30 Years ago, I made a little car with a datsun 1200 engine. I put it up on blocks and now (18 years later) I'm going to be running it again.
25 years ago I changed its cam & valve springs, I don't remember how it idled then but now it idles at 2000 rpm and zings right up to 6000.
(Its cam card says"
232 degrees intake & 242 degrees exaust at 50 thousandths)

Now my question: What rpm characteristics should one expect a Datsun engine to have? One with a little more duration than stock?

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The stock 1200 camshaft will zing right up to 6000 with a good carburetor. And idles at 600 rpm.

The stock cam pulls hard from about 2000-6000 RPM. It is a 248 degree cam.

So it would then seem that there is little reason to change out a stock cam. Can I assume the stock 248 degree cam is measured at 50 thousandths?

You may assume that, but Nissan doesn't say.

Go with a longer duration cam if you want to rev the engine higher.

Thanks, I appreciate your advice.

It revs high enough (always did) but the idle went away. It does idle somewhat slower with the power valve air vent plugged.

A couple of things here:

The numbers from the cam card suggest it's likely 275-280 advertised duration and probably .420 lift.....is the Cam card Nissan or something else. If my guess is correct I'd expect that the lowest idle you will achieve is 1200-1500 RPM's. Do you remember what valve springs you fitted?? I suspect that with that Cam the motor will rev upwards of 7500 RPM's but obviously it would need the proper springs.

Finally that is a very cool car, can you tell us more about it.

Tom

Right Tom, the advertised duration is 270 intake and 280 exhaust.
my notes say I changed the springs
crane springs 80lbs closed 215lbs open
intake opening .441"
exhaust opening .462"
as the cam change was 25 years ago, I remember only that it is a crane cam, so the springs I probably bought with the cam.

The car has a space frame of 1" square tube, a VW type 3 front axle and vw steering but its steering wheel is moved into the center with a #50 chain and sprockets.
The instruments, engine and drivetrain is datsun 1200.
The car weighs 1100lbs (wet). A panhard bar and a 4 shortened Dodge pickup tie rods locate the rear axle. I put overload springs over scout shocks to support the rear of this car.
I made a fiberglass body enclosing the engine and frame.

After it was completed, I found that I'd made a formula junior car (except that the engine was slightly too large to be competition-legal).

Thanks for the compliment.

more details:
- wheelbase 90 inches ( without its removable section)
-Mercedes had a large enough grille to cut down to fit.
-I use a garden tractor battery [lighter and cheap].
-At 200 lbs (complete) the front axle was too heavy, but it had the advantage of being easy to build into the frame. Everything else in it is light.
- I added flat sheet aluminum motorcycle style fenders so it is street legal.
- I made it a tandem seat car with a removable, bolt-in, center section and permanently removed the bolt-in section after a divorce...the car steered much better.

very cool!

Dennis a couple of notes;

On the VW beam axle, that goes back to the 30's Porsche design for Auto Union GP cars. Also Formula Vee got started when Nardi (I think) built a formula junior using Beetle parts. So your while Carrol Smith considered them horrendous they do the job well enough despite the inherent flaws. As for the steering formula vees mount the box dead center but on many of the chassis your feet slip under the tie rods, meaning they are between tie rods and the beam.

Due note that formula junior cars had several engine sizes over the life of the class, before formula ford did the class in

As for the driving position does the gear lever stick between you legs with feet either side of the bell housing or is the driver offset.

Tom