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 engine mount frame brackets
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bradhooker
Buffalo

USA
43 Posts

Posted - 31 Dec 2010 :  3:49:47 PM  Show Profile  Reply with Quote
hi,all, was all ready to slip my fresh 400 with 350 turbo into the 70 gto,but have ran into a problem. was thinking all that was reqired was moving the crossmember up towads the front to work with the 350 trans. instead of the400 turbo that was original.but it seems i'll have to move engine mount brackets back a hole towards the firewall.this appears that it will get me the correct distance of around 35 inchs.is this correct? seems that it will be close to the firewall.looking at my 70 lemans that trans came out of the mounts appear to back closer to wall.i'm confused any help would be appreciated.thanks.

Phil
The Great White Buffalo

USA
6417 Posts

Posted - 31 Dec 2010 :  6:04:25 PM  Show Profile  Reply with Quote
Brad, STOP! First, don't move the engine mounts to suit the trans! It's the other way around. Are you certain the GTO last had a Pontiac engine residing in it's engine bay?

Second, same question for the LeMans?

Third, use the setup (mounts and locations/bolt holes) from the last known car with a Pontiac engine.


"Chevy": even the name sounds cheap.
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Phil
The Great White Buffalo

USA
6417 Posts

Posted - 31 Dec 2010 :  6:06:05 PM  Show Profile  Reply with Quote
Oh yeah, if you have the engine frame mounts in the correct holes, the trans mount will "find" it's intended holes as they are all there courtesy of GM.

"Chevy": even the name sounds cheap.
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bradhooker
Buffalo

USA
43 Posts

Posted - 31 Dec 2010 :  8:09:08 PM  Show Profile  Reply with Quote
yea,am sure about the lemans,350 motor 350 trans.but that frames engine crossmember has no extra bolt holes towards the front of the car.was thinking maybe because that frame was never to recieve a 400 motor 400 trans combo.been looking at some installtion drawings shows bracket back towards firewall. says to use plain washers against slots on RH side crossmember only.the right side back holes are slotted making me think that holes closer to the wall is correct.looks like the brackets were installed towards the front holes at the factory,because when i removed them there was bare metal under the brackets.to complicate matters the motor and trans were out of the car when i got it. in its place was a 301 with some sort of automatic behind it. thanks for the reply and help brad.
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Phil
The Great White Buffalo

USA
6417 Posts

Posted - 31 Dec 2010 :  8:57:42 PM  Show Profile  Reply with Quote
Better make sure you have the correct Pontiac mounts to start with. I've owned both 70 LeMans and GTO and the frames had the same holes. The GTO is still in my garage and even an 80's 200-4R bolted right in without drilling the frame!

"Chevy": even the name sounds cheap.
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bradhooker
Buffalo

USA
43 Posts

Posted - 31 Dec 2010 :  10:22:43 PM  Show Profile  Reply with Quote
yea that came to mind but they look just like the ones in lemans.and i know there correct.im just going to use the back holes and see what happens.according to my measurements it should be spot on. with the lower control arm on the backup nuts are a bear to get to. no fun at all!
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bradhooker
Buffalo

USA
43 Posts

Posted - 01 Jan 2011 :  7:30:23 PM  Show Profile  Reply with Quote
well the engine is in! used the back slotted holes, and trans crossmember all the way towards the front.getting excited about the notion of firing this puppy up!while on the subject of bracket and mounts,has the topic been discuss of the reason the engineers deemed it nessasary to change bracket and engine mounts for the 455? Phil thanks for help and imput. brad
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cortcomp
Coyote

USA
4369 Posts

Posted - 01 Jan 2011 :  7:50:22 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
I don't believe they ever changed bracket and engine mounts for any of the pontiac motors. There are extra holes on some blocks for mounts to fit the smaller F bodies, but i believe for any pontiac engine the holes in the frame and on the motor are the same for a given body.
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pete w
Cochise

USA
456 Posts

Posted - 02 Jan 2011 :  12:02:27 AM  Show Profile  Reply with Quote
i've seen pontiacs for sale on ebay with chevy frame mounts. when you ask if they have pontiac frame mounts for it they say they are on the frame
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PontiacMatt
Many Ponies

USA
1393 Posts

Posted - 03 Jan 2011 :  09:23:47 AM  Show Profile  Reply with Quote
My Lemans had a chevrolet motor in it. the frame mount brackets are completely different than Pontiac frame mount brackets.

