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Old 05-16-2013, 11:18 AM
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Engine Health?

I bought a rod with a 454 Chev engine a couple of years ago. Engine runs fine with the exception of a very rough idle and some oil use at sustained highway RPMs. The car was built in the last 10 years and the top of the engine is all dressed up. I coded the engine and its a 73 SS model block with oval port heads. The bottom of the engine, pan and skirts are encrusted with crud and look like they have been in place for 40 years. It carries 20 LB of oil pressure at hot idle and is running fine on 89 octane.

Hopefully the rough idle is a mild cam. Seems likely with a edelbrock intake and replaced water pump. Sounds funny but its running stock exaust manifolds and very small straight through mufflers.

Given the above, and I'm a novice, how can I determine the overall engine health? Assuming a mild cam, both vacuum and compression checks would be low? Is this a correct assumption?

While doing a compression check I'll look for uneven readings and try some oil in the low ones to determine if its valves or rings. The oil use isn't a lot --I just noticed it --first time out on the highway.

Any other thoughts appreciated. Thanks

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Old 05-17-2013, 05:34 PM
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Quote:
Originally Posted by Doubleclutch View Post
I bought a rod with a 454 Chev engine a couple of years ago. Engine runs fine with the exception of a very rough idle and some oil use at sustained highway RPMs. The car was built in the last 10 years and the top of the engine is all dressed up. I coded the engine and its a 73 SS model block with oval port heads. The bottom of the engine, pan and skirts are encrusted with crud and look like they have been in place for 40 years. It carries 20 LB of oil pressure at hot idle and is running fine on 89 octane.

Hopefully the rough idle is a mild cam. Seems likely with a edelbrock intake and replaced water pump. Sounds funny but its running stock exaust manifolds and very small straight through mufflers.

Given the above, and I'm a novice, how can I determine the overall engine health? Assuming a mild cam, both vacuum and compression checks would be low? Is this a correct assumption?

While doing a compression check I'll look for uneven readings and try some oil in the low ones to determine if its valves or rings. The oil use isn't a lot --I just noticed it --first time out on the highway.

Any other thoughts appreciated. Thanks
Put a little oil in all of the cylinders, this how the engine runs with rings being lubricated. Old Chevies tended to burn a bit of oil even when new, till you see oil consumption getting over a quart between say 3000 mile oil changes there isn't any cause for alarm.

Oil consumption and loss of compression are exclusive events having one doesn't mean you've got the other. They just happen together sometimes simply because of wear on the cylinder wall taper which keeps the rings busy flexing in and out or the combination of wear on the walls and piston that lets the piston rock which breaks the ring seal to the cylinder wall. Then of course there is actual ring failure or gumming up.

Bogie
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