V6 in a 1970-72 Jimmy?

[1969_CM2590D]

4wd or 2wd? Has anyone tried it or pondered it? What might need to be done if it would be practical?

I've been thinking this as well as (in GMC tradition) a Pontiac (OHC) 6...

[FetchMeAPepsi]

Ive seen them in a 50's model but they were marketed as a replacement for those anyway. Coyote has a V12 in one and it looks awesome.

I guess with enough machining and passion anything is possible. If you do it take a bunch of pics and let us know how it goes

[GMCDAC]

4wd or 2wd? Has anyone tried it or pondered it? What might need to be done if it would be practical?

I've been thinking this as well as (in GMC tradition) a Pontiac (OHC) 6...

Hello Dennis,

Are you an owner of a '70 Jimmy?

I have a '70 K5 Jimmy. This conversion won't happen to this particular GMC as it has been in the family for 43 years and besides seats, wheels and tires it is staying the same way that it was when Mom bought it in 1971.

Now I'm not saying this wouldn't be a very cool conversion. If I ran into a Jimmy that I had no historical connection to, it could easily be game on for a V-6 swap! Sounds like it could be a pretty simple deal, especially since the V-6 was available in this era of GMC.

I have to ask, is that your brochure? If it is would there be any way you could scan the whole thing for me? I have run into '71 and '72 brochures for fair prices, but never a '70!

Thanks for that pic!---DAC

[1969_CM2590D]

(BTW, I ahve no idea why I put this in Marketplace, but if someone wants to move it to General Discussion, feel free.)

No, I don't have a '70 Jimmy... yet. But they do pop up from time to time and are physically identical to my'69- so I like the idea of a matched set. I'm looking for something in probably forlorn shape, if I do it. I'm not into cutting up a good original one. I'd be game for a different engine and a New Process gearbox (since I really like the on in my truck).

My big concern about a V-6 would be the weight. It would weight nearly more than double a 250 and obviously a bit more than an SBC. I'm thinking it would need a beefed suspension. Would the shortened 1/2 tom frame need reinforcing?

So with that in mind, I also thought about another unique GM engine, the Pontiac OHC six. It makes more juice than the Chevy sixes in 230 or 250 CID guise. Since it's based on the Chevy six, I'd guess swapping wouldn't be much of a hassle. Not to mention that GMC's used Pontiac sizes for many years...

I got the 1970 Jimmy brochure from the Old Car Manual project site. Lots of cool brochures, manuals, ads, and articled to look at. Here's the link: http://www.oldcarmanualproject.com/ Here is the link to the Jimmy brochure: http://www.oldcarbrochures.org/NA/GM-Trucks-and-Vans/1970_Trucks-Vans/1970-GMC-4WD-Brochure

That reminds me, I need to get my '69 brochure scanned...

[bigblockv6]

The Jimmy frame was still based on the 1/2 ton truck frame so the added weight will not be a problem. The problem will be with the front springs, you'll need some from a 1/2 ton GMC KM-1500 series if you can find them or just go with an add a leaf. My 68 KM-2500 tended to sit lower in the front even with a factory installed V6, at one point I installed an add a leaf on each side which makes the truck sit level now. Back in the era of 70-72 GMC light duty trucks the V6 was no longer offered from the factory but dealers were equipped to do such a conversion at a customers request, GMC did advertise these conversions in their "Points" magazine.

[bigblockv6]

As far as the Pontiac OHC cam inline six the 230 version shared the same bottom end as far as crankshaft rods & pistons s the Chevrolet six. The rest of the engine including the bellhousing pattern are traditional Pontiac or "BOP". The 250 OHC version that came out in 68 had a whole new bottom end based on Pontiac's V8. The only time GMC used Pontiac sixes was back in the 30's when they were Flatheads.

[GMCDAC]

Thanks for that link, Dennis! I have tried to get on that site several times and I could never get it to load. Your link worked perfectly.

DAC

[Ed Snyder]

I can attest to bigblockV6's statement that dealers were equipped to install the V6 in 1970 to 1972 light duty GMC trucks. I was in the market for a new pickup in 1972 and got quotes from International, Chevy, and GMC dealers. The quote from International was for a 3/4 ton 4WD pickup with short wide bed, 392 V8 and 5 speed transmission. It was beyond my budget. The Chevy quote was for a 1/2 ton 4WD short wide with 350 V8. The GMC quote was also for a 1/2 ton 4WD short wide, but with a 351 V6. The Chevy was about $1,000 cheaper, so that's what I ended up buying. When it was stolen and never recovered a couple of years later, I bought a used 1972 GMC Jimmy with the ubiquitous 350. Forty years later my wife still talks about the Jimmy being her favorite vehicle out of the 60 or so that we've owned.

[1969_CM2590D]

Well, there's one a few hours from me. I've called and emailed about it, but no response so far. If this is a dead end, there will be others. If I do get to see it I'll let you know and take pics, etc...

I've got the download of the dealer book for the 1970 Blazer from GM Heritage. I'm assuming by 1970 the Jimmy would have been a badge engineered Blazer. Or would have offered more options in the mechanical end of things?

Thanks bigblock for the suspension and frame information. It's nice to know that won't be a hassle. I wonder if there is any literature/info on conversion packages, what all they consisted of, tech info, and documentation? Obviously the OHC won't be as easy as I thought. I'm glad the link worked Doug. I use that site a lot.

