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Well if your car really has 3.08 gears.
1. Using arbitration number of 400 ftlbs. Times 2.45(first gear ratio) equals 980 ftlbs. Into the driveshaft.
980×3.08=3018 at the wheels
So that is the obvious benefit.
Going from 3.08 to 3.91 is a 1.27% increase in rpm your trap rpm from your post is 4300×1.27%= 5461 rpm that uses all of your engine in a 1/4 mi.
2. My suggestion to go with 4.88 would limit you to 1/8mi only. Or build 2 pigs to run the 2 different tracks.
Going faster 101 more fuel and air through the engine the more work it does. Spin it faster with bigger gears, car will get faster.
That converter is working hard to wrinkle that slick thatuch with tall gears.
That’s the only 1/4 mile race we have around here. Once a year thing. So I’m going to set everything up for 1/8th. I’m sticking with my one shift plan for now as it’s working. Car is too consistent to veer off that path. Consistent 60 foots too. Yea a 4.88 is a lot. As the car develops who know what it will have. Another thing to consider. As I put more gear in it I’ll reduce the available time the car is on the track. Lower ET’s thus reducing the amount of time the car has to peak those RPM #’s.
I can live with that.
And if you own the 3.55 already even better.
Would it be fair to say that going to a 3.55 spool would pick up a tenth in the 1/8th. I can’t find a calculator for that. My second gear ratio I believe is 1.54
It should. The 3.55 should make your gains in the 60'. Second gear is 1.45
Ok good I was hoping so. That plus some weight reduction & a little more tuning should have a pretty quick car with just one shift.
One of the roving Motorsports photographers got this post burnout pic of FURYIOUS
i ran 3200 rpm converter , 4.56's in my 63 fury , with a 30'' cheater tires , 6200 through the traps , through the mufflers . still working on its new engine . rb block 4.40 - 4.5 bore , 4.5 stroker crank = 547 - 572 . max wedge setup , but vi'll leaning towards my mech hilborn setup in have . this was intake i had been running , the new motor would get the newer max wedge intake , match ported with my (chapman ) mopar stage 6's . man i miss driving that car around , drove everywere . bob your a lucky son of a gun . how those 3.54's do it for you . that the gear i run in orangey .
Haven’t put the 3.55’s in yet.
do you have any thing deeper ?
Don’t want anything deeper right now. I’m doing a one shift 1/8th Mile
I don't remember what diff the car has, 8 3/4 or 9 1/4.
8 3/4 currently
The 1.45 throws my math off. I had used the 1.54 to get a trap rpm of 5500 with a 3.55. So plugging in the 1.45 second gear it shows a trap rpm of 5650. A bit more than I want but I believe that’s based on a lighter car so sounds like a 3.73 gear is what I need. When I plug in my current numbers with the 1.45 second gear is says I have a 2.94 gear. As I’m currently trapping at 4400
2.94 is a normal Chrysler ratio, the 3.08 you mention is a GM ratio. You will want a 3.23 of you stay on the path you want to go with one shift.
Why the 5500 rpm ceiling?
The guy I bought it from shifted at 5500 on pump gas. 92/3. It’s got a 6200 pill in it but he said to turn it that high it need Race fuel. And since so many things on this car I had to fix because it was Mickey Mouse engineering I’m not sure I trust the engine much higher than that. If I get time & I doubt I will I’d like to pull the pan & look at the bearings. This has been a very low budget car so far. I see so many guys especially Chevy guys just run the crap out of their cars. Spin the piss out of them & gernade a Motor & they are done. Takes a year before they can afford another motor. Just to go a little quicker in a bracket car.
Something wrong with the math on post 315. A 1.45 is taller than 1.54 so the rpm should be less at trap speed, not more. Which should keep you in the direction you want to go.
Agreed. That’s what I’m saying so now I need a 3.73
3.73 will turn you higher at the trap?