Tire shake with P/G
 

We have an FED with a blown 542. Our convertor is a JW 10 " and is supposed to stall at about 5,000. We tried to leave at idle and just hit the throttle and it just went into tire shake instantly. We tried to stall it a little and come off the trans brake and it did the same. We don't use a tach so I can't give any stall info there, but the previous 8" convertor we balloned. Any way what my question is, shouldn't there be some slide of the convertor, because it acts like it just locks up period. I am an old lenco guy and am new to this convertor stuff so all you convertor wiz's help me out please. The convertor was just checked by JW before this race.
Thanks,
Rick

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Rick,
I ALWAYS had My BLOWN/Alcohol converter set-up as TIGHT as they could make them!Thats what the Blower is For,........!Sounds to me Like your Tire Pressure is OFF?Or maybe take some B/V away and get After it a little HARDER!!
Hope that Helps,its NOT Much,but sometimes thats alls YOU Need?
Later
G 8)

Yeah, we had it real fat since it was all new, didn't want to cook anything. Did you leave from an idle on your set up or did you nail the convertor and use the trans brake?

Rick

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Flat FOOT from a Dead IDLE 12-1500 RPMs,that Fat B/V could have ALOT to do w/it.............?
Later
G 8)

Re: ?
 

Thanks for the info, we will lean the puppy out and put a little more timing in it.

Rick

Tyre shakes caused by not enough power to the ground. If that convertor has a 5000 stall you shouldn't be leaving at 1500. I'd say put a transbrake in there and use that convertor the way its meant to be used.

that is great advice, mine will shake your teeth coming off a idle also.

Well we have tried just about everything, except transbraking it to 5,000. We usually use about 3-4000 rpm. We have tried changing the low end tune up, different tires and tire pressures. The tracks in this area are not the best, but they do prep them pretty good. I guess what I was getting at is that if there is a possibility the convertor is just locking up from the launch, in other words should I send it back and have it set up for a "softer launch" (if there is such a thing). We used to run lencos and could adjust the clutch a little for the shake but I am lost with this convertor/tire shake.

Rick

Tire shack
 

It was said above, but how about the combo where they use a tight 1800 - 3000 RPM stall large diameter converter for certain blower applications? I would think using a transbrake with a blower could make tire shake worse.

Re: ?
 

TIGHT CONVERTER!!!!
Later
G 8)

Rick, call Greg at FTI and tell him I sent you there for some info. Most think you need a 10" converter with a blower to kill some of the hit, which is just the opposite most 10" stuff is more aggressive then a 9".

2 months ago a customer at the shop I wire for had massive shake issues with his blown dragster. We went to the track with him and a few different converters, tire shake massive with the 10", put the 9" in it and picked up 2 tenths and no tire shake. Went 6.92@191.

Re: ?
 

BB Chevy,
Do you mean we need a tight converter or our problem is a tight convertor?

Thanks,
Rick

Thanks David, I will call Greg when I get a chance and pick his brain. We are going to try our 8" converter that was just re-done even though it is built for an injected SBC in this set up. It may just give us the info we need, then I can get someone like Greg to build us a converter that will help us.

Thanks again,
Rick

Re: ?
 

Rick Yes you NEED a TIGHT Converter,3000-3500 Range!
Later
G 8)
GOOD Luck with that 8",.........

You'll find Greg knowns his stuff, do you know if you JW 10" has 8" internals like most other 10" converters do ? The blower car we worked on, was 6600 on the fallback stall, the right guy in a lighter car can get the loose converters to work well, which makes them deadly.

I run a 4000 stall 10" with my blown sm/blk, but it's probably apples and oranges because it's a door car. What most people donot understand is that a good blower is all in at 3000 rpm, you're not going to get more boost after that just more air flow.

Zip.

Re: ?
 

Thanks for the help BB Chevy.

Rick

Thanks David for the help.
Rick

Zip you nailed it with the apples and oranges on the door car, with the lighter cars you can get away with the loosened converter.

"Apples and Oranges" . . Definitely!

