Throttle stop using 2 carbs

roseracing · 07-27-2009, 09:07 AM

We just added a 3rd car (Undercover dragster) to our team and will be installing a 630ci Mopar Indy motor.

The motor has 2 Demon carburetors and we want try and run it in S/C this way.

Does anyone have any advice for throttle stopping a car with 2 carbs?

Any advice would be helpful.

Thanks,
Brad Rose
Rose Racing Team

Bill Baer · 07-27-2009, 01:42 PM

I don't think the car will know or care how many carbs it has on it.
You will still need to get the on the stop RPM down in the 4000-5000 range and you may need a little larger throttle stop cylinder (both bore and stroke) to acomplsh this and overcome the extra effort needed to open both of them up.
But with the motor breathing through eight venturi instead of the typical four it may be a little less affected by changes in the weather but that's a good thing!

Just my 2 cents worth!

roseracing · 07-27-2009, 03:51 PM

Thanks Bill. I've heard that turning the CO2 regulator to somehwere between 100 - 125 lbs. would help as well.

I appreciate your help.

Brad

S/ST4707 · 07-27-2009, 04:10 PM

Reagan Wilson runs two carbs on his 632 powered Super Street truck and has pretty good success. I think he runs two under the carb stops but am unsure of the linkage. He often visits this site so hopefully he will enlighten us more on the subject.

Tom Goldman · 07-27-2009, 09:25 PM

[
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But with the motor breathing through eight venturi instead of the typical four it may be a little less affected by changes in the weather but that's a good thing!

Just my 2 cents worth![/QUOTE] A fact that many overlook when telling you all the reasons you should not run a tunnel ram. ! .....I ran one for years on my AMC'S and on my small BBC'S with great results. .....I used the Bill Mitchell 1" bore cylinder @125# ,with the Enderlie linkage. ....I had to fab a longer arm on the bell crank to get a lever ratio that worked ,but that was about it. .....I have a friend who has a TS car he occasionally runs in SG with the same setup on a 638 ; to run 9.90 @ 178 mph in a 2600# car,so your setup should work. .......Good luck ......Tom

roseracing · 07-28-2009, 09:23 AM

I'm really interested to see how the two under carb stops work. Dedenbear and Biondo have both recommended in linkage stops, but I like the under carb stops better.

I guess the whole thing comes down to consistency. If an in-linkage stop is just as consistent as under carb stops - then I guess I'd like saving the money.

Brad

Rick Bailey · 07-28-2009, 10:17 AM

under card stops.......... that would be interesting..........you would almost have to tie them together, and just use one actuator , other wise setting the drop would be a real pain. I would think anyway.

just my 2

Rick

Bill Baer · 07-28-2009, 03:32 PM

Well if you use under the carb stops, you will not get the accelerator pump shot when the stops open which if you don't open the stops slowly enough. could cause the motor to stumble or bog Besides I'm a big fan of K.I.S.S.
Make darn sure that if you use a pneumatic cylinder in the linkage that you have a positive (solid) stop under the pedal or it won't repeat and will drive you nuts, but you probably knew that already.

Jeff Beckman · 07-29-2009, 09:38 PM

Mark Cooke from Badman Racing engines does it, so does Josh, Josh is #1 in D3 S/C right now. 2 dominators, under carb stops I beleive.

roseracing · 07-30-2009, 02:14 PM

Another concern I have is if the under carb stops will "puddle up" and "bog" when they come off the stop.

It's glad to hear someone doing well with a dual carb setup in S/C D3. I was just doubting this setup because I haven't heard of anyone doing well with a dual carb setup and throttle stop, until now. I thought Ray Connolly used to use a dual carb setup on his dragster?

Maybe we'll try it in S/C for a year and then move to Top Dragster if it doesn't work out. My brother will be driving this setup and he's never driven anything down a dragstrip before. This is why we want him to run in S/C. That way he has a second or two to think about things. He is going to Frank Hawley's school in February, so that should help. I guess because we MIGHT move him to Top Drgaster later, maybe we'll just go with the in-linkage stop. Who knows. He's not racing until next year and I've changed my mind 3 times this week about which throttle stop to use. It ought to be an interesting fall/winter.

Thanks for all the advice.

Brad

07-27-2009, 01:42 PM	#2
Bill Baer Senior Member Join Date: Jul 2007 Location: Nothern IL Posts: 596 Likes: 1 Liked 1 Time in 1 Post	Re: Throttle stop using 2 carbs I don't think the car will know or care how many carbs it has on it. You will still need to get the on the stop RPM down in the 4000-5000 range and you may need a little larger throttle stop cylinder (both bore and stroke) to acomplsh this and overcome the extra effort needed to open both of them up. But with the motor breathing through eight venturi instead of the typical four it may be a little less affected by changes in the weather but that's a good thing! Just my 2 cents worth! __________________ Bill Baer 3391 SC, 339B SC, QR

07-27-2009, 03:51 PM	#3
roseracing Member Join Date: May 2009 Location: South Sioux City, NE Posts: 108 Likes: 0 Liked 0 Times in 0 Posts	Re: Throttle stop using 2 carbs Thanks Bill. I've heard that turning the CO2 regulator to somehwere between 100 - 125 lbs. would help as well. I appreciate your help. Brad

07-27-2009, 04:10 PM	#4
S/ST4707 Junior Member Join Date: Nov 2006 Posts: 23 Likes: 0 Liked 0 Times in 0 Posts	Re: Throttle stop using 2 carbs Reagan Wilson runs two carbs on his 632 powered Super Street truck and has pretty good success. I think he runs two under the carb stops but am unsure of the linkage. He often visits this site so hopefully he will enlighten us more on the subject.

