So I have the Summit 850611 ignition box on until my msd comes back. When I installed it I set the rev limiter to 5k, thinking I'd never hit that mark with the mild street racing/playing I do. (Just don't like a certain type of driver to pass me, ha ha).

I've never driven with a tach, so I don't have a sense for rpm's. I also have a C6 (tricked out), so surely I wouldn't hit 5k. But ... I was racing some guy and winding out in second when the secondaries opened and that long moan from the engine began, and rpm's started climbing, and I stared to pull ahead, when the engine just crapped out. It kept running fine, but hit a ceiling with the rpm.

Could I have hit 5k rpm? (Or is the box poorly calibrated?) Is that possible with an automatic? I'll have to dial it up to 6k and see if there is a change.

 

Stock carbureted [which yours certainly is not] falls flat by 3500 RPMs!

 

Heya K,

I have a 3.00 rear end in mine, so the gearing is long, and I can hit 4500 - 5000 RPMs without even thinking twice (same with my previous engine). It's easy to do. It also always felt like there was plenty more power to be had (never fell flat), but I just usually stop there to be nice to the engine.

You also shouldn't be limited by an automatic. The C6 is known for being a power hog, but from what I've read, that's only off the line and affects low end torque. That drain decreases as the RPMs increase. So, you may have a few less HP at 4000 - 5000 RPMs than you would with a manual due to slippage, but you're definitely not going to straight up feel it hit. The C6 is used in drag racing, FWIW.

The only time I ever felt any of my 300s fall flat over 4000 RPMs was when my wife's '84 had an issue with the distributor and the mechanical advance was sticking.

Otherwise, I think you hit your limiter. If you've never hit it before, I think you've been babying that engine of yours!

 

Do you know how fast you were going at the time?

RPM = (Speed * Transmission Gear Ratio * Final Drive * 336) / Tire Diameter


I don't recall what your rear end gearing is or your tire diameter, but a C6 is:

1st: 2.46
2nd: 1.46
3rd: 1.00

So, if you have a 3.50 rear end and 30 inch tires and were in first gear and know you were doing at least 50mph:

RPM = (50 * 2.46 * 3.50 * 336) / 30

Or 4800 RPMs.

 

AB: No, I can't say how fast I was going with certainty. It has happened twice now. I'll to get unlazy and open my hood and turn the rev limiter dial. Sigh.

Well, after the worst experience I have EVER had with a company--10+ calls, on hold for 30 minutes once!!--I think I got the Texas two step from the techs in El Paso where the repairs are supposed to be made. After two weeks I got the box back with a note that said it not economically feasible to repair!!! And I was paying for the repair. I just want that ... company out of my life.

So I'll stay with the Summit box. I just need to upgrade to a CD coil. I really felt the msd gave better power.

Note of interest: When I had my DS2 dizzy rebuilt/recurved, the guy said to run a base timing of 16*btdc. With the msd I had it set at 8* due to pinging. Without touching the dizzy, when I installed the Summit box, the timing jumped from 8* btdc to 16-18*btdc. It is difficult to tell exactly b/c it is at edge of the scale and haven't degreed the dampener.