Author Topic: calming the car down on the starting line  (Read 3980 times)

Offline crider

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calming the car down on the starting line
« on: July 18, 2018, 03:19:07 AM »
Finally got the car out for the first time this year, and picked up right where it left off last fall. It 's 178" David Beard chassis with a 604" BBC. I had made around 30 runs with the new engine last year and ran straight as a string but not performing up to potential. I finally tried pulling the timing back to 32 degrees and the engine seems to love it, but it has made the car for the most part undrivable. I've tried both raising and lowering the wheelie bar but it just hits the bars hard and gets loose. I'm running 33-10.50 tires and a 4.20 gear. Right now I'm thinking either a gear swap or a front weight bar. What would be the right thing to try first?

Offline fuel749

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Re: calming the car down on the starting line
« Reply #1 on: July 18, 2018, 05:46:38 AM »
While I was at the track that day I might have gone back to the original setup just to see if it would get off the starting line.  What were the incrementals when it got down the track?  Injected or carbureted?  Leaving at idle or off the trans brake?  When you say not performing up to potential, what are you expecting from it?  It sounds like its dead hooking

Offline retroboy

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Re: calming the car down on the starting line
« Reply #2 on: July 18, 2018, 05:53:37 AM »
Interesting to see that three of the last five posts are about start line and rear gears. I have a similar problem with the car being something I have to fight off the start line. I put weight on the nose which helped a little bit but I going from 4.3 to 3.89 rear gears hoping that helps. I have a 3 SPD with a 2.45 first gear and a 31" tyre.

Offline rooman

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Re: calming the car down on the starting line
« Reply #3 on: July 18, 2018, 06:03:58 AM »
How far out is the motor?  How long is the wheelie bar and how rigid? ?  'glide with 1.76 or 1.82?  Does it jerk the front end and then get loose with the bar up? Does it spin at the step with the bar down?

Roo
Yeah, I am from the south--any further south and I would have been a bloody penguin.

Offline fuel749

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Re: calming the car down on the starting line
« Reply #4 on: July 18, 2018, 07:43:33 AM »
I'm thinking I built that with the motor 42" out but I originally built it for someone else so I could be wrong. I only build them with the motor further back by customer request.  If I built the bar it's probably between 48"-60" with enough give to not unload or shock the chassis unless things are going bad fast.

Jim, when you say the wheelie bar was low how low was it.  On our small block altered  (4.56, 33x10.5W, 1.76 low, probably 450 horse) I run the wheel almost touching the ground to unload the tires and generate wheel speed.  On occasion the owner/driver gets a hair across his ass for some big wheelie pictures so I put the bar up and it wacks the bar hard enough to unload the tires and send him for a ride. 

Offline dusterdave173

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Re: calming the car down on the starting line
« Reply #5 on: July 18, 2018, 11:51:07 AM »
I'm thinking I built that with the motor 42" out but I originally built it for someone else so I could be wrong. I only build them with the motor further back by customer request.  If I built the bar it's probably between 48"-60" with enough give to not unload or shock the chassis unless things are going bad fast.

Jim, when you say the wheelie bar was low how low was it.  On our small block altered  (4.56, 33x10.5W, 1.76 low, probably 450 horse) I run the wheel almost touching the ground to unload the tires and generate wheel speed.  On occasion the owner/driver gets a hair across his ass for some big wheelie pictures so I put the bar up and it wacks the bar hard enough to unload the tires and send him for a ride.


I agree that wheel a couple inches off the ground with driver in the car is all my car wants--higher and it is a wild ride
38 lbs on the nose in a 200 in car with maybe 425 HP  Get wheelie bar where you can just get your shoe tip under it
Leave from idle on footbrake and just see   Any RPM and it is going to be wild for sure with that much engine

I have always had a fascination with fast cars at the expense of more normal character development

Online wideopen231

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Re: calming the car down on the starting line
« Reply #6 on: July 18, 2018, 12:22:41 PM »
 Can not say how well it works yet, I set my car up with motor 50" out,fuel tank and battery on nose.I also went with 1.60 low and 4.10 rear gear trying t make it soft at hit. I am wondering about tire size with that much motor. Since can not read op and most reply at same time I am thinking you said 10.5 tire? why not at least 12" and maybe taller to ease up on hit. Anything that can pull timing and ramp it back in? Besides old TA/FC IHRA racer should be use to not going straight. LOL
Relecting obama is like shooting right foot because it did not hurt enough when you shot left foot

