Bill, I can't speak for GMC, but Chevrolet part numbers don't match the
casting numbers. Could it be that simple?
Mike Boteler
'56 8400 Wrecker
Hughesville, Maryland
----- Original Message -----
From: "Hanlon, Bill" <Bill.Hanlon@COMPAQ.com>
To: <oletrucks@autox.team.net>
Sent: Friday, June 02, 2000 3:24 PM
Subject: [oletrucks] GMC V8 head questions
> My '57 GMC truck came with a Pontiac 347" V8.
> The Master Parts Manual for my truck lists a
> part number of 524370. These are low (7.8:1)
> compression ratio heads that I believe were only
> used on the trucks, not on Pontiac cars.
>
> If I am looking in the right place, the heads
> on mine are part # 523298. Looking at a head
> the leftmost exhaust port near the exhaust
> manifold has "GM" cast on it, the middle exhaust
> port near the manifold has "523298" cast on it
> and the rightmost exhaust port near the manifold
> has "2" cast on it.
>
> My Master Parts Manual does not list 523298 for
> any (55-59) of the years that Pontiac engines were
> used in GMC trucks.
>
> Do any of you know the origin of this head?
>
> And another question. The Maintenance Manual for this
> truck shows an "Intake valve vent" that connects each
> intake valve guide to the outside of the head about an
> inch down from the lip that the valve cover seals to.
> This appears to be a small drilled hole that would allow
> atmospheric pressure to reach into the intake valve
> guide about half way along the valve stem.
>
> The only reference to these vents in the Maintenance
> Manual is "valve guides are cast integral to the head
> and intake valve bores are vented to the atmosphere".
> What is the purpose of these vents? The only thing I
> can imagine is that it would prevent the vacuum
> developed by the intake stroke from sucking oil through
> the valve guides.
>
> Thanks in advance.
> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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