[dozer7120]

I have a 78 Grand Am. It came stock with 301. I have a pretty mean 400 for it. Most of install is common sense or Google. I need this to look nice and able to use the hood. Am I correct the 301 mounts will work. If not please speak up. Even bigger question is headers. This car is a survivor so no mods to make fit. I've tried to find headers and RA3 exhaust manifolds. Nobody seems to have in stock. I need help please!

[Goatracer1]

Yes the 301 mounts will work. I went the other way and replaced a 400 with a 301. Yes, I know! But I had a 301 with only 1500 miles on it.

[MarkS57]

Originally Posted by Goatracer1

Yes the 301 mounts will work. I went the other way and replaced a 400 with a 301. Yes, I know! But I had a 301 with only 1500 miles on it.

Agree. I replaced a 301 in a 79 Bonneville with a Pontiac 350, worked perfect. Thinking the 68 - 72 A body RA III manifolds might work in a 78, seem to remember something like that but nothing I can point to. Maybe others will chime in.

[grandam1979]

Long branch manifolds fill work also on the Grand Am.

[dozer7120]

My Car only has 43000 m8les. Plan on pulling motor and trans and storing it for later circumstances. The 400 doesn't sit too high? What about exhaust?

[Sirrotica]

Only one company ever made specific headers for the 78-87 G body cars with Stratostreak V8s, but they folded many years ago. You could advertise in the wanted section here to see if anyone has a used set hanging around. Indian Adventures is the company that used to sell them.

The RA III manifolds do allegedly work also, but right now they're pretty scarce, and expensive if you find a set.

I seem to remember that the universal 3 tube D port headers also fit a late G body, they're fairly easy to come up with, new or used.

Link to Hedman 3 tube headers:

https://www.summitracing.com/parts/h...0/make/pontiac

There are also the shorty headers that mimic the RA III cast iron manifolds, but they're priced pretty hefty to buy new:

Link to shorty headers:

https://www.summitracing.com/parts/h...0/make/pontiac

I hope something here helps you out.........

[Mr Twister]

Call Mad Dog headers. I got some G body round port headers years ago from him.

[RocktimusPryme]

Didn’t Ames just start making manifolds? I feel like I saw that in one of the other board sections.

[dozer7120]

So hedman shorties will work and also west brand manifolds. I searched for west branch and took me to pypes website.. is that correct. The ra3 manifolds would be nice but can't seem to fi d much in stock or not too pricey.
The engine sit low enough for air cleaner clearance.
Another question i have old 400 alternator bracket. I need ps and ac brackets.
The car is probably one of lowest mileage car out there. I want to this correctly with no to very little modifications to do this swap.i love the car but despise the 301. 4 barrel of 150 screaming hp! Lol
Does someone have a part number for west branch or pypes exhaust manifolds. I liked the look of the pypes brand but didn't see pontiac.
Thanks guys!

[MarkS57]

Originally Posted by dozer7120

The engine sit low enough for air cleaner clearance.

Thanks guys!

Well, the 301 dech height is ~ 1.1" lower than a 400 deck but at a 45 deg angle from centerline and if I remember my basic trig correctly the resultant deck height to center would be ~ 0.75" higher. However, the 301 head height is probably different but again at 45 deg. The std 4bbl Pontiac or Performer manifolds are probably higher than the 301.

[Skip Fix]

You will need 400 alternator and P/S brackets and pulleys due to the different deck height. Need the 400 PS [pump brackets also.. If a rotary A/C compressor 301 bracket will work as it just bolts to head.