326 help - Pontiac GTO Forum
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post #1 of 10 (permalink) Old 12-15-2016, 09:11 AM Thread Starter
 
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326 help

I have a 66 326 two barrel car with 094 heads. I would like to change it to a factory four barrel setup. The heads are too fresh to justify changing. I'm wanting to know if this will work at all and if I will see any significant performance increase. Thanks.
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post #2 of 10 (permalink) Old 12-15-2016, 06:12 PM
 
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Any increase will be limited by the current compression ratio (CR) and possibly the cam. For reference:

1966 326 2-bbl; 250HP @ 4600 RPM & 333 ft.lbs torque @ 2800 RPM

1966 326 4-bbl: 285HP @ 5000 RPM & 359 ft.lbs torque @ 3200 RPM

The cam in both engines has the same I/E lift, though the 4-bbl most likely has different timing events. Both heads use the same size valves, and your 094 heads have an 8.6CR whereas the 095 4-bbl heads have a 10.5CR. Swapping to a 4-bbl is relatively easy especially if going with a factory setup, however with the 4-bbl being the only change you won’t see any significant performance increase.

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post #3 of 10 (permalink) Old 12-16-2016, 01:35 PM
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You will indeed see "some" improvement by changing to a 4bbl. Significant? That depends on what you judge to be significant I guess. It's not going to knock a half-second off your quarter mile times, MAYBE a tenth or so if all goes well.

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post #4 of 10 (permalink) Old 12-16-2016, 02:47 PM Thread Starter
 
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Thanks for the input much appreciated. And the Spec Info.
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post #5 of 10 (permalink) Old 12-18-2016, 05:50 PM
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You can even bolt a tripower on it. Did that in my youth and it was a huge improvement, although a bit overkill. 326's can really run. I say go for it with the 4bbl...ran a Holley 600 with an adapter on a stock 4v intake on a 326 I had and it worked very well. Way better than a 2bbl would have, but the engine had a hot cam in it and headers..........
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post #6 of 10 (permalink) Old 12-20-2016, 09:16 PM Thread Starter
 
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I'm thinking of using a gm 066 equivalent cam with an original manifold and carter carb. Also stock cast iron exhaust manifolds with dual exhaust. What a about changing the rockers to the 1.65s would that help those lower compression heads any? I have a 700r4 with what I plan on changing the 373 gear to a low 300 gear. The car has been ground up restored I unfortunately got some bad advice on the drivetrain. Its got a rough idle, loud headers and loud flow masters, poor fuel economy, And piss poor manners in general. And I'm on the second EFI system and they both equally stunk. Just trying to get back to basics with a "factory feel" to the motor and a modest performance increase. I think it was quicker all tired out with the two barrel on it. Any opinion much appreciated. Thanks.
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post #7 of 10 (permalink) Old 12-21-2016, 07:15 AM
 
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Put a Summit 2800 cam and a properly set up Quadrajet on a 67-72 stock Pontiac intake. Make sure your timing curve is good. Dual exhaust. You will be happy with this set up.
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post #8 of 10 (permalink) Old 12-21-2016, 11:13 AM
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Having built my 461 with 1.65 rockers (and having a problem with them last summer on the Power Tour), I'll share my opinion --- that's all it is, opinion. YMMV and all that. 1.65's (factory on the Ram Air IV's) do two things: they add a tiny bit more lift and duration without having to change the cam, and they also put more stress on all the other valve train components. When I rebuild mine (hopefully soon) I'm going to go back to 1.5 rockers and instead have a cam ground that gives me the lift and duration I want with them. Result: same lift/duration specs but with less stress on all the parts. However, don't think that you can just replace rockers with 1.65's as a low cost way to get a little more out of your present cam. That's because the different geometry (the pushrod seat is closer to the rocker stud) also moves the pushrod lower in the head where it will almost always rub --- so to do it right you have to pull the heads and grind out the pushrod passages anyway to fix the rubbing problem. At that point, you've already done the majority of the work you'd have to do to swap cams. For me, why add the stress to the valve train when I can get the exact same results by using 1.5's and a different cam profile?

You said you're already not happy with the idle quality and fuel mileage. Going with a "bigger" cam (or swapping to 1.65's) is only going to make that worse, not better. As has been said before many times, Pontiacs are not chevys. You can't take the Chinese menu approach (1 from column a, 2 from column b, throw a handful of darts at a Jeg's catalog, etc.) in building one and get good results. You've got to consider everything about the car from bumper to bumper, including what you want it to do (race only, street, highway cruise) and how you're planning to drive it (highway, city, track), including that always a pain question of that pesky budget, and come up with a plan for the whole car. This includes rear gear ratio, transmission, torque converter (if an automatic), braking ("big" cams tend to kill vacuum and thus power brakes), fuel availability (compression ratio vs. octane) and more --- then come up with a plan that fits both your needs and your budget.

It can be done, but you have to think about it. Also the realities of the marketplace will mean that it will be more expensive than building "just another bowtie". Personally though, I find it much more satisfying

Bear
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post #9 of 10 (permalink) Old 12-22-2016, 03:02 PM Thread Starter
 
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Agreed much more complicated than initially thought. I've got a lot of perfectly good parts that just don't work together. Including the rest of the drivetrain not just the motor. Gonna leave the heads alone go back as factory as possible with the motor. Change the ridiculous torque converter and too tall rear gear. And hope they at least got the machining right. It's only money already in way too deep to stop now. Thanks for the input.
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post #10 of 10 (permalink) Old 12-22-2016, 03:17 PM Thread Starter
 
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It would've been too easy to go buy one done. This car probably should have been used for parts it is truly a resurrection. It will be another fine Pontiac on the road where it belongs one day soon.
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, LeMans & GTO Engine Tuning and High Performance

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