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Old 01-10-2001   #1
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400 GTA?

My friend and I were considering putting an old Pontiac 400 in my '88 GTA, and we were wondering if that is possible as far as electronics go. I do not know if this topic has been covered before so if it has I apologize. Any help is greatly appreciated.
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Old 01-10-2001   #2
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400 engine

Anything is possible when it comes to changing engines. Back in the day I helped a friend install a 427 big block in a Chevy II. It all boils down to how much effort you want to put into the switch. I read an article on the third generation web link from this page covering this subject. Sorry, I can not recall the exact location. It might take you some time to find it. At the very least you will need to scrap the current wiring harness and retro fit. In addition you will need to make sure that the accessories will bolt to the 400. Motor mount location is also important when it comes time to hook up the tranny. On a good note the 400 is basically the same block as the 350, but the some small differences can create big problems. I am good shade tree mechanic and this project would be beyond what I would be comfortable with. Might you want to make the current motor into a 383. This option appears popular for cars like ours. Good luck.
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Old 01-11-2001   #3
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GTA Year: 1988
GTA Engine: 350 TPI Automatic
Re: 400 engine

I agree with jcyoung on this one.....

As tempting as it would be to have a Pontiac-powered ThirdGen F-Body.... and a 6.6L one at that..... I think you'd have much less trouble going with a 383 stroker kit, a new GM crate engine, or something similar that is engineered more for your particular application.

You'd get just as much performance (or more) from this kind of a swap, and you'd leave all the installation and/or conversion headaches "at the garage door", so to speak. There's something to be said for "ease of installation".

That's just my humble opinion......
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Old 01-30-2001   #4
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Not as difficult as that

I disagree. I think a 400 Pontiac in a 3rd gen Fbody would be great and not overly difficult to do. I wouldn't drop it in a GTA though but maybe an 82-83 TA or 87+ formula. As for the
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Old 02-01-2001   #5
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Re: Not as difficult as that

sorry I got cut off...and I am now known as L98GTA...not poncho....
a 400 pontiac block is not the same as a 350 (or any small block) chevy. There is an article in Feb. 2000 of Hot Rod talking about a guy who put a pretty radical 455 in a 3rd gen. It is something that has intrigued me and I might attempt in a year or two...

I imagine it will require alot of fabrication but I also think it would make a great project...

A mild 400 fuel injected with edelbrock aluminum heads mated to a 6 speed would be a head turner especially with some T.A. 6.6 stickers!
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Old 02-02-2001   #6
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400 swap

Yes, L98, you are correct in pointing out that the two engines are different. I was merely commenting in general terms surrounding engine dimensions and block construction.

I was speaking with my bother-in-law, who is a certified GM mechanic about the swap we are talking about. He indicated that "lots" of fabrication would be required to pull it off. He would like to know the age of the Pontiac 400 motor and what it came out of. If Ma na could provide this info he might be able to give a list of the specific modifications required.
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Old 02-02-2001   #7
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Re: 400 swap

no prob jc...just making sure everyone understood the differences. I agree that basic size and dimensions are the same...

I also agree that there would be some fabrication to be done. It would need pontiac engine mounts, but what difference does the year of the block make? From what I know the "modern" 400 block from Pontiac circa 1970s is the same through the years. the only think that changes is 4 bolt or 2 bolt, crank materials and so on, but that's internal. Externally all pontiac blocks are the same essentially from the '50s (atleast I think, so correct me if I am wrong)

What would make the biggest difference is the heads whether they are round port or d-port.

If I were to build this, and I would like to in the future, I would look for a 77-78 TA 6.6 block, throw on a set of edelbrock aluminum heads (match the rest of the parts, i.e. cam, intake...) and a set of reproduction SD exhaust manifolds. Throw on an aftermarket fuel injection and a good 2 1/2" exhaust and you got the making of a very streetable 12 second firebird. Obviously match the chassis as well with frame connectors, suspension and brake updates. Overall a true performer. A car like this wouldn't cost all that much, atleast less than a new Formula or Trans Am and would out perform them as well as being a show stopper. Sort of a "what if" Pontiac continued without the corporate engine?

Just thinking outloud I guess.....
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Old 02-03-2001   #8
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400SB and all other SB's

Hey guys... I always thought that the 400SB and all the other SB's were essentially the same construction, except for performance provisions, bore, stroke etc etc... I come to believe that the earlier TPI setup should bolt onto the 400SB with not too many difficulties.. or even look into swapping TPI heads onto the 400SB, then the swap would be easy
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Old 02-04-2001   #9
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400 swap

The reason for the age and original platform of the 400 motor was exactly what you indicated L-98, internal differences in compression, crank.... The B in law wants to know if it is out of an old TA or other passenger car. He is assuming that cost is a factor and would want the best platform to start with. If you could get one out of an older TA that would be cool.

As far as grafting a TPI induction system complete with heads to a Pontiac small block, I have no clue. Another e-mail to the B in law. I probably would try to improve the current induction system on the Pontiac motor. L-98 seems to have it well thought out. It is also my understanding that the stock cast iron TPI heads are restrictive.
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Old 02-04-2001   #10
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Re: 400 swap

I wasn't talking about droping on a tpi set up from a small block checy, that won't bolt on. But there is aftermarket makers of fuel injections and though I have yet to research it I am 99.99999% certain there is an application out there for Pontiac motors.

As for the heads, once again "TPI" heads as you refered to them are off a SBC not a pontiac and again will not bolt on.

I would as I mentioned in my previous post go with a set of Edelbrock heads or if the budget wasn't there a set of 6X pontiac heads. My brothers 77 TA with headers and exhaust runs mid-high 13s and 98-99 MPH and 300-500 LBS heavier then a 3rd gen. This is a bone stock, never opened TA 6.6 with original, cam, intake, carb and everything else. Just tuned, small tube headers, 2 1/4" exhaust with an H-pipe and sticky tires. Stock 3.23 gears and 4 speed.

I used to have a 78 TA with a 74 station wagon 455 with a stock rebuild .030 over ith flat top pistons to raise compression to 9.8:1, stock 4X heads(untouched), .480 lift cam and a HO Aluminum intake. A put small tube headers and lousy exhaust with 3.73 ran 12.72 at 106 mph with shitty short times. car had potential for mid 12.5-12.6 at 107-109 mph with tuning and working it out. Totally streetable engine would run 12 flat in a 3rd gen!!!!!

Now my goal is to get my GTA in the 12s with very little noticable mods. I want a stock looking, sounding and feeling 12 second GTA. Anybody here do it yet? please list mods and results
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