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Old January 26th, 2021, 07:29 AM
Prowbar Prowbar is offline
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Location: Friesland, the Netherlands
Truck: 1965 GMC 1500, 478 V6, SM420
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Default Re: Impco article, running 401 V6's on LP

Quote:
Originally Posted by BobBray View Post
I grew up in Los Angeles, and for many years the L.A. Times ran V-6 GMC Steel Tilts on LP. I wonder if that's the newspaper that had the issues! Von's Grocery also ran V-6 H7500 series tractors on LP. I have a lot of experience with CNG conversions on modern engines and not much is needed beyond hard valves and seats, as CNG is a 'dry' fuel. Never had any issues with the V-6's PCV system, though on light trucks there are only 2 valves. Never had a valve spring issues either, I wonder if the newspaper in question was trying to use old worn out valve springs on their rebuilds. Interesting article, thanks for posting!
Thanks for the reply. Could be very likely that this is about the L.A. times. Yeah it makes you wonder what went into the rebuild of these engines. I read in the 65-66 manual that the 351, 401 and 478 have a hardened exhaust (not intake) valve seat made from 'Eatonite'. The exhaust valves on these engines are also of the sodium cooled type. Makes you wonder why, as these engines had excellent cooling capacity with the high flow water pump.

The article also mentions turning up the idle speed, which I doubt is useful as the camshaft dips its lobes into an oil bath so it could not be a lubrication issue?

When I start using LP as a fuel for my 305E, I'll have the heads machined for Stellite valve seats with new valves.
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