Who recommend this ratio? 4000 or 4500 lb car, which is it? Can we narrow down the stroke? I can't or won't even take a guess with so very little information. If this is a drag car, we also need a track length and max rpm.


Hutch

 

Hutch is this a valid SLR chart?

https://www.cartechbooks.com/media/wysiwyg/8.JPG

Thanks
Tom

 

If its anything but a N/A car you can forget about that. I would be on the rev limiter at the 1/8th mile if I went by what that said.

 

Looks like a decent guide to get you in the ballpark.


Hutch

 

Update weight is somewhere between 4000-4500, havent hit a scale. Its a 4.5 inch stroke motor with a roots blower. I was using that chart to figure the ratios. That being said my trap rpm qas the biggest concern.
The big question is how does a torque convert vs a clutch effect this ratio. Is that chart na manual cars only? Does converter torque multiplication play at all, does tire size get calculated into it also.

 

Ok, so target rpm at the finish line, a rough hp number and track length would help determine a rough ratio number.


Hutch

 

Hutch my slr is 12:10 ,car is way to violent on the line. I'm going thru the lights at 7800 which is where I want to be. 1250 dyno hp and racing 1/4 mile. 2.48 first gear 400 with 4.88 gear and 33.5 tires. I'm concerned that if I change first gear or rear gear I won't have the rpm in the lights. HELP

 

Change first gear ratio lower?

 

Car weighs 3420 with driver. 8.30's in quarter at 158 mph 5.30 in eighth at 130 mph. Pulling 3.5 to 6.5 degrees on launch for 2.5 seconds to calm it down.

 

2.10 might work out well in that case.

I based my guess around 7800 at the stripe. 4.88 on a 33.5 diameter tire. 1250hp.

 

In that case anything is possible.

 

How much would it kill it to let the converter slip at the stripe? Why not run a 4.10 or 4.30? That puts you in the same ball park for SLR as a 2.10. For sure a cheaper test.
Doug

 

Funny you said that Shawn I just sold my th400 that had the 2.1/1.4 in it and am switching to a glide with a 1.64 first in it. I had so much timing pulled at the hit for 2 seconds then ramping up, as well as rolling the nitrous in so slow that I’m dead set I’m leaving .3 on the table from all of it at a minimum, car was extremely hit or miss before the wreck, dead hook and go or totally blow the tires off, and the gearing I suspect was making this way way worse..... see what happens when it goes back together. I expect the rear gear to need a change but I’m leaving it alone initially, since the trap rpm was about where I wanted it.

 

Should also mention cars losing 200-300 lbs when I’m done fixing, so I expect that to aid The 1.64 working out as well, lots less weight to get moving