How much ballast needed on a 60's FED?

[Mister_Fitz]

Hi
I have an old 60s FED with 150" WB, motor 30.5" out and a total weight of about 1250 pounds without driver.
I'm having some trouble getting the car to launch straight and have now started to think of adding some weight to the front of the car.
I have added a weight of about 30 pounds to the front axle and I will try this next weekend.
But will I see any difference with this 30 pounds? Or do I need to add much more? What weight ration between front and rear axle should I aim for?

[rooman]

Every race car is different due to variations in tires (and tire pressure), driveline, horsepower etc. Available traction, launch rpm etc also come into play. If the car is not going straight with the front wheels off the ground I would first check the rollout on the rear tires. Then make sure the rear end is square in the car. When such parameters are correct most cars can carry the front wheels and still go straight. If the car still wants to turn at the launch with everything square and even you may need to add a little pressure to the slick on the side that it is turning towards. Adding weight to the front end to enable you to steer the car is really just crutching the problem rather than curing it.

Roo

[dreracecar]

If it's a new crew, make sure they back you up far enough to allow you to drive the car straight into the beams. Too shallow and crooked in the beams is not good, just be careful that they don't put you back in the warer

[racerken]

Does the rear end have a spool ore is it an open rear end?

[JrFuel Hayden]

All the fast FED I know of run spools.

[gregm784]

When i was learning to drive my car, i carried a lot of weight to help the steering.  I'm down to a 360# front axle weight now and it leaves nice. I've tried 330# and it hits the bar so hard it would unload the tires and the 60' numbers went down .040. 

[Mister_Fitz]

The rear end has a spool. The FED is all updated to the latest SFI spec. The "old" thing about the car is the engine placement that is way back. Shorty PG with coupler direct into the rear end.
I think we are quite good on backing the car up straight. I agree that it will make a big difference.
Roo. I agree that adding weight will not fix the real problem. I will try it next race and hopefully I can remove it later on.
When adjusting tire pressure to get the right traction and wheel speed. How small pressure adjustments will have impact? Is lowering pressure by 1 psi at the time a too big change?

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[JrFuel Hayden]

Yes a one pound difference will make too big of a change. We only made a 1/4 # difference from side to side. 

[racerken]

I enjoy the driving side more than the mechanical side so I don't profess to be very technical.  All I know is that I have a 185" Boogie Scott FED (Hall of fame chassis builder)  He says not to run a spool. I run 8.70"s 150 mph straight as a string..  Also,  about 15 years ago I bought  a Mark Williams car from a friend of mine. He never knew which direction the car would go in when he launched.  I put my motor in it and took the spool out and never had an issue going straight.  Like I said,  I can't tell you why,  I am only sharing my experience,  for what it's worth.

[dreracecar]

The open diff is masking problems with either the chassis or rear end housing. And I have run mis-matched tires with a spool, and the car still went straight

[JrFuel Hayden]

Ken, it might be going straight because you are running a kinda big tire to be running 8.70 @ 150, so you are kinda dead hooking the tires , not trying to get the tires to spin some to keep the motor in the rpm range where it's making good power. But if you are running an 8.70 or 8.60 bracket or dial in, then keep on trucking.
Again I don't know of any fast cars that run open rear-ends.

Jon

[BK]

 My FED had a short glide with a coupler direct to the rear but was 175" WB and had similar problem.
 I did get it to launch with about 60#s up front and set the wheelie bars to roll some weight to the right. Worked OK.
 I tried as much as 11/2# difference left to right in air pressure on Scott Wenys recommendation. It helped but not enough.
 I was bracket racing it and low ET wasn't my main priority so the thing that worked best was to put a pneumatic cylinder with a needle valve to slow the opening rate of the throttle a little. I lost 1 tenths in 60' and 2 at the finish line but it was deadly consistent. Still needing the weight and wheelie bar also.
 It would go 1.14 to 1.18 60s at 8.45 to .50 inconsistently with out the cylinder and 1.24 at 8.63 with.

[slingshot383]

To large of a slick is a common problem with a FED having a launch problem. They work better with a narrower slick, especially if the engine is back.

[gregm784]

To large of a slick is a common problem with a FED having a launch problem. They work better with a narrower slick, especially if the engine is back.

Agreed.  Tire speed is your friend.

[PSweeney]

I've had the same problem recently but it was down to a cold and poorly prepped track.  I run about 60lb on the nose of my 138in car with the shorty glide combo.  It still hits the bar but a lot softer now.  Running 31 x 10.5 tires @ 6.5psi.