Rear End Ratios for STREET & STRIP
 

I am building A 31 coupe for Street and Strip. I have acquired most of the parts for the engine build which consist of .80 oversized pistons, 1.70 intake valves, a Brierley cam, 6.5 head, dual strongberg 81’s, reds headers and a FSI centrifugal distributor. I plan on using a 39 synchromesh 3 speed tranny with lightened flywheel and V8 clutch.
I am running 1936 Ford 16 inch wheels with 6:00x16 tires.

This brings me to the rear end and what ratio will be best suited for both track and street. I plan on racing in the race of gentlemen which is on the sandy beach of Wildwood NJ.

I am looking at a 325:1 which will give me good road speed but wonder if that is too high for drag racing on the sand at TROG. I notice most guys start in second gear in the sand but with the 39 synchromesh tranny with a 1st gear ratio of 2.82 and a second gear ratio of 1.607, it could make up for the higher rear end ratio by starting in first and speed shifting with the fully syncro trans.

What are the thoughts of the Ford Barn Guru's that have a lot more experience at this that I do.

Are there others I should look at? I would like a quick change unit but they are very expensive and hard to find.

Re: Rear End Ratios for STREET & STRIP
 

This is one question you might think about asking over on the V8 forum, only because those guys have a lot more experience with the kinds of mods you're using here.

Re: Rear End Ratios for STREET & STRIP
 

I'd stick with the 3.25:1, solid compromise for both road and sand if you're running that trans.

Re: Rear End Ratios for STREET & STRIP
 

What about running a quick change rear end? That way you could change ratio at the track depending on results.

Re: Rear End Ratios for STREET & STRIP
 

How about a Mitchell Overdrive.

Re: Rear End Ratios for STREET & STRIP
 

OP says, "I would like a quick change unit but they are very expensive and hard to find."

Re: Rear End Ratios for STREET & STRIP
 

Tell us more about the street side of the use. How fast do you want to go, how long do you want to go at those speeds? What engine rpm are you building for?

A 3.27:1 is a tall gear, you'll can get up to 40-45 mph in second with a built engine. That's probably too tall to start off in 2nd with a 3.27.

Re: Rear End Ratios for STREET & STRIP
 

https://www.pacificquickchange.com.au/
Not hard to find if your ok with a new one.

Re: Rear End Ratios for STREET & STRIP
 

Many years ago I built a small solar cell powered car for a drag race contest. The contest was sponsored by Sandia National Labs and was part of a conference. They provided the cells and motor.

Among other innovations, my car had a variable speed transmission consisting of audio tape (remember those?) that wound between two pulleys. The tape started out on the output pulley on the rear axle and the input pulley, attached to the motor, was bare. As the tape wound onto the pulley on the motor and off the pulley on the axle the ratio would change.

My car was at least twice as fast as the other cars.

I am just wondering if something like this could be used for 50's drag racing. Maybe a steel tape could be used. A solid axle could be used with a large pulley on it. A differential is not needed for drag racing. In my mind I see another pulley attached to a right angle gear system which is lined up with the pulley on the axle. Of course this could only be used for racing.

What do you think?

Re: Rear End Ratios for STREET & STRIP
 

Interesting concept :)

Re: Rear End Ratios for STREET & STRIP
 

Kinda like the variable speed used on Rokon Motorcycles and snowmobiles?

Re: Rear End Ratios for STREET & STRIP
 

That's 1 hell of a neat idea using an audio tape a cassette tape I'm assuming as a variable speed transmission in a small car application I'm gonna have to remember that!!!

Re: Rear End Ratios for STREET & STRIP
 

I ran a 3.27 rear in my speedster for awhile, and didn't like it. Starting from a start was not good, on the highway was great. Trying to race it, you'd lose right at the start!