Will I have been out of pocket because I have changed job's. I am a lot closer to home how.

I have had some issues with the truck. First my fan came aprt and did some damage to the rad. Put an electric one on and a larger alt. Then I it was using a lot of oil fo a new engine. Found out it was come threw the PCV valve.

Now when I take it up to high RPMS for a few seconds when it comes back down it wants to run rough for a few seconds like may be a weak valve spring or bad lifter. I put new lifters in but did not replace the valve springs.

Can anyone help it is a 351W.

 

Can you run a compressio test or better yet a leakdown test? You can probably borrow the tools from Autozone or other chain stores. Is this a rollerblock engine or an older 351W? Carb or EFI? Cam? Definitely need more details if you want informed advice.

Weak valve springs will often act like a rev limiter at high rpms. Those symptoms not likely a lifter unless perhaps there is debris causing it to stick when fully pumped. Stock style oil pump wiith normal oil pressure right?

 

It is not a roller motor. Oil pressure is right at 45 al the time. It does not tick at any RPM's. Just run's rough when it come back to idle. Vac. is right at 18 and steady. total timing at 30.

 

steady vacuum is certainly a good sign internals are likely good. If you had a bad spring vac would flutter at higher rpms. Wonder if perhaps the carb is having a problem with fuel level control coming off higher rpm? Any chance it is flooding a bit when the problem occurs? Just a wild guess of course since I can't observe it. What carb and fuel pump you running?

 

I have one acting exactly the same way, I dont know what carb you have
mine is a 2bb Holley and thats definately dirty air idle passage. Runs
perfect pushing snow then stop shift to reverse runs like crap like its
running on a half bank > thats air idle.

 

I have anew Holley 600. I did not even think about that. I all so have not checked my vac. at high RPM's. But it is really steady at Idle.

 

What you are describing sounds a lot more like a carb issue than a valvetrain problem. Don't know how clean your tank and lines are, but trash in the carb can cause lean or rich conditions at different rpms.