What gears ?

Discussion in 'Drag Racing' started by Rudydog, Jul 28, 2015.

  1. Rudydog

    Rudydog Member

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    Getting ready to pull the trigger on a 9" gear, just haven't decided what gear to go with. Bought a rear with Moser 35 spline axles, and a locker, a set of Cal-tracks. Pump gas motor, but will hit the track alot. I won't be driving it down the interstate so 4.11 or something in that area is not a concern. Lookin' for help

    My car: '73 Comet street and strip car,
    363 ci.
    9:71 cr
    AFr 185 heads
    Comp cams hyd. roller .565-.574 lift , 282-290 dur. 112 sep.
    RPM air gap w\750 HP
    C4 3200 stall(we'll see)
     
  2. Maverocket

    Maverocket Bob Williams

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    How tall of a tire are you running?
    1/8th or 1/4 mile track?
    What is shift RPM?
     
  3. groberts101

    groberts101 Member

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    Assuming this is a .060 over 351W motor, which has a smaller bore/longer stroke than a big bore 347 would have, I would stay more conservative with the rear gear or you'll risk outpacing the cams available rpm range. Keep in mind that your car is light and 3.70's would be a pretty nice setup with the cam you have there. The dual plane and stall choice you mentioned will also compliment it as well.

    Much more gear than that and you'll want a bigger cam to take advantage of the higher rev range and then the stall speed requirement will also go up as well.
     
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  4. Rudydog

    Rudydog Member

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    It's a Dart SHP block 4.125 bore and 3.400 stroke. 8.200 deck.
     
  5. Maverocket

    Maverocket Bob Williams

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  6. Rudydog

    Rudydog Member

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    1\4 mile and 28" Tire.
     
  7. groberts101

    groberts101 Member

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    Ok, so you say you want to go to the track a lot and don't necessarily care about the downsides of a short rear gear. But does that mean you don't care about rpm ranges remaining just a tad more civil for the street? Is this going to be a trailer queen with pure slicks?

    And you do realize that an air-gap is not typically used with 4.30 rear gears, right? There's a major reason for that. They don't breath well enough to rpm a big bore 363 where that short gear really likes to run. The more serious guys will always have a single plane matched up to a 250+°(@.050) cam with your combo. Just depends on how fast you want to go?(more like how much you're willing to spend?), and how much sacrifice and compromise you don't mind giving up to get there, is all.

    And then there's the bigger issue of engine wear and tear to consider as well. Really short gears with loose stalls will have you slip sliding around and cruising around everywhere at 3,500 rpm and eventually takes its toll after a while. Not even remotely saying don;t do it because it sounds like a blast to me but do you plan on re-ringing and freshening this thing up every year or two?.. or do you want to play for a bit longer before digging back into it?

    So, and no disrespect intended here, what kind of quarter mph are you looking for out of this combo? As much as possible as in.. strip only? Or to simply maximize what you already have for a hot street/strip setup?

    Ok, let the bench-racing session begin. Assuming you want to go as fast as possible with your long block(and even though the heads are on the small side and will need kickass springs.. and also assuming the internals are built "power-adder strong" to do so).. you'll need to get into a more aggressive camshaft profile with a tighter lobe separation angle, more lift(around .650'ish),and considerably more @.050 duration of around mid 250's - 260° or so. Put a Super Victor on it matched up to a 4.56 rear gear, hell, why not even a 5.13 gear?, and you have a solid 10 second beast under your right foot. Extremely fun for sure but a bit on the temperamental side for quick jaunts to the corner store. Your suspension and drivetrain cost will start to go sky high to allow hooking that thing up and you will be into that motor every year or so to insure that it will all stay together as intended. Speed costs.

    Assuming you want to maximize what you currently have there for the current parts combo?.. lose the dual plane and run a Vic jr with a 4.11 rear gear and TRUE 3,800 rpm stall converter(which will likely be advertised as a "4,200 - 4,400 stall speed"). And badda bing, badda boom, quick and easy high 11's that can be daily driven if your into it. Cheaters will be required to get the power down but it'll last you a while with that 6,200 rpm or so peak power number. I'd still really like to see a bit more cam duration though.
     
  8. Paul Allen

    Paul Allen The Maverick is back!

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    Good advice. You really need to decide what you want to use the car for, street strip, street with a little racing, or all out assault with little drivability.
    Things you gotta decide early, drivability and budget. I think these two things have to be decided first. Everything else falls in line after that.
    Have fun! It's a great time!
     
