1968 327 PCV system - Chevelle Tech
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Old Feb 21st, 08, 8:29 PM
Steve67L-79 Steve67L-79 is online now
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Default 1968 327 PCV system

Can someone with an original 68 327 tell me how the factory hooked up the PCV system? I saw a set of supposed L79 valve covers for a 68 that had no holes for the system, so am curious as to how GM had the system designed.
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Old Feb 21st, 08, 11:05 PM
Tom Mobley Tom Mobley is offline
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Default Re: 1968 327 PCV system

'68 L79? I didn't know they were made in 68. better check on that.

engines with solid valve covers had a block that had a breather hole cast into the back. These engines have a can baffle mounted in the valley. the other end of the system was the oil fill tube at the front of the manifold. if the PCV was at the back the oil fill tube had a vented breather cap. If the PCV was screwed into the side of the oil fill tube it had an airtight cap and the inlet air came from the bottom of the air filter housing, a large diameter hose went to the breather hole at the back of the block.

Both work to ventilate the engine, but the later deal with the PCV screwed into the oil fill tube had filtered air being fed into the engine.
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Old Feb 21st, 08, 11:37 PM
midshark midshark is offline
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Default Re: 1968 327 PCV system

Check out this thread: http://www.chevelles.com/forums/showthread.php?t=210751

Take a look at the pic- it sure looks to me like a hose is going into the valve cover behind the alternator.
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Old Feb 22nd, 08, 7:37 AM
DZAUTO DZAUTO is offline
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Default Re: 1968 327 PCV system

ALLLLLLLLLLLLLLLLLLLLLL 68 small block engines DID NOT have the hole in the rear of the block for crankcase ventilation.
IT IS POSSIBLE, ALTHOUGH, EXTREMELY UNLIKELY, THAT ANY VERY EARLY 68s HAD LEFT OVER 67 ENGINES WITH THE HOLE IN THE REAR.
AGAIN, POSSIBLE, BUT EXTREMELY UNLIKELY. The reason is specifically because 68 is the year that crankcase ventilation changed from the rear of the block to the valve covers and that configuration would have been the same for all engines at the beginning of 68 production.
As I commented elsewhere, I personally have seen and owned a 68 327 that had the boss in the rear of the block for the crankcase vent hole, but it was not machined, now was there a boss on the underside of the bell housing flange which would be required to machine a hole for the passage into the rear of the lifter valley.
Therefore, beginning in 68, on all small blocks (BBs began in 65), the crankcase/PCV setup was accomplished with holes in the valve covers. Also, 68 was the LAST year for an oil filler tube at the front of the intake manifold. The 69s got an oil cap in one valve cover (BBs always had an oil cap in one of the valve covers).
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