I know these posts have been beaten to death, but because the gear ratio is so specific to the engine and driving style, I thought I'd post up my specs and get some recommendations.

The specs on the engine are located here:

http://www.tuffdawgengines.com/ford_302_375hp.htm

The car is a '65 Mustang 2+2 with a 5 speed and 225-50/15 tires. The Currie 9" rearend (about 40 miles on it) has 3.25:1 gears because the engine at the time was a 351W with almost too much torque off idle to put to the pavement. I do know that this new motor will require some lower gearing to get out of its own way, but really don't know how low to go. My '65 GT had 3.50:1 but I don't think that will be low enough for this application.

A safe bet would probably be 3.75:1 but I'd like either some confirmations from others or other recommendations. FWIW, the vehicle will be a weekend warrior, cruiser about town or up Pacific Coast Highway on a warm summer evening (with the occasional dropping the hammer as required ). If it matters at all, the car has the full Global West suspension.

Also, any second guessing on the engine for this application? My old engine was a 351W with solid lifters and a lot more lift so I didn't think this one would be too much for the street for tooling around.

Thanks!!!

 

I think the actual number is 3.73:1, but that is the gear I would consider for your application and driving style. If you are going to go to the strip often, then step up to the 4.10:1 Consider some traction bars if you don't already have them.

 

whats the final drive ratio? if your final drive ratio is 1 then 3.73 is a bit high and 4.11 would be extremely difficult to ever take on the highway. In my caprice (i know not a mustang but its the same principle here) i had 3.73 gears with a tranny taht had a final ratio of 1. And at 60 i was running somewhere around 3500+ rpms. I swapped in a tranny with a .7 final ratio and bumped the gears to 4.11s and now at 60 i am closer to 2200 rpm. Just my 2 cents

 

btw this site has a nice little tool to use, http://www.csgnetwork.com/multirpmcalc.html

 

Drive the engine with the 3.25's first. You may be pleasantly surprised.

With OD, 3.73 is fun. I have 3.80's with a 302 and have trouble keeping the tires from turning into smoke. And, it's likely your 5-speed has a deeper first gear than my Top Loader. Knowing your tranny ratios would be helpful, too.

 

Tranny gears are 2.95, 1.94, 1.34, 1.00 and 0.80:1. CompCams recommends a 2500 stall speed and low gears which makes me think that the 3.25:1 won't be enough with the manual transmission. The OD is not that tall at only 0.80:1, so 3.75:1 (all the charts list this, not 3.73:1) would be the equivalent of 3.00:1 in a non-overdrive car. For sure I'll try the gears that are in there but I'll be surprised if I have enough gear.

Thanks.