250 6 cyl engine problems - need some input

[ScottH]

Recently bought a 72 C10 with a 250 3 speed drive line. When I bought it the exhaust leaked really bad, thought the doughnut was shot along with the tailpipe. Found out the exhaust manifold was badly cracked, so replaced it.

Got it started after replacing the exhaust manifold and it ran really crappy.
Rebuilt the carb and still running lousy. Checked timing and it would only run half way decent way advanced. Decided to do a compression test and found cylinders 5 & 6 very low (90 & 60). The oil shows no sign of water in it, except that it is over the full mark.

I'm thinking a blown head gasket. I just dont want to put a lot of work into it only to find out the head or block has problems. As it is I would have to replace the carb and still not sure about the timing issue (checked TDC was correct, plug wires correct, etc.).

Any ideas or suggestions what to do next?

Thanks
Scott

[zeeklu]

When I got mine(67 k10 292) it had really low compression but ran pretty good. It could just be worn out. I had a lot of problems with vacuum leaks where the intake meets the head. How did it run before you replaced the exhaust manifold? Chris
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[ScottH]

ran rough, figured it was the exhaust leaks or carb.

I've got to decide on whether to fix/replace the 6, or just put in a small block.
I was planning to go sbc eventually, but wanted to run it with the 6 for a bit.
I have a new create 350 and a T5, so may just bite the bullet and install them.

Either way it wont be till spring now.

[68gmsee]

As I mentioned in a post on the engine and drive forum, don't spend money on it if you are going to swap it out anyway. Use it to help with the swap cause you won't recoup the money.

However, if it's not burning oil and you want to run it for a while just replace the head gasket. It's a one day job.

[Longhorn 70]

had a 64 that acted that way....LOW power and lumpy. I pulled the plugs and ran a compression test. found that there was a leak between 1 and 2 holes. replaced the head gasket and drove it till I sold it. Ran great after that and I was able do the work for about $50.

if you can't do a compression test, just bring each cylinder up to top dead center on compression stroke. put a tight fitting hose in the cylinder and blow in compressed air....You'll hear where it is leaking from.

[ScottH]

Thanks guys.

Longhorn 70, great idea. I will fill the cylinder with compressed air and see what happens.
Why didnt I think of that? lol.

Scott

[BMERDOC]

A leak down test should always be performed in concert with a comp test.
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[ScottH]

Thanks to all......looks like at least 2 bad valves, and possibly head gasket.

[BMERDOC]

So are you gonna keep it or junk it in favor of the small block? It'd be nice to have that small block in before warmer weather.

[ScottH]

Still deciding, kinda depends if I come across a cheap 6 locally.