I'm having the heads inspected by a machine shop. I took my cam info with me and after reading it and looking at the heads, he thinks the valve springs were coil binding. In other words, perhaps the wrong springs were used. We'll see, but that's today's update.

 

Got a call from the shop, and he said the problem in his opinion is the wrong valve springs. He said they were coil binding, basically trying to over compress, with the exhaust at .055 over , and the intake spring coils by .035 (hopefully I'm indicating "thousandths" correctly.
His thought is the builder built the heads to a stock cam, while putting a larger cam in the motor.

Any thoughts?

 

That is a very good possibility. Based on the cam what is the recommended valve springs? Does the cam you have require a different spring than stock? Once these questions are answered I like you will have a better understanding what is the real problem.

 

Dutchman -
Did you ever figure out your bent push rods? I had my 390 in my '73 F100 "professionally" rebuilt. It keeps bending push rods. I have lost confidence in the "professional" that rebuilt it and don't want to tow it back to him again.

 

His last post was 3 years ago. Don't hold your breath waiting for an answer.

 

See my post in this thread. the problem was that the builder didn't account for the new cam specs when he assembled the heads. If I recall correctly, the new shop put the proper valve springs in that matched the lift of the cam, and I've not had an issue since. The stock springs he used wouldn't allow the proper valve lift.
Hope this helps.

 

Each pushrod should also be measured.

 

Thank You DutchMan. This does help me. The "pro" that rebuilt my 390 suggested that he upgrade the Cam to what he called an RV Cam. I figured he new how to account for the RV Cam when putting it back together. But I guess it has to do with the RV Cam. I brought this up with him several times over the six months he took to rebuild the motor twice. Well the second time he put it on a test bed and had me observe it running for all about 30 seconds. So maybe I did something wrong when I was breaking it in.

Anyone know an honest and competent old Ford mechanic in Southern Maryland?

 

This just cracked me up. I would think the same thing but there ya go, out of the woodwork! Haha

Is it repeatedly bending the same pushrods? Intake only?

If he built it and ran it he should have been the one to break it in?? I'd want to know exactly what cam he put in, springs and lifters he used, as well as what oil he used. I learned a long time ago to not leave it up to a mech without knowing exactly what was going in and what they were doing. A good mechanic should have no problem being upfront about everything.

 

Stock valve springs will coil bind at anything over .500 valve lift, many RV style cams have lifts in the .508-530+ lift range and will not work with stock springs.
Anytime a aftermarket cam bigger than stock is used the recommended valve springs for that cam should be installed.
Had a cousin install a .508 lift cam in his F-250 years ago, he went through 4 sets of push rods before I could convince him to change valve springs, not issues after the correct springs where installed.