My buddy has a 70ish 350 in his 85 c10. Well we had to replace the head gaskets, cam, lifters, pushrods, we tore the heads down real good and seated the valves and everything. Well its together now and running BUT its bending pushrods like CRAZY.

Especially on the exhaust valve of #2. It will be so loose it doesnt push the valve down. Slowly tighten it till it pushes the valves ever so slightly and POW bends the rods. We have seriously bent at least 30 pushrods. Some have broken into Z shapes. All are doing ok now besides #2.

This is getting dumb. Something is not right. The new cam is a Lunati 0000016....very very mild cam. I think the lift was like .420 if that.

Heads are the 083 casting. Old 400 smog heads. New springs, pushrods.

The problem is getting dumb. Any ideas????

 

OK, are the pushrods STOCK.. I'm guessing so since you have gone through so many.. WHAT ARE YOUR VALVE SPRINGS RATED AT.. you might have gotten too strong valve springs for the rods, also are you using STOCK rocker arms, if not and you are using 1.6 arms ... did you get the rod holes in the heads widened
DID YOU REPLACE THE LIFTERS.. you might need to check the lifters... lifters can hold oil pressure, which pushes the rods up WITH OUT the lifter moving... it might have been too much for the poor little rod... JK. check it out.. .I'm no expert but I have done my occasional rod/rocker arm change... GOOD LUCK
Ben

 

need to check valve train geometry.SA rockers on a non SA set up, or vice versa?

 

It has the stock rockers arms on there. It seems like most of the stock pushrods are holding up better for some reason. The lifters are ones that came with the lunati camshaft.

Im not sure which springs he got but they are from autozone. When we go to get parts for this truck we usually get stuff for a 79 350 because his has a drivers side dipstick.

 

I'll bet you a copy of your favorite beverage that you have a rocker slot/retainer clearance or other valve train interference problem. What is the base circle of that Lunati cam?

 

My bet is one of the longer intake bolts used for the front of the intake (longer due to the air conditioner bracket) is in the center intake bolt hole (above #2 exhaust) and it's contacting the pushrod as the lift increases.

 

You have a binding issue somewhere in the valvetrain. You sure about that casting #, 083 castings are 87-up tpi heads and normally require self-aligning rockers.

 

083 is not a 400 head casting. 882 and 624 are the common 400 ones.

083 is the later-model TPI head. Should have center valve cover bolts. This would prety much rule out them being a 70s head.

If you're using stock 70s rockers on 083 heads with no guide plates, then you have nothing holding the rockers aligned to the heads. Every time the push rod tries to open the valve, the rocker slides off the valve and onto the retainer.

Put some self-aligning rockers on it.

Make sure the intake bolts are the right length; that's a good suggestion, a more common gotcha than most victims are willing to admit.

 

882 sounds about right actually.