hey sundat1200 if in fsp I would recomend having the engine preped by Rebello but note very pricey and then add fuel injection with throttle bodies and crankfire ign. the stock rating of the a12 is 68 at the crank 90+ hp at crank is possible. I have a datsun comp header and a 3.90 limited slip rear I may part with also a pair of mukuni's without manifold when I upgrade to FI I am also in san jose Pm your phone # . Note only a few people have been able to get away with running a locked diff and they are more likely to break

I am still looking for a 4.37 gear set for my h145a possible trade for my spare 4.63 gears

Man, 90 HP out of a street prepared motor? I'm curious to know how that's done without alot higher compression, a cam or serious head work. I'm sure it invloves careful blueprinting and boring the thing and decking the head to the max limit allowed. But even then its hard to imagine 90hp out of a street prepared engine that makes barely 40hp in stock trim.

Got any tips on finding an H145 LSD? It was my impression the things were made of unobtanium.

I'm thinking at least 160HP probably more like 200HP before you would need that kind of power.
Given you will be seeing maybe 90HP out of a Rebello prepped motor in street prepared I would leave it be.
I've had the H145 LSD on the car for something like 15 years now and it's been trouble free......I've road raced, autocrossed and rallycrossed the car with it. (save the money , you'll be happy in the end). I went 3 years or so without one and managed to do well enough. (On occasion I even managed to beat my friend who's since become National Champ in F125).

Tom

Thanks for the info guys. According to the rules of FSP, I must use the stock A12 engine with only bolt on modifications like a header, carbs, etc. I guess the locked diff would be out of the question then. Exactly how much power would I have to make to justify a locked diff?

What class/setup are you running?

The only time locked diffs are fast is when you have huge amounts of power. With lower power setups the open diff is the winner.

Locked diffs also give your car a Jekel and Hyde personality. At lower cornering forces the car understeers like crazy. As the cornering force increases you reach a point when the weight transfer causes the inside wheel to loose most of it's grip. At this point the car switches to oversteer. Basically your car will understeer or oversteer.

Locked diffs are lots of fun but can be slower with a lower power car.

One mod I did years ago (and just receintly too) is to shorten the radius rods and pull the front wheels forward. 3 things are gained with this mod. 2 big gains and a small gain...

Big gains-
1. Wheels forward shifts weight to the rear.
2. Pulling wheels forward increases the castor (think dynamic camber).

The increased camber from the castor during turns will increase the grip of the front. This allows you to reduce the roll stiffness of the rear suspension or increase the front roll stiffness of the suspension tuning. Either one will help keep more load on the inside rear wheel helping the wheel spin issue.

Small gain-
Increasing the angle of the strut away from vertical increases the rotational antidive of the front suspensioin which can help breaking a bit.

It would be running in street prepared class. It looks like the 1200 is in FSP now according to the moutons SCCA site.

Unless you have a fairly stout motor do not weld up the spider gears to create a locker. Lockers work great for oval track because you can run stagger (smaller inside wheel).
The car will understeer with the locked rear end and given how tight some of the hairpins at autocross are you WILL be hating life. (some of the courses are tight for my son's Jr Kart) I've driven some open wheel cars with locked rear ends on road courses and the same class of car with a LSD and the handling differance is worth every penny.
An easy way to tell what to do is , get one of the more experianced/faster guys to drive your car, if they go faster then the car has more speed just the way it is..........personally save your pennies for a LSD and deal with the car in the meantime.
I should have asked first but what class are you running H-stock , DSP or EP??

Tom

If you are gonna be making left & right turns with a locked diff. then make sure you have no stagger on the outer circunfrence of your tires. in the rear, because if you do then the one that is smaller will turn more revolutions than the bigger one = bad handling.

My dad used to do oval-track racing, and they always locked the diff, because of wheelspin. They would then put the car in a proper 4 wheel drift, and maintain a much higher speed through the turns. A proper 4 wheel drift is where you are still going around the turn/bend, but with your wheels facing slightly in the way you are going, no counter steer, then it doesn't count...

Not like this new drifting thing where you have to counter steer to keep from wiping out. It looks far more spectacular, but it much slower.

I would say if wheelspin is a problem with an open diff then go the locker, but otherwise stick with the open