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Old 11-21-2012, 06:05 PM
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Pontiac 400 into 85 chevy

Hello all rodders. I am putting a 1970 pontiac 400 into my 1985 chevy k10 pickup. The motor mounts on the 400 sit more in the center of the engine, while the mounts on the original 350 are more to the front of the engine. Is there an adapter bracket made for this or will i need to fabricate a mount? Also, will I need a conversion plate to mount to my chevy transmission? Any suggestions will be greatly appreciated. Thanks

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Old 11-21-2012, 06:08 PM
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i think you can use firebird mounts---will try to find the link.

Also, i think you need an adapter plate for the trans and this puts the torque converter about 1/4" further out from the transmission input shaft; i'm not sure how to take care of that issue, if it's even an issue?
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Old 11-21-2012, 06:13 PM
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Not familiar with this swap but you might want to look at 2nd gen firebird motor mounts to begin with. It was a vehicle that could be optioned with either a small block chevy or a short deck pontiac v8 in it's later years. Not sure if you'll find your answer there, but it's a place to start.
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Old 11-21-2012, 06:13 PM
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Quote:
Originally Posted by against all odds View Post
i think you can use firebird mounts---will try to find the link.

Also, i think you need an adapter plate for the trans and this puts the torque converter about 1/4" further out from the transmission input shaft; i'm not sure how to take care of that issue, if it's even an issue?
just noticed your post. I'm slow tonight haha.
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Old 11-21-2012, 06:18 PM
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I think all you would need to do is get a dual pattern tranny. Don't know if there is a TH400 dual pattern or only Th350's I put one of those in my Skylark with a 300 (same bolt pattern as your Pontiac "BOP") to update the trans.

But the Buick Th400's aren't a whole lot of money so you could go with one of those. I put a 455 Buick in a 1978ish Chevy pickup one time, yes motor mounts needed to be built but we used a Buick TH400 and put it right in. From what I remember, but my memory........the drive shaft may have been needed to be modified. But really was a pretty easy swap.

Brian
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Old 11-21-2012, 07:12 PM
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Why do you want to do this? i think it would be easier, cheaper, faster to use a chevy engine.


Here is the link anyways:
Pontiac 400 in an '82 GMC truck - PY Online Forums
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Old 11-21-2012, 07:22 PM
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Why wouldn't you want to do this? You can find a lot of factory 400+ cube BOP motors that came ready to rock from the factory. Since we live in this "chevy-centric" world where everything gets swapped for various generations of the SBC, the other brands v8 mills can be found inexpensive because most people think that 350's are the be-all, end-all of performance motors.

- Cameron
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Old 11-21-2012, 07:28 PM
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Well, the reason why i personally would stick with chevy is:

1) It will be much quicker than using an engine that was not originally installed in this chassis; i can install a SBC in a car that originally had one in about 4 hours. It would probably take much longer with, for example, a pontiac v-8 because you would have to hunt down the mounts. The alternator and starter are on opposite sides, so now you got to extend the wires. Yes, i know, not a big deal but it will take more time. Then we got to deal with the trans adapter.

2) It will be cheaper in that we don't have to worry about obtaining the extra parts needed. I.e., different mounts, adapters, hardware etc.
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Old 11-21-2012, 07:51 PM
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I can see where you're going but in this case to me those seem like small inconveniences. There's really no replacement for displacement and when we're talking making a full size truck go fast, it's probably going to take deep wallets or more than 350 cubes.
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Old 11-21-2012, 08:04 PM
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I know why we did it to that truck back in the seventies, it was a no brainer. This truck pulled a 5 horse fifth-wheel trailer. They had a steep driveway that they literally couldn't drive out of with the trailer full, the 350 couldn't do it. They wanted a big block and the big blocks were BIG money. We bought the guaranteed Buick 455 with the TH400 for something like $500. If the 400 is owned already and in good running order it will pull circles around a small block.

Brian
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Old 11-21-2012, 08:32 PM
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the 400 I have is in great condition and will be used for snowplowing and towing.
Also got a good deal on the moter. Anyone know the site to get the swap motor mounts?
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Old 11-22-2012, 06:38 AM
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I have entertained thoughts of putting a pontiac motor in a chevy truck also.
Hey... they did it from the factory in 1958.
And , like was said, big power for plowing, pulling trailers etc.
I totally like the Idea, I will be watching this thread.
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Old 11-22-2012, 07:14 AM
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Quote:
Originally Posted by bwconnell View Post
the 400 I have is in great condition and will be used for snowplowing and towing.
Also got a good deal on the moter. Anyone know the site to get the swap motor mounts?
From the link against all odds posted:

"Speaking of mounts, I used the stock Chevy mounts with the Firebird's brackets. It fit like a glove."
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Old 11-22-2012, 07:19 AM
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Putting a 472 or 500 cad motor in it would also give good results, if you had one of course.
Having a K 10 or K 20 with big tires , like 44s and trying to drag it around with a whimpy SBC just dont get it. The torque of the pontiac or caddy motor would do very well.
The pontiac makes good sense. Lots of money is spent on stroking the 350 to a 3.75 inch stroke , for more torque of course. The pontiac is allready there. Even though the pontiac is more expensive to build...

I also think the firebird mounts would be the way to go, just be sure your block has the front pads for the mounts as the 3 pads to the rearward posisiton are for the A and B body cars.
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Old 11-22-2012, 07:35 AM
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Quote:
Originally Posted by LATECH View Post
Putting a 472 or 500 cad motor in it would also give good results, if you had one of course.
Having a K 10 or K 20 with big tires , like 44s and trying to drag it around with a whimpy SBC just dont get it. The torque of the pontiac or caddy motor would do very well.
The pontiac makes good sense. Lots of money is spent on stroking the 350 to a 3.75 inch stroke , for more torque of course. The pontiac is allready there. Even though the pontiac is more expensive to build...

I also think the firebird mounts would be the way to go, just be sure your block has the front pads for the mounts as the 3 pads to the rearward posisiton are for the A and B body cars.
whoa.. let's not forget Olds and Buick either

Good tips btw, good to have some that knows Poncho motors helping out in the thread.
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