A wife's endorsement is something a man should pay attentions to, even if he's single...

Edit: It pays to dig- just found the original leather key fob from the dealer in the dirt in the glovebox, where I also found the dealer emblem that was glued to the tailgate at one time. I wonder if the Protect-o-Plate will be under the seat? :D

[GMCDAC]

Well, there's one a few hours from me. I've called and emailed about it, but no response so far. If this is a dead end, there will be others. If I do get to see it I'll let you know and take pics, etc...

I've got the download of the dealer book for the 1970 Blazer from GM Heritage. I'm assuming by 1970 the Jimmy would have been a badge engineered Blazer. Or would have offered more options in the mechanical end of things?

Thanks bigblock for the suspension and frame information. It's nice to know that won't be a hassle. I wonder if there is any literature/info on conversion packages, what all they consisted of, tech info, and documentation? Obviously the OHC won't be as easy as I thought. I'm glad the link worked Doug. I use that site a lot.

A wife's endorsement is something a man should pay attentions to, even if he's single...

Edit: It pays to dig- just found the original leather key fob from the dealer in the dirt in the glovebox, where I also found the dealer emblem that was glued to the tailgate at one time. I wonder if the Protect-o-Plate will be under the seat? :D

Yeah bigblock's and Ed's info was interesting to say the least! I knew that this frame and suspension configuration had V-6 engines before the Jimmy was introduced for the 1970 model year but had no idea that ordering one was possible! That would be the rarest Jimmy ever! It would really be fun to build a clone to look like what could have been ordered!

I dated my wife in the Jimmy we now have when Mom would let me drive it and we have been married coming on 36 years so this Jimmy was not only my Mom's but it has been part of her life since she met me! Wife endorsement in my case is a no-brainer!

I can't say about your '69 which I assume you are referring to with the key fob and dealer tag reference, but the Protect-o-Plate was attached to a brochure in the glove box in Mom's '70 Jimmy. I still have it too.

DAC

[Ed Snyder]

Just to clarify -- you couldn't "order" a 70-72 GMC with a V6 from the factory. You ordered one with a V8 and the dealer would perform an engine swap, removing the V8 and installing the V6 in its place. That's what made the price so high. For that reason, I doubt many buyers had that swap done to brand new trucks. More likely after their V8 wore out.

[1969_CM2590D]

I know in the '60's GM offered a few swap kits for vehicles. One was for the early Chevy II's. No V-8's were allowed by corporate policy for the first couple of years, but an SBC kit was offered during that time for "competition" use. You bought the whole car, straight six and all, plus the kit, plus a new V-8 engine, plus dealer labor. It had to be done this way for the warranty to stick and to be legal for "stock" classes at the strip or track. Maybe the dealer would give you a discount if you were pals. I'd wager by the time you added all the figures up you could have bought a new 283 or 327 Impala coupe (or a Monza Spyder with change left over). These Chevy II's did do well at the strip though...

I dunno, maybe you could have done a COPO for a V-6, Ed? Not that that would have been any cheaper.

[Ed Snyder]

While I'm not aware of any COPO V6s, Dennis, I suppose it was possible back in those days. The factories did entertain some special orders back then. For example, the brochures for GMCs from 60 to 66 don't show 3/4 ton Suburbans or panel trucks being available (they did become available in 1967). But I know for a fact that some do exist, possibly built originally for the military. Anybody out there know more about this?

Exterior paint colors were probably a common special order back then.

[bigblockv6]

The V6 was dropped in the light duty series in March of 1969 period! So you can forget about any fantasies of a COPO V6 from 1970-72, from that point on it was a dealer installed option, As of 1970 GMC light duty trucks were no longer assembled at GMC's Pontiac Michigan plant rather just GM assembly plants, Suburban's and Jimmy's came of Chevrolet assembly lines. GMC's Suburban models starting in 1967 came only available with the ubiquitous small block Chivy V8 and inline six. The GMC dealer in San Francisco where we got our 68 had a 67 K series Suburban in the showroom that was converted over to the V6, this was back in November 1967.

[1969_CM2590D]

Yes, indeed! Mine's a last of the line '69 (that rhymes!) that came out of Baltimore.

[BobBray]

GMC actively marketed the V-6 as a replacement for large gasoline engines in other makes of trucks. Catalogs and spec.sheets exist for some of the more common swaps. One in particular that was pretty common was the 351 or 401 into the White 3000 series cabover. The old White flathead sixes were reliable but not efficient.

OHC Pontiac 6 into a GMC pickup would be interesting

[1969_CM2590D]

I don't want to stray too far here, but along with the Pontiac OHC six, the Buick aluminum 215 is interesting as well. Rover took it over and left it largely unmolested in some ways, but cured many weaknesses- many Buick items will still fit. The last version was 4.6 liters (281 CID) and showed up in Land Rover Discoverys until 2005, so it is likely more available than an OHC 6, as well as being proven in an off road 4x4. It's got a GM heritage as well. The dry weight of 318 lbs makes it quite attractive- that's over 100 lbs. less than any of the "lightweight" Chevy sixes! The Rover versions are strengthened, but still weigh just 375 lbs dry.

The Buick/Rover V8 is probably the most hopped up V8 outside of North America, and the most hopped up V8 worldwide outside of those of the Big Three. You can get lots of stuff for it.