FrontEngineDragsters.Org Forum
Drag Racing Discussions => Front Engine Dragsters => Topic started by: grapro on April 23, 2014, 06:01:20 AM
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Looking at purchasing a complete center section from Strange and have used all the calculators and have a bit of confusion. don't want to rev too high and been talking to some of the local racers and debating between a 3.89 and a 4.11. Just running a small block 355 alcohol injected with aspirations of maybe some nitro someday and wondering what is common for a ratio.
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What HP level, MPH, tire size, and RPM's are you going to spin the engine
when I ran injected alky 8.20-40's in my FED I ran 4.30's and 31x11 tire
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Injected SB generaly runs NE2 (8.60 @ 155) but still more info is needed
Are you running a trans? what gearing is in the trans? how much does the car weigh with you in it? where is the listed "sweet spot" on the cam? 1/8 or 1/4 mile? what tire? most converters slip 10/15mph on the top end. The difference between gear changes is around 200rpm
I would not go taller than 4.30"s
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I am running a glide with a 1.76 and have a 30 x 10 tire. Motor is fully balanced and printed 355 with built aluminum heads used to run it at 7000rpm in my truck but not that crazy anymore and going to alcohol with it now. would like to keep the rpms to 6000 for starters, 5000 stall in convertor has a brake but not sure if I will use it at the beginning, not quite sure of the car weight but a pretty basic fed. I am new to all of this just hoping to find a happy medium in the gears, will buy a pro gear set with large stem pro gear pinion, parts are all too close to my privates to buy brown paper gears as I already had cancer down there and don't want to lose them now to cheap parts. But not quite sure of which set to start with. Novice to all of this.
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We run a powerglide with a 1.69 first gear.
4.30 gear in a 12 bolt.
Goodyear 2585 31x12
I use to leave off of a transbreak and 2step but found that my 60' times are way better when I swap feet at first sight of amber. 1.07 - 60'
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Why are everybody afraid of rpm ? A smallblock dose not really make any power till it's over 6000rpm ! My son's 565 big block crosses at about 8500 Just sayin .
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I run 5.43:1
32" tires for the strip and 34.5" in the sand.
I rev the snot out of it.
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Cajun...what rpm through the traps?
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Quarter mile is 8400+-
That's not too high in jr fuel though. Some shorter stroke motors cross at well over 10. Maybe pushing 11
I've talked to guys that have 7" converters that stall over 8000!!!
All boils down to $$$
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I posted allot of info on this subject, but it's not here ?
Most Heritage Jr Fuel teams have 7" converters, and most stall at 8300 to 8700, except Park's which stalls at 9200.
And yes we shift at 9500 to 10500, and cross finish line about the same.
But I'm sure that's not what you are looking for.
Maybe my post with tire, gear, converter, and motor combo recommendations will show up later.
Too bad. Just trying to help !
Jon Hansen Hayden ent
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Why are everybody afraid of rpm ? A smallblock dose not really make any power till it's over 6000rpm ! My son's 565 big block crosses at about 8500 Just sayin .
They have never ran alky dragster. 6500 to 7500 off line change at 10,000. Now sbc love to be spun unless it all crank motor. My problem has always been I love to spin a motor upwards of high as heck(see Glen caught myself).
I agree no need to spin 10k on most stuff.I have never understood why folks get excited about 8500 or so on a motor thats built for racing.Heck I spin my Harley to 7000 and most street engine I have ran I would hit 8000 and never blink.
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Im running 4.11 as a happy medium. Need to be consistent with my deal mostly brackets. I figure 3.90 would work but would rather have more bottomend.The 4.30 would probably be better for et except on some of the crappy tracks around. So 4.11 happy medium. IMO gear change is fairly cheap tuning tool.Pro gear about 350 after lightened and on grand scale of what you spend thats pretty minor.
Will be running 1.69 low PG also.
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Why are everybody afraid of rpm ? A smallblock dose not really make any power till it's over 6000rpm ! My son's 565 big block crosses at about 8500 Just sayin .
They have never ran alky dragster. 6500 to 7500 off line change at 10,000. Now sbc love to be spun unless it all crank motor. My problem has always been I love to spin a motor upwards of high as heck(see Glen caught myself).