07-27-2009, 09:25 PM	#5
Tom Goldman VIP Member Join Date: Jan 2003 Location: Allentown,PA Posts: 2,477 Likes: 893 Liked 883 Times in 237 Posts	Re: Throttle stop using 2 carbs [ . But with the motor breathing through eight venturi instead of the typical four it may be a little less affected by changes in the weather but that's a good thing! Just my 2 cents worth![/QUOTE] A fact that many overlook when telling you all the reasons you should not run a tunnel ram. ! .....I ran one for years on my AMC'S and on my small BBC'S with great results. .....I used the Bill Mitchell 1" bore cylinder @125# ,with the Enderlie linkage. ....I had to fab a longer arm on the bell crank to get a lever ratio that worked ,but that was about it. .....I have a friend who has a TS car he occasionally runs in SG with the same setup on a 638 ; to run 9.90 @ 178 mph in a 2600# car,so your setup should work. .......Good luck ......Tom __________________ Tom Goldman 1500 SG , 1506 STK

07-28-2009, 09:23 AM	#6
roseracing Member Join Date: May 2009 Location: South Sioux City, NE Posts: 108 Likes: 0 Liked 0 Times in 0 Posts	Re: Throttle stop using 2 carbs I'm really interested to see how the two under carb stops work. Dedenbear and Biondo have both recommended in linkage stops, but I like the under carb stops better. I guess the whole thing comes down to consistency. If an in-linkage stop is just as consistent as under carb stops - then I guess I'd like saving the money. Brad

07-27-2009, 09:07 AM	#1
roseracing Member Join Date: May 2009 Location: South Sioux City, NE Posts: 108 Likes: 0 Liked 0 Times in 0 Posts	Throttle stop using 2 carbs We just added a 3rd car (Undercover dragster) to our team and will be installing a 630ci Mopar Indy motor. The motor has 2 Demon carburetors and we want try and run it in S/C this way. Does anyone have any advice for throttle stopping a car with 2 carbs? Any advice would be helpful. Thanks, Brad Rose Rose Racing Team

07-28-2009, 10:17 AM	#7
Rick Bailey Senior Member Join Date: Sep 2002 Posts: 502 Likes: 5 Liked 10 Times in 7 Posts	Re: Throttle stop using 2 carbs under card stops.......... that would be interesting..........you would almost have to tie them together, and just use one actuator , other wise setting the drop would be a real pain. I would think anyway. just my 2 Rick __________________ Rick Bailey 3439 SC

07-28-2009, 03:32 PM	#8
Bill Baer Senior Member Join Date: Jul 2007 Location: Nothern IL Posts: 596 Likes: 1 Liked 1 Time in 1 Post	Re: Throttle stop using 2 carbs Well if you use under the carb stops, you will not get the accelerator pump shot when the stops open which if you don't open the stops slowly enough. could cause the motor to stumble or bog Besides I'm a big fan of K.I.S.S. Make darn sure that if you use a pneumatic cylinder in the linkage that you have a positive (solid) stop under the pedal or it won't repeat and will drive you nuts, but you probably knew that already. __________________ Bill Baer 3391 SC, 339B SC, QR Last edited by Bill Baer; 07-28-2009 at 03:36 PM.

07-29-2009, 09:38 PM	#9
Jeff Beckman Member Join Date: Nov 2007 Location: Columbus Ohio Posts: 308 Likes: 0 Liked 0 Times in 0 Posts	Re: Throttle stop using 2 carbs Mark Cooke from Badman Racing engines does it, so does Josh, Josh is #1 in D3 S/C right now. 2 dominators, under carb stops I beleive. __________________ Jeff Beckman 318J ET, SG 318T SC

07-30-2009, 02:14 PM	#10
roseracing Member Join Date: May 2009 Location: South Sioux City, NE Posts: 108 Likes: 0 Liked 0 Times in 0 Posts	Re: Throttle stop using 2 carbs Another concern I have is if the under carb stops will "puddle up" and "bog" when they come off the stop. It's glad to hear someone doing well with a dual carb setup in S/C D3. I was just doubting this setup because I haven't heard of anyone doing well with a dual carb setup and throttle stop, until now. I thought Ray Connolly used to use a dual carb setup on his dragster? Maybe we'll try it in S/C for a year and then move to Top Dragster if it doesn't work out. My brother will be driving this setup and he's never driven anything down a dragstrip before. This is why we want him to run in S/C. That way he has a second or two to think about things. He is going to Frank Hawley's school in February, so that should help. I guess because we MIGHT move him to Top Drgaster later, maybe we'll just go with the in-linkage stop. Who knows. He's not racing until next year and I've changed my mind 3 times this week about which throttle stop to use. It ought to be an interesting fall/winter. Thanks for all the advice. Brad