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Projects 302 GMC SIx or a Pontiac OHC Sprint Six?

Discussion in 'The Hokey Ass Message Board' started by Torkwrench, Sep 6, 2016.


302 GMC or Pontiac OHC?

Poll closed Sep 13, 2016.
  1. 302 GMC with Nicson 2x1 intake and headers.

    10 vote(s)
  2. Pontiac OHC Sprint Six,with a factory Q-jet and split exhaust manifold

    17 vote(s)
  1. Torkwrench
    Joined: Jan 28, 2005
    Posts: 2,568


    Just bought a 1941 Pontiac Streamliner project car. It was bought without an engine or trans. It already has a 74 Nova front clip installed.

    The two possible engine choices are either a 302 GMC, or a Pontiac OHC Six, out of a 1969 Firebird. I'd be using a T-5 5 speed for a trans, with either engine.

    The GMC is a NOS short block that is still in the shipping crate. A used big port head goes with the 302. I already have a complete small port 270 GMC out of a 56 grain truck, and a Nicson 2x1 intake for a 302. Do not have any headers.

    The Pontiac engine was swapped out of a 69 Firebird, (for a 455), about 30 years ago and has been stored since then. Supposedly, it ran well when it was pulled, and was well oiled up to preserve it. It had a 3 speed behind it, but the trans is gone. I don't have any experience with the OHC engines, but have worked on several GMC / 235 Chevy sixes.

    So.....How do these compare? What are the advantages / disadvantages to each one?

    I'd like to keep the 41 all Pontiac, but also like the idea of a GMC Six in it. After a quick look around the internet, it looks like parts are easier to get for the GMC??? However, the pan clearance on the GMC is a question mark.
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 50,933


    see how much room there is for the oil pan....the front crossmember is probably pretty far forward, that's how old cars were built, but they were moving the front wheels back starting around the early 40s.

    The OHC has issues with the cam housing wearing out. And any engine that's been sitting that long could have had all kinds of bad things happen to it...I'd want to do some taking apart, before spending money on it. Or at least turn it over by hand, if it won't turn, then it's probably not worth much (unless it has a good cam housing)
    Torkwrench likes this.
  3. Most will be mad at me about my choice but I would go with the Pontiac OHC motor. You have to work with your gearing some to make it work with the OD transmission but you should really like it.
  4. gas pumper
    Joined: Aug 13, 2007
    Posts: 2,957

    gas pumper

    I am a big fan of the 302. But pan clearance is gonna be an issue with the Nova clip. You can make the step in the pan move a lot towards the flywheel. and shorten the depth on the front and still get 8 qts of oil in it. The Flying Seven has these modifications, it has a Camaro clip.

    But I think the Pontiac OHC is a very unique engine, it would go well in your Pontiac.
    timmy2times likes this.

  5. 41atsaltaccessroad.jpg The OHC six came in a 69 firebird...same front clip as a 74 nova. You should be golden as far as oil pan clearance with the little Pontiac engine. The OHC pontiac came with an aluminum cam cover that housed the cam and the bores were drilled into the aluminum with no removable bearings..when they wore out it was an expensive proposition to have it drilled oversized and some kinda cam bearings pressed in. I never cared for that arrangement. Not sure anybody even does that kind of work anymore.
    I'd go with the 302 Jimmy. Yeah, it's heavier but I doubt it's much heavier than the original 239 Pontiac flathead 6 engine. Plenty of hotrod stuff available for the 302 from Patrick's and a few other places...not sure about pan clearance for the 302...tape meassure will tell the story.
    My old 41 had a good, tight 239 so I left it in place and drove the shit outta it.
    PS...mine weighed 3350 lbs...maybe a little porky for a little Pontiac OHC engine
    Torkwrench likes this.
  6. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    Member Emeritus

    I bought a new Firebird in '69 with the OHC six. I liked it fine. Wasn't really fast. I have also had several 270 and 302 GMC engines in my Bonneville cars. Liked them fine, also. The OHC motor is more interesting, I think. Either way you are way ahead of the 350-350 crowd.
    Johnny Gee and Torkwrench like this.
  7. D.N.D.
    Joined: Aug 15, 2012
    Posts: 1,385

    Member Emeritus

    Use the Gimmy 302 and find a Wayne 12 port head, side drafts on one side and a cool header on the other and you will be styling

  8. Yea stylin' at the homeless shelter. :D Man those 12 port heads are high priced pieces. But a Gimmy with one it tits and that's a fact.
    Torkwrench likes this.
  9. I'd consider the OHC Pontiac ONLY if you are sure that you can get a replacement timing belt and if it is the H.O. (4 bbl carburetor) version. If not I would go with the GMC 302. And I'm a Pontiac guy, have not been without owning at least one since 1970.

    The OHC was only a four year model run from 1966 to 1969.

    I guess I'm leery of the timing belt situation because of another O/T engine. I was asked to try and find a timing belt for a 75 Cosworth Vega. From what I found they are only available to members of a Cosworth Vega club. They own the rights to produce them and the manufacturer is under contract to them and only them to sell it.
    Last edited: Sep 6, 2016
    dan c likes this.
  10. Gofannon
    Joined: Feb 8, 2007
    Posts: 769


    I'm pretty sure GMCs were made in the Pontiac plant.
  11. You could get around that BS with the manufacturer. It may not be worth the trouble and probably way easier to join the club.

    As for the rubber band for the Pontiac it should not be a problem. I think that there are more then a few OHC Pontiac owners here on the HAMB.

    The 302 sounds like a pretty good deal, being an NOS short block and all. It could also have its pit falls, but if it has not fallen prey to mice or hornets it would be fun to own and use.

