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post #1 of 14 (permalink) Old 05-22-2013, 01:30 PM Thread Starter
 
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new to this got a question.

1st off thanks to everyone for the information in the other forums, ive spent days reading and building knowledge looking in proper places for info now because of you guys so thank you. I just got into Pontiacs i bought a 1969 GTO, it has a 428, bored .030 with 455 #64 heads, offenhauser intake, 2x4 afb 600cfm carbs. Thats about the end of aftermarket or stock upgrades. My two questions are 1st i am puting in a 12 bolt rear end, i am stuck on what gears to put in i currently have 3.55, i am running a muncie m20 4 speed. Its mainly going to be a street car, occasionally might hit the track. 2nd i am completely unfamiliar with running duel quads, they seem to be tuned well, should i leave it be or go to a single 4bbl. and if you need to know what cam i am running its a factory 428 H/O cam stamped N
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post #2 of 14 (permalink) Old 05-22-2013, 04:43 PM
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Welcome to the forum,

First question, a 3.73 gear would be good for street and strip and a 4.11 would be good if you plan to spend alot of time at the strip.

Second Question, If you can afford $4.00 a gallon I would keep the dual quads, they are almost as cool as 3 dueces.

Randy


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post #3 of 14 (permalink) Old 05-22-2013, 05:42 PM Thread Starter
 
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Yeah 4 dollars a gallon fine by me didn't buy the car for fuel economy. That being said when I called currie and a few other local shops they all seem to want 3.42, and all said the 3.90 is too low. This is my problem I am running into. I called three big shops all recommended different gearing. So when the experts can't agree do you go with your gut?
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post #4 of 14 (permalink) Old 05-22-2013, 05:45 PM
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I would not go any lower then a 3.55 gear ratio.
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post #5 of 14 (permalink) Old 05-22-2013, 08:34 PM
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With your M20 4 speed and your combo, if it were my car, I'd run 3.23 gears. Great off the line, good at honest highway speeds. With a 428 (heck, even a 389 or 400) there is no need for 3.55 or lower gears, IMO. Not with traffic moving at 75-80mph. If your car was an auto, I'd go with 3.08 or even 2.93 gears. The tallest gear that Pontiac put behind a 4 speed car was the 3.08.....anything lazier is hard on clutches. Just about everyone I know (me included) who drives their car often and has switched from a low gear to a taller gear is very, very happy with the change. Especially now, with the $$$ fuel.
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post #6 of 14 (permalink) Old 05-23-2013, 09:54 PM
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If it's got stock Pontiac rods, you don't want to push it on the RPM. In a 428, 5200 5300 tops - lower than that in a 455.

Since you said mostly street, occasionally race - then I'd say no more than something in the 3.50 range. Agree that 3.23 would be a good "all around" gear.

Now, put some good forged rods in it and we'll talk -maybe- a little more gear, but only with a more aggressive cam, better heads, etc.
Commit this to memory: Pontiacs ain't chevys. They make tons of torque down low and don't NEED a bunch of gear to be quick.

Bear

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post #7 of 14 (permalink) Old 05-23-2013, 10:46 PM Thread Starter
 
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Yes Bear I've been getting a steady lession on they're not chevys. Which it good because I wanted a Pontiac, now the learning curve is much greater then I thought, its been a fun process so far. Plan on having the engine pulled and upgraded in February. Still working on the knowledge part to figure out exactly what I want to do. Ill let the engine builder do his job but I want to make educated choices. Thats where I got into issues with both my questions. Which from responses the duel carb must not be that much of an issue. So where I am at with the gears I keep falling back to 3.42, and its a young and dumb logic I wanted 3.73 or lower. But after reading on this forum and others I started to see Pontiacs didn't need that. But still want low, 1st muscle car and all. But I thank you all for your consistent info, makes it hard to make a bad choice
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post #8 of 14 (permalink) Old 05-24-2013, 08:09 AM
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Good choice - I bet you'll have a terrific car when you get it all going. I love the dual quads just because they're different, and having all that air "on tap" isn't a bad deal either. You've got the potential there for a real screamer. 428's have enough inches to make some serious 'motivation', but still with a stroke that doesn't prevent them from getting into some elevated rpm given good rods and the air flow to get there. Witness Rick Holladay's '65 rag-top in the attached photo that's carrying a CVMS-built .060 over 428 (440) and runs mid 10's.

My own car is a 69, running a 461 (4.250" stroked 400 with .035 overbore) that has run a best of 11.86 @ 113 mph, that's at 3900 lbs "or so", in Drive with the automatic up-shifts happening at about 4900-5000 rpm, running 3.50:1 gears in a Moser 9-inch. At a 70 mph cruise it's turning about 3100 rpm. On the street, even with Nitto 275-60 15 drag radials, I've got to roll gradually into the power otherwise it just blows them away.

Oh yeah, you're going to have some fun

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post #9 of 14 (permalink) Old 05-24-2013, 06:42 PM
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Another thing to consider: the 'big journal' 421,428,455 blocks with the 3.25" mains do not like cruise speeds of over 3000 rpm. They can spin bearings. BTDT with my own 428... and have seen it on other big journal blocks. No problem with a 3" main block like Bear's stroker....that's why stroker motors are so popular: big inches and they hold up better. Stronger block, too. Big journal engines have oiling issues on the mains due to the huge bearing size, and like lower rpms to do their heavy work. That's why I recommended a 3.23 rear gear, or even taller. If you were running a stroker or a 400 or a 389, a 3.42 would be a great choice. Simply not needed with the torque monster 428. Many folks have actually run slower with a 3.50 gear and a big inch block than with a milder gear simply due to traction problems with the stump puller gear. Your car, up to you. If you do run the 3.42 and it revs too much for your taste, you can always install taller rear tires to drop the rpms.
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post #10 of 14 (permalink) Old 05-25-2013, 12:22 AM Thread Starter
 
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Ok I decided not to wait untill February for the motor. Theres a delay to get the rear end by a few weeks so if I am not driving it mise well be building it. Any suggestions on what way to go? What to avoid and what to make sure I do.
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