Messages

1

Rear Engine Dragsters / Re: RED setup

« on: June 11, 2014, 05:15:40 PM »

Back from the dyno. Engine made 1000 teens at 9400-9600 and still had 540#'s plus torque at 9400 rpm. Peak torque 7900-8100 just shy of 600 ft lbs. Would like to stay under 10,000rpm out the backdoor. Going to start with a 4.71 gear with a leave ratio of 10.5:1. Hoosier 33x12x15 tire on 12" wheel, tire pressure 6 3/4, leaving at peak torque with 70/30 weight distribution, car weight at 1530#, wheeley bar 2 1/2-3" of f track. will probably short shift 1st gear about 9000 rpm, 2nd about 9600 rpm. Assuming converter stall 8700-8900 rpm. Engine configuration is a little odd but we are trying something other than what everybody else is doing. If it doesn't shake the tire, I'll probably have to check the drivers shorts at the end of the track. Even if they are dirty, i'll bet he'll have a big grin on his face. What is the is the prefered way of controlling tire spin/wheel speed? Power? air pressure? rpm? I think I would like to see 690-700 rpm at .8 sec after transbreak release if the tire will hold it. We've been 670 rpm with a 1.025  60' on that tire/wheel combination before but not with this much power.

2

Front Engine Dragsters / Re: What is everyone using for as a gear ratio

« on: April 25, 2014, 07:36:06 AM »

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   

3

Rear Engine Dragsters / Re: RED setup

« on: April 23, 2014, 05:44:39 AM »

Ricardo, 10.5's 10 years young at 10 lbs. thats traction alright. having done that, when you go back to the track and the conditions are the same what are you going to do? Hey guy's help Ricardo out, landings from this altitude are not fun. My avaitar. Setup was 6.5 lbs of air, tires were Hoosier 12x33x15's on 12"wheels, launch rpm was 7500rpm. This was a test session with a new driver with a under power mule motor (307 ci, 650  hp), on a good track, good weather. In our case, one change at a time. We put 20 lbs of weight in the nose. Right or wrong ? Not enough power to turn the  tire? Next pass still pulled the front a bit but went down the track at 177 mph 7.76. 60' was junk. What else should we have done, anyone? you make the call? higher/lower rpm launch, more/less air pressure, more weight in the nose. car weight was 1565 lbs, weight, bias was 75.1/24.9%. Moving 20 lbs to the nose changed the bias to 74.8/25.2%. Anyone run the 10.5's or the 12x33 on a 14-16 wide wheel? what air pressure.

60' comment: definitely it should run sub 1.0's, the question is how to do it. the fast guys in the class are running 500 ci pro stock motors or 480 ci power in B/DA with 60' in the 1.02 range. There is a C/D that went .96 and a C/ED that runs consistent .99's in 60'. with the exception of the B/DA cars these cars are probbly within 40lbs and 100 hp of one another and they have done it on the 12x33x15 tire. One question is where is the transition between large and small ci power that allows you to give up .02-.04 on 60' using a bigger tire and pick it all up down track. comments anyone?

4

Rear Engine Dragsters / Re: RED setup

« on: April 22, 2014, 10:08:55 AM »

Yes, of course, as well as the weather, engine power aviabable, tire pressure etc.. If the starting line is junk the bias tire probably won't do well either and you'll have to detune. A good tool to use is your experience. Walk the track along with crew chief before competition starts, Grade the track and starting line on a scale of 1-5. Crew Chief checks starting line again before burnout and sets final air pressure. After burn out crew chief grades the the starting as he guides the car back to starting line and sets launch rpm if its different than you predicted. If you are at a national event try to catch one of the top fuel guys when they are evaluating the starting line. I think with your experience you could add a bunch more. Be consistant in your preparation and remember you are racing the track not the guy in the other lane. 

5

Rear Engine Dragsters / Re: RED setup

« on: April 22, 2014, 05:46:19 AM »

I tend to agree with all that you have said. The radial was developed for cars with suspension and a RED has virtually none except chassis length and tires. The whole issue is getting it off the line, as the tires are built to dead hook and if you break them loose they may not recover. I think it still has to do with tire management in the first 5’ or that first .5 seconds from transbrake release. Lets say it takes .15-.25 seconds from brake release until it hits tire. At that point the bias slick is wrapped up and starts to spin about 1-2 turns before it catches and leaves on the edge of breaking loose. The radial on the other hand dead hooks and spins and catches itself or driver pedals it, in any case, lets say it recovers but to much time is lost to post an acceptable time.  My thought is that you would want to manage that point in time at launch as it starts to spin that 1 1/2-2 turns to allow the tire to recover, get up on the tire and hopefully have enough wheel speed to continue the launch without breaking the tire loose (kind of like a super comp launch but not quite, a pfft+). If this was the case, I think you would want the softest compound, widest tread and the lightest radial you could find. I would also think about swapping out the legal ignition and plugging in one with traction control (test only) to see what the rpm, trans output shaft rpm and wheel speed needs to be to launch successfully. Having said all this it could very well indicate that you need a different converter or tire and compound and rear gear to make it work on a RED. Sounds tedious, but interesting. Thanks for the info. Anyone else have some insite and want to share?   

