Differential ratio

[bozo]

I'm building a stroked Dart small-block engine for a 1965 Mustang convertible with a 4-speed manual transmission. The engine uses AFR 1450 heads, a CompCams XR268R cam, solid roller lifters, and a 750 CFM carburetor. It should make at least twice the horsepower of the stock V8.

The stock differential ratio is 2.80:1. I'm adding a limited-slip carrier and will replace the original ring gear and pinion. What differential ratios can I use with this engine and transmission combination? What differential ratios will give best performance? Are there any ratios that shouldn't be used?

[Awesome Bill]

355 would be your best bet and nothing over 373. Your not going to make twice the HP. Maybe 50-100 more than stock. 400hp is a ton and most people don't even get close to that.

[bozo]

Bill,

Thank you for the advice on the differential ratio, but I hope you are wrong on the engine's performance. We used a sophisticated simulation program (Engine Analyzer Pro v3.3) that knows the exact characteristics of the cam, heads, intake manifold, carburetor, and exhaust system. It's detailed enough to care whether the piston-tops were coated (they were). It says the engine, at 364 cubic inches, will make 534 horsepower at 6500 rpm. Max torque is predicted to be 483 ft-lb at 5000 rpm. To make only 100 HP over stock, this simulation would have to be very wrong. I don't have the engine in or running yet, but if I get only 50-100 HP, it would have been much cheaper and quicker to just by a good crate engine.

[Awesome Bill]

You have to have a real dyno calibrated correctly to really know what you have. If you think your going to make 1.467032967 per cubic inch, then you have a great bit of trust in a simulation program. I would be willing to bet real e.t. proves way different. But you always can try it and see? Any good engine will tell you that is very unrealalistic goals. If I done 450hp with that combination on pump gas I would be very pleased. That is a more realalistic 1.226 hp per cube for pump gas and a little engine @ 6000 rpm or so.