Piston Slap: False economies and engine rebuilds

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1968 red corvette garaged hood open
Redvette

Redvett writes:

I have a 1968 Corvette with the 327 CI engine that smells like an oil refinery. The car has 101,400 miles and compression is low but the car runs good. How do I tell if the car might just need a top end rebuild or a complete rebuild?

Sajeev answers:

It smells like an oil refinery? Strong oil smells generally mean there are leaks from gaskets, not failing engine internals: Check the valve covers for leaks that could drip oil on the exhaust manifolds, and transmission fluid leaks too. That said, none of this answers your question.

Engines with low compression and an oil consumption problem (blue smoke, intake manifold blow-by, soot on spark plugs) usually need a complete rebuild. Maybe do the compression test again with a different gauge? And if your Corvette passed compression test with flying colors but burns blue smoke at start up or when engine vacuum is highest, you could maybe get away with replacing the valve stem seals.

Perhaps a machine shop needs to do more than seals on your heads, but consider this: Top end rebuilds aren’t worth the effort on a desirable classic (i.e. not one of my value-less antiques) with a hurt motor. All that time and money reinstalling refreshed heads on a low-compression short block is a false economy.

Do the Corvette a favor and save up for a full engine rebuild. Save all your receipts and consider this as a valuable investment whenever its time to put it on the market. And let’s be real here, small-block Chevys are relatively easy and affordable to rebuild, I bet there are several shops in your area that would love to rebuild your motor for a fair price.

That Corvette clearly deserves a strong mill under its elegant hood! What say you, Hagerty Community?

Have a question you’d like answered on Piston Slap? Send your queries to pistonslap@hagerty.com, and give us as much detail as possible so we can help! If you need an expedited resolution, make a post on the Hagerty Community!

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