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Old 06-28-2004, 01:51 PM
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1978 grand prix chevy 350 swap

I have a chevy 350 and turbo 350 tranny inside of my 78 grand prix right now but I am having a hell of a time with the motor mounts. I got motor mounts from napa for a 1978 monte carlo with a 305 (the same mounts used for a 350, I checked the napa part number) but these mounts will not bolt up. Do I need to drill new holes for these motor mounts, or should I just weld the new ones on? Or did napa give me the wrong mounts..... which is very possible.... The old ones have three bolt holes on them, and the new ones have four which do not line up with any other holes on the frame...
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Old 06-28-2004, 02:04 PM
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The three bolt design mounts are for earlier chassis. The later chassis uses a square/rectangular rubber mount that bolts to the frame and a large metal "Shell" that bolts to the engine, with three bolts . There are several different shell heights, so be carefull.
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Old 06-28-2004, 02:11 PM
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alright, well then I should go back to napa and see if they have any other motor mounts with the three bolt design? Or should I try one of these engine jerry rig mount kits or something? But you have already helped a lot, I will check if they gave the wrong mounts to me today.
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Old 06-28-2004, 02:14 PM
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I've got a 79 Monte and it had a 267 in it. I put a 283 in it now. I used the same mounts and put poly bushings in it. They have 4 holes on the mounts and it's so far foward I can only use 3 of the holes.
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Old 06-28-2004, 03:12 PM
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I believe you need the "clam shell" motor mounts.I have a 406sb in a 84 cutlass and used the clam shell. Tell Napa you need "clam shell" mounts for a G-body(78-87)...Also I too have the mounts foward ,where I am only using 3 of the 4 holes.I would also get urathane instead of rubber
there are 2 types of GM motor mounts ----http://www.energysuspension.com/mt tr1.html

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Old 06-28-2004, 07:54 PM
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well i just decided to say screw it, i'm pressed for time so i'm just gonna weld the mounts on, I need this thing to run asap and don't have time to play "find this part for me" with napa as I have the last 3 months. Going to borrow a stick welder from a buddy and get them in there and hopefully get it running by saturday.
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Old 06-28-2004, 11:30 PM
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right now im thinkin about putting a bigger motor in my 81 grand prix I was wonder what kind of motor will drop right in without modifications. The trans shop told me the trans is a 250 or a 350 the motor in it now is a 3.8 L v6.
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Old 06-29-2004, 01:41 AM
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Quote:
Originally posted by grandprix601
right now im thinkin about putting a bigger motor in my 81 grand prix I was wonder what kind of motor will drop right in without modifications. The trans shop told me the trans is a 250 or a 350 the motor in it now is a 3.8 L v6.
My 81 GP came from the factory with a small block chevy (267) and a th350 tranny. So yup, it'll fit and it should be easy. It'll make things easier if you can take the engine mounts and maybe transmission crossmember from a wrecked G body with a sbc. With a v6 car you'll probably have to switch to V8 front springs and maybe the radiator too.
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Old 06-29-2004, 09:12 AM
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So a chevy motor will drop right in???? But someone told me my trans is a oldsmobile 350 trans so I will have to get another trans also?
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Old 06-29-2004, 10:28 AM
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That would be true if you have GM still made Olds and Pontiac and Buick engines. GM sometime in the 70's quit make the different engines. They use to have 2 different transmissions to go with the B O P engines.
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Old 06-29-2004, 12:43 PM
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Quote:
Originally posted by grandprix601
So a chevy motor will drop right in???? But someone told me my trans is a oldsmobile 350 trans so I will have to get another trans also?
The transmission will need the chevy bellhousing bolt pattern. If you have a BOP tranny it will not work and you'll need to swap it. Some transmissions have both bolt patterns, so they will work on chevy and BOP.
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