  9. Rudydog

    Rudydog Member

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    Yeah I know, this isn't my first rodeo as I'm 50 yrs old. I intended to keep this car in the 2500 to 6500 range. Cam, intake and heads I thought were a decent match with the pump gas compression I went with. I was just looking for the best gear for my present combo. Drivability is not a big deal. I've had a low 11 second street car, not a daily driver, but a pretty fast car for a .030 over 351w, but with a hotter cam, intake and head combo with 4.30 gears. It went down the track many, many times to a best of 11.27 and very drivable and reliable. Just lookin' for advice.
     

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  10. Paul Allen

    Paul Allen The Maverick is back!

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    You want to go 1/4 mile with a 28 in tire. A 4.10 should get you in the rpm range you desire. I would not go more than that. I would most likely stay in the 3.73-3.91 range to maintain driveability.
     
  11. aussie maverick

    aussie maverick Member

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    I recently grenaded/split a xxx windsor 347 engine....pretty common I hear.lol. I'm currently getting a shp 4.125 363 built, hoping that it will last me a good while. Lunati crank and h beams, trickflow cam 304/308 duration with 595" lift, heavily modified 195cc pro comp heads( the only thing pro comp is the castings) weiand accelerator single plain 750 mighty demon. Convertor is Hughes 3000 rpm, and 3.80 rear gears. All I want is a reasonably stout street car that I can drive to and from the track and run an early to mid 12 sec quarter. Am I expecting too much from this combo? Cheers. G Roberts I really like your replies to everyone on this forum as you seem very knowledgable and down to earth. And would love to get your feedback / advise
     
  12. groberts101

    groberts101 Member

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    Ouch!, hopefully you didn't drive over the pan when it happened. Not entirely uncommon and pretty easy to surpass the stock blocks power threshold with that particular stroker combo. The heavier thrust loads from higher rod angles only adds insult to injury as it eats even further into the safety margin. At work now so you don't get my usual 1,000 word response this time around. Lol

    Short answer is this. Lose that little manifold and step up to a bigger one that can breath nearer the heads/cams potential flow levels. Heavily ported Vic jr or even a mildly ported Super Vic would easily pick up another 300-400 rpm of rev range due to the larger port cross sectional area and larger plenum volume. An easy 20 horsepower or slightly more. And that's a fairly stout cam for a measly 3,000 stall speed. 600 -800 more rpm will wake the midrange up and help reduce rpm drops during shifts. Also keep in mind that the bigger you go on the intake manifolds port cross sectional area.. the more stall the combo will like. I would even lean upwards of 4k stall speeds for the Super Vic combo. Far too often guys get too scared to run higher stalls on the street but the reality is that the converter only ever stalls that high at wot/full flash speed. Otherwise you can snooze it around town around 1800 rpm without issue. Just add more trans auxiliary cooling capacity and life is good.

    What mods you do to those Pro comp cssting? Sleeved with offset pushrods too?
     
  13. Cruzin Illusion

    Cruzin Illusion Enigma

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    I have a 363 striker and a 9 inch in the rear. I am running 3:89 gears. I was looking for a happy medium. I am also running a Lentech AOD.
     
  14. Adrian Way

    Adrian Way Member

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    I have the same bore stroke combination in my Mustang II. Love it! Dart heads full race chassis. Solid roller deal on injected alcohol. 32X14.5X15 tire power glide trans brake. I shift at 6900. Currently I have a 4.56 gear to calm the car down at launch a bit to win bracket racing......faster with a 4.88. 5800 to 6000 stall converter trans brake dropped at 4600 shift at 6900. Runs 5.80's 1/8 mile bracket racing. Good Luck
     
  15. aussie maverick

    aussie maverick Member

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    The heads have lots of bowl work for more plug exposure, swirled intake ports, k- line bronze guides,arp studs Manley valves triple cut seats. I have a funnel web intake manifold, but won't install it as I can't bring myself to cut up the grabber hood! I know the manifold is a sore point for the engine, but assumed its a better option than destroying a hood. It has been match ported to the heads. The reason I only went with a 3000 stall is simply for driveability on the street and to keep trans temps down( trans has deep b&m pan and external cooler). I know there is room for a lot more power with a couple of small changes, but I think this combo should still be good for a mid 12 which I think I will be happy with for the moment. The higher stall speed could be a wiser choice after reading this advise. Thanks for your input mate
     

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