Cracked Head?

[Spline64]

Hey all,

Have a Chevy 350 motor in my GMC C2500 '73 3/4 ton pickup. Original was a 454 but someone replaced that before I purchased it. I would post in the 73+ section but don't have permission to post.
Was smoking so bad had to change the valve seals without removing the heads which did fix the smoking problem but during that process noticed that when air pressure was applied, the left head was pushing back coolant to the radiator in two of the cylinders. Figured I had a bad head gasket so I waited till my vacation to pull it and replace.
Well now it's vacation and I'm not sure that what I think I found is even possible. I see what appears to be a hairline fracture on the bottom of the head that travels up to the exhaust valve. The intake valve is also shiny compared to the other intake valves. The spark plug from this cylinder is normal with no buildup (dry).
I didn't perform a compression test as 100 psi air pressure caused it to leak back so knew something was wrong. the engine is gutless as heck. Never hits passing gear except from first gear and basically half throttle is the most you will ever get for acceleration. The gasket looked fine so was wondering if any of you have seen a leak through the actual head that could cause this type of behavior?
I have attached a photo but hard to see the actual crack.

thanks guys,
Pat

[trac209]

This is a common crack seen in sbc heads especially the light weight casting 882 head.
Posted via Mobile Device

[Spline64]

So ruined correct?

[trac209]

Originally Posted by Spline64

So ruined correct?

Yes ruined,good news is there's tons of them lying around practically free.
Posted via Mobile Device

[Spline64]

Thanks Trac
Not almost free in my neighborhood but have no choice.

Thanks again,
Pat

[Spline64]

mmidle,

After I took off the left head, cylinder walls were smooth as a babies bottom but not sure if you can only feel the crosshatch after the honing process.
Was getting 110 off of the right side but never tested the left. Knew I had to take it apart anyway.....

Pat

[mmiddle]

That Combustion Chamber looks like it is a late 70s-80s "light weight" head. The crack is noticeable for me. I'm not surprised at all. These heads crack really easy. Chances are there are other cracks as well especially between the valves. Junk them and get a set pre 73 or late 80's vortec.

As far as gutless??? Many things could cause that. If the valve seals made that much of a difference on smoking then I would bet the entire motor is just worn out.

[GASoline71]

If you need to replace heads... which it sounds like you do, look to the aftermarket for heads. After you find a set thats worth a damn to rebuild, the machine shop does all the work to them, you'll have close to $500 bucks in them. For not much more than that, you can have a good set of heads that flow way better than stock.

Not crappy offshore junk either. Brand name stuff.

Gary