Raising the safe rev limit on a 3.2?

[911st]

For fun I looked in my old Bruce Anderson Performance hand book.

They took a stock 3.2, put full racing exhaust, and 46mm Webber's on it at made 265hp at 7000rpm. I assunm this was a US compression motor.

If it is a street car I might be tempted to set the red line at 7k and not abuse it. Race car, no.
6800 should be safe on a race car.

You are leaving power on the table with the rev limit and the muffler so those are now your limiting factors.

As someone noted above, re-timing you cams might add some. I would look at early SC valve timing specs. This might fill in you mid range some and probably not cost you much up top. This might give you more total power under the curve between shift points.

Enjoy.

[safe]

I might re-time the cams, if there is enough clearance for it with 10.3:1 pistons. I think I will hold of on that until I drop the engine next time and just enjoy it for now
I'm definitely leaving power on the table, to be exact 4.5 hp, cause it made 269.5 at 7000.....

Have to research a little if I can find a better muffler that's still reasonably quiet.

[911st]

The HP difference may be more as you would roughly compair the HP at the extra 200rpm up top against the Hp at where the shift point begins. That is at 4500rpm you were in the 200hp range compared to the 265+hp. Thus, as much as 60hp difference over about 200+rpm of acceleration.

I hear is it difficult to beat the factory 2/1 stock mufflers when it comes to noise suppression v HP. You could add a second pipe to the left side of the muffler and cap it or put a remote valve. This is about 5-10hp at your HP range I would guess.

[911st]

Second pipe would be on the right side, sory.

[911st]

I am not an expert buy you got me thinking.

I looked at a gear chart for my 85 Carrera to see what our shift points are.

Taking it to 7k may help the power between the first/second and second/third a bit. I do not see much advantage above that because the HP curve gets more flat at upper rpm and the shift points out of 3rd and 4th are above 5k rpm.

Want to go faster, do the gears and tighten up 1-2 and 2-3.

For example, if we shift at 6500 first to second, we drop down to 3632rpm. On my car if I could reduce this to 4500rpm I would have about 28% more power going into second.

Gear chart for 85/ 915 please?

[safe]

My rpm drop is a little bigger than on your car.




I'll take it to the track for the forst time (with this engine) on june 7th.

[304065]

Originally Posted by safe

Thanks, John!

Not sure why the curves cross at 3500, or if that is good or bad?
4th is top gear in my car. Yes, full throttle and clutch at readline.


The muffler is a stock -74 Bischof 2 in 1 out. I wonder if I have more power to gain by a better muffler?

I figured it out. The HP and Torque scales are different. It's only when they are the same that the curves cross at 5252.

[911st]

John, you got it.

See post #18 & 20.

[911st]

Gears my Friend, gears!

Instead of coming in at 3500rpm at 150hp you could be coming in a 5000rpm and 225hp.

It will transform your car.

Good luck at the track.