[billdini]

Hi guy's, I have a number matching 68 Chevelle that is very rare as equipped. When I bought this car the motor was pulled and put in storage until I bought it 5 years ago. Everything looked pretty good for an 80,000 mile engine and brought everything to the machinist for a rebuild. This engine is completely number matching including carb and distributor. However when I was putting the top of the motor (bottom was assemble by machinist) I noticed two studs were pulled about 3/16 inch and called the machinist. Well we replaced 3 studs with shoulder less threaded studs and put the head on. Well 1000 miles later the stud is in place but two pushrods (one really bad) was bent. One additional fact, one head is a 291 and one is a 462. Both are 2.02 64 cc heads. The difference is the 291 has the head tapped for a temp sender and the 462 only has the non tapped boss however the date is only two weeks apart indicating the car was built or corrected shortly after the factory build. I have some cash into these heads. So should I try and fix what is wrong again, buy a 291 head or buy a set of Dart 2.02 64cc heads to restore my faith in the heads.

 

[shovelrick]

To keep it #'s matching for resale or do you take it to shows to be judged? if resale I'd buy new AFR or Dart heads and save the original heads for when you want to sell, if she's getting looked at under her skirt either repair the bad head or take a crap shoot on finding another 291 casting and have your machinist go through it but any idea on cost to fix the damaged head because that would be my first game plan, also a stud coming out would cause PR's to bend? edit when one of my Harleys was going through a PR bending problem I found it was caused by geometry being out of whack so maybe the stud lifting threw the geometry off ? Edit #2 more I think maybe the PR came out of rocker and caught the rocker at the base of the stud since that PR is bent pretty bad, wonder if this thread would be better in Engine or Performance ??

 

[kmakar]

I have a set of 291 heads, but I'm putting them on my 327 (out of a 67 camaro that was wrecked with 31k). I'd get another 291 head and have it done.

 

[shovelrick]

Bill I'd probably find another 291 head, keep some $$ in my pocket Oh do you know if the other head is worth repairing yet? and I think after market heads mean measuring for new PR's too, then roller rockers too $$

 

[Lew540]

Keep you OEM heads fix them (put them in storage) but buy something new like AFR or Dart. If you sell car you can point to the OEM heads as part of the package.

 

[BillK]

Any idea why the pushrod bent ? It may not have anything to do with the head. Why do you think the head is damaged ?

 

[tom3]

Keep in mind there are a couple spots where a too long intake bolt will hit a push rod. Found this out the hard way myself.

 

[Malibu ss 64]

Maybe

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[bobm67]

Is the 291 head before the engine assembly date on the engine front pad.

 

[shovelrick]

I read the TFS heads use a 7/16-20 rocker nut..?? I thought SBC was 3/8? I also didn't see acc. bolt holes, I don't remember what the camel humps look like but did see a dbl hump on them

 

[billdini]

Is the 291 head before the engine assembly date on the engine front pad.

I believe the 462 was two weeks prior. The machinist has the 291 now and will see what is going on.

 

[billdini]

I read the TFS heads use a 7/16-20 rocker nut..?? I thought SBC was 3/8?

Any SBC can use heavier studs if bought that way or modified. 7/16 is normal for the old heads

Edit 3/8th top with 7/16 bottom is normal for SBC. i installed 3 of these in the head

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[BillK]

To keep it #'s matching for resale or do you take it to shows to be judged? if resale I'd buy new AFR or Dart heads and save the original heads for when you want to sell, if she's getting looked at under her skirt either repair the bad head or take a crap shoot on finding another 291 casting and have your machinist go through it but any idea on cost to fix the damaged head because that would be my first game plan, also a stud coming out would cause PR's to bend? edit when one of my Harleys was going through a PR bending problem I found it was caused by geometry being out of whack so maybe the stud lifting threw the geometry off ? Edit #2 more I think maybe the PR came out of rocker and caught the rocker at the base of the stud since that PR is bent pretty bad, wonder if this thread would be better in Engine or Performance ??

It sounds like it bent after he fixed the stud ?

wonder if this thread would be better in Engine or Performance ??

Good point, I will move it to engine

 

[billdini]

Any idea why the pushrod bent ? It may not have anything to do with the head. Why do you think the head is damaged ?

The engine originally had two pulled studs on the #2 and #4 when I got it in a not runnable state needing full rebuild. We installed shoulder less screw in studs and since it couldn't pull them out the pushrods bent IMO. Standard Chevy 110lbs springs and L79 stock cam. Something is binding. I just brought the head over to the machinist and he is going to find out what might have gone wrong. He still thinks the heads are original as built by Chevy because of the close build dates (2 weeks apart). I don't agree, I think the head may have been a problem since built and the Chevy dealer may have changed one. This engine had 80k on it and the guides were perfect which surprised the machinist and is gonna take a much better look now. Both valves in #2 were bent, exhaust much worse then intake. The good news the valves, cylinder wall, pistons, lifters and the cam all look awesome so nothing hit. The top of the valve itself is damaged on the side when the rocker slid off to the side. So my little mouse that could will do so again soon

 

[Lou Merrell]

If I had a car I personally wouldn't be running the original numbers matching engine until the car is ready for the shows.

 

[Lou Merrell]

The engine originally had two pulled studs on the #2 and #4 when I got it in a not runnable state needing full rebuild. We installed shoulder less screw in studs and since it couldn't pull them out the pushrods bent IMO. Standard Chevy 110lbs springs and L79 stock cam. Something is binding. I just brought the head over to the machinist and he is going to find out what might have gone wrong. He still thinks the heads are original as built by Chevy because of the close build dates (2 weeks apart). I don't agree, I think the head may have been a problem since built and the Chevy dealer may have changed one. This engine had 80k on it and the guides were perfect which surprised the machinist and is gonna take a much better look now. Both valves in #2 were bent, exhaust much worse then intake. The good news the valves, cylinder wall, pistons, lifters and the cam all look awesome so nothing hit. The top of the valve itself is damaged on the side when the rocker slide off to the side. So my little mouse that could will do so again soon View attachment 707609

What the heck is going on with the top of that valve stem? What does the bottom of that rocker arm look like?

 

[billdini]

If I had a car I personally wouldn't be running the original numbers matching engine until the car is ready for the shows.

Maybe Lou but being in my 60's I do not like changing engines anymore and I still have to do the wife's 71 Camaro

 

[billdini]

What the heck is going on with the top of that valve stem? What does the bottom of that rocker arm look like?

Actually not bad! I will not reuse it but it looked good considering what the pushrod and the valve looked like

 

[Lou Merrell]

Maybe Lou but being in my 60's I do not like changing engines anymore and I still have to do the wife's 71 Camaro

'Nough said!

 

[Lou Merrell]

Actually not bad! I will not reuse it but it looked good considering what the pushrod and the valve looked like

Any oil burn/loss?