The Stovebolt Forums Forums The Shop Area The Engine Shop What next? Engine break in completed.

The engine would need to be at least idling to get an idea of proper rotation of the pushrods. The lifter preload is right- - - -DO NOT overthink this and start doing any unnecessary tinkering! Remember that the pushrods are not mechanically linked to the lifters- - - -the offset of the lifter to the cam lobe makes it spin, and it may or may not transfer that spin to the pushrod. If you're that concerned about pushrod rotation, align those dots again, disable the ignition, and spin the engine with the starter for 15 seconds or so.
Jerry

Very slight bend in #5 exhaust pushrod (left). Rats.

Were those new pushrods, or did you re-use them from the previous buildup without checking for straightness? Check them by rolling them on a piece of glass.
Jerry

New

I installed a spare STRAIGHT 283 pushrod in #5 exhaust. Then confirmed proper installation in the lifter with a bore scope. Notice how the straight rod has almost zero clearance as it passes through the head? That’s exactly what the bent pushrod looked like, which is why I pulled it out. I suspected it was bent.

I can't imagine that bend was the result of anything you did during assembly or run-in. Chances are it was defective from the beginning. I always check things like that in the process of an engine buildup, even with brand new parts. Bummer!

When we would install large diameter heavy duty pushrods on the race engines, we always opened up the holes in the head for extra clearance. We also used screw-in rocker studs and pushrod guide plates. None of that is really needed on a street engine, however. The holes in the heads with stamped steel rocker arms keep the rocker tip aligned with the valve stem, so a little pushrod/head contact isn't a problem. The pushrod is hardened, so rubbing on the head occasionally doesn't do any damage.
Jerry

Maybe I had it too tight?

Not unless you had it tight enough for the valve to hit a piston, which would have also bent the valve. You just got a defective new pushrod. Since it's virtually impossible to buy single pushrods, just pick out a straight used one and press on. Some professional level parts stores such as NAPA sell replacement pushrods in sets of two if you're going to insist on "everything new". If you're going to store the engine for some time, loosen up ALL the rocker arms to keep the valves closed and prevent humidity from rusting the cylinders with valves open.
Jerry

Rotation of the push rods is a good way to check for a healthy camshaft, but it's not a 100% accurate when not running. If the engine was idling, you would probably see all 16 rotating. Cams can fail at anytime, but most do it relatively quick when things go bad. I have seen them go in 10 minutes, 200 miles, and six months later, just depends on the parts. If the lash checks good, and no noise was heard while running, precede as everything is good to go. The only true way check it out is pull it back apart, but most are not willing to do that, I wouldn't.

One could always put it back on the test stand and run it for awhile if the truck isn't ready for it yet.

**** MYSTERY OF THE BENT PUSH ROD ****

****** SOLVED ******

I’ll get to the bottom line.

It was caused by an intake manifold bolt that was TOO LONG! The #5 exhaust push rod was in constant contact with the end of the circled manifold bolt.

Same was true with #4 exhaust pushrod, but not enough to bend it.

If you like stories that are bizarre, this might rank high on your list.

Lifters and rocker lash were set by me BEFORE the intake was bolted on.
Everything seemed fine.
I bought intake bolts on eBay. Nice grade 8 bolts with 12 point heads.
One of the bolts stripped the threads in the head. Rats!!!!

Frustrated and not wanting mismatched bolt heads, I went to the hardware store and bought grade 5 hex head bolts. Made sure they were a little longer so I’d capture the threads where the other one had stripped out.

Pulled the intake off because I hadn’t installed the rear seal correctly. Used RTV up front and at the rear this next time. Worked great. Installed the new (longer) intake bolts.

Run stand break in went fine.

Being extra thorough, I decided to check for loose rockers. Found a bent #5 exhaust pushrod. Hmmm?!?! But why? I also noticed that the rod wanted to lay firmly against the hole in the head that it passes through. But why? All the other pushrods were centered in their holes. Hmmm??

Completely removed the #5 exhaust rocker and noticed I couldn’t hand turn the pushrod WITH THE ROCKER OFF. The pushrod still wanted to sit eccentric in the pushrod hole in the head.

I decided to drill the hole in the head to 7/16”. That went well. Shavings were easily retrieved with an antenna magnet. You can scold me later. Let me finish the story.
Now I could spin the pushrod by hand, but barely. Hmmm?

Then I managed to get the antenna magnet stuck on the lifter. Yep. Tears flowed as I realized the #5 lifter was up and COMPLETELY OUT of the lifter bore. Oh crud. More on this at the end.

Out came the bore scope. Shoved the bore scope down the #5 INTAKE pushrod hole so I could hopefully guide the lifter back where it belonged and then ALL BECAME CLEAR!!! Eureka!!!!

It was staring me in the face. Bolt threads of the intake bolt just above the #5 exhaust were staring at me. I had already galled them quite a bit with my 7/16” drill bit, but there was no doubt it was the cause of my bent pushrod.

Pulled the bolt and chopped it shorter. Did the same with the bolt right above the #4 exhaust pushrod on the other side. EVERYTHING checks out OK now.

I’ll wait for Jerry to say he’s seen this happen before.

Part 2.

Yes, after 1/2 hr of surgically precise work, through the pushrod hole no less, I was able to maneuver the lifter back into the lifter bore. Right side up no less!! I could see what I was doing using the bore scope, so technically it was arthroscopic surgery! Haha!

Can you imaging how miserable it would have been trying to diagnose this problem AFTER it was in the truck and started to miss or worse?

Be nice guys and gals. I’m telling this story with humble pie in my mouth with a second helping of eating crow for dessert. I thought you’d like a good story, but please give me credit for being thorough.