Hi, I am going to be putting some better heads and a cam in my cars current motor which has stock rods with good bolts but has the heavy sealed power forged pistons. Most guys are telling me that it will run in the 10s if it runs like it should. I am going to be upgrading to a spool in the rear end. and I will have a choice between a set of US gear 3.73 gears that are made to fit a 4 series carrier or a set of 4.10s. I was running 4.10 till the ring gear broke. On a good day it was running about 5800-5900 rpm in the lights at only 114-115 mph. I am wondering if the car picks up to say 117-118 mph range with 4.10 gears will I be turning the motor to high in the lights? What would be considered a safe max rpm with the heavy pistons? I have been trying to keep the max rpm to about 6000 but I have been to about 6400 in the burnout when not paying attention to the tach a couple times. Would I be asking for trouble if it hits say 6200 in the lights? Or should I play it safe and go with the 3.73s? I run 29.5-10.5 slicks. Also would going down to 3.73 gears from 4.10s slow the car down allot? Now that I have everyone all confused with my ramblings, what do you all think? I don't want to hurt the motor if possible but I also don't want to be loosing ET/MPH by being geared to high. o No:
I have 30x9's and often wonder how 4.10's would work. I have the gears just dont feel like changing them.
HI well i think that your car ran pretty good with your org setup now you are going to a wilder cam etc///this will change your hp curve//it most often gives you more hp at the hi end but you lose some at the low end////////so if you have set 6k as your red line you have to drop to the 3.7 unless you can get a bigger tire under it LOL BUT the frist rule in drag is do ONE thing at a time MY take is stay with the 4.10 //se what it doeswith the new cam etc then go from there ////////////////// luck and let us know pete
I found some racing calculators on the TCI web site this morning. I got it pretty close to what my old setup was doing and was suprised to see it didn't gain much in rpm to go from 115 to 118 mph with same tires and gears. So going by this calculator the 4.10s would be the ones to use. I even tried some 4.33 gears and the rpm didn't go ski high. I will copy and post a link to the calculators, they are neat to play with. http://www.tciauto.com/tech_info/calculators.htm
RPM calculators dont factor in convertor slippage. I use the one on Richmond gear site all the time. I found , if they tell you to run 4.56 run 4.10. With my stick car it was right on.
I'm getting my Regal ready right now. With a 29" tire, you're good down to 10.40 or so with a 3.73 gear and no more than 6,000 rpm's. With a 4.10 gear, you'd be spinning at 6300 rpm's. I'd go with the 3.73's, especially if you end up wanting to go even faster (I know that's never happened before).
I put a link to the TCI calculators in a post a few back. They have a bunch of different ones. One is for figuring converter slip.
