Old 11-03-2021, 02:37 PM
AJ- AJ- is offline
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Default mounts and headers

Considering doing a pontiac swap into a gbody. I have a 350 and a bunch of spare parts laying around and a roller so I'm getting ideas.

A couple of questions:

Can anyone confirm if hedman 3-tube headers fit in gbodies?

How crucial are the gbody 301 motor-side mounts to make this work? I have some motor-side mounts from an fbody but I hear they make the motor sit too high. How high are we talking here? I feel like 301 mounts might be pretty hard to find.

Old 11-04-2021, 12:11 PM
Ken MacNicol's Avatar
Ken MacNicol Ken MacNicol is offline
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The early 70,s Firebird mounts (rubber on block, solid on frame) work just fine, and if I remember the 3 tube fit also

Old 11-04-2021, 01:13 PM
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Hammertime Mike Hammertime Mike is offline
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Originally Posted by Ken MacNicol View Post
The early 70,s Firebird mounts (rubber on block, solid on frame) work just fine, and if I remember the 3 tube fit also
X2 on the motor mounts, I used Mad Dog 2" headers.

Old 11-04-2021, 02:01 PM
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unruhjonny unruhjonny is offline
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I cannot attest to which headers work, but in the late 1990's a friend bought a stupid mint 1978 Grand Prix (it his cousin's neighbors, and I'd often drool at it in years prior).
It was a pretty loaded 301-4bbl car, and when the head gasket needed replacing (if my memory serves me) he opted to build a 1971-400 for it;
I believe that he needed nothing fancy to make it work - I believe the same mounts were used.
I cannot recall if he went with headers, but my gut says he used F-body exhaust manifolds.

1970 Formula 400
Carousel Red paint on Black standard interior
A no-engine, no-transmission, no-wheel option car.
Quite likely one of few '70 Muncie three speed Formula 400's left.

1991 Grand Am: 14.4 @ 93.7mph (DA corrected) (retired DD, stock appearing)
2009 Cobalt SS: 13.9 @ 103mph (current DD; makes something north of 300hp & 350ft/lbs)
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Old 11-04-2021, 02:35 PM
AJ- AJ- is offline
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Join Date: Apr 2020
Posts: 25

Thank-you for the replies! I do have rear exit manifolds in addition to the 3-tube headers so I guess worse case scenario I could use those. Headers would be better on a couple of fronts.

The motor mounts I have are late '70's firebird/trans am. So the rubber part will be on the frame. They look real similar to the 301 ones. The car is currently set up for sbc. I have the pontiac motor, the correct alt/ps pump and brackets, a BOP tranny, and I'm not too worried about figuring out the wiring/fuel line. I guess the mounts are the x-factor. Hopefully with a stock intake and a drop base air cleaner it will fit okay.

Old 11-04-2021, 02:38 PM
AJ- AJ- is offline
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Join Date: Apr 2020
Posts: 25

Looking at some pics of the early 70's mounts -- I USED to have a pair, but I believe I chucked them. Ill have to look again. One of those things you hang onto for years and then finally get rid of them only to realize you should have kept them.

Are those mounts going to work better than the late 70's ones I have?

Old 01-06-2022, 09:06 PM
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tininjun68 tininjun68 is offline
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Default How goes it??

Hey AJ,
Make any progress on this build? I rarely stop in G Body forums but I did and started reading up cause it caught my interest. My first dependable daily was a ‘78 GP. Had a 70/71 400/BOP350/10bolt, 8.5” posi. This was 1996 when I bought it so it was very clean. Looked great with the landau roof (made the side window proportioned well IMO) Best driving Pontiac I had for a while! Best of luck with your build and post some photos when you can!

You know me, "Safety Forst"
68 GTO-Verdoro/Black/Black, what else was available in 68? Has to be longest resto in history.
69 GTO Vert-Liberty/Blue/White Top, 4spd, match #s
68 Mustang FB-Green/Black (Bullitt)

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