Blowers and Rear Gears

[99CobraP1SC]

I need advice. I have been running a P-1SC with 4.10 gears. I love the pull from a roll, but the launch s@cks. I am running 12PSI also, but I never seem to get beyond 9-11PSI before I hit the REV LIM (6.8K, I got a 99 cobra) depending on the gear. I also got a PowerPipe.

Now, I am upgrading the internals of my engine and boring the 281 by .020. I am upgrading my P-1SC to a D-1SC and going with an 8RIB setup. Plus adding BBK LTs. Not sure what to do with the 4.10s.

Should I go to 3.55 or 3.73 gears? I have been told to stay 4.10s because if I go 3.55s or 3.73s I will need to shift into 4th gear too close to the trap. Right now I seem to be exiting the trap very close to 6.6-8K (now sure but high in the RPM band) in 4th gear, with my current setup and 4.10s.

I am most interested in running the 1/4 with this car.

J

[WA2FAST]

Are you planning on running more boost with the D-1SC? If so, then you have to figure more power... the .020 alone with a fresh re-build isn't worth too much (unless your rings were in bad shape), but you may want to change over your gear depending on how much more power you are going to be running. Figure out how much power you should be laying down and then go from there as to what gear to run, you may not want to change, but you never know. I personally am going to be running out of gear because I already am running 4th out at the track with my 3.73, so I need to step it down a little after the blower install I'm sure.

[99CobraP1SC]

I would like to run 15PSI, I think I will hold off any gear change, like you suggest, and just see how she runs with the D-1SC, 15 PSI and 4.10s. Then make the call.

J

[WA2FAST]

Stepping up from ~#10 of boost to #15 is going to give you substantial power increases and you are going to be trapping a good ammount faster than you were before. I think that you will find that a gear change is in your near future because you don't want to run out of 4th near the end. You should be able to ball park what you will be trapping at once you find out how much power you actually are laying down, and at that time you will be able to do the math and figure out if a gear change is neccessary with out going to the track to do so. I think with that kind of power increase, you will find that you are more than likely going to need to step down to a 3.73, otherwise 4th will probibly run a bit short. Good luck with it and let us know how it turns out.

[99CobraP1SC]

Thanks. If I am seeing near the end of 4th today, I will probably require a shift into 5th gear with 4.10s at 15PSI. I will keep you posted as the project progresses.