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After a standard rebuild, my 390 runs like crap, cannot get above 3000 rpm without lifter clatter, its like it has low oil pressure and lifters are pumping down (hydraulic cam), but its got a high volume pump with lots of pressure.
its got me stumped. all other areas seem normal. pulls 17" vacuum with a .475 lift cam. soon as you try to rev it, it starts breaking up with lifter clatter, Help !!
Did you put a differant cam in it, and if so did you get new push rods or are you using the old push rods?
Kurt
Is it possibly detonation you're hearing? Did you use pistons with a shorter compression height on the rebuild?
I had one that did the same thing some years ago when I switched cams and you would not hear the lifter at low RPM's but after you revved it, you would start to hear them chatter. I had used the same old push rods and they were just a tad to short because of the new higher lift cam. So I got some new longer push rods and the problem went away. Had a buddy come over with some kind of ajustable push rod to measure the right length. The old ones were about 1/4 of a inch off. Kurt
Cam lobes going flat---
That was going to be my next guess, Jerry.
He needs to remove the valve covers and look at the rocker while it's running and maybe measure the rocker movements to see if the intakes are all the same and then the exhaust to see if they are all the same.
Kurt
Louey
These engines were famous for the lifters not spinning in the bores and killing the cams--
If he runs it without the valve covers he can see if the lifter/pushrod is spinning and if the valve seems to be opening about the same as the others. Also without the valve covers to amplify the sound he will be better to pin point it.
Jerry
ok guys, 1st, thank you for all your replies and input. I will try to answer all your questions best as possible. The engine is original 70,000 mile motor, 390 Thunderbird engine, 390/300.
By standard rebuild, I meant all standard sizes, bores, rings, rods, mains, all standard sizing. Camshaft is a new Doug Herbert GN4 hydraulic, Doug Herbert lifters, matching Doug Herbert valve springs, melling high volume oil pump, new stock rocker arms and shafts, comp stock length pushrods.
The engine was assembled by myself and the block was prepped by my engine builder who is also Ford specialist, as were the heads.
I pulled the valve covers off, seems to be plenty of oil getting up top. problem seems to be with #4 & #8 intake valves, I'm going to try to sneak those lifters out without pulling off the intake manifold. I want to visual those lifters for damage on the bottom, also for any blockage in lifter valving. let you know if I find anything. But I'm inclined to think the push rods may have a lenght problem because of the new cam.
I always use the rod down to the oil pump and turn it with the old drill.
Then I make sure the oil is getting to the top of the motor at least with the hydrolic cams. You can get the old petro really flying like that.
I had a motor builder that would over tighten the rockers down with out pre oiling the lifters. I got to his shop to pick up my motor at lunch time when he was out to lunch.
Some other custumers were sitting around talking about how they started up thier new motors and broke rocker arms and flattend cam lobs bent push rods. So the first thing I
did after I picked up my motor was go home and loosen all my rocker arms.
Sure enough I to would have had a broken rocker arm, bent push rod or a flat cam lobe.
And the lifters were not even pumped up with oil, so he didn't soak them or pump them up. You have to watch some of these guys building your motor.
Right away you start thinking what else got messed up during your engine build?
Kurt
Do those lifters/pushrods spin while running???
I don't believe so but I could be mistaken.
But I was allways using roller rockers and guide plates.
Not sure if that would make a differance or not with the harden push rods.
Kurt
if the lifter isn't spinning you have a flat camshaft(or will soon)
Well that helps, HE! HE! He said he's running a hydrolic cam.
But will it allways spin the push rod up top by the rocker arms?
Kurt