Gentlemen,
I found out why my car was backfiring out the carb above 4000rpm at the strip a couple of weeks ago. The one of the "new cheap" pushrods supplied with the engine rebuild kit is in two pieces now, and I was only revving to 6000rpm. It was bent into an S shape, but now it is two pieces not lifting the valve at all. My cam was pretty mild only a 268H. I just want to give the heads up to anyone revving their engine above 5000 rpm on a regular basis. Please invest in good valve train components. I will get some chromemoly .080" wall pushrods soon. I was just lucky it broke into only two large pieces, as it was fractured in many spots. I can hardly wait to repair the problem and go back to the strip next season.

Regards

CurtiSS 69

What engine are you running? The early 375hp 396 engines (1965) had a problem with lift and pushrods. It seems the slot in the stock rocker arm wasn't long enough and the rocker would bottom-out on the stud. Chevy solved the problem by introducing a new rocker arm with a longer slot. It was stamped with an "H" on the front. I learned of this by owning a Corvette with the '65 375/396 that would bend pushrods at random times.

Just a thought!

could be a bad push rod but i would bet it was something else in the valve tran that caused it loose rocker arm or to tight and coil bind better look close

could be a bad push rod but i would bet it was something else in the valve tran that caused it loose rocker arm or to tight and coil bind better look close

My thoughts too -- even cheap pushrods won't break like that for no reason.

Last cheap pushrod I had galled and crumbled on the ends -- never came out or broke though.

ps. I agree though that good valvetrain parts are important. Especially pushrods, rocker arms, and lifters.

Gentlemen,
Here's what I found after I took the intake off and removed the lower pushrod piece on cylinder 8 intake. What I found was a concave worn lifter on cylinder 8 exhaust, and the lobe was very worn as well. All of the other lobes and lifters looked good. The cam and valvetrain has 5000+ miles of very hard street use. I looked closer at the pushrod and it is a classic example of a column buckling, and once it started bending it got caught in the slot where it goes through the head and broke there. It could have been a bad pushrod -but it lasted quite awhile before failing- or the "flat" exhaust lobe on cylinder 8 could have put more pressure on the intake valvetrain causing to fail at the weakest point. Regardless, I need new cam, lifters and pushrods. I knew I put the quick change timing cover on for a reason!

Regards

CurtiSS 69Gentlemen,

Gentlemen, I knew I put the quick change timing cover on for a reason! Regards, CurtiSS 69Gentlemen,
Smart move!

Sorry to hear about the wasted cam lobe. I think the lobe went first, loosening up the valvetrain. When it loosened up the pushrod probably bounced out of the cup and got stuck sideways -- I bet that's what made it bend and break.

Good luck fixing your cam, I know that can be a lot of work.

coil bind will wipe out a cam pretty quick so be sure and check it

Hello Don, sorry to read about your troubles. I didn't realize you were planning on racing. When I completed my rebuild I used Comp roller tip rockers and new Comp pushrods. I sure hope they are not "cheap" push rods.

FYI = COMPS High Energy push rods are "cheap" and the Magnums and HiTek's are the "good" ones. :cool:

I vote for the one piece pushrods over the kind that have the ends welded in too.

Actually this is a strange one. The worn lobe was on the exhaust side and the broken pushrod was on the intake side. The intake lobe looked great like all the rest of the lobes. It all happened on cylinder 8. I'm going to check to make sure I didn't bend a valve, and run a leak down test. I will also check for valve geometry trouble too.

Regards

CurtiSS 69

I had a mild Comp cam in a mostly stock 350. I loaned the pickup to a woman while I was elk hunting. When I got back, the truck was very broke. I pulled the engine and also had the s shaped push rod. Both lobes on #8 were gone. The engine and one head was a total loss.

I found the root cause...a spring damper broke in two places and the pieces migrated to another spring and the result...S-Shaped pushrod. I need to change the title to: "Don't use cheap valve springs!" I have replaced the springs with some Isky Tool Steel springs. I also upgraded to Pro Magnum Rockers,Trick Flow Pushrods, and an Elgin Cam (Dema Elgin gave me quite an education on flat tappet cams and why they fail). I can't wait for the strip to open again. It is great to pull cleanly over 4000rpm again! Sorry its taken so long to reply. I have been having fun driving my Camaro!

Regards

CurtiSS 69