327 340 hp engine has dead cylinders

by BOB
(surrey canada )

1963 327 340 HP runs & sounds well @ throttle but idle isnt good - has tach drive dist with points - all wires/ plugs new with points too - new carb base gasket - has fuel all plugs fire to ground when removed yet each alternate plug ---wire-- when removed on drivers side doesnt change the engine -run response - compression is 150 across all cyl - suggestions here is that the cam is worn - or might has the wrong intake / heads match - ? do 327n 340 Hp engines have unique intakes - or breathing issues ? can you help ? in a quandree tree here MMV thank--ing you kindly

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Oct 31, 2011
Dead cylinders
by: Corvette-web-central

Having dealt personally with this very same issue on a 1965 several times with the same 327 340 hp engine I think we can get you to your answer faster. The problem that we think your experiencing would be caused by the change in the oil formulation. The path to figuring out what it was involved removing the valve covers and using a dial indicator to check the lift of the valves. We found the pass side intake valve to not have the same lift as the others. Upon removal of the intake and the lifter we found the cam lobe and lifter face severely scored and worn. This also sent metal shavings into the oil system and impregnating in the engine bearings. We highly suggest checking out this potential problem before you cause further damage.

Our first question is what kind of oil do you run? Its important to know exactly the brand and type.

Why it matters is a recent reduction of Zinc or ZDDP in oils. Typically this is joined with phosphorus as a normal balance of oil.

Questions about zinc:
Has Zinc Been Removed from Motor Oils? I have seen problems of engines failing and I think it is the result of the removal of zinc from the oil. I was told by two separate racing engine builders that the EPA ordered the removal of the zinc from over-the-counter motor oil. I use Mobil 1 5W-20. Is this true and do you think a zinc additive might help?

The active ingredient that you are talking about is phosphorus which is added thru a component called ZDDP. For products that meet the new ILSAC GF-4 specification the phosphorus levels for the oil must be less than 800 ppm phosphorus. The ILSAC level for phosphorus has been reduced to protect the catalytic converter and other emission protection equipment. The engine manufacturers are confident that this level of phosphorus will protect both new and older engines. However, there are Mobil 1 products which have a higher level of phosphorus (phos) and can be used in engines in racing or high performance applications.

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