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Trying to put a Pontiac GTO 400 engine in my Chevrolet truck.

I've been planning this truck for years and have nearly finished. After contemplating for so long about what engine I wanted in my truck I run across this Pontiac GTO 326 engine, it's basically the same as a 400, plus it's been bored out to a 400. I bought it with the hopes it would be going in my truck with so many agreeing it would be a good idea but now I'm not so sure. CAN I PUT A PONTIAC GTO ENGINE IN A CHEVROLET TRUCK? I want to go with this but now that I'm starting on the swap people have started telling me that it wont work. I'm confused, will it or wont it? Help!
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Comments

  • andre1969andre1969 Posts: 21,590
    Well, anything will fit if you're wililng to put enough time and effort into it. First off though, what year is this Chevy truck? At the very least, the bolt pattern for the transmission is going to be different, and most likely the engine mounts, as well. I can also see exhaust issues, and possibly the way the hoses hook up to the radiator.

    FWIW, GM used to put Pontiac engines in their trucks. The 1957 GMC used a Pontiac 347, and I wouldn't be surprised if the 1958 used the 370.1. I'd imagine there are other examples. The 347, 370.1, 326, 400 et al, and even 455 can be traced back to the old Pontiac "medium block" (Pontiac never did the big-block/small-block thing like Chevy, Mopar, Olds, or Buick) 287 from 1955.

    So, if nothing else, if you got some schematics and diagrams of the old GMC trucks that used Pontiac engines, you might be able to see how they fit in versus a Chevy engine.
  • I wouldn't do that. Get yourself a Chevy crate engine---you'll get lots of HP, a warranty, and much less trouble in mating everything up.

    Also that 326 was not bored out to 400. I don't know who told you that, but it's not possible. Boring out a 326 to .30 over only gives you a 331cid, and .60 over is about the limit for most engines.

    You can build a 326 to be very robust, but boring it out is the least of the process to get decent HP.

    This is why, if you want a healthy engine, use a Chevy crate---just buy as much power as you can afford or want.

    Or if you buy a used engine, hear it run and take compression and oil pressure readings, or just forget it.
  • 0patience0patience Posts: 1,542
    You'll have to modify the engine mounts, most probably have to move the transmission crossmember and possibly have to cut or lengthen the driveline.
    While it can be done, you would be far better off to take mr shiftirght's suggestion.

    We've put a 455 in a 70 chev pickup, but it was a lot of work and to be honest, I wouldn't do it again.
  • isellhondasisellhondas Issaquah WashingtonPosts: 17,355
    Excellent advise.

    That was never a "GTO " engine. The 326's came in Le Mans and lesser models.

    It wouldn't be worth the trouble and headaches that would be involved.
  • andre1969andre1969 Posts: 21,590
    That was never a "GTO " engine. The 326's came in Le Mans and lesser models.

    Yeah, that's what I thought. I know there was a wussed-down version of the GTO in later years, but at least it was still a 400 V-8. I think it was a low-suds 2-bbl version designed to run on low-octane fuel. Basically, the credit engine that they offered on the Catalina?

    I do always get fascinated by these engine swaps mother nature never intended, though. But, they should only be done if you have money to spare, and don't care about taking a loss.
  • isellhondasisellhondas Issaquah WashingtonPosts: 17,355
    Someone in these forums was buying one of those wimpy GTO's awhile back.

    I never understood why that would have made such a thing or why anyone would have bought one. It's either a GTO or it's not.
  • I know this is late and I did just find this thread but I have been putting Pontiac engines in 60-87 chevy/GMCs for a long time. There are componebts made that make it a bolt in deal. NO, the cross members don't need to be moved and NO it isn;t a hassle. A 70 or newer engine block is the most easy bolt in.
    Pontiacs bolt right in just like a weak kneed chevy small block. Differance is tha TORQUE for any stock pontiac is far beyond any chevy mouse motor.
    NO, a 326 can not be bored to a 400.
    I have detailed build photos showing a 400 hp 413 ft/torque 350 pontiac motor in a 79 GMC that is used to pull a 2 car car trailer. Bolted right in with NO fab work necessary.
  • MrShift@EdmundsMrShift@Edmunds Posts: 43,648
    edited April 2011
    The original poster was asking about putting in an old 326 motor (??) of dubious origin and specs, so that's where our advice was directed towards possibly a Chevy crate engine. He didn't mention access to other Pontiac engines at the time. The Pontiac 350 is not an engine most people want, except maybe the earlier 68-70 ones, but in the right hands can certainly produce a lot of power. But you have to bore it and you'll need head and camshaft work to get anywhere. This is why I suggested to the poster to just buy crate power.
  • andre1969andre1969 Posts: 21,590
    The Pontiac 350 is not an engine most people want, except maybe the earlier 68-70 ones, but in the right hands can certainly produce a lot of power.

    After '70 or so, didn't Pontiac mainly look towards the 400 and 455 for their performance engines? I think one reason Chevy put out high-performance 350's was because the 454 was so heavy, so a high-output lightweight smallblock had a lot of uses. But Pontiac didn't do the biglock/smallblock thing. Instead, they had more of a "medium block" design that served all their displacements, so a Pontiac 350 probably wasn't any lighter than a 400 or 455. So, say, if you wanted a 350 hp engine, it was just simpler to get that 350 hp out of a 400 or 455, than a 350.
  • MrShift@EdmundsMrShift@Edmunds Posts: 43,648
    The bore is too small, and so if you wanted to use a big cam and valves you have to bore and modify for clearance. But it can be done---you can *make* a Pontiac 350 put out impressive horsepower but it requires a good deal of machine work.
  • andre1969andre1969 Posts: 21,590
    The bore is too small, and so if you wanted to use a big cam and valves you have to bore and modify for clearance. But it can be done---you can *make* a Pontiac 350 put out impressive horsepower but it requires a good deal of machine work.

