pontiac car to gmc truck/engine&transmission

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  #1  
Old 11-17-02, 08:25 PM
68chevelle
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Question pontiac car to gmc truck/engine&transmission

Attempting to transfer a 400cubic inch big block and transmission from a 78 pontiac bonneville to a 76 gmc 3/4 ton 2 wheel drive truck. Can it be done with out any major problems? In other words will it bolt up? Please help Thank you for any help that anyone might have.
 
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Old 11-18-02, 05:19 AM
bigpoppax2
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Are you asking about the motor mounts? What engine and transmission is in the truck currently? Do you plan to use the existing tranny in the truck?
 
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Old 11-18-02, 05:35 AM
Joe_F
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While this is a novel idea, you'd be best to stick with a Chevy V8.

A Pontiac V8 will not bolt up to a Chevy bellhousing without an adpater. Also the mounts are different, among other thing such as the fuel line routing.

Save the 400 for something worthy, like a Trans Am . Stick with Chevy power in the truck.
 
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Old 11-18-02, 12:07 PM
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What about this?

Joe- in that 86 Cutlass Supreme, 307auto that I have, I'm thinking of one day (in the next two years or so depending on cash flow) replacing the 307 with a 350 and 400tranny. The 307 has sufficient power for the average guy, and I can live with it, but I'm sure a thoroughbred 350 will spice things up.

Since this is an olds engine, what would the best route be? I've had people tell me to find an old Camaro LT1 engine, others say find one out of an older Cutlass (like a 70something) and have it rebuilt, others say just order one from Pep Boys or Advance or something.

Since I plan on putting a performance intake, slightly aggressive cam, Holley 750 carb (or similar), and performance ignition, I really don't want one of those rebuilt crate things since it will be filled with stock or near-stock spec components.

Given a choice, with ease and cost in consideration, what would you do? Olds engine and tranny or Chevy engine and tranny? My goal isn't a drag racer. Just a nice, strong car that can do 0-60 in 6.0 or something.
 
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Old 11-18-02, 12:31 PM
Joe_F
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The G body is an excellent platform for a 350 conversion. You're looking at 2 grand (minimum) to make it run like a champ and run correctly. It also is not emission legal in most states and will net you a headache during inspection time.

Skip it, drive the 307 for what it is (a nice cruiser) and just keep it going.

I own a 400 and a 301 Pontiac and let me tell you the 307 has them beat for luxury cruising. Yes, there is nothing like the sound of Pontiac V8 .
 
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Old 11-18-02, 12:50 PM
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SC has no emissions checks. I'm sure that there is a cat that will fit and keep emissions under control, as I don't care to be polluting unecessarily.

I may eventually just have the 307 rebuilt. It's got another 50K miles on it it seems, but at the rate I'm piling them on there it won't be long. 25K per year is my norm.

Butch at the store I mentioned says his friend put a power chip in his Cutlass and got a pretty decent result. Not a *dramatic* change but got better mileage and a tad more acceleration. May be worth a looksie.
 
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Old 11-18-02, 03:43 PM
Joe_F
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No emission checks today, but they are a comin' . You might find yourself with a very nice lawn ornament if you cannot get it to pass

That 307 will last well over 200k with the proper maintenance. Mine has 144k on it and I don't plan on stopping any time soon. Drive it until you hear it let go and knock (which will be a VERY long time on a 307 if you maintain it).

Zero benefit to adding a chip to a 307. Waste of money, spend it elsewhere on the car where there is benefit. The 307 is a slug and would get whipped by any of today's 4 or 6 cylinders with half way decent pep.

A 307 is what it is. A luxocruiser that runs forever with basic TLC. Drive it for what it is and it will reward you with many years of meritorial service.
 
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Old 11-18-02, 07:24 PM
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68chevelle,

I had a 68 chevelle/chevy malibu! Mom bought it new. Two tone blue - bucket seats.. great fun car. It became mine in 77. Sold it in 79 for a mere $225 - cause I thought a $100 repair bill every other month- (for 2 or 3 months)- meant the car was falling part and I had to get rid of it and get a full efficient car. Was I crazy or what?

Anyway, your name brought back memories so I thought I'd share!
 
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Old 11-18-02, 08:20 PM
Joe_F
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Note to original poster:

There's no Pontiac "big block". They are externally dimensionally identical from the 265 vin S all the way up to the 455 vin W.
 
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Old 11-19-02, 09:21 AM
68chevelle
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Talking

BIGPOPPAX2

I was mainly concerned with the motor mounts. I also plan on using both the engine and trans from the pontiac, since the trans in the truck is pretty much shot. At least I think so. Its only catching one gear and banging it hard when it shifts. I have put a new filter in it. seemed to smooth out the shifting to that gear, but still no lower gears. Is there still hope for the transplant?

Joe f

Thanks for your info on pontiac. I thought all makes of v8's had both small and big blocks. Tells ya how much i know about pontiac
 
  #11  
Old 11-19-02, 09:25 AM
Joe_F
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No the motor mounts won't work.

Neither will the tranny (Buick, Olds and Pontiac share the same bellhousing pattern), or likely much else.

It's a collosal headache to do this, so my question is why? .

Put a regular 350 Chevy engine in there and it will be fine.
 
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Old 11-19-02, 09:42 AM
68chevelle
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That really bites. To answer your ? why, is because both the engine and trans are free so I thought what the heck. What about the trans currently in the truck. Any advice on fixing the problem without a rebuild?
 
  #13  
Old 11-19-02, 09:48 AM
Joe_F
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It sounds like it has internal failure. Change the fluid and filter and see if that helps. Barring that, rebuild time. A rebuilt THM400 (what is likely in this thing) is probably under 500 bucks if you take out the old unit yourself and put it in, having a shop do the rebuild.

Sell the Pontiac motor on the open market. The 400's are harder to get. The last 400's were cast in mid 1978. 1979 400 engines (such as what is in my 10th Anniversary Trans Am 400 4 speed....one of 1,817 cars made) is actually a 1978 W72 400.

Properly speaking, even the 79 motor is really a 1977 casting. My motor and parts of it were made in October of 1977. They didn't get installed in a car until April 1979 (when my T/A was made).

Pontiac stockpiled these motors and then limited the availability of it to the public, and in 1979, only used the 400 in the Trans Am and Firebird Formula that year...no other GM or Pontiac!

I know it's rare, because when I finally contacted the first owner of my ' 79 (after 2 years of looking for him), he stated to me he had to bribe the salesman 500 bucks to have them order the car for him, as well as actually buy a 403 and then drive it into Maryland to another dealer to swap it for a 400 (the dealerships were limited in what 10th Anniversary cars they could order) !!!

What a story! LOL.
 
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