Does anyone know how high a stock A12 engine can rev?

A stock A12 is good for 6,000 RPM, and any good condition used one should rev to this.

The A12GX engine came with dual valve springs and was good for 6,400 RPM.

The stock bottom end (block, pistons, rod & crank) is strong enough to rev to 8,000 RPM, but you'll need a different cam and cylinder head to do that.

A12 stock will run to 6800 in 1st and 2nd, 5800-6000 in third and 5500 in 4th on flat ground................after you'll need a hill

I've run the GX motor in my car for something like 15-16 years now. 1st and 2nd it will go to 8100 and then float the valves, 3rd 7500 RPM's, and at a reeeeally fast track like Willow Springs 7200 in 4th.............keep in mind this is with 60 series tires and a 4:11 rear gear. The head has been mildy cleaned up along with a 2" exahust and header. Also I run velocity stacks with no air cleaner.

Fully tuned A series engines will rev to 9500 on a near stock bottom end..................be prepared to take it apart every 6-8 hours of run time. This is the reason mine is so under tuned, that and the stock gearboxes are to widely spaced for such a cammy engine.

Our eventualy goal is the 95-100hp range. (Flywheel) I seem to recall a race A12 makes 140HP at the flywheel (100HP or so to the wheels)

Tom

Hi RT, good info.

By near-stock at 9500 rpm, I'm guessing a stress relief on the rods? Would you need forged pistons for that?

For the 6-8 hour teardown is it the main bearings that go bad?

So i'm good for 6800 rpm?

Quote:

I would balance the bottom end to run it reliably. Mine is a GX and stock standard.
At 6000rpm it does'nt like me anymore.

i have mostly stock a12 just extractors exhaust, 32/36 and it has been to 6200 and all is good but doesnt make much power there

Ok if I remember correctly the 9500 RPM wonders have shot peened rods with 14-1 pistons and the whole assembly balanced, the one I had used cosworth pistons. The parts needing to be replaced were rings, rod and main bearings and rod bolts.(maybe $250 in parts) I seem to recall the head needing a refresh about every 6-10 events. The Nismo option 1 & 2 cams do nothing below 5K and one of them comes on at something like 5800. There was an east coast engine builder that did Jeff Werth's Run-offs winning A-series engines who built for torque and those "only" revved to 8500.

As for 6800 in a stocker, nothing bad is likely to happen but as mentioned with 68 HP your not likely to see it in anything but 1st or 2nd gear. The only reason I revved the original A12 that high was because of the 3000 RPM drop between gears........I was just trying to keep the motor above 4K during races. Frankly unless you Pony up for a close ratio gearbox your better off tuning the car for mid range.............you can rev the snot out of an A12 but I'm not sure anything is gained. In fact when I manage to finally find a mid close 4 speed I will only be reving the engine to 7500 RPM's

Tom