Pontiac swap - The 1947 - Present Chevrolet & GMC Truck Message Board Network

1972 C10 · 05-06-2021, 12:41 PM

I apologize for posting the same question again, but I still have no clear answer. I want to install a 76 Pontiac 400 in my 69 GMC originally 305 V6. I really want this to look factory and have found vague references as to what frame "towers" to use but would love to hear from someone who has done this w/details.
THANX

**kwmech** · 05-06-2021, 01:24 PM

short search found this
https://67-72chevytrucks.com/vboard/...ac+engine+swap

sick472 · 05-06-2021, 01:46 PM

I reread your older post and it seems you are looking for some OEM parts to make the transplant. I don't know if this is possible. Olds used some Pontiac motors in cars (and/or vice-versa), but I can't help but think that those mounting parts would not bolt up in a truck. I'd love to know better, if you have the info.

But, I did put a Pontiac 400 in my truck. I think the block was a 70 or 71. Here's the story...I went to buy some C10 parts from a guy and one of the longhorn trucks had a Pontiac 400 in it...loving the Pontiac motors, I bought the motor, trans, and mounts...many years later, I have a Pontiac 400 C10.

I know very little about the parts I purchased. The rubberized mounts are definitely Pontiac. I think the towers are Pontiac too, maybe late 70’s firebird mounts. The Pontiac 400 that I purchased out of the longhorn was a YX block which may help determine what car the tower brackets came from IF the Pontiac parts all came from the same donor car. I would estimate that the motor/fan sits about an 1 to 1-1/2" higher that the original Chevy 350 as I had to relocate the Chevy fan shroud upwards in order for it to work properly. There is only one fabricated piece and it is the flat plate that connects the top of the tower to the frame. Here's some photos...

sick472 · 05-06-2021, 01:48 PM

Flat plate that connects the top of the tower to the frame photo...

sick472 · 05-06-2021, 01:55 PM

I just got mine on the road a few weeks ago. Here's some encouragement...

sick472 · 05-06-2021, 02:07 PM

Side notes:

1.) I had to move my V8 x-member and shift linkage bracket back to the more rear set of holes in the frame to accommodate the TH400, but all the auto shift linkage parts worked fine.

2.) You may want to put the battery on the other side so the battery cable is not so long and snaking around. I bought the auxiliary battery box and tossed the passenger side one as it was toast.

**BigBird05** · 05-06-2021, 02:41 PM

My thoughts are to change the towers over to 73 and up. Then you could use the frame brackets and motor mounts from almost any Pontiac V8. Probably best to get a donor car for radiator, brackets, hoses, wiring etc.

**special-K** · 05-08-2021, 10:41 AM

I need to save this thread. Great info. I have a 327 built for my '67 GMC project, but still toy with the idea of going Pontiac. GMC began use of V8s in '67 but I think it was later in the year. A GMC/Pontiac marriage just seems natural

**1970cstblazer** · 05-08-2021, 12:25 PM

Love this. Having owned several Pontiacs over the years, I appreciate the ease of working on, the appearance, and the power of a traditional Pontiac V8.

Greg58 · 05-08-2021, 04:20 PM

Quote:

Originally Posted by BigBird05

My thoughts are to change the towers over to 73 and up. Then you could use the frame brackets and motor mounts from almost any Pontiac V8. Probably best to get a donor car for radiator, brackets, hoses, wiring etc.

100% agree, the later model Pontiac V8 engines used a clamshell arrangement, similar to square body truck engine mounts.
Way better than the 60s Pontiac mounts.
I have always thought a Pontiac would be a great truck engine because they make a lot of torque.
Greg

05-06-2021, 12:41 PM	#1
1972 C10 Registered User Join Date: Oct 2013 Location: Amarillo, Texas Posts: 49	Pontiac swap I apologize for posting the same question again, but I still have no clear answer. I want to install a 76 Pontiac 400 in my 69 GMC originally 305 V6. I really want this to look factory and have found vague references as to what frame "towers" to use but would love to hear from someone who has done this w/details. THANX __________________ 64 Chevy Suburban/Carryall 4x4 72 C10 Highlander LWB 34 Chevy 5 wdo Street Rod 64 Corvette Roadster w/AC 78 TransAm WS6 78 GMC Jimmy 2WD Slammed SOLD!

