GM Intake Manifold

Hello all; Years ago while purchasing parts for my '73 Firebird from a private party in Washington state, I was offered a GM intake manifold with a Holley carburetor mounted on it for a nominal extra cost. I bought it and later found out when I went to rebuild the carburetor that it was a rare, factory original/factory optional racing unit for a 1956 .312 Thunderbird. Ever since, I have sporadically tried to identify the intake manifold with no success. The person that sold it to me said it was for a big block Pontiac, but I've not been able to identify it through the casting number. That number is either 488140 or 486140. What I believe to be a date code (but very possibly not) is cast as D215. Any help in identifying the application for this intake manifold would be greatly appreciated.

The date code you list could be April 21, '55, '65 or '75. Did the Holley carb bolt directly to it, with no "adapter"? Are the bolt holes to the head "in line" or some significantly lower than others? Is there a protrusion underneath with large pipe plugs installed?

Answer these and I can narrow it down for you.

Jim

Hey Jim; Thanks for the reply. I just went out and looked at the manifold again. After vacuuming off all the spider webs and eggs I noted that the bolt holes are not in line. The interior two bolt holes on both sides are offset from the outer two bolt holes by an inch or so. I don't know if that qualifies as a significant difference, but the bolt holes are definitely not in line. There is also a large, circular hole through the intake in the valley next to the thermostat housing on the passenger's side. Also on the passenger's side protruding from the middle port (a water port, I think) is a looped tube that has the appearance of being the business end of a sensor of some type. There is a time clock for the casting on the underside that indicates it was made on dayshift at approximately 8:00 a.m. There is also a large #4 cast into the manifold near the time clock. The manifold itself is of the double plenum variety, and has the look of a high rise, but that remains to be seen. I bought the manifold so long ago that I can't remember if there was an adapter with it, but it did require an adapter when I mounted the carburetor on a Chevy .350 intake. There does not appear to be a protrusion on the underside with large pipe plugs. Thank you for looking into this for me.

Paul

The slight mis-alignment of the bolt holes and the date code indicate a '65. If the Holley flange "fits", the oriinal carb was a Carter AFB. Pretty common intake. Valuable to restorers, but not much else. The '66-later Q-Jet intakes are more desired.

Jim

Thank you, Jim. So this is a 1965 Pontiac big block intake manifold? I'm kind of curious as to why it is so difficult to track the casting number on this part. I very much appreciate the time and trouble you've gone to in order to identify this for me. Thank you.

Paul

Paul,

No problem.

BTW, inside the "Pontiac world", there is no such thing as a "big block". All Pontiac blocks (except the 301/265) are the same "size". Bore spacing, deck height, rod length, etc. are constant from '55 through '79. We simply refer to it as "the Pontiac".

Jim