stock 302 crank

Discussion in 'General Maverick/Comet' started by cityboy, Jul 7, 2003.

  1. cityboy

    cityboy Member

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    How many rpm's do you think a stock 73 302 can take without breaking.
    Also, how much nitrous oxide can the stock rods and crank take after I have them checked and reconditioned and new rod bolts added.
    I would like to use 175 or even a 200 shot. Also, I am going to use forged pistons and a main girdle.
    I will be able to fix or replace 302 parts as opposed to a stroker motor if it comes apart.
    I am not sold yet on how much more power a stroker or 351 will make over a 302/306.
    Thanks Steve
  2. PINKY

    PINKY .....John Ford.....

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    I have been doing alot of research on NOS. The BIG problem people run into when running NOS is their fuel system. If you do not have enough fuel, you will run lean, and thats bad. I have a chart at home that gives you the amount of fuel needed to run NOS according to the shot. If I remember correctly a 150 shot requires 7-8 PSI of fuel to be used safely. I would not recommend running NOS on a stock fuel pump. Get you a Holley "blue" or better with a fuel pressure regulator. I am always reminded of the words I read in a magazine: "error on the side of over-kill". Good luck.
  3. Darracq

    Darracq Member

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    Re

    My friend turns his 8000 to 8500 all the time im not joking. It has been going for 2 years. Races most weekends. Shifts at 7500 most of the time. Roller camed victor jr headed .060 over 302
  4. bmcdaniel

    bmcdaniel Senile Member Supporting Member

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    Like Maverick 5946 said, you don't want to go lean. You also don't want the nitrous to flow at too low rpm and the timing needs to retard. A good nitrous controller like the Jacobs Nitrous Mastermind is a good place to start. Forged pistons and reworked rods are necessary for the power level your talking about and a steel crank is also recommended (not necessarily billet, cast steel should be ok). I'm running a stock crank, rods, cast pistons, and a Carter high volume mechanical pump, but only with a 125 hp spray. Timing retards 6 deg, rev limit set at 5000. My car is a cruiser, not a bruiser, the cam tops out at 5000 rpm. The Jacobs controller babysits the motor for me so I don't hurt it. It is also very important to run a high energy ignition and electronic switched distributor- no points because they bounce.
  5. mavman

    mavman Member

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    I seriously doubt you'll break a 302 crank. I personally have never seen one let go. It's usually the block that breaks first at around 600 HP.
  6. CometGT1974

    CometGT1974 Gearhead

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    Mavman is right, it's not necessarily the crank that is weak. The weakest link in most "HIGH" horsepower (302) applications is the block. I have seen the front of a block split apart and that allowed the front of the crank to break. This was on a motor that had well over 100,000 miles on it and had seen many, many bottles of nitrous but nothing bigger then a 150 shot!!
  7. bossmav

    bossmav Drag racing nut

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    I agree, but doesn't the block crack from the side load after the crank starts to walk from the extra pressure of NOS? If you don't have the bottom build strong enough to hold the extra horses the block and crank can give away. Just a thought!


    Terry Gates
    AKA Bossmav
  8. Lightning

    Lightning Member

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    Same here I have only seen one windowed 302 . It was behind a 4 speed that let go in the air .
    Still ran though ...........kinda cool actually
  9. Old Guy

    Old Guy Member

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    Crankshafts etc.

    Thought I would put in few words here, stock cranks are pretty tough little buggers. Have one in mine that is over ten yrs old and has been dragged raced for all that time, anywhere from 6 to 8 thousand burn outs and currently being shifted at 7200. This is on the motor only, laughing gas is not my thing. Would advise to radius the oil holes on the journals and make sure the end play is correct. When I build a bottom end I snug up all main caps except the thrust bearing, pry the crank foward and hold it then tighten it down. this aligns the two bearing shells so the crank can move back and forth as required. Torque the bolts or studs, in two or three incremnts of the total torque for which ever ones you use. I would invest in a good set of H beam rods with the 7/16th bolts bottled gas can be a real grenade on stock rods and puny bolts along with the slugs attached to them. Reminds me of the old commercial of "Pay me now or pay me later ":D Have also blown to stock balancers apart this year at 7200 rpm so got a semi cheap fluid unit off ebay and did see some vibrations go away. Just a few things to think about.
  10. cityboy

    cityboy Member

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    Old Guy,
    Thanks for the info, I will look @ all of these things and if you or anyone else have any more suggestions, let me know.
    Also, what do you think about notching my shock towers and putting in a 351 windsor?
    Thanks Steve
  11. mavman

    mavman Member

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    let's see..the 302 is lighter, smaller, etc, and can be stroked to 347 easily. BUT, if you ask me, the 351w is a MUCH better engine. Had a 393 last year in the bracket maverick, ran well...but the stock rods aren't all that great (even truck rods). Went to a a stock-stroke windsor this year, so far so good. Also runs just as well, if not better than the 393 did. Headers are a PITA though, though I'm seeing that the 6208 Hookers fit ok. STill have to notch the towers, though I think, could be wrong. Oh by the way, Old Guy says he's not had any crank problems with 8000 rpm shifts....well I used to burn out (just for giggles) at over 9000. Once saw the tach flash to 10 once....but never wanted to do that again for fear of breaking the converter/trans etc. Yes they're tough!
  12. bmcdaniel

    bmcdaniel Senile Member Supporting Member

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    Cityboy was asking how his stock crank would hold up under the effects of a 200 hp shot of nitrous. In my earlier reply I simply repeated what the nitrous kit makers suggest for engine longevity (a steel crank). All the talk about 7000, 8000, & 9000 rpm shifts don't mention the use of nitrous. Nitrous imparts a tremendous spike in cylinder pressure, often described as a pounding. Normally aspirated engines actually see a decrease in cylinder pressure after peak torque rpm (not as much time to fill the cylinders). Like others have said in this post, better to overkill, especially when using big shots of nitrous.

    A good nitrous controller brings the spray on more gradually according to rpm instead of just hitting a button and having full nitrous flow at all rpm's. This is really critical at low rpm's. At low rpm the cylinders have more time to fill up so cylinder pressure and "the spike" are more pronounced, and destuctive.
  13. fordman

    fordman Member

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    i run a std 302 stock crank i give it hell just about every sat i break a bell housing ever now and then but aint the crank
  14. bmcdaniel

    bmcdaniel Senile Member Supporting Member

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    :) I like it!

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