I agree no need to spin 10k on most stuff.I have never understood why folks get excited about 8500 or so on a motor thats built for racing.Heck I spin my Harley to 7000 and most street engine I have ran I would hit 8000 and never blink.
Very nice, I run 3:70, running a stock block Pontiac 462 does no like high RPMs, run through the traps at 6500 at 162
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We are running 3.54 behind the big Ford & Turbo 400 & 33 " tire . I have a lower launch ratio than Glides & low ratio rear gears. I get a good 60ft. without having to buzz the motor in the lights.
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Running a 4.30 in mine on a 33 M&H. Launch @ 3800, shift @ 6500, cross the stripe@ 7100. I run a stroker smallblock mopar, so I don' t care to twist it as hard as if it were a 340. I have thought about going to a shorter time though, just because it seems like all of the tracks are running super- pro on the. 1/8 mile now.
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I’m not an FED guy but this seems pretty basic. Sounds like your going to waste a bunch of money, then spend some more. First I would spend the money to put it on an engine dyno to find out what you have for power and torque. There is a big difference between running the motor in a 3000+ lb truck and a 1400 lb dragster. Initially, set the car up to run at it’s maximum potential, you are going run it there at some point in time. If your going to try to use the converter out of your truck, forget it, you won’t be happy. If you ran this motor on the street you are probably talking 10.5:1 compression and maybe 500 hp if it’s well prepped. Rpm wise it’s probably all done between 5800 and 6200. Now that you know what your engine can do you can set the car up to run at maximum potential, determine what maximum rpm the engine will run out the back door, lets say peak HP plus 1000 rpm,, from the number above that’s about 7200 rpm. Next look at tires, what is everyone running. Running a street engine you’ll be on the lower end of the power curve. You have a choice, select the tire based on what power you have or select one that suits your combination in the future. Now select the rear gear. Realize that different manufactures tires grow at different rates. For this exercise lets say the growth is 1.5 inches at 150 mph, add 3” to the diameter of your tire and calculate the circumference of your tire at speed. Manually calculate the rpm out the back door. A good 7” race converter is going slip about 2 ½-3% down track, that’s 250 rpm at speed, subtract that 250 rpm from the 7200 rpm and recompute the rear gear ratio at 6950 rpm. Time for low gear, the more power you have the less gear you need. Ask around, what gears are they running. To determine a 1st gear launch ratio ( 1st gear ratio x rear gear ratio example 1.96 x 4.11 = 8.05). If you have less power you will have to run more 1st gear, 2nd gear is whatever is available, if you have a choice probably the higher ratio. Don’t worry if its more than everyone else, its based on your power and you are only there for a second. Where to spend the money. Dyno 1st $500-$750, torque converter, you’ll need your dyno sheet for this $1000-$1500, if you can find a good core you can send it back and for about $500 they’ll rework it to your requirement. See if you can find a set of good used tires that will work $100-$300, Rear gears depending on what is in the car now, you can buy ring gear sets for around $150. Learn how to set up the rearend gears yourself. I don’t know about transmission gear sets but, probably about the same as ring rear sets. Become an expert on changing gears for your combination, its not that difficult. If you haven’t bought the alcohol setup, don’t until your ready to switch. Having said all this, race what you brung and use a rev limiter and chip it down. Just my $.02
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What has not been said is are you going to run and INDEX class or an OPEN ET? If you are planing to run a comp style/handicapped class you must go with what is described above, Being a self proclaimed novice I would think that you are planning to be more of an INDEX/Bracket racer, so all that above info does not help you that much unless you have monies to put into dyno time and for that cost, one could get the gears changed and get some money back from the previous set. Stick a 4.30 in it and learn how to make what YOU have work-- that is your first step into this thing.
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Mark williams has an online calculator that is very helpful when picking a gear and tire size .
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Everyone is not you. Everything is a factor to consider. I would start with a clean sheet and lay it out here or look at some online calculators.
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I calculate the peak RPM for power which is where I want to be at the finish line from the cam duration specs at .050" I use figures I gleaned from 40 plus years building motors. I gear the car for that. Currently I run a 3.91with 29.5s and am very happy with it. Tach is right where I want it in the eyes.
don
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