driving me crazy....

[paint2361]

We have a new pontiac engine. 400 block, now a 440.
custom grind cam from comp with comp hyd lifters, zero lash plus 1/4 preload.
The engine fires easy and idles good with a fresh set of lifters.
Shut down, and will not restart. It did this with two sets of comp lifters.
We checks valve train geomatry many times. roller scrubing in the center of the valve stem, the rocker is a 90 degree to the valve at 50% lift. used a light weight valve spring to check and messure everything.



We are at a total lost with this one.... Any ideas?

[1BADBET]

Why did you think it was a lifter problem/ replace them? Does it turn over and just won't fire?

[paint2361]

After it sitting over night we came back and reset all the lifters to a zero lash. it fired up and idled fine but and as soon as the lifters pumped up (about 45 sec of running) we started to get popping out the exhaust and intake. Leads me to believe the lifters are acting funny and holding valves open.

[1BADBET]

If it was the lifters pumping up at idle like that you would have to have less seat pressure on the spring than oil pressure.... Do you know the seat pressure of the springs? When you say you reset it to zero lash you mean zero preload right? (Just want to make sure I get this correct, this I a hydraulic cam right?) if there is no preload how could they pump up? Just curious where abouts are you in CA? I'm in Anaheim, I'd be interested in taking a look at it see if we can figure it out....
Few more questions

Is this a new build or did you just change the cam (or anything else) basically did it run fine at some point.

What ignition are you running?

What carb?

Sounds more like an ignition issue, check the coil and plugs. I had a NEW plug that broke (porcelain separated from the threaded part of the plug) and it did something similar

[paint2361]

brand new MSD dis with 6A box. Replaced it this we have a weak spark. We have a fast EZ efi. We tried a carb with the same results. We think the problem is the lifters are not bleeding down when not on max cam lift. Only some cylinders have lifters that are hard.

[1BADBET]

If there is no pre load the lifter can't pump up and hold the valve open. As soon as you have oil pressure the lifters are filled with oil, if they weren't it would be making an aweful ticking noise till the did. You said you changed the lifters and it still did it.... I reeeeeeeaally don't think that's the issue. I'd go through your ignition system and make sure the cap, coil, plugs and wires don't have any damage and you have a good ground. A loose wire, bad ground, cracked cap, cut in plug wire insulation causing a cross fire.... Sound more likely, it's highly unlikely you would get two bad sets of lifters from a quality company like comp.

[TheJDMan]

I agree, two complete sets of bad lifters is highly unlikely. Adjust the rockers to zero lash then take them 1/2 to 3/4 turn more.

[MonzaRacer]

Way to check if it is lifter pump up, after it won't start, loosen lifter 1/2 to 1 round, try to restart. If it does, that's issue, if not then look else where.

[Skip Fix]

Which lifters? the "old" Comp 857s are known to have issues -usually not the whole set though. They have been replaced by the 857S version and most guys are doing OK with them.

Because of that lots of guys are using solid rollers on HR cams with tight lash and doing good.

[paint2361]

all this crap and it ended up being piston rings stuck in the piston. Found out by doing a compression check and 4 cylinders had less then 50 psi. back to the builder it goes....

[1BADBET]

Did you tear the motor down and see the stuck rings?