70 350 Cracked head

[Bob L.]

Just found a crack in head it starts about 3/4" below the value cover bolt hole closest to the firewall and goes forward about 3" can this be repaired?

[Joe L.]

Re: 70 350 Cracked head

Just found a crack in head it starts about 3/4" below the value cover bolt hole closest to the firewall and goes forward about 3" can this be repaired?

Bob------


Usually, such a crack can be repaired. However, the only repair methodology I recommend is "stitching" with special, overlapping tapered pins. You'll need to find someone in your area that can do this type of repair. However, it can be costly because it's very labor intensive. Sometimes, it can be less expensive just to find a good used head.

[Don L.]

Re: 70 350 Cracked head

Bob, perhaps if you posted the pics that you showed me, it might help to better communicate the magnitude of the challenge you have.

The crack runs laterally, approx 3/4" below the rocker cover land, on the outboard side, between cylinders 6 & 8. What could cause this?

BTW, Bob's got a nice '70 L46 red/red convertible.

[Bob L.]

Re: 70 350 Cracked head



These are the pictures that I sent to Don. I'm interested in finding a new head.

[Bob L.]

Re: 70 350 Cracked head

The casting number of the head I'm looking for is 3927186 350/350 L46.

Thanks for your help

[Patrick H.]

Re: 70 350 Cracked head

Ebay, Driveline, swap meets - those may be your best bet.

I had a similar crack with my 1971, and installed a different-numbered-but-similarly-configured head on the engine so I could keep driving it. The head is still on the car, and the replacement correctly dated unit is waiting until I someday have to work on the engine again.

Patrick

[Edward J.]

Re: 70 350 Cracked head

Bob, its hard to make anything out in the pic. I myself have never seen a head crack at this point, (being a auto mechanic for 40 years and a former GM tech). what is the problem with the crack, leaking oil? if this was only picked up for reason you saw the crack and no issues I would be reluctant to repair. Casting can sometimes fool the best of us as being a something to be concerned with, this is just my point of view, if there was a coolant passage near by then it may cause a problem. my advice if you want someone to give you a better opinion then talk with a veteran machinist. If the cylinder head has never been removed than its likely been there sine day one.

[Patrick H.]

Re: 70 350 Cracked head

Ed, if you look on the outer surface of the head I think you'll see where the crack goes through and the orange paint is missing. There is evidence of a leak there.

[Edward J.]

Re: 70 350 Cracked head

Pat, I see some oil outside, I see the screwdriver pointing inside. this just lead me to believe it was inside. Are we sure its cracked outside on the bolt hole?

[Mark E.]

Re: 70 350 Cracked head

Is it leaking?

Is it possible the oil on the outside is from a leaking VC gasket? And is the black stuff gasket sealer?

If there is a surface defect, is it a crack or a casting flaw?

If it is a crack, is it an issue (e.g. leaking, getting bigger)?

[Bob L.]

Re: 70 350 Cracked head

Mark
It does leak on the out side just below the bolt whole,today I cleaned the inside right and left of the tip of the screw driver and no visual crack there.

[Bob L.]

Re: 70 350 Cracked head

Mark
It does leak on the out side just below the bolt whole,today I cleaned the inside right and left of the tip of the screw driver and no visual crack there.

[Michael B.]

Re: 70 350 Cracked head

I have seen cracks in that area because of Winter freeze without antifreeze, but a crack in that area is likely to leak coolant and not oil.

[Bob L.]

Re: 70 350 Cracked head

Michael
It was antifreeze that leaked and probably a freeze didn't want to put a welded head back on I was able to find a brand new head dated F 22 69 never been on a car the guy bought it brand new in 69 had it ever since and only lived 9 miles up the road.

[Joe L.]

Re: 70 350 Cracked head

Michael
It was antifreeze that leaked and probably a freeze didn't want to put a welded head back on I was able to find a brand new head dated F 22 69 never been on a car the guy bought it brand new in 69 had it ever since and only lived 9 miles up the road.

Bob------


I never recommend welding to repair a cylinder head or block. If a cylinder head or block cannot be repaired using pinning, the best plan is to scrap it.