Slowing down a 3 3/4″ with 33mm

[67CudaRacer]

So I bought my oldest a new to us 7.90 car with a 3 3/4″ ZR4 on it. I haven’t weighed it yet, but it has a bunch of weight on it (As much as I’m really willing to put on it) and he only weighs about 80 lbs at the moment. Talked to JR about a tall gear package to kill it out of the hole, but we are worried it will run over 85 mph. They suggested trying to take the 42mm off of it and slow it down with a 33mm, but he really had no idea how much it might slow down. So I was wondering if anyone has experience with doing that and the results.

[Matt Parlett]

Do you know what the total weight of the car is with driver right now? In general I have found that a heavier car is more consistent and less effected by the wind. I consider anything under 430 light and anything over 530 heavy.

Also, do you know what it ran with the previous kid and what the driver weight difference is? Knowing what the current engine, clutch and gearing combo is gives us a baseline to adjust from.

So you may be better off leaving it alone and adding the weight but it would help if we knew where your weight is. And I know these engines can get really angry and temperamental if they don’t have the right amount of fuel. Choking it down that much may cause more problems.

www.Computech.com

[67CudaRacer]

No, I don’t really know the total weight of the car yet. I need to get it on some scales. I believe the previous driver was around 165 lbs and my boy is only around 80 lbs. I still need to look at the front sprocket, I saw the rear was a 66 when I was trying to clean it up a bit. I know I still have some homework to do to figure all this out as far as knowing total weight, gearing, etc. but was checking on the smaller carb as an option.

[LAVAR LEWIS]

I couldn’t get a 33 carb to work with my Craws 3 1/2. With a 42 carb, 1050 restrictor plate, 15-69= 4.66 gear ratio and -3 degrees of timing. Total package 560 lbs. This is how I slowed down my 8.90 car. 2017 Mike bos car with ever weight tank filled.

[67CudaRacer]

Was it consistent with the restrictor plate Lavar?

[LAVAR LEWIS]

I’m getting there slowly but surely. Definitely going A to B every pass. This weekend at Rockingham it was definitely doing good.

[Derrick Bailey]

1. Our car was running 9.90@ 60mph with a 7.50 gear , I wanted to slow it down  and went to about  6.00 gear and half  throttle  ended  up at about 11.00 at 59 mph so that  did not work

 

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