As for the 455 brackets, I'm not certain, but seems like there might be a different bracket for the 455 than used for say a 400. have to do a little diggin to figure than one out, unless someone here is more knowledgable on the subject. (And I'm sure someone is)

What did your gto have, for frame mount brackets, before you did this motor install?

*72' Pontiac Lemans* - Work in Progress

Edited by - PontiacMatt on 03 Jan 2011 09:23:58 AM
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Phil
The Great White Buffalo

USA
6417 Posts

Posted - 03 Jan 2011 :  09:29:04 AM  Show Profile  Reply with Quote
They are the same because the exterior dimensions on the Pontiac blocks/bolt holes & bosses are identical that year.

Brad, did you take any pictures of this that you could post?

"Chevy": even the name sounds cheap.

Edited by - Phil on 03 Jan 2011 09:30:26 AM
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bradhooker
Buffalo

USA
43 Posts

Posted - 03 Jan 2011 :  8:52:20 PM  Show Profile  Reply with Quote
hi guys, didn't take any pics,now that the engines in everythings kind of cover up.the frame brackets and motor mounts for the 455 are differnt as shown in ames catalog. thus my question of way the engineers changed them,as they could have used the 400 setup.same holes in the block.looking at picture in the catalog they look to be a little wider and bigger maybe to handle the extra torque.thats way 70's on frames have these extra holes.this is my reasoning, probability wrong though.
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cortcomp
Coyote

USA
4369 Posts

Posted - 03 Jan 2011 :  9:50:22 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
it might have different holes for engines that were optioned with the chevy straight 6 from the factory.
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Chicagogoat
Cochise

USA
654 Posts

Posted - 04 Jan 2011 :  12:21:29 AM  Show Profile  Visit Chicagogoat's Homepage  Reply with Quote
Brad, the larger motor mount your refering to for the 455 was only for the second gen F-body. Engineers decided to beef up the mount design on the second gen's with the new and very torquey 455. This design does not work on an A-body chassis however. Ames screwed me over once when I ordered a new set of Mity Mounts for my 70 GTO and they sent me those larger ones for the F-body. Of course I sent 'em back for the right ones but I mocked it up just to see and it clearly wasn't gonna work.

Randall

Pure Pontiac: learn it, live it, love it!
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bradhooker
Buffalo

USA
43 Posts

Posted - 04 Jan 2011 :  10:41:02 PM  Show Profile  Reply with Quote
hi Randall, the GTO assembly manual on page 140 shows an drawing for installing these brackets and mounts on a 242 a-body frame with the w/L75 455 engine.

Brad
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Chicagogoat
Cochise

USA
654 Posts

Posted - 05 Jan 2011 :  12:05:32 AM  Show Profile  Visit Chicagogoat's Homepage  Reply with Quote
I thought you were talking about the 3 bolt mount which are much wider (compared to the standard 2 bolt) and the 3rd bolt mounts to a raised pad mid-way up the side of the block on a 455. I'm runnin Doug's D-port headers which block that 3rd bolt. A Firebird guy I know said that mount is specifically for 70-74 F-bod's sporting a 455.

Pure Pontiac: learn it, live it, love it!
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mike mcarthur
Pony that Jumps

USA
2471 Posts

Posted - 05 Jan 2011 :  06:16:18 AM  Show Profile  Visit mike mcarthur's Homepage  Reply with Quote
That 3 bolt mount is also the same one that came on my 301 powered 79 Lemans wagon which now has a 400. I think we may have just answered a question for G body people doing swaps.

It's the stuff you learn after you know it all that's important
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