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Switched to a smaller CFM to slow car........... #2694226
09/04/19 08:02 AM
09/04/19 08:02 AM
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S.E. Michigan
cl440 Offline OP
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Since we started running the Daytona at WOT it has become deadly consistent.

The car will only cert to 8.50 so we had a mechanical throttle stop under the pedal to keep it around that 8.70 - 8.80 mark. The problem was it wasn't very consistent. We decided to try some WOT passes and it really came around. Problem was it ran low 5.40's in the 1/8 and low 8.50's in the 1/4. Very close to the cutoff for our cert.

Not wanting to run into issues of making an 8.40 pass when the weather got really good we decided to remove the 1050 Dominator (Alcohol) and install a new Quickfuel 4150 950 (Alcohol) carb. Set the floats, idle mixture and speed and went racing!

Car ran the exact same # as it did with the 1050 Dominator!!! 8.53@158MPH.......I was shocked that it ran the same # I thought for sure it would slow a tenth or two. I guess the old 540 really likes the smaller CFM carb! LOL

I was really impressed with the Quickfuel carb as it was setup perfect right out of the box! No stumble, no down track issues just stab the throttle and hang on! I do not have an AFR but watching the change in water temp from start to finish it was the exact same (10 degree increase) as the 1050 Dominator.

TURR5107.jpg
Re: Switched to a smaller CFM to slow car........... [Re: cl440] #2694237
09/04/19 08:56 AM
09/04/19 08:56 AM
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Clanton Offline
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I have seen some restrictor plate kits that work well you can look into using


GOTBOOST!New improved with Victor heads.
http://www.enginelabs.com/mopar-big-bloc...t-of-necessity/
Re: Switched to a smaller CFM to slow car........... [Re: cl440] #2694240
09/04/19 09:06 AM
09/04/19 09:06 AM
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That is interesting.... in most cases it seems to make a difference. What’s the Venturi size and throttle bore size on the 4150?

Re: Switched to a smaller CFM to slow car........... [Re: J_BODY] #2694247
09/04/19 09:27 AM
09/04/19 09:27 AM
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S.E. Michigan
cl440 Offline OP
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Originally Posted by J_BODY
That is interesting.... in most cases it seems to make a difference. What’s the Venturi size and throttle bore size on the 4150?



Throttle bore is 1-3/4" Not sure on the venturi size

Re: Switched to a smaller CFM to slow car........... [Re: Clanton] #2694248
09/04/19 09:29 AM
09/04/19 09:29 AM
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S.E. Michigan
cl440 Offline OP
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Originally Posted by Clanton
I have seen some restrictor plate kits that work well you can look into using


We were looking at the EZ plate system. Decided to go new smaller carb instead since our dominator is old and we would probably need a new carb eventually anyway. Jokes on us! LOL

Re: Switched to a smaller CFM to slow car........... [Re: cl440] #2694251
09/04/19 09:32 AM
09/04/19 09:32 AM
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Chuck..I think someone here recommended the ET Genie...Pretty expensive but it works well.


Need your rear end checked out? Contact Grizzly!!
Re: Switched to a smaller CFM to slow car........... [Re: cl440] #2694256
09/04/19 09:38 AM
09/04/19 09:38 AM
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S.E. Michigan
cl440 Offline OP
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Originally Posted by cl440
Originally Posted by J_BODY
That is interesting.... in most cases it seems to make a difference. What’s the Venturi size and throttle bore size on the 4150?



Throttle bore is 1-3/4" Not sure on the venturi size


I just found on the web if it's correct........1.45 venturi

Re: Switched to a smaller CFM to slow car........... [Re: tboomer] #2694269
09/04/19 10:22 AM
09/04/19 10:22 AM
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Originally Posted by tboomer
Chuck..I think someone here recommended the ET Genie...Pretty expensive but it works well.


The EZ Plate company is out of business. I bought the ET Genie for my wife's car so she can run Sportsman 12.0 and slower. Her car has ran 10.97 with it wide open. You check your settings with a dial indicator so you can really dial it in. Last weekend at Pacific Raceways I had it running 12.02 all out. That way the car is still full throttle, normal timing, normal shift points etc.