05-06-2021, 01:24 PM	#2
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,389	Re: Pontiac swap short search found this https://67-72chevytrucks.com/vboard/...ac+engine+swap

05-06-2021, 01:46 PM	#3
sick472 Registered User Join Date: Jul 2015 Location: Sedalia Mo. Posts: 1,130	Re: Pontiac swap I reread your older post and it seems you are looking for some OEM parts to make the transplant. I don't know if this is possible. Olds used some Pontiac motors in cars (and/or vice-versa), but I can't help but think that those mounting parts would not bolt up in a truck. I'd love to know better, if you have the info. But, I did put a Pontiac 400 in my truck. I think the block was a 70 or 71. Here's the story...I went to buy some C10 parts from a guy and one of the longhorn trucks had a Pontiac 400 in it...loving the Pontiac motors, I bought the motor, trans, and mounts...many years later, I have a Pontiac 400 C10. I know very little about the parts I purchased. The rubberized mounts are definitely Pontiac. I think the towers are Pontiac too, maybe late 70’s firebird mounts. The Pontiac 400 that I purchased out of the longhorn was a YX block which may help determine what car the tower brackets came from IF the Pontiac parts all came from the same donor car. I would estimate that the motor/fan sits about an 1 to 1-1/2" higher that the original Chevy 350 as I had to relocate the Chevy fan shroud upwards in order for it to work properly. There is only one fabricated piece and it is the flat plate that connects the top of the tower to the frame. Here's some photos... Attached Images __________________ He who is without oil shall throw the first rod. Compressions 8.7:1 1972 C10 1976 C10 (parts truck) 1985 K20

05-06-2021, 01:48 PM	#4
sick472 Registered User Join Date: Jul 2015 Location: Sedalia Mo. Posts: 1,130	Re: Pontiac swap Flat plate that connects the top of the tower to the frame photo... Attached Images __________________ He who is without oil shall throw the first rod. Compressions 8.7:1 1972 C10 1976 C10 (parts truck) 1985 K20

05-06-2021, 01:55 PM	#5
sick472 Registered User Join Date: Jul 2015 Location: Sedalia Mo. Posts: 1,130	Re: Pontiac swap I just got mine on the road a few weeks ago. Here's some encouragement... Attached Images __________________ He who is without oil shall throw the first rod. Compressions 8.7:1 1972 C10 1976 C10 (parts truck) 1985 K20

05-06-2021, 02:07 PM	#6
sick472 Registered User Join Date: Jul 2015 Location: Sedalia Mo. Posts: 1,130	Re: Pontiac swap Side notes: 1.) I had to move my V8 x-member and shift linkage bracket back to the more rear set of holes in the frame to accommodate the TH400, but all the auto shift linkage parts worked fine. 2.) You may want to put the battery on the other side so the battery cable is not so long and snaking around. I bought the auxiliary battery box and tossed the passenger side one as it was toast. __________________ He who is without oil shall throw the first rod. Compressions 8.7:1 1972 C10 1976 C10 (parts truck) 1985 K20 Last edited by sick472; 05-06-2021 at 02:10 PM. Reason: typo

05-06-2021, 02:41 PM	#7
BigBird05 Senior Member Join Date: Aug 2019 Location: Cheraw Posts: 1,305	Re: Pontiac swap My thoughts are to change the towers over to 73 and up. Then you could use the frame brackets and motor mounts from almost any Pontiac V8. Probably best to get a donor car for radiator, brackets, hoses, wiring etc.

05-08-2021, 10:41 AM	#8
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,863	Re: Pontiac swap I need to save this thread. Great info. I have a 327 built for my '67 GMC project, but still toy with the idea of going Pontiac. GMC began use of V8s in '67 but I think it was later in the year. A GMC/Pontiac marriage just seems natural __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

05-08-2021, 12:25 PM	#9
1970cstblazer All stock and staying that way Join Date: Jul 2003 Location: Elkland, PA Posts: 1,277	Re: Pontiac swap Love this. Having owned several Pontiacs over the years, I appreciate the ease of working on, the appearance, and the power of a traditional Pontiac V8. __________________ 1970 K/5 Blazer CST 4WD, Bronze, 93k ACT. miles, 350, 4 speed, positraction, 16.5" x 8.25" wheel option, tilt, tach, vacuum, AM/FM, manual throttle...Dad ordered and purchased new 4/70. Currently frame off restoration in progress... 1972 Cheyenne Super 20 2WD, DK Blue/White, 90K ACT. miles, 402, TH400, 4.10 open, tilt, tach, vacuum, A/C, AM/FM, manual throttle.. A mostly original paint never rusted Texas survivor... 2017 Sierra 1500 SLT 4WD, Black, 41k miles, 5.3, 6L80E, 3.42 LS, 20" polished wheels, everything but moonroof and 6.2... 2019 Canyon SLT 4WD, White, 60k miles, 3.6, 8L45, 3.23 LS, 18" wheels



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