Help with a new motor

[Mark1968]

I've got a buddy with a newly rebuilt 454 that won't run. New cam, pistons and bearings.
I wasn't present for the break in so I dunno how that went. When it does run it smokes from both sides of the exhaust.

It sat untouched for a while after break in and couple weeks ago we wanted to figure out what was going on. Plugs 1-6 were covered in oil, 7 and 8 were somewhat clean. We checked compression and pressures were all over the place. The motor has no miles on it, just the 20-30 minutes of break in time. Is it possible to have no compression at all on a cylinder after a break in?

 

[FAB454]

Bad timing, improper ring fit? First 2 things that come to mind

 

[Kain]

or valves way off in adjustment

 

[4X4HIGH]

My guess is someone didn't adjust the valves properly and now they are bent.

 

[Mark1968]

I've no idea how the valves were adjusted, so I guess that is possible. Any way to id a bent valve without pulling a head?

 

[y5mgisi]

Valve adjustment. How to id a bent valve, i would back the rockers off until they are just off "zero lash" and then do a compression check. Outside of that, a leak down test would tell you where the compression is going.

 

[y5mgisi]

Just FYI, I'll tell you a story. Not long ago, a friend put "corvette" heads on his 350 along with a "corvette" cam. Upon reassembly, they just tossed the cam in paying no attention to the cam timing, and tightened all the rockers until they were TIGHT. And then came to me asking why it wouldn't run.... Didn't take long to figure it out after several fire balls out the carb. I timed the ignition and still fire balls out the carb. Adjusted all the rockers and still fireballs out the carb. Then i quizzed them about cam installation. He was like, What? Pulled the timing cover off and sure enough, it wasn't even remotely close. It was in the neighborhood of 45* off. Re timed the cam, re timed the ignition, and it ran fine. I couldn't believe they didn't bend any valves....

 

[FAB454]

So, smokes from both sides... raw fuel or burning oil?

 

[folkenheath]

I would do a leakdown. If cam timing was off I would expect them to have similar crappy numbers, but when one cylinder is zero something may be bent or a rocker could be too tight, etc. Or both. You are dealing with the unknown, leakdown and compression is what I would want, along with rocker adjustment. You could also degree the cam if you remove the accessories to check cam timing as well.

 

[paratrooper307]

I would do a leakdown. If cam timing was off I would expect them to have similar crappy numbers, but when one cylinder is zero something may be bent or a rocker could be too tight, etc. Or both. You are dealing with the unknown, leakdown and compression is what I would want, along with rocker adjustment. You could also degree the cam if you remove the accessories to check cam timing as well.

Basically start with the easy stuff and work your way to the hard. Verify ignition timing and do a leakdown/compression test to try to isolate any problem cylinders if applicable. Verify valve lash adjustment, pushrods, and valves, and then check cam timing. Ultimately you may have to pull the heads. If you know who built the motor, they might be helpful in determining what was installed, which could lead you to a problem. With it running that poorly, the issue should be pretty obvious once you find it.