327 rear main leak and more leaks - Chevelle Tech
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  #1  
Old Apr 25th, 11, 7:19 PM
tmach tmach is offline
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Default 327 rear main leak and more leaks

I have a 1967 Chevelle 327, frame off restoration. I purchased the car 3 years ago as a nut and bolt, original 24,000 mile frame off restoration. Car looks good, BUT. The engine is, i was told rebuilt. After 500 miles the rear main started to leak, at the end of last year every seal in the engine was blown. Intake, oil pan, timing cover, valve covers, oil pump and rear main approx 1500 miles since restored. I had the engine pulled and disassembled and discovered that the PCV port in the intake manifold was blocked off by a plate under the carburator. Don't know why this would be done?. Purchased a Felpro seal kit, and a double lip, offset rear main seal. re-assembled and repainted everything. re-installed the engine, (this was done by a shop, $1000.00 + gaskets, oil, antifreeze and paint). They let the car run for over an hour, no leaks. Then another 1/2 hour and still no leaks. Drove the car home 1 mile, parked it and 3 days later took it out to clean it up and I have a pool of oil and it looks as if it is coming from the rear main, dripping out through the inspection cover. I was present when the work was done and feel the rear main seal was properly installed.

Can anybody give me any thoughts. My only possible thought is that the crank was polished up the first time the engine was rebuilt and the seal is to big. The only problem there is it originally took 5-700 miles to leak and nothing has changed. But 1 mile????????

Also any thought on why the block off plate would have possible been installed. I am assuming this let pressure built in the engine and blew out all the seals, but why would you put it there to begin with????

Any help would be appreciated. This car is becoming a money pit

Tom
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  #2  
Old Apr 25th, 11, 7:57 PM
Mike Mike is offline
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Default Re: 327 rear main leak and more leaks

The crank may have been polished to a size the installed seal can't handle as you suspect.
Also ,your 67 should have a small journal crank (Mains-2.30") and possibly they installed a seal for a medium journal (69 +up Mains-2.45") seal but not likely.
Just a shot but with the engine being run without a load ,there's no load on the crank thrust bearing.
Was the crank thrust checked while you had the engine apart?
When you drive it you subject the crank to thrust and your rear seal may not be hitting a decent surface.
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  #3  
Old Apr 26th, 11, 6:47 AM
Tom Mobley Tom Mobley is offline
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Default Re: 327 rear main leak and more leaks

up front, I don't know of any 327 that has the PCV port in the intake. there's an exhaust heat crossover passage in the front of the carb mounting pad, it's sealed from the carb by a thin steel shim that's shaped just like a carb gasket. Your engine should be vented via a fitting next to the distributor and a breather/oil fill tube in the front of the manifold. 327s generally didn't have vents in the valve covers until 68 or later.

Can you put up a pic of the top of your engine with the air filter removed?
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  #4  
Old Apr 26th, 11, 12:42 PM
Tom Mobley Tom Mobley is offline
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Default Re: 327 rear main leak and more leaks

anybody got pics of an early to mid 60s 283/327 with factory PCV setup? some had the PCV inline in a hose coming from the crankcase vent next to the distributor and an oil fill, breather tube in the front of the manifold. Others had sort of the reverse setup with a PCV on the breather tube up front and a breather hose coming from the vent hole in the back.

anybody got a handy pic of the heat crossover track in the carb mount pad?
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Old Apr 26th, 11, 12:53 PM
Rich-L79 Rich-L79 is offline
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Unhappy Re: 327 rear main leak and more leaks

The '65 L79 has the large breather tube from the back of the block to the air cleaner (you can see the tube here) which is the air INLET:



The air is then drawn out by a vacuum line from the carb attached to the oil fill spout.



Other 327s with a PCV system (early versions just had a oil filler cap breather and a road draft tube) had a similar set up that differed somewhat based on what carb and manifold was used.

I'm going to guess that the OP's problem is caused by a lack of a functioning PCV system. The seals would all work fine until you up the RPMs (like when driving) which ups the pressure in the crankcase which then pushes oil out of the seals.
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  #6  
Old Apr 26th, 11, 8:22 PM
Tom Mobley Tom Mobley is offline
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Default Re: 327 rear main leak and more leaks

I'm sort of figuring that neither one of the shops involved had any idea what they were looking at. built it with no ventilation, then re-did it the same way.
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  #7  
Old Apr 26th, 11, 10:53 PM
Tom Mobley Tom Mobley is offline
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Default Re: 327 rear main leak and more leaks

Did I mention I have a 327 I built in 1985, a nice engine for sure, but has at least 200K miles on it, most of it in traffic in Phoenix. No leak ever, front or rear main.
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  #8  
Old Apr 27th, 11, 11:47 AM
tmach tmach is offline
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Default Re: 327 rear main leak and more leaks

Tom,

The shop that did the last work putting in the new gaskets left that plate out you mentioned covering the crossover passage. Will this cause me any problems?

Tom
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