1940 flywheel

[JSeery]

Rumble Seat quote:
"The 'lip' type flywheel used a 9" clutch and weights 38.7 lbs. They came in all of the early V8's. They are my preferred flywheel because they use the lightest clutch (bet you've already figured out I'm some kind of nut about light rotating mass)...Machining the flywheel's lip off, chamfering outward from the edge of the pressure plate to the starter ring gear, dishing out the rear of the flywheel to reduce the flywheel thickness, will reduce the 38 lb weight of a lip type flywheel to about 20 lbs. Combined with the lighter 9" clutch, they are my preferred combination for a street flathead."

 

[JSeery]

Interesting information. So the answer is... go with the 9". Now, as a hypothetical, why not go ahead and engineer an even smaller (Dia.) set up like, 8" or even 6". Would that increase the performance even more than the 9"?

Yes, but you are moving into the realm of racing application vs a street setup. Also throw in an aluminum flywheel, etc. But for a street setup I would go with a lightened stock flywheel and a 9 inch clutch (by the way, I run an aluminum flywheel!).

 

[Seth Swoboda]

Guys, tonight I weighed a 59A flywheel, clutch disk, and 10inch pressure plate on a state of Illinois certified scale (legal for trade). The whole assembly weighs 50 pounds.

Now, another question. Is there any advantage to cutting the lip on the 40 flywheel, 9 in pressure plate for an otherwise stock 1940 engine? Will cutting that weight off be noticeable in this set up?

 

[JSeery]

Now, another question. Is there any advantage to cutting the lip on the 40 flywheel, 9 in pressure plate for an otherwise stock 1940 engine? Will cutting that weight off be noticeable in this set up?

It all depends on what you are after performance wise and what type of car it is (weight wise, gearing, etc). The lighter the car the lighter the rotating assembly can be which equates to faster acceleration. What's going on is inertia, the heaver assembly takes longer to "wind up". A heaver car/truck needs the added inertia to get it going. So weight, rear gear ratios, etc all come into play. Two extremes as examples, a light weight striped down 32 or 33 car would do well with a light weight assembly. On the other end a truck used to tow or haul heavy loads benefits from a heavy rotating assembly. It is just going to depend on how you drive it and what kind of performance you are interested in.

My suggestion would be if you have it apart have it resurfaced and machine the lip off in the process and stick with a 9 inch clutch. But I don't think it is worth taking apart to machine if it is currently working well.

Note: Grumpy seems to think it was worthwhile (#9).

 

[Seth Swoboda]

JSeery, thanks for the info. 1940 tudor sedan I have not gotten into the engine rebuild yet but I will be doing so. I'll cut the lip and stick to the 9 inch clutch. The '31 Victoria in my avatar has the lip cut off the model A flywheel and then some more. I'm also using the V8 clutch and pressure plate in that set up behind a stock Model A engine.