Switched to a smaller CFM to slow car...........

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.

I have seen some restrictor plate kits that work well you can look into using

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

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

Chuck..I think someone here recommended the ET Genie...Pretty expensive but it works well.

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

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.

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

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.

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?

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.

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?

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!

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)!

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.

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!

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

Thanks! I will check it out!

Yeah a smaller carb will kill some top end power but usually the rest of the power curve is the same and sometimes the lower end of the power curve will even be higher with a smaller carb. So it is quite possible for a car with a smaller car to run just as quick if not quicker with the smaller carb. It really all depends on the torque curve and how well the car hooks up.

Nothing wrong with using the smaller carb, especially if the car runs better with it. Pulling some timing is probably a good way to slow the car down but you'll want to be careful that you don't cause any problems with the retarded timing. The engine will build more heat with retarded timing so keep an eye on the gauges.

Got it. Thanks for the info. Headed to Indy Thursday morning for team finals. Hoping for a good weekend of racing.