yes, the heads were tapped and new screw in studs added in place of press in studs.

 

[AShipShow]

Didnt know Merc had vortec motors yet in 96... you sure it's a vortec head? How many bolts on intake manifold?

 

[76SeaRay]

I am scratch building the engine. Yes, it is a true vortec set of heads on an 880 block.

 

[Scott Danforth]

No, they never were non-adjustable. Stock 1996 vortec uses non-roller tip stamped steel rockers on studs. Yes, the heads were tapped and new screw in studs added in place of press in studs.

so, 3/4 turn past zero lash.

 

[Dentar]

so, 3/4 turn past zero lash.

I just adjusted my valves on my 1997 mercruiser 5.7 with vortec heads.
Went with 3/4 turn past zero lash as adviced. Once done i comptested the cylinders, turns out 0 compression on all of them !?

Came back here and read TS post with 1/4 + 1/2, so i backed all valves 1/4 turn and lord behold compression is back! went back another 1/4 and compression increased 3-10 psi on each cylinder. so in the end im 1/4 turns past zero lash.