A SCARY Bent Pushrod Story

[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.

[geezer#99]

I had the same thing happen over 30 years ago. The bolt I had wasn’t holding the pushrod in place but it was just long enough to induce a strange rattle in the motor. Pushrod and bolt would make contact once in awhile. Really hard to find.
I always watched bolt length after that.

[Lugnutz65]

It’s been recommended that I do a Heli-Coil repair of the stripped bolt hole and then go back to the shorter bolts. That would help the next person messing with this engine.

[AcampoDave]

Wow, quite a story. You handled it though. Patients and perseverance prevailed and saved your motor.

[truckster]

Originally Posted by Lugnutz65

It’s been recommended that I do a Heli-Coil repair of the stripped bolt hole and then go back to the shorter bolts. That would help the next person messing with this engine.

Definitely.

It's a good thing you broke it in on an engine stand. Good luck with the rest.

[MySons68C20]

Great story no shame! I learned something new today thanks for sharing!

[Lugnutz65]

Just bore scoped cylinders #4 & #5 and no evidence of damage to the pistons or valves.
Time to pull that intake off, heli-coil the stripped hole in the head and install shorter bolts.

[mattfranklin]

Nicely documented! Glad you got to the root cause.

[AussieinNC]

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.

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....

[Lugnutz65]

Originally Posted by AussieinNC

Nicely presented work thru....
always concerned when I see a lifter fully pushed out of a lifter bore....

I understand your concern, but I’m the one who accidentally got my telescoping magnet too close to the lifter. So I’m the one that accidentally PULLED the lifter up and out of the bore with my magnet. I can hardly describe the way I felt once I realized what I had done. Haha! Glad I was able to finesse it back into the bore hole.

[Lugnutz65]

I pulled off the intake to repair/Heli-Coil the stripped hole in the DS head. Pretty easy repair actually and will be 100% as strong. Also, with the intake off I could get a very clear picture of the bolt hole (a completely different bolt hole) that caused my bent pushrod (because my bolt was too long).

[mattfranklin]

Thanks for sharing. I had a close call with that. When setting valve lash, I think I noticed that one pushrod wasn't very easy to spin. Then in the back of my mind I kind of remembered some kind of warning from an old David Vizard book. I thought my bolts were short enough, but apparently not.

[Lugnutz65]

Originally Posted by mattfranklin

Thanks for sharing. I had a close call with that. When setting valve lash, I think I noticed that one pushrod wasn't very easy to spin. Then in the back of my mind I kind of remembered some kind of warning from an old David Vizard book. I thought my bolts were short enough, but apparently not.

Yeah, but with mine, I set the valve lash with the intake off. That seemed best because I could actually see that the lifter was at the base circle for each adjustment. Then when I bolted the intake on, a bolt that was too long bit me in the butt!