Thread: keep on breaking/bending

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406 roller motor,new cam/bearings,everything cam wise..279/286.....679/645......specs keeps bending push rods and breaking rockers..anyone know the exact timing on this also?ty go fast

Sounds like either your valves are making contact or your springs are compressing to the point where they run out of room. Slowly have someone crank the engne while looking and listening to the heads. If your springs arent at full compression, pull the heads and check for bend/hammered valves and wounded pistons due to valve contact.

we have the turn =screw in stud adjust......again ,how about timing?h ow far should stud girdle slide down over screw studs?

For exact timing I would contact the cam grinder. No one would know better than they would. Did you get your springs with the cam? Are pushrods bending on all cylinders or just some?

Pat

could the cam have too much lift?

Possibly, but it could affect either the springs putting them in a bind trying to compress them to much, or it could be causing the valves to hit the pistons. The second is less likely, I would check the springs first. Is it happening on both intake and exhaust or just one or the other?

Pat

On Stud girdles. I usually put them near the top of the locking nuts. That way You won't have a chance that the rocker will hit them.
I agree with the others you are either binding springs or hitting valves on the pistons, I am leaning more towards spring bind though.
Again are your springs correct for that lift and as important, are the springs installed to the correct height? What OD springs are you running with that set-up. They should be at least 1.55 springs and probably be installed at about 1.9 to 2 inches installed height. You may have the wrong spring retainers on their also. What brand cam are you running? See if you can get the specs on the spring installed height and recomended spring retainer.
I am running a very similar setup with a little less lift than you and have never had a problem with rockers or springs or valves.

I run timing on my 377 at 36 degrees btdc total timing, that's about where most folks are running the small block chevy's. At least it's a good starting point.

I have a more similar set-up. The lift on my cam is .630 and I'm real close to coil bind, so you must be past that point. Stud girdle, like 73RS said, is about 1/8th of an inch down on the adjusting nut. I'm sure if your valves were hitting the top of the pistons you would know it by now. You'd have a few bent valves that would be staying open, so it's time to look real close at the springs.