Quote:
Originally Posted by Lugnutz65
**** 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.
This 1966 283ci engine was rebuilt by Jasper years ago and just sat in plastic. I bought it as you see it in the first picture. I collected the correct pieces to complete it. I bore scoped the cylinders, pulled the oil pan and inspected everything.
Then I began assembly.
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 pushrod hole in the head. 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 exhaust 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 that lives just above the #5 exhaust pushrod 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.
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. 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.
Obviously I was VERY lucky. If the pushrod had jammed with the valve open, then the pistons would have hit exhaust valves #4 & #5 causing serious damage to an otherwise great little engine. Lesson learned.
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Nicely presented work thru....
Am always concerned when I see a lifter fully pushed out of a lifter bore....two reasons...the nose of the cam lobe is usually beat up by the lifter floating around before finally being dislodged out of the bore...and, when a Chevy pushes a lifter out of a bore it immediately loses oil pressure....might be worth checking the lobe and bearings whie its out of the truck...
or you could just take the chance....