Online wideopen231

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Re: calming the car down on the starting line
« Reply #7 on: July 18, 2018, 12:26:24 PM »
Maybe before adjusting timing it was spinning some and made car more driveable. Go back to square one.iF that works you might look at tire pressure if adjusting timing back down.Just like with your old TA/FC a little spin can be good if its controlled.
Relecting obama is like shooting right foot because it did not hurt enough when you shot left foot

Offline crider

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Re: calming the car down on the starting line
« Reply #8 on: July 18, 2018, 03:25:00 PM »
To answer some of the questions. It's a glide, 1.76 gear. Leaving off the brake at 4500. 6200 converter. I've tried the rear bar from as low as 1.5" off the ground up to about 5". up. With the bar at it's lowest, it was quick yank up on the front end then instant spin and hard left turn. With the bars up about 4" it's still came up hard, but I was able to ride for 60ft or so before things unloaded and more bad spin. It's was running 5.40's before the timing change. Car should be easily capable of 5.00's or a little better. The one pass I was able to pedal it and get down the track under power it went 5.35 so it would appear that the timing change has helped the hp, if I can just figure out the right combo on the car. I like a car that takes a little skill to drive, but I also like to be able to make it all the way down the track too

Online wideopen231

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Re: calming the car down on the starting line
« Reply #9 on: July 18, 2018, 03:38:39 PM »
what where last years runs like? Any other changes other than timing? With 604"BBC I think you have low expectations. Maybe way off but I would think you should get well below 5.0's once you get it tuned out. I have had situation where tuning soft just screwed everything and had opposite where I backed it down and it hauled butt. If only change is timing I wold backup and punt. Then I am also rooking at tuning a FED so my 2 cent maybe over valued. If that don't work and you don't have a retard capable system then I would go after fuel. Richen it and lean it shortly into run. Electric solenoid would be best and use rpm switch or timer if have delay box.
Relecting obama is like shooting right foot because it did not hurt enough when you shot left foot

Offline crider

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Re: calming the car down on the starting line
« Reply #10 on: July 18, 2018, 03:59:22 PM »
last years runs were low 50's high 40's. Timing was only change. I made the change before the last run I tried to make last fall. Haven't made a clean pass since the change. But also have only had the chance to get it to the track once since then either. I'm still on a carb, so jetting is about all the fuel tuning I can do right now. My hilborn setup is at spuds place as we speak. I think the 5.0-4.90 expectation is pretty close for the topend I have right now. The heads are only flowing just over 400 at 700 lift. Too small for this motor I think. I wasn't planning on going this big, but a great deal on a high dollar crankshaft came along right after I had bought the new block, so here I am. The heads and cam were off the old 526 that the block died on before ever getting a full pass

Offline hemidakota

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Re: calming the car down on the starting line
« Reply #11 on: July 18, 2018, 06:43:04 PM »
What air pressure in slicks?
If it jams force it, if it breaks it needed replaced anyways

Online wideopen231

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Re: calming the car down on the starting line
« Reply #12 on: July 19, 2018, 03:05:03 AM »
After reading your OP i realized not answered question. I would do weight bar first. I have noticed most guys have added weight to front to make car work.Although sacreligious  to add weight its faster than sideways and /or lifting off throttle. Also cheaper than gear swap and easier to change if need.
Relecting obama is like shooting right foot because it did not hurt enough when you shot left foot

Offline crider

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Re: calming the car down on the starting line
« Reply #13 on: July 19, 2018, 03:15:29 AM »
Hemi Dakota, I had 7.5 lbs in them. I would have tried adding a pound or 2 but had forgot the air tank at home

Offline PSweeney

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Re: calming the car down on the starting line
« Reply #14 on: July 19, 2018, 03:29:33 AM »
I think theres 3 aspects.  Weight, tire pressure and the bar height.  Get the nose weight and tyre pressures balanced so it doesn't dead hook and you get some wheel speed so it reduces the shock load on the bar / tires, then set the bar to just above the tire squat height, about 2" assuming the weight/tire pressure ratio is right.