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Mod | | | Forums66 Topics128,197 Posts1,057,261 Members48,466 | | Most Online14,466
Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
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| | | | Joined: Oct 2016 Posts: 2 Moderated | | Moderated Joined: Oct 2016 Posts: 2 | I was wondering if anyone had ever heard of this swap or how much work it would take to make it fit with a 4 speed trans. If i did this swap i would keep as close to original as possible so if i ever want to i can put back the 235 and hydramatic. | | | | | Joined: Apr 2005 Posts: 2,832 'Bolter | | 'Bolter Joined: Apr 2005 Posts: 2,832 | GMC used the 287ci Pontiac V8 in the 1955 pickup so parts should be available for a straight out swap. You don't say if it is the granny 4sp you want to use but if just a 4sp then many many GTO's, Firebirds, Trans Ams, etc came with 4 speeds on 389 engines.
Evan
| | | | | Joined: May 2001 Posts: 7,438 Extreme Gabster | | Extreme Gabster Joined: May 2001 Posts: 7,438 | Double posting won't get you better answers. | | | | | Joined: Jun 2011 Posts: 5,096 Crusing in the Passing Lane | | Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | Make sure your Pontiac crank is drilled for a pilot bushing, it probably is.
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
| | | | | Joined: Mar 2005 Posts: 1,636 'Bolter | | 'Bolter Joined: Mar 2005 Posts: 1,636 | Did they use the Pontiac engine in the 1st series 55?
| | | | | Joined: Sep 2001 Posts: 29,270 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,270 | Did they use the Pontiac engine in the 1st series 55? If you are referring to a GMC, there was a 54/55 Z-series (47-55 New Design body style). There were no small truck 8-cylinder engines available in the Z-series New Design 1955 GMC trucks. The 8 cylinder engines in GMCs small trucks became available in later 1955 (Y-series - go figure) Blue Chip GMCs. | | | | | Joined: Nov 2002 Posts: 2,774 Carburetion specialist | | Carburetion specialist Joined: Nov 2002 Posts: 2,774 | GMC used the 287ci Pontiac V8 in the 1955 pickup so parts should be available for a straight out swap. You don't say if it is the granny 4sp you want to use but if just a 4sp then many many GTO's, Firebirds, Trans Ams, etc came with 4 speeds on 389 engines. Being ridiculously "picky", no Firebirds, Trans Ams, etc came with a 4 speed on a 389 engine; as neither were introduced prior to the demise of the 389  Of course, the 4 speed with the 400 will fit the 389.  Jon.
Good carburetion is fuelish hot airThe most expensive carburetor is the wrong one you attempt to modify. If you truly believe "one size fits all," try walking a mile in your spouse's shoes!The Carburetor Shop | | | | | Joined: Aug 2002 Posts: 154 'Bolter | | 'Bolter Joined: Aug 2002 Posts: 154 | I had a 1965 pontiac catalina 2 door hardtop, black on black bench seat and a factory 389 and muncie 4speed. THEY WERE OUT THERE. | | | | | Joined: May 2001 Posts: 7,438 Extreme Gabster | | Extreme Gabster Joined: May 2001 Posts: 7,438 | If i did this swap i would keep as close to original as possible so if i ever want to i can put back the 235 and hydramatic. One of the problems to overcome when putting a V8 in an AD truck is getting the left manifold to clear the steering column and box. On a 389 you also have the starter on the left side. It is going to be difficult to "keep as close to original as possible" while overcoming these problems. Of course it can be done but it is going to be work. And it will be way cooler than a SBC engine. | | |
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