hey guys.. i was wondering what the reving, or RPM limits are on the LT1?

but what would be the redline on the stock form LT1 as opposed to a modded one with an LT4 HOTcam and heads? guestimates are OK


question #2... have any swappers in here ditched the opti-spark in favor of the Opti-direct?

i know that the opti-spark coil charging is 20% less effective at 5000rpm's and 40% less effective at 6000rpms.. (GMHTP Nov 04) i would think the Peak HP and Tq #'s would move up the RPM scale .. anyone have thoughts or experience..?

 

Only thing I can chime in on, the rev limiter is set at 5880 so I would estimate that the redline is 5800 if it's done like my Mustang which the rev limiter is at 6250 but redlines at 6000.

If you are going to change the cam, I have heard that the LT4 cam doesn't increase much at all, and with the Trick Flow heads, you might be better of with a CC306 or one of those cams to take full advantage of the heads.

 

ok cool.. thanks for the info...

but the cam is the LT4 HOT cam.. not the LT4 cam.. its a good deal bigger then a stock LT1 cam..

so there is no way to raise the RPM limiter in the PCM? or is that just a bad idea to begin with?

 

Well, the Hotcam is the same as the cam that was in the LT4 Corvettes, when GM released it, they called it a "hot" cam since it was hotter than the stock LT1 cam and I know someone who has the entire setup with the intake, heads and cam and he stated to me that it didn't help the car much at all. You can program the rev limiter in the PCM to whatever you want it to be, the cars also have a fuel cutoff as well that will need to be programmed as well, but to be safe, I would stick with the stock rev limiter as that the redline isn't as much for the cam as it is for the rods

 

the hot cam from gm performance parts has shorter LSA and slighty more lift and if you get the kit it comes with 1.6 rockers to gain even more lift

 

No they are two different cams. The '96 production LT4 motors had a cam slightly larger than the previous LT1 cams. It was a similar grind with no fuel pump lobe. The hot cam is considerably larger and has a fuel pump lobe. It is sorta a generic hydraulic roller cam that can be used in Gen I (with a mechanical fuel pump for carb applications and modified dowel pin) and Gen II motors. It was advertised to be to be an over the counter GMPP upgrade for those motors. However, it has the afore mentioned features to be used in other motors.

Your motor will be RPM limited based on the bottom end and overall power curve. With the right cam you can make power up to and past 6500rpm. However, the bottom end may let go if it is not built for it. You will have to figure out what kind of power you want and build the bottom end to match it if it entails high RPM's.

LT4 production cam (with 1.6 rockers)
203/210 duration with .476/.479 lift on a 115° LSA
No fuel pump lobe

LT4 Hot Cam (with 1.6 rockers)
218/228 duration with .525/.525 lift on a 112° LSA
Has fuel pump lobe

 

and GM NEVER put the HOT CAM in any production car from the factory.. it was aftermarket..

 

The redline on my stock auto 94Z's tach appears to be about 5700-5800 or so, shifts right at redline at WOT. No idea what the limiter is at.

I've heard you'd want to bump the redline/shiftpoint up to 6100-6200 w/ the hotcam if my memory isn't failing me.

 

i've got a question.. i was toying with the idea on a 383 LT1.. all forged internals with a carb sitting on top... is there anything special with an LT1 that I would want to limit my rpms at or is it the same as an sbc

 

With just bolt ons, I set my rev limit at 6500 and regularly shifted at 6300. It would pull to 6500 but I never tried past that. It also helped me get the mph I got by turning it that much.

 

I used to shift at 6300 until I dyno'd it and found out peak power is at around 5900. I shift out at 6100 now.

 

Well, Texas, you know dyno numbers don't show the whole equation. When I was n/a, my peak power was way below what I shifted at. But if I shifted at my peak power rpm, I would run slower. Making more power longer is where you get your best track times. I am not saying your car would run faster(read, you know your car better) if you shifted later. Every one is different.

 

oh yeah I definitely know what you mean, I still go past it. I just figured I'd save some wear and tear on everything and shift a little lower and still run fast.

 

Don't compromises suck?

I guess if tenths don't matter, it isn't a compromise. But I can't help it. I have to wring the most I can out of it. It will bite me one day.