here is the problem:
i have a fresh 355. it has comp cams magnum roller tiped rockers (1.52:1). i set all of my lash on my valves. 1/2 turn past 0. i went to start it and the motor just turned as it had no compression. i loosened the rockers back up a 1/2 turn before 0 lash. it fired right up. it seemed like my lifters we not plunging (acting solid) . i replaced my lifters, set my valves and the went to start it. it started and ran for like 10 secs then shut off. im assuming the new lifters filled up and stopped plunging. i went to set the valves once again. but i looked closely as i went 1/2 turn past 0 lash. instead of the lifter plunging, the spring was compressing and opening the valve. thus no compression. ive talked to a few people about this problem and they dont know what it is so i figured i would ask here. any info would help, thanks

 

You're over tightening them. "Zero" is just where the pushrod contacts the lifter.

And that's when the lifter is on the heel of the cam lobe. Are you turning it over so the lifter you are adjusting is on the heel of the lobe?

 

yeah you have already taken up all the slack and then used all of the preload on the lifter.... there probably isnt anything wrong with the other set of lifters either...

use your favorite method of aligning the engine to achive properly closed valves... then instead of spinning pushrods like every manual say to you want to try and move the push rod up and down so that you can feel when all of the slack is gone between the lifter and the rocker... dont even try spinning them that is an art not a science... then add your 1/2 to 1/4 turn of preload and you are good to go

 

i tried the up and down rathe rthan the spinning method. i got the same results. no compression. could the rocker ratio be off?. what is stock ratio? 1.5

 

rocker ratio does not matter with valve lash... it can be set correctly with the .02 change in ratio... the only real way i could see this happening is user error... if the lifters are up on the cam lobes when you set the lash even if you were 1 or 2 turns to tight on the rockers when they came down you would again be to lose so i think you have the engine in the correct positions and are just over tightening

 

yes....the valves are being adjusted on the base circle of the cam

 

ok. thats what i thought. but i just dont understand y i am having this much trouble setting theese. ive set many valves on many engines and this is the first problem i have encountered

 

Are you sure you have hydraulic lifters in the engine?

Try setting all the valves to zero lash. Start the engine. The rockers should clatter. If they do then add 1/2 turn to each rocker for the preload. If you have solid lifters, tightening the rocker 1/2 turn from zero lash will open the valve.

Solid cams need valve lash, not preload.

When adjusting hydraulic lifters start with the rockers full loose. Back every one off and wait a couple of minutes for the lifters to reset. The rockers should flop around. Tighten the rocker on the cylinder with the lifters on the base circle until just when all the play is gone from the rocker as in the above mentioned up and down method. When you tighten the rocker another 1/2 turn. The pushrod will become loose again (spin) after the lifter bleeds down slightly. Do not tighten more thinking it's still loose.

If you have no compression, I can only think of a couple of things. Rockers are still too tight keeping the valves open. Zero lash to 1/2 turn more should not open the valve. The second thing I can think of is rockers were too tight before and opened the valves too much which may have bent the valves contacting the piston.

You can check the valves with some sort of leak down tester. A compression tester hooked up to shop air will work also. Back off all the rockers, take out the spark plugs and put air into the cylinders. If any valves are bent, air will be heard coming out the intake or exhaust.

 

Tell us your method for adjusting the lifters.

I do not think you have the lobe on the heel.

When Exhaust opens set intake.

When Intake goes to full lift and almost comes completly down set exhaust

 

lets say you didnt have the lifter on the base circle... then set zero lash... as the lifter travels down the ramp you will again have to much play that cant be the problem as he is(as far as he say) setting the lash properly it could only increase the lash not decrease

 

True.

Either those are solid lifters, or there is something we aren't hearing.

 

they are hydraulic lifters. im 100% sure because i put them in. im setting the intake when the exhaust opens and setting the exhaust when the intake comes all the way up and then 1/2 way back down

 

Set them to zero. Get it started, then take them down another 1/2 to full turn while the engine is running.

 

Exactly. Set them while the engine is running. Fool proof (aside from being a bit covered in oil...)

 

there are anti-splash clips ( ? ) available . makes adjusting valves much less messy . IMO the only way to adjust valves . good luck .

 

That doesn't sound right. It's possible you're setting the valves on the overlap and you might not be on the base circle of the cam.

Rotate the crankshaft until the timing marks line up. Determine if you're on #1 or #6 cylinder compression stroke.

When #1 is at TDC compression stroke adjust
INT 1,2,5,7
EXH 1,3,4,8

When #6 is at TDC compression stroke adjust
INT 3,4,6,8
EXH 2,5,6,7

 

but again...

 

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