    Decisions decisions. LOL
  12. mr.chevrolet
    Joined: Jul 19, 2006
    Posts: 8,135


    either one is going to be expensive, get a 292 cu in inline.
    JeffB2 and Hnstray like this.
  13. belair
    Joined: Jul 10, 2006
    Posts: 8,864


  14. I checked a little further and found the Pontiac OHC belts ranging anywhere from $66 to $125, the cheapest was on eBay and the highest was Kanter Auto Products. So I was a bit paranoid on the belt but working in a car dealership parts department we are seeing a lot of late model parts being discontinued at a quicker pace than say ten years ago.
    Torkwrench likes this.
  15. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,613

    Rusty O'Toole

    I vote for the OHC Pontiac. An overlooked and under rated engine. When it was new, the idea was that Pontiac wanted to offer something special for the six cylinder buyer, and the engine turned out to be a honey. Very economical on gas, with the power and performance of a small V8.

    It's nice to keep it all Pontiac. The engine itself looks good when shined up. As to the cam bearings, how often do they wear out? Keep good oil in it and should not be a problem.
    Torkwrench likes this.
  16. gnichols
    Joined: Mar 6, 2008
    Posts: 11,114

    from Tampa, FL

    Just based on looks... I'd go with the OHC - reminds me of the old 4-banger conversion kits. Gary
    Torkwrench likes this.
  17. junkyardjeff
    Joined: Jul 23, 2005
    Posts: 8,232


    Usually I would have said the GMC but be different and go with the OHC motor.
  18. Torkwrench
    Joined: Jan 28, 2005
    Posts: 2,568


    Thanks to everyone for the advice and knowledge. Part of the engine decision depends on what the plan for the car is. Build it for myself? Or build it to resell? If I build it for myself, it will get either the GMC, or OHC and a stick shift. If it gets built to resell, it'll probably get a Pontiac V8 with an auto trans. No matter what.....It will not get a 350 / 350. Well....Unless it's a 350 Pontiac V8.

    According to Hollander, GMC sixes used two different oil pans. A shallow pan in the 100 - 280 series trucks, and a deep sump in the 300 - 500 series. This explains why the pan on my 270 is so huge. It came out of a 1956 350 series grain truck.

    I'm still waiting to hear back from the guy with the OHC for sale. By the way, it's a factory Q-jet, dual exhaust engine. The 302 GMC belongs to one of my nephews.
  19. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,695

    Member Emeritus

    I'm on board with the Pontiac OHC also, but only because of the Nova front clip; it's pretty wide to make mounts for an early style GMC six, and there are factory mounts to bolt the OHC six right in. Plus, the OHC engine is going to be much lighter. JMO.
    I drove a customers NEW 69 Firebird with the Sprint package (4 barrel carb, cast iron headers, better cam) when in high school while working in a Standard Chevron Dealership, and it was plenty fast! I am Butch/56sedandelivery.
  20. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    Member Emeritus

    I went through several GMC engines. I saw at least 3 pans. A quite shallow pan that I used with the engine in my Vega, A deeper pan that worked well with the engine in my 32 five window. And a really large two piece pan that would have been fine in a ready mix truck, but didn't fit anything I had.
  21. Blues4U
    Joined: Oct 1, 2015
    Posts: 6,466

    from So Cal

    I've always like that OHC engine, one of the coolest looking American engines IMO.
  22. xderelict
    Joined: Jul 30, 2006
    Posts: 2,477

    Member Emeritus

    Having owned a GMC 302 in a 54 Belair I have to say I loved that engine.
  23. dan c
    Joined: Jan 30, 2012
    Posts: 2,347

    dan c

    no substitute for cubic inches!
  24. Kruzer63
    Joined: Dec 6, 2004
    Posts: 638


    I vote OHC as im a fanatic. I've ran a 67 pontiac Sprint OHC 230 in my 53 pontiac since 1994 and still strong. Keeps up with everyone just fine. I went more radical in my latest car but still OHC pontiac backed with 5 spd this time and it's a blast. It's a 66 230 in the model A. Woodland motor sports sells everything including belts for these. Nothing is that difficult to get and they work great.

    Attached Files:

    kiwijeff, hendelec and timmy2times like this.
  25. Bird man
    Joined: Dec 28, 2009
    Posts: 741

    Bird man
    from Milwaukee

    302= more bottom end torque. The OHC will buss to 6K all day long & provide much better hwy mileage.
    Lots of OHC support out there.
    timmy2times likes this.
  26. That's why I like fat gurls. :D
    hendelec likes this.
  27. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    Member Emeritus

    I believe that with the proper swapping of parts you can get a 292 OHC SIX.
    Ned Ludd, dan c, timmy2times and 2 others like this.
  28. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,306

    from Quincy, IL

    Teaser! :D ............Tell us more, please!

    (I have 292 stuff on hand)

  29. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    Member Emeritus

    Well the 250 Chevy six and the 230-250 Pontiac OHC engines share most bottom end parts. And so does the 292. Same family of engines. Look into installing a 292 crank in the Pontiac. I don't know if the 292 pistons will work. Some looking at both engines would point you in the right direction. But it has been done before.
    JeffB2 likes this.
  30. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,613

    Rusty O'Toole

    The 292 block is taller than the 230 - 250 by quite a bit, I'm thinking an inch or more? If the crank fit the block you would need to use the 230 rods and custom pistons. Don't know if this would work but it seems like the easiest way.

    When you get into that much work and expense I can't help thinking it would be easier to just get a V8.

    The OHC six in stock form is pretty good with a 4 barrel carb and dual exhaust, putting out 215HP from 230 cu in.

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