Tire Shake, basically, is caused by not enough tire speed to keep the sidewall wrinkled and the sectional profile in a rectangle . . The cure is as varied as the vehicles susceptible to it . .

A FED really shouldn't be exhibiting a lot of it because of the inherent design and weight bias . . But it does happen . . Perhaps not enough negative pitch on the crank centerline . . More common on rear motored cars, blown altereds and blown door cars built to run in the 7 second and faster range . .

I'll go with the Tighter Converter suggestion. Awhile back I was the crew chief for a Blown Alky Altered and we stalled at 5000+ on the starting line . . 500" B Chrysler, 8-71, Hoosiers, 7 second car . . never had a tire shake problem.

On the Blower deal . . "3000 RPM and you're done" . . not really. Depends on your Blower and the pulleys you use . . If that were the concrete case, you wouldn't need to overdrive a Blower like we all do on a competition Engine . . and I underdrive the little 144 on my Street Rod so that in high gear I'm not running against compression, yet when I stand on it it starts working at 2650 engine RPM . . Noticeably!

Qoute:

On the Blower deal . . "3000 RPM and you're done" . . not really. Depends on your Blower and the pulleys you use . . If that were the concrete case, you wouldn't need to overdrive a Blower like we all do on a competition Engine . . and I underdrive the little 144 on my Street Rod so that in high gear I'm not running against compression, yet when I stand on it it starts working at 2650 engine RPM . . Noticeably!

I didn't say that you couldn't flow more by overdriving the blower, boost is directly relative to how good your exhaust system is. IE- valves,headers, cam size, and timming. As you see in top fuel and top alcohol dragsters, they run short headers, to relieve the pressure. In the top alcohol funny cars you always see them spray WD 40 for a de-icer on the injection butterflys. This is because the pressure backs up and blows the alcohol back up thru the blower and freezes the butterflys open if they donot spray them, causing stuck throttle blades. Yes they run 40 to 60 percent overdrive on the blowers to produce 50 lbs plus boost, it flows a lot more fuel therfore more HP. I run a 1471 Littlefield blower with a buzzard catcher on a sm/blk chevy at 20% overdrive on alcohol pushing 40 lbs boost with zoomies. Heck i could run 50% overdrive, but i couldn't get it out the exhaust system.

Tire shake, i don't know much about that since i run door cars.

Zip.

PS, i ran my first blower car in 1964 on gas

Just sent the convertor back to JW who built it, and they are going to set it up to be less aggressive on the launch but not affect the top end . We run with a blown show and no electronics and not that fast 7.50. We have no problem running the number if we are not screwing around with shake on the line. I will let you know if it makes any difference. Thanks for all the responses.

Rick

Re: ?
 

Well BB Chevy, you are correct, we finally put everything back together and JW told us the same thing you said and they tightened the convertor, and I cannot believe the difference. The car just launched 3 time perfect, no shake no wheelies, just perfect. It ran a 7.34 at a density altitude of 7,700 ft with a 1.04 60 ft.
Thanks for all the help.
Rick

Re: ?
 

glad ya got her figured out :)

We just went though this with a another blower combo 522 though, we had opposite findings for the fix again. Wonder if its due to the lower elevation or car difference we run in ? Very interesting.

Re: ?
 

Rick,
I started out with a Blown Alchol F/C Chassis,had all parts Motor & Trans(No Converter)Listened to some So Be-It,Knowit-All?Buy a Loose converter 5-5500 Stall.So I did,I fought that Combo for almost 2 seasons?Changed Every Part on the Car,thinking that NO Way there could be a C/Verter Issue It NEW!
Guess what,went back to all the Parts Org.on the Car,purchased a New 10"2500-3000 stall converter,from a Company that I'm not even sure is still around(Munsinger),...................BINGO,the Car went down the Track Better and Faster than Ever before,and deadly Consistant!
Later
G 8)

I know his is gonna sound crazy....but I had the problem in door car. tried new tires, different tire pressure,on and off the brake. It still did the same thing. I was running out of options and really couldn't figure it out. Out of desperation, I fattened the barrel valve a half of turn...guess what, problem solved...who the heck knows?