Pontiac 303?

Discussion in 'Technical' started by 84FordMan, Mar 2, 2008.

  1. Is there any information on this short-deck race engine from the 70s? Shortly I am inheriting a car with a Pontiac 301, which from what little information is available on the 301, is that it is a descendant of the 303, carrying over such items as a two-counterweight crankshaft (Instead of five) and the light-weight connecting rods and just overall less weight than the comparable Chevy 305.

    However due to the uniqueness of the 301 and it being the very last Pontiac-built V8, everyone has given up on it. I don't want to give up on it.
  2. Give up on it. Even the turbo ones lose over a second in the 1/4 to the smogged out 400s and 403 Oldsmobiles they replaced. I have some funny Hot Rod articles from 80-82 on them, basically nothing is usable on a 301.
  3. I refuse to lump it into the bin just because it was a CAFE requirement engine, only maybe if it were a completely retooled engine but Pontiac didn't have time for retooling to meet CAFE requirements. They took a Pontiac 350 and cut the deck height down by around an inch and they took the connecting rods and pistons from the Iron Duke project (Which also happen to fit right in SBCs [6.00" rod length, 2.00" journals]). The thickness of the casting walls was reduced and did not effect normal operation of the turbo and NA 301s.

    The crank had some of it's counterweights removed and re-balanced (At it's ends, not across it's length) to provide quick acceleration and less rotating mass. Single-plane intake replaced a dual-plane for weight savings. To match the intake, the center intake ports on the heads were siamesed and the port sizes decreased over the 350 head to create higher mixture velocities. On bench they found even mixtures at all engine speeds between all cylinders.

    What wasn't modified Pontiac 350, was parts bin Pontiac V8 parts. Timing cover, camshaft, rockers, engine mounts, water pump, water outlet are just a few of the parts I have found so far that are all shared with all Pontiac V8s.

    The Iron Duke was also a CAFE requirement engine, but look at it. A popular engine among midget and grassroots racers, even GMPP with the Super Duty Iron Duke churning out near 400 BHP.

    I am going to have some fun with this 301.
  4. The 301 can't use heads or intakes from other Pontiac V-8s. There is no aftermarket 301 head or intake. There is no reason to custom build everything for a Pontiac 301 when parts are available for every other Pontiac V-8. There is no reason to use a Pontiac 301 to make less horsepower then a 98 Grand Am.
  5. Is there a need for an aftermarket head or intake? That is the real question. As I pointed out, the heads and intake are perfectly matched. Even fuel and air distribution to the cylinders, exhaust gas temperatures the same on every cylinder.

    As for volumetric effeciency, that is a blank to me, because, to my knowledge, no one has ever put a 301 head on a flow bench. The comments people make about the 301 head remind me of the Ford 300 cylinder head, stock restrictive, but when cleaned up by a professional machinist, flows quite well, not quite as well as the crossflow 300 or NHRA 300 cylinder head, but far better than stock.

    As for the intake, actually did a little more research on it and I found someone along the way had designed and sold adapter plates to mount the single-plane 301 intake on 350/400 Pontiac V8s, basically to swap the 301's turbo setup over since the turbo itself was unique to the intake design.

    The next thing I thought about was the 4-bbl Quadrajet M4ME they installed. If memory serves from all the articles I've read over the years, the factory Quadrajet is rated about 700 to 800 CFM. On a 301 that only spins up to about 4,500 RPM, a 800 CFM 4-bbl carb is overkill, at 100% VE, it's only drawing in around 450 CFM. Overfueling and the 8.2:1 compression ratio hurting things?
  6. The heads and intake are made to go with the tiny cam and low compression they got. Even the hotter stick shift cam had under .370 gross lift. You can't port the heads much at all, they are ultra thin to save weight and have almost no deck to grind off the bottom to reduce the massive 72cc chambers. The quadrajet is totally reworked just for the 301, and since it's a quadrajet it can't overfuel regardless of cfm, as long as the metering rods are correct.
  7. So you say the 301 is junk and incapable of making power? Just through more research I have found two people who disagree with you. One being Herb Adams, being a GM guy you should know who he is, in case you don't, he created the Trans Am and went on to work as chief engineer at SLP. Apparently he fathered an article about the 301, stating in full race tune, it is capable of generating up to 500 BHP. So we jump from speculation.. to fact.

    Someone out in Fort Lupton, Colorado wanted to race his Firebird in SCCA and class limit is 305 cubic inches. He could of run a SBC 302 or 305 and be fine, but instead, he picked up a 1980 301 for a little over $100. Disassembling it, he found alot of the same I had found in research. Yes the bolt pattern for other Pontiac heads IS THE SAME as the 301s. The only reason why you see the note in Edelbrock and Holley's catalogs about "these heads do not fit 265 or 301s" is the valve clearance. This particular owner went with a set of No. 16 Poncho heads, small valve variety (1.95/1.66) and required only minor chamfering to the block for valve clearance, beyond that, they bolted right up. Here is the remaining modifications:

    Crank: Stock, shot-peened, chamfered, polished, relieved.
    Rods: Eagle Alloys H-beam 283-327 6.125" Chevy, with the offset machined out of them to fit the pontiac crank.
    Pistons: Ross, custom ordered for No. 16 heads, 12.5:1 Compression at 4.030 bore.
    Camshaft: CompCams Pontiac 51-244-4 with Howards Direc-lube lifters.
    Heads: 1966 Pontiac No. 16 casting, with 2.04 intake and 1.66 exhaust, ported, polished, and relieved around pushrod holes. Also equipped with hardened valve seats with a three angle valve job, and waisted stem Manley valves.
    Intake: Narrowed Edelbrock Torkker II pontiac.
    Carburetor: Holley model 4150 750cfm.
    Distributor: Mallory Ulilite, Pontiac. With make-to-fit Mallory 8mm silicon core wires.
    Headers: Heddmann Pontiac Tri-Y with 3" collectors.
    Exhaust: 3", exit in front of rear tires, with 3" crossover.