6

Rear Engine Dragsters / Re: RED setup

« on: April 20, 2014, 12:06:59 PM »

I tend to agree with you regarding the wheely bar. I may have to use it as a crutch to get the car to leave properly, but personally don't care for them. I think you can get most slicks, within reason, down the track by manipulating launch rpm and timing, the question is: is that the ideal combination for the quickest ET. I also tend to agree with you regarding radials on a dragster. You'll not find the answer in 1 or2 laps down the track, it may take hundreds. My thought is how do you make them work? We use the bias belt slicks and spin them just enough to get the car moving and the correct wheel speed for that combination. Radials don't like spining and have a poor recovery. You would like the tire on the edge of breaking loose all the way down the track. Take a C/ED short deck sbc that is 307 ci and makes 800 hp vs this combination. The power to weight ratio for the C/ED would be .521 while B/DA  combination would be .668 both at the same weight. Both classes of cars have run the same tire, 12x33x15. What did they have to detune to get that tire to work on the B/DA car. I have some thoughts about radials but would like to talk with someone who has tried them to see what their experience was. Any thoughts on tire pressures and adjustments. How much tire pressure have you run. We used to have a combination that would get the car down any track: 7 lbs of air pressure, 5,000 rpm launch, take 12 degrees of timing out for 1.2 seconds. Thanks for the response.

7

Spud Miller's Cave / RED initial Setup

« on: April 20, 2014, 04:37:35 AM »

Spud, I realize this may be out of your wheelhouse but I'm looking for some initial setup guidance for a RED. Chassis is 235 ",NA 380 ci 1025 hp @ 9800 rpm, 610+ lbft of torque around 8000-8200 rpm, pro flite 3 speed auto trans. Have gear sets for 2.09, 2.20,2.23 lows with 1.40 or 1.45 second gears. Tires available are 10.5 x33x15 (11.2" wide) 103 rollout, 12x33x15 (12.2" wide) 101.5 rollout, and 14.5x32x15 (14.5" wide) 102" rollout, wheels are 11",12" and 14" wide. Rear gears available are 4.71, 4.88,5.00, 5.29, 5.37. would like to keep the rpms down to 10,300. (10,000 initially)  Front to rear, weight distribution is estimated about 30/70 with the ability to move some ballast. I don't know whether 450 lbs frontend static weight  is enough to keep the nose from flying Less tha a foot or so. Run weight is 1530 lbs. My initial thoughts, using what I have are the 2.09/1.40 low/second (maybe could be a bit taller), 5.0 rear gear, the 32x14.5x15 tire on the 14" wide wheel. Launch at peak torque with a bunch of timing out of the motor. Have a 72" wheely bar, but don't want to run it unless we have too. Will run it initially just for safety. Will set it for a frontend lift of about 1 foot or so. Your thoughts?

8

Rear Engine Dragsters / Re: RED setup

« on: April 20, 2014, 03:16:01 AM »

Car is a little dated like me . Originally built by Al Swindahl, backhalfed and narrorrowed by Harry Clack, Front halfed by Brad Hadman and was raced as a C/ed car. Engine originally was a 341 ci  C/A motor with Little Chief  heads, which made good power, it has been stroked to 380 ci to make the weight for B/da class. Have to wait until its off the dyno to make some decisions. I have searched the net looking for articles which might dicuss procedures for setting up the car opposed to running it down the track a dozen times trying to find the sweet spot without shaking the drivers brains out and using up parts, however, I haven't found any yet. I think the car is a bit short for the class and power at 235" but we'll have to see. Probabably start with pieces that  we currently have 5.0 rear gear, 2.09 low with a 1.40 second and 32 or 33 inch by 14-14.5 inch wide tire, put some air in the tires and take some timing out and see what happens. I rember crewing on an A/D 20+ years ago at Bakersfield, we had the about the same power, tightened up the clutch, put a little air in the tires and black tracked the whole 1/4 mile. I don't know if I can get enough weight on the frontend to keep it down on launch and still have enough tire after 60' to get it down the track. Would like to run mid 6.80's at 195+ if there is enough power. Another subject. Has anyone attempted to run radials on a FED or RED car. If so, would like to hear from you.     

9

Rear Engine Dragsters / RED setup

« on: April 18, 2014, 10:43:36 PM »

Looking for some setup/adjustment guidance for a NA 235” RED. I have some familiarity with the car at a lower HP. New freshened engine (almost together), 380 ci middeck should make about 1025-1050 hp, 600 lbft of torque, peak torque around 8200, trans is a Proflite with 2.09/1.40 gear (thinking maybe a higher 1st gear in the 1.90+ range). Haven’t ordered a converter yet. Would like to keep engine rpms below 10,300 (initially 10,000) out the backdoor. Have  4.71, 4.88, 5.0 and 5.29 rear gears. Have a selection of tires 10.5” -14.5” wide with 101”-103.5” rollout, wheels 10, 11 & 14” wide. Have a long wheely bar, 72 inches (will run initially), but don’t want to use it. Need to determine weight bias, car weight will be 1530 lbs. would appreciate any guidance you might have regarding setup, launch technique and adjustment after run. Have questions about tire size, weight bias, 1st gear, tire pressure, balancing tire width for launch with traction down track. Currently thinking 13.5 to 14.5 tire width with rollout of 101-103.5” and a stiff wall. Does anyone have any information as far as softness of compound comparison between GY D6, Hoosier D06, D07 and MT M5, M8, X8, L8? Any rules of thumb regarding setup and adjustment would be appreciated. Thanks in advance. Another old new guy.