Small Tire drag race combos

[bracketchev1221]

Since a majority of the members of the club are trying to get down the track on small tires, let's get a discussion going on what people are using. Maybe we can get started on getting some of these cars down the track by getting them to leave better. There are several cars here with low 11 potential just not with the 60' to support it. I'll start with my old combo, which was upper and lower SSM bars with Moroso trick springs and Competition Engineering 3 way shocks. Having the same parts in the front of the car also I was able to leave off of the trans brake at 4600 and go 10.40's at 127 on Phoenix 10.5X29.5 tires on 10" rims.

[chvl71402]

I am looking at ways to improve my 60ft times. 114mph trap speed has the potential for 11.60's. Saturday my 60ft time was only 1.85.
The car has done a 60ft 1.69

I run MT 275 50 with 3.73 gear. SSM's airbag in the right spring,
Competition drag shocks on the rear.
Front springs are Hotchkis.

I really think the 2400 stall 11" converter is lugging the motor off the line.


I am considering a converter change.

[bracketchev1221]

What motor is in the car, and what cam is in it? Also the front end is important to look at to get the car out. The front end should want to rise quickly, the Hotchkis springs being more of a handling spring may not be allowing the transfer to the rear quick enough.

[chvl71402]

It has a 402BBC with a 700r4 trans.
The cam is Comp solid roller using XR street lobes. 273/285 at .015. 113LSA installed at 108.

The front does not pop up on launch. The whole car just seems to rise.
That iron head BBC is heavy.
May need to consider getting better weight transfer.

[bracketchev1221]

What is the .050 duration on that cam? That will dictate the rpm band of the cam and basically where the motor should make peak torque. This is what you will need to know for converter choice.

[chvl71402]

The cam .050 duration is 236/248.
I reviewed my past time slips and the 60ft times are inconsistent. The best was a 1.69
Typical was 1.70-1.75.
Peak power was at 6000 and torque peak 4500. on a dynojet.
My thinking originally when installing the 2400 converter was that the 3.06 1st gear combined with a 3.73 final and 26"tire would work.
The combination appears to be a mismatch.
I am considering going to one of the 9.5" lockup converters with 3000-3500 stall.

[bracketchev1221]

I think you are the right track with your 3000-3500 range. I realize that this is a street driven car and once again there is a trade off between street life and E.T. You want something that will help the car leave, but not be unbearable to drive on the street. Optimally you want a converter that will stall around peak torque of the motor but that would not be practical for street driving. Now on your 60' times, are those all the same day or different days? Here is a question that is sometimes overlooked, did you drive the car exactly the same every time? Was it staged the same, was the starting line rpm the same?

[CHELKAMINO]

I am running stock upper arms with stock boxed lowers. I have urethane bushings though. I put air bags in the coils with 3 way adjustable drag shocks at all 4 corners. I have American Racer bias street tires with 16 lbs in em. My 60' times were 1.90 with a 4 speed. I am looking at some after market arms soon.

BTW bracketchev......you got a stock width 12 bolt posi rear laying aound by chance??

[bracketchev1221]

No, the only 12 bolt I have is the one in the car. It's been in the car from day one and still works fine.

I had the 3 way's in my car with the front at 90/10 and the back at 50/50. I wouldn't even worry about a bag in the drivers spring. If you go with the Moroso springs in the rear, the passenger spring has an extra coil eliminating the need for bags. Urethane bushings on the rear won't hurt you. I ran the Comp Eng. solid aluminum bushings in my stock control arms before I went to the SSM bars. Don't discount the stock bars yet, I was into the high 10's with the stock bars. If you do change them you want something that will change the imaginary intersect point of the bars. Just having upper adjustables to change pinion angle really doesn't help the traction of the car. It just reduces friction loss through the u-joints.

[chvl71402]

I have experimented with different staging RPM's. The best short times were acheived when leaving from 2000 rpm(all the manual drums would hold).
I am thinking I should be able to footbrake higher with a looser converter.

What are your thoughts on any gain acheived by going from an 11" converter down to a 9.5"?

[bracketchev1221]

Well 2 things, the size of the converter really has little to do with it. It's the size of the turbine and stator in the converter that will effect stall. The smaller in size, the faster they need to spin to create the hydraulic pressure to drive the car this is what causes a higher stall. However it is less rotating weight to get moving. I know everyone wants to leave at a higher rpm, but have you tried leaving just off idle. For a footbrake car it does a few things. 1. It allows the suspension to be more relaxed to take the hit of acceleration rather than just the tires. 2. It gives the engine a running start at the drivetrain. If the coverter stalls at 2500 and you are powerbraking to that point the engine is like hitting a wall. But if you leave at 1500 the engine gets a 1000 rpm running start at the drivetrain effectively hitting it harder. Now granted your converter is very tight for your combo, but with a higher stall converter you will get a greater converter "flash" and hit the tire harder.

[chad]

Drag Racing 101! This is a great thread thanks for all the info.

[bracketchev1221]

Well I'm glad to help. I've been running this car in different stages from 1995 and racing since 1990 in others. I'm willing to share everything that I have used and tried in that time. I've always tried to run this car without going broke, so there are a lot of things on this car that aren't fancy or the most expensive. My motor doesn't make as much power as some in the same size, but all of the parts can be replaced through the Summit catalog and it doesn't require constant maintenance so it works for me. If anyone ever has any questions, I'll try to help and if I don't know I can try to find out.

[chevguy65]

My tires are 235/60/15 mt/et's
Mostly a stock suspension although I am thinking of going to trick springs in the front with 90/10 uplocks.

Back consists of new upper and lower control arms, new shocks and a stiff spring.
I have some anti-hops but have not installed them yet.

As my video shows traction is a bit of an issue, although it is not fair to comapre a burnout in an empty parking lot to that at a well prepped track.

Still my best 60' is 1.85 and with a 3.06 1st gear and 3.73 rear I should be into the 1.70's

My converter is a 9 1/2" 3400 stall.

Not sure if I need to bag one side as it launches straight as a pin, and still debating whether the no-hops will be that much of an improvement.

Any ideas or suggestions?

[bracketchev1221]

Getting the front end to extend is always a big help, just be careful that it doesn't take away from street driving. My car right now has nothing more than moroso trick springs, the lightest rate BB springs, and the 3 way comp engineering shocks. That is what was in the car when it was in the 11's on the street to now. The no hops will probably show a benefit because you will be moving the lever arm of the rear and this will help plant the tire harder. As far as the airbag goes I would just watch the body and if it does start to roll over then add the bag. One other thing you may want to consider is you say you have a stiff spring in the rear. If this is not allowing the suspension to compress and absorb some of the hit you may be just relying on the tires again which will also cause tire spin.