Probably a bit overkill for what you're trying to kill but just thought I'd offer my experience.

Re: Switched to a smaller CFM to slow car........... [Re: Forest] #2694289
09/04/19 11:06 AM
09/04/19 11:06 AM
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Ask yourself is this a long time solution or a short time solution. Are you going to upgrade the cage to 7.50 over the winter for both safety and room to go faster


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Re: Switched to a smaller CFM to slow car........... [Re: cl440] #2694336
09/04/19 12:52 PM
09/04/19 12:52 PM
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What intake do you have? If you had a Dominator on a 4150 intake with an adapter then you might not have lost any power. If you put a 4150 on a 4500 intake then you probably lost some power but you might have picked up some torque down low so the car goes just as quick. If you changed intakes at the same time as the carb then you have two variables so anything could happen.

Re: Switched to a smaller CFM to slow car........... [Re: cl440] #2694360
09/04/19 01:48 PM
09/04/19 01:48 PM
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A possible reason why the car works well with less CFM: the A:F curve raises faster with the closest jets due to higher vacuum. Perhaps a bit rich was helpful?


Boffin Emeritus
Re: Switched to a smaller CFM to slow car........... [Re: polyspheric] #2694383
09/04/19 02:40 PM
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what about retarding timing a few degrees? Seems all the OEMs are doing it during tranny shifts to cut power and make trans last longer. That would keep all your shift points exactly the same and not increase the chance of tire spin from more TQ down low when the weather gets real good.


I am not causing global warming, I am just trying to hold off a impending Ice Age!



Re: Switched to a smaller CFM to slow car........... [Re: AndyF] #2694394
09/04/19 03:44 PM
09/04/19 03:44 PM
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S.E. Michigan
cl440 Offline OP
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Originally Posted by AndyF
What intake do you have? If you had a Dominator on a 4150 intake with an adapter then you might not have lost any power. If you put a 4150 on a 4500 intake then you probably lost some power but you might have picked up some torque down low so the car goes just as quick. If you changed intakes at the same time as the carb then you have two variables so anything could happen.


Hi Andy! This is what I needed the adapter/shear plate for that I got from you. Same 4500 intake all I did was bolt on the shear plate and the new 4150 carb. 60' numbers are the same. In fact all the incremental numbers stayed the same. Maybe my 4500 carb wasn't as good as I thought it was or the new 4150 is just really, really good?

Re: Switched to a smaller CFM to slow car........... [Re: HotRodDave] #2694395
09/04/19 03:48 PM
09/04/19 03:48 PM
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cl440 Offline OP
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Originally Posted by HotRodDave
what about retarding timing a few degrees? Seems all the OEMs are doing it during tranny shifts to cut power and make trans last longer. That would keep all your shift points exactly the same and not increase the chance of tire spin from more TQ down low when the weather gets real good.


Currently pulling 5 degrees at launch and ramping back in over 2.5 seconds. I may pull some more. Heading to Indy for division 3 finals next weekend. The cut off for that race is 5.40 (1/8 mile)

I may be just fine but would hate to get tossed if I click off a 5.39 on a pass!

Re: Switched to a smaller CFM to slow car........... [Re: cl440] #2694403
09/04/19 04:03 PM
09/04/19 04:03 PM
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Originally Posted by cl440
Originally Posted by AndyF
What intake do you have? If you had a Dominator on a 4150 intake with an adapter then you might not have lost any power. If you put a 4150 on a 4500 intake then you probably lost some power but you might have picked up some torque down low so the car goes just as quick. If you changed intakes at the same time as the carb then you have two variables so anything could happen.


Hi Andy! This is what I needed the adapter/shear plate for that I got from you. Same 4500 intake all I did was bolt on the shear plate and the new 4150 carb. 60' numbers are the same. In fact all the incremental numbers stayed the same. Maybe my 4500 carb wasn't as good as I thought it was or the new 4150 is just really, really good?


Or maybe that shear plate really works! I guess it is hard to say for sure without getting it on a dyno. It is possible that your 4150 carb is working better than the 4500 carb. Usually a good 4500 carb will pick up 20 or 30 hp over a good 4150 carb but when you compare any two carbs the results can vary all over the map.