    Total output measured on the engine dyno? 476 BHP @ 6,000 RPM and 451 ft-lbs @ 4,500 RPM.

    Also found a High Performance Pontiac article in which they put a 400 crank in a 301, May 2007.

    "Starting out life as an '80 Turbo 301 block that carried a 4.0-inch bore by 3.0-inch stroke, a stroker short-deck combination was crafted that resulted in a 359ci combination when factoring in a 0.030 overbore. A Pontiac 400 crank was chosen and sent to Edward's Auto Machine in Wilmington, North Carolina, where the 2.25-inch rod journals were reduced to 2 inches, and the crank was destroked from 3.75 to 3.52 inches. Back at the Carter's shop, the crank counter-weights were turned down nearly 5/8 inch to provide proper clearance and reduce weight before the rotating assembly was balanced.

    Scat 6-inch, small-block Chevy (SBC), Eagle I-beam rods with 2-inch rod journals were chosen, and the Carters assembled the engine using ARP rod bolts and Clevite 77 bearings. KB Hypereutectic 0.030 over 327 SBC pistons with 0.125-inch raised domes provided the proper deck height for this combo...."
  8. I never said a 301 couldn't make power, I said "There is no reason to custom build everything for a Pontiac 301 when parts are available for every other Pontiac V-8"

    For the money they spent on custom pistons, narrowing the intake to work on a shortdeck motor, and machining the rods the 1st guy could have started with a 400 or 455 and ended up with more horsepower and drivability.

    The 2nd guy spent a lot of money to use a 400 crank to get 359ci, when he could have spent way less on simply using the whole 400, and had a better start.
  9. And valve clearance isn't the reason behind the edelbrock heads not fitting 301s
    The 350 has a smaller bore then the 301 and the 389 has only a very slightly larger bore.

    The real reason is the 301s intake doesn't line up to the edelbrock head ports
  10. He (The first guy) could have, but then he wouldn't be able to race the car in the 305 and under class restriction. Kind of hard to pass a 400 or 455 past the tech inspectors. And if he had done a little more research like HPP did, custom machining the rods and custom order pistons would have been unnecessary. 327 and 350 pistons are drop-in. A simple compression ratio calculator could tell you what piston and rod combo would get you in the 301. Set of Eagle I-Beams, $268, set of KB hypereutectic pistons, $250.

    No machining required, just drop-in. Just because it's not listed in any catalogs as fitting the 301, doesn't mean it's custom build, because parts available for every other Pontiac V8, fit the red-headed, lightweight stepchild 301.
  11. The 2nd guy managed to use them in his offset ground stroker because he had already customized a crank to work with the 327 compression height and and narrowed the rod ends, that are offset differently then Pontiac. Hell, the 327 and 350 pistons don't even interchange with each other, let alone fit the Pontiac without mods.
    Plus the Pontiac valve angles are different then Chevy, and when your getting 12.5 to 1 compression using big pop-ups like he did, that makes a huge difference. He did what he had to do to get under 500hp, which was a lot of custom work that would have been avoided by using a proper motor from the start.

    You aren't class limited, you have no reason to build a 301.
  12. Interesting thread. I'm a newbie here and trying out my wings. Not sure if this is working yet. I agree with both in that the 301 isn't very popular, but has its benefits, depending what you're looking for.
  13. Hello and welcome. I sincerely hope you're a genuinely new member and not yet another second account. If you haven't done so already, go to the new member introductions forum, and read the Tips for n00bs thread. Also, don't post pictures in your signature. It's a bit obnoxious. We get it, you like turbo pontiacs. Stick to a short quote, or nothing at all. Cheers! <A BORDER="0" HREF="http://www.supercars.net/PitLane?displayFAQ=y"><IMG BORDER="0" SRC="pitlane/emoticons/smile.gif"></A>

    Also, don't bump old topics unless you have something interesting or useful to add. Thanks.

  14. I was trying to be a new member, but I guess you guys are exceedingly anal in your demands and really don't care about anyone but yourselves.So if that's the way you want to be, take your weird sponsers and "Foxtrot Oscar".
  15. this is pretty much the only serious forum on these boards. He was also just trying to be helpful to keep you from getting flamesauced mercilously.
  16. This is what I get for trying to be helpful in the Technical Forum.
  17. Why would anyone want to work on this engine?
  19. i like this diagram
  20. Don't give up on the 301, there is hope. Here is what needs to be done, get 400 crankshaft, turn the rod journals down to 2.5 inches in diameter to 2 inches and destroked from 3.75 to 3.52 inches. Use 6 inch Small block Chevy connecting rods with 2 inch rod journals and small block Chevy 327 pistons of what your choice of overbore is..030 overbore will give you 5.9 liters or 359 cubic inches, .040 should get you into the 6.0 liter range. The biggest drawback are the Siamese port heads, a good set of conventional Pontiac d ports heads would be a good starting point, say some 6X-4 heads used on 77-79 W72 400 and 75-77 350. The intake manifold now is the only issue because of the 1 inch shorter deck height of the 301, maybe a the choice. Most of this info can be found in the May 2007 issue of High Performance Pontiac Magazine which you can pick up on ebay. This basic procedure was done on a 4th gen Trans Am and fuel injection was added as well putting out 300rwhp at 340 lb-ft torque.

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