Drag Strip Gear Question

[BattlestarGalactic]

For a quick change, take off the 90/10's and put a stock shock back on.  That might slow the front end down and help take some of the bite out.

How tight is the gap on the slapper bars?  Make it tight, so it doesn't allow the tire to dig in as much.

[tall69]

For a quick change, take off the 90/10's and put a stock shock back on.  That might slow the front end down and help take some of the bite out.

How tight is the gap on the slapper bars?  Make it tight, so it doesn't allow the tire to dig in as much.

I had stock shocks and heavy front springs on it 2 years ago, same result.  I maybe have a 1/4" gap now between the rubber bumper and spring.  If I eliminate the gap, would that reduce downward pressure on the tire?  I've been contemplating removing the slapper bars because it rides like sh*t on the street.

Has anyone tried the clutch tamer setup that gets promoted on different websites?  Seems like snake oil to me, but maybe there's some validity to it.

[57 lima bean]

What about a narrower tire?

        http://www.mandhtires.com/M-H-Racemaster-Drag-Slicks/8.00-8.50-14#.WOPUdVXyuUk   


      Put them on an eight inch wheel run 30 pounds

[BattlestarGalactic]

Yes, taking the gap from slappers makes it ride rough.  Been there with my '69 F100.  I want to get ladder bars back under it someday, but the slappers at least get me by.  Tightening the gap takes some of the stored energy from the springs wrap up from hitting the tire.

Ya, for this I would look at the Clutch tamer(did I say that? LOL).  What could it hurt?  It basically slips the clutch for you, which is what you need.  I have no personal experience, but have done some reading on his website.

A narrower tire is another good idea, but maybe the Tamer is a better start?

[shady]

what rpm are you dropping the clutch at on the tree?

[tall69]

what rpm are you dropping the clutch at on the tree?

Up to 4800RPM.  The higher the launch, the faster it seems to go.  Something has to give though.  So far, I've been lucky.

[BattlestarGalactic]

Yup, the higher the RPM, the quicker it is recovering/less bog and it will go faster.
You have 3-4 more tenths in it if you can get it moving.  I used to go 11.5's at 116-117 mph.

[shady]

I don't know if I would change anything. Sounds like it is working good. Up the rpms some more so it doesn't bog down out of your power range & hang on. If it goes faster with more rpm, the chassis is working. If something breaks, then replace it with something stronger.

[Falcon67]

Okay, so no to a bigger tire.  I need to introduce tire slippage into my program.  I was under the impression that increasing tire pressure should theoretically create less traction.  Is this not accurate?  I've tried 18-22 psi and it still dead hooks.

The more pressure you run in a DR the quicker it goes, up to some point.  So here's another problem to consider - if you want to induce some spin in your launch program, you may need to switch to slicks.  DRs do not recover well from spin like a slick.  They dead hook or blow off, not much in between.

[tall69]

The more pressure you run in a DR the quicker it goes, up to some point.  So here's another problem to consider - if you want to induce some spin in your launch program, you may need to switch to slicks.  DRs do not recover well from spin like a slick.  They dead hook or blow off, not much in between.

I'm running Hoosier QTP's, which are a DOT legal bias ply drag tire.  I switched from MT ET Street Radials for the reason you mention.

...If something breaks, then replace it with something stronger.

 

Yup, the higher the RPM, the quicker it is recovering/less bog and it will go faster.
You have 3-4 more tenths in it if you can get it moving.  I used to go 11.5's at 116-117 mph.

Good to know.  Another astute drag racer suggested that the bog might be, in part, fuel related.  This is quite possible.  My pump shot is probably all used up at my launch RPM level.  I can switch to a 50cc pump shot and delay the cam to ensure I have some fuel left for launch.  I've attached a graph showing my RPM and AFR of my 11.90 run last year.  It does go way lean at the launch and every time I shift.  The black line is the RPM, and purple the AFR.

[BattlestarGalactic]

What carb are you running?

[tall69]

What carb are you running?

QFT Q-series 1050

[BattlestarGalactic]

That should be able to push enough fuel to not lean out.  Might look at the pump shot.  Start the car, run it to your launch rpm and see how far the throttle is open.  Then shut it off.  Compare that setting to how much pump shot is left, even on the back side. I would likely bet you aren't that far into the throttle to use up the pump shot.  Maybe move the pump cam to the next spot and see if that gives you a later shot.  Cheap way to test it.

[My427stang]

Are you launching on a rev limiter?  We've had good luck on a 440 inch Rat that runs about the same times by holding it to the boards and letting the limiter hold it on a launch pill.  Takes one less movement out of the equation

[tall69]

Are you launching on a rev limiter?  We've had good luck on a 440 inch Rat that runs about the same times by holding it to the boards and letting the limiter hold it on a launch pill.  Takes one less movement out of the equation

No, but my MSD has a two step feature that I'm going to try.  So, a question about this.  When you stage against a rev limiter with the carb at WOT, the pump shot is out of the picture obviously.  Would fuel on the primary and secondary side be flowing and balanced effectively through the boosters before launch?

What's the best way to enable the two step?  A momentary switch on the clutch?  Tie it to my line lock on my shifter handle?

That should be able to push enough fuel to not lean out.  Might look at the pump shot.  Start the car, run it to your launch rpm and see how far the throttle is open.  Then shut it off.  Compare that setting to how much pump shot is left, even on the back side. I would likely bet you aren't that far into the throttle to use up the pump shot.  Maybe move the pump cam to the next spot and see if that gives you a later shot.  Cheap way to test it.

I've tried this.  On the primary side, it's nearly out of stroke.  My secondaries don't come in until 2/3 throttle, so none of that shot is used while I stage.  I could try a different cam, or a different cam position.  I'll have to do some reading on accelerator pump tuning.