Re: Switched to a smaller CFM to slow car........... [Re: AndyF] #2694409
09/04/19 04:17 PM
09/04/19 04:17 PM
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cl440 Offline OP
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Originally Posted by AndyF
Originally Posted by cl440
Originally Posted by AndyF
What intake do you have? If you had a Dominator on a 4150 intake with an adapter then you might not have lost any power. If you put a 4150 on a 4500 intake then you probably lost some power but you might have picked up some torque down low so the car goes just as quick. If you changed intakes at the same time as the carb then you have two variables so anything could happen.


Hi Andy! This is what I needed the adapter/shear plate for that I got from you. Same 4500 intake all I did was bolt on the shear plate and the new 4150 carb. 60' numbers are the same. In fact all the incremental numbers stayed the same. Maybe my 4500 carb wasn't as good as I thought it was or the new 4150 is just really, really good?


Or maybe that shear plate really works! I guess it is hard to say for sure without getting it on a dyno. It is possible that your 4150 carb is working better than the 4500 carb. Usually a good 4500 carb will pick up 20 or 30 hp over a good 4150 carb but when you compare any two carbs the results can vary all over the map.


No doubt that plate works good and was exactly what I needed to adapt the 4150 carb to the 4500 intake. Like I said maybe that Dominator has more in it. I really believe that Quick Fuel 4150 carb is really really good though (Obviously)!

Re: Switched to a smaller CFM to slow car........... [Re: cl440] #2694493
09/04/19 09:45 PM
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Originally Posted by cl440
Originally Posted by cl440
Originally Posted by J_BODY
That is interesting.... in most cases it seems to make a difference. What’s the Venturi size and throttle bore size on the 4150?



Throttle bore is 1-3/4" Not sure on the venturi size


I just found on the web if it's correct........1.45 venturi


Interesting..... of course I’m running VP C12 fuel, but my 1050 seemed to wake my car up quite a bit from a 1.48 Venturi 1.79 4825 Braswell (4150 based) carb.... just wish I hadn’t swapped the 727 to the 904 at the same time so I could really tell how much.

Re: Switched to a smaller CFM to slow car........... [Re: J_BODY] #2694672
09/05/19 11:56 AM
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Just pull timing the entire run. We do it with our dragster as my son can only go 7.50 and the car will run 7 teens in Vegas. In fact we pull 12 degrees the entire run and use a small 1050 on it here in Vegas. The carb alone is worth .25 on the 572


As for your results I would be willing to bet it is a tune issue more than anything. Most dominators OOTB tend to be PIG fat throughout the RPM band which is NEVER fast. Pulling a vacuum test on the dyno will tell you if it is to big of a carb or just a tuning issue. We run VERY large carb on the 572 on the dyno compared to what its raced with

Last edited by Al_Alguire; 09/05/19 11:59 AM.

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Re: Switched to a smaller CFM to slow car........... [Re: Al_Alguire] #2694718
09/05/19 03:43 PM
09/05/19 03:43 PM
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S.E. Michigan
cl440 Offline OP
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Originally Posted by Al_Alguire
Just pull timing the entire run. We do it with our dragster as my son can only go 7.50 and the car will run 7 teens in Vegas. In fact we pull 12 degrees the entire run and use a small 1050 on it here in Vegas. The carb alone is worth .25 on the 572


As for your results I would be willing to bet it is a tune issue more than anything. Most dominators OOTB tend to be PIG fat throughout the RPM band which is NEVER fast. Pulling a vacuum test on the dyno will tell you if it is to big of a carb or just a tuning issue. We run VERY large carb on the 572 on the dyno compared to what its raced with


We were just talking about pulling it for the entire run. We may try this. Thanks!

Re: Switched to a smaller CFM to slow car........... [Re: cl440] #2694951
09/06/19 12:18 PM
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HotRod's Frieburger and Dulcich plus Steve Brule on the Motor Trend Engine Masters tested the affects of too small or large of a carb and too much or little timing on performance and the carb mattered the least timing was the power killer. If you can find the episode its well worth a watch


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