    Yeah, a Chevy 350 is a 4.00 bore and 3.48 stroke, while the Pontiac 350 was a 3.88 bore and 3.75 stroke. So the Chevy was more of a revver, but I guess the Pontiac was better for torque?

    The Chevy 327 had the same bore but an even shorter stroke, so would it have been a better engine to hop up than the 350?
  • MrShift@EdmundsMrShift@Edmunds Posts: 43,648
    I think it would depend on what you were trying to achieve and how radical you got.
  • "The original poster was asking about putting in an old 326 motor (??) of dubious origin and specs, so that's where our advice was directed toward possibly a Chevy crate engine."

    I didn't address the "GTO 326" mainly because it just doesn't exist. Pontiac never put a 326 into a GTO.
    No 326 can't be bored to a 400, that is a laughable statement.

    Early Pontiac blocks, (326-428) 69 and back, can easily bolt into a GM truck, 60-87, but the 70 and newer blocks (350-455) have a center boss that the motor mount can bolt to that makes it even easier to bolt in.

    "He didn't mention access to other Pontiac engines at the time. The Pontiac 350 is not an engine most people want"

    Most people do not know the true potential of any Pontiac engine. However, most people cop out (when making the sacrilegious swap of a Chevy into a Pontiac firebird, GTO etc) and take the small block route because of limited money and make the compromise of going with an inferior motor. I know that isn't the point of the OP but it goes along with what is being discussed.
    Loads of Pontiac 350's were offered with big valve heads and a minor notching of the block needs to be done to use them IF the block isn't factory notched already, many were.
    The biggest problem in building a Pontiac is people use "Chevy" thinking when addressing Pontiac's and frankly, they are as different as day and night. A Pontiac 350 can easily make 350-360 HP in stock configuration.

    The answer to the original poster is this, yes you can use a 326 in a GM truck. It along with a BOP trans will bolt right up and go. A 350 Pontiac is a better choice because of torque potential. The 400 would be overkill unless you are pulling heavy loads or you are building a performance truck.
  • MrShift@EdmundsMrShift@Edmunds Posts: 43,648
    A 326 has a cast crank and pistons, doesn't it? Another not so great feature.
  • Yes, a 326 does have cast pistons and crank. I had one in a 67 tempest that had 338,753 miles on it when it was pulled. Ran good, didn't smoke and had good compression and a .006" lip. If maintained well those high nickel blocks wore very well.
    The application dictates the parts necessary for the build in any build. Cast pistons and crank are perfectly fine in the right application.
    58 GMC trucks came with a Pontiac 370 engine from the factory. I have one on an engine stand with over 700,000 verifiable miles on it. It will clean up at .020".
  • MrShift@EdmundsMrShift@Edmunds Posts: 43,648
    I agree, cast crank and pistons are fine for everyday use but woe to the man who attempts to add significant power to an engine built that way. It's not going to end well.
  • andre1969andre1969 Posts: 21,590
    I agree, cast crank and pistons are fine for everyday use but woe to the man who attempts to add significant power to an engine built that way. It's not going to end well.

    I think Mopar switched from forged to cast crankshafts sometime in the mid-1970's, and I've heard a lot of people groaned about it. Would that have given them a higher failure rate in everyday use as well, or just cause problems when you try to hop them up?

    If you have an engine that uses a cast crank and pistons, could you just put swap in a forged crank and pistons? Presuming, of course, that an older version of the engine with the exact same bore and stroke used forged at one time?
  • omarmanomarman Posts: 676
    edited April 2011
    I don't remember Pontiac cast cranks and pistons from that era being trouble prone for street/strip use. Nodular cast iron or Armasteel (PMI - not steel despite the name) was used for most Pontiac V8 crankshafts except early super duty (racing) engines. Depends on your definition of "significant power" though.

    For example, and maybe a true Pontiac guru out there can take a better whack at this, I looked up factory GTO Ram Air engines:
    The original Ram Air 400/360hp ('67?) used cast crank and pistons.
    Ram Air II 400/366hp = cast crank and pistons
    Ram Air III 400/366hp = cast crank and pistons
    Ram Air IV 400/370hp = cast crank and forged pistons
    Ram Air V *crate engine* factory HP rating? = forged crank and forged pistons

    Super Duty engines prior to the '73-'74 455SD used forged steel cranks. But other than the Ram Air V crate engine, was there any factory GTO Ram Air engine with forged crank+pistons? I'm thinking that if you are driving a Pontiac street machine and have problems with damaged cranks or "holed" pistons, there may be other issues causing that -- detonation, excessive wear or poor assembly?

    If the OP was considering a Pontiac 326 swap into a GM truck for the street then forged crank and pistons sound like overkill to me. Just depends on how heavy duty the truck's purpose will be.
  • tjb1hamtjb1ham Posts: 2
    I am looking to put a Pontiac 400 into my '72 GMC Pickup (already have both).

    To:num1pontiacman
    You said you have pictures and info to do a stock parts bolt-in?
    Care to share?
  • tjb1hamtjb1ham Posts: 2
    I am looking to put a Pontiac 400 into my '72 GMC Pickup (already have both).

    To:num1pontiacman
    You said you have pictures and info to do a stock parts bolt-in?
    Care to share?
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