My son and I are building a 79 F150 and have gotten it all built and now working on getting it running well. Here are the symptoms and I'll follow up with what I do know about the motor.

1. Starts and idles, not rough but not smooth as it should.
2. I get a clacking coming from the pass side head. Definitely from head and not a rod.
3. I also get a backfire every few motor rotations.

This is motor was running when we swapped it in. Its a Ford 460. The heads are the DOVE-C style. The push rods and rocker arms are Comp Cams. They mount over a stud bolt with a lock nut. The piece inside the rocker is a grooved 1/4 circle piece. I don't know if the previous owner did head work. I don't know if he did piston work. It sounds like he did change the cam. I don't know to what. It has the edlebrock intake and carb. It has edlebrock mechanical fuel pump and waterpump. So he put some money into it.

I just want the motor to run solid while we get the new 460 with D3VE-C heads rebuilt the way he wants it.

Any help would be appreciated. I've looked and I can't seem to find the info/help I need. Im learning here so please don't hammer me. I guess I need to know, are these valves adjustable or is this idle/backfire/clacking a timing issue? I wish I knew more .

 

Do you know if the cam was replaced?
If it was, do you know if it was broken in before this?
Are you familiar with the specific cam break-in procedure?

And I have no idea why, but for the last 20 years, Valve and pushrod problems have been a big issue with Ford engines.
Not so much the Windsors, but heavy on the 460s and especially the 335 series.
Seems like right after a rebuild, a pushrod two gets bent out of shape for some reason.
I have not seen any rhyme or reason or consistent issues or known problems. Just that it happens.
So you might check compression, or pull of valve cover and check valve action.

And when you say backfire, is it backfiring through the exhaust, or spitting through the carburetor?

 

I don't know anything about it other than the fact that it was running well when the kid who owned it rolled. It was running when I bought the truck from him. He doesn't know what the guy he bought it from. Im sure its an aftermarket cam, i dont know if he broke it in.

The backfire or popping is coming from exhaust. It's not terribly loud

 

the 429 and 460 did have some issue's with recessing valves into the head usually after a lot of miles but if running propane for fuel a lot quicker, Now on the studs is it a long nut with a allen head screw in the center? if it is and it has solid lifters it is adjustable if hydraulic lifters it is sort of adjustable meaning you would set them like any hydraulic lifter tighten them till no more clatter and then a half turn. sounds like one maybe to tight. and oneton is correct they do have an issue with bending push rods but that is usually caused from valve recession.

 

Get a Ford service manual for a 1970 engine and there is a way to adjust the valves with the engine not running.
Remove the valve covers and just turn the engine a little at a time and feel each rocker arm, since the engine was laid up for a while you might have a stuck valve which will bend a pushrod.

 

No Allen in the center. The push rods seem straight. I guess I can pull each one and inspect again.

Right now they are all torqued to 17 ft lbs, which is the minimum

 

All you can do with your set up is check your preload. just to see if it's close bring a piston to TDC compression and check those pushrods. you should be able to spin them with very little resistance, but they should have no slack.

There's a long list of possible causes for your problem you're going to have to dive it and get a little more specific information.