Its getting better but still wrong.

[mrsmothers]

Well I got my 50 on the road runs pretty good. I set the valves the other day while it was idling and got them all nice and quite. When I get in to 3rd gear you can hear a rattling , if i get to far up on my rpms it back fires. Also keeps blowing the pcv valve out of the valve cover. its a 350 btw.

So the question is why is it doing this? valve to tight, valve to loose, timing off?
should I re adjust the valves at higher rpm?

[NEWFISHER]

Swap an inliner in it

sounds like a timing issue if you are backfiring( assuming valves were done correctly). Check vac advance pot, re-time it.

[Nordic]

If the pvc is coming out you need to do a compression check.

[Rufton]

I'd run vacuum tests, verify cam timing and ignition timing.
Adjusting hyd lifters at low rpm or while engine is off is ok.
If no joy, I'd do other tests.

[Wrenchbender Ret]

Besides the PCV valve you must have a vented oil cap or tube going to the air cleaner. If not that is the problem. If you have smoke comeing out of the pcv hole with the engine running then you have excesive blowby. You will need an engine o-haul or at least new piston rings. As far as cutting out at high RPM, check the spark plugs. Idling & testing can build up black carbon on the plug with todays gasoline. You may need to clean the plugs.

[kornfed]

Could also possibly be a broken/collapsed valve spring? Is it backfiring through the carb or exhaust?

[mrsmothers]

Its back firing through the carb. have no smoke coming out of the pcv valve. I am going to play with the timing a little today and see if i can get it

[Rufton]

I'd double check that all plug wires are plugged in correct location.

[lmdangerous]

I second the vented oil cap- even with the PCV valve. I went through this and swore it had to have blow-by. Engine had no smoke going down the road, ran fine - just would either blow the dip stick out or the PCV. Put a vented cap on - It went away.
I would check the vaccum pod, plugs, and the timing - specifically the mechanical advance and make sure something is not stuck , broke , etc. Also check the valve springs- have actually had one broken before that did not drop the valve - just missed and popped when under a load.
LMD

[crossfire84]

you should check to see if your distributor is off by one tooth on the cam.

[Coupeguy2001]

sounds like the heads have a bad intake valve or leaking/mismatched intake gasket, and the intake gaskets are leaking. When it back fires, it blows hard past the leaking intake gasket.
It may also be running too lean that way, and with the timing off a little, the fuel mixture ignites before the intake closes, blowing out the intake.

[mr48chev]

Did the truck run ok before you decided to adjust the valves? If not what were the symptoms?

If you have a vacuum gauge or access to one you can usually tell if you have a valve problem by the readings. It also helps you tell if your timing is off.

I'd start with the simple things"
Check the plug wires to make sure that each one is tight in the cap and on the plug and that they are indeed in the correct firing order.
If you have a compression gauge, run a compression test to make sure that the compression is even and up to snuff compression wise.

The pcv valve blowing out is either because there is pressure building up in the crankcase because it isn't venting right or because it is being blown out when the engine backfires. If you have a vented breather cap I'd think that the backfiring is causing the pcv to blow out of it's grommet.

If the distributor was a tooth off it wouldn't affect the timing unless you can't turn the distributor enough to get the timing set where it needs to be. If you can turn it to where it needs to be there isn't a problem.

Timing or the carb leaning out is probably the cause of the backfire. If you hit the gas and the accelerator pump doesn't give it a good shot the engine leans out and can backfire. If the timing is off it could also happen.

[mrsmothers]

Figured it out vented oil plug was clogged . bought a new one and its running great thanks for the help.