JADIII35

Hey everybody,

I have finally organized all my time slip data and compared my dyno pulls. I need advice on which rear end gearing to upgrade to: 3.23 or 3.42. I have 2.73 posi now and they yeilded me these numbers.

190 rwHP at 3750 rpm
280 rwTorque at 3400 rpm

0.834 2.418 15.646 87.740 average
1.137 2.663 16.104 90.190 max.
0.599 2.130 15.308 86.030 min.
Reaction 60 ft 1/4 et 1/4 mph

I don't care about gas milage, but I still need the car to be able to travel highway. Are 3.42 going to be to much

305 H.O. TPI rebuild
cran cam roller cam
shaved heads
ported plenum
slp headers
3" cat back
700R4 rebuild w/ shift kit
suspension

Thanks for any advice,
Jim

JADIII35

Another bit of info is that my engine pulls strong until 5000 rpm which also just shy of my shift point.

Thanks everyone,

Jim

nsimmons

Your dyno pull shows your done at 4000rpm why shift at 5000. With a curve like that your going to want to keep the gears numerically low, like a 3.08. That will keep it in its power band longer ie. more torque being applied over a longer period of time.

Steeper gears seem like a good idea, but all your going to do is take the car quickly through its power band. It may seem better from a stand still when you can roast your tires easy, but you'll run out of gear and rpm in the 1/4.

Now if you swapped to a carb your going to gain at least 1000 usable rpm and then i would say get 3.73's like me. 2500rpm on the highway with a t5.

JADIII35

Yes it is true I peak out rather soon in the rpm range, but I only lose about 10-15 hp thru 4500rpm. I do however lose more torque. Any other advice? What if I were to change heads down the road?

Thanks again,
Jim

nsimmons

You can mod everything as much as you want but the tpi is the bottle neck its clearly show by the dyno. In my car the party's just starting at 3700.

For example my dad has a stock 95 5.0 mustang with an auto and 2.7x gears. When it passes 4000 rpm it stops making power you have to slowly wait for the engine to spin out till it shifts at 5000, but your just wasting time as the rpms slowly creep up. As soon as it shifts it drops it back to the torque peak and it starts pulling hard again.

Putting steeper gears in his car would just make it run through the torque curve faster, and provide less acceleration.

My advice, invest in a holley stealth ram, super ram, mini ram, or a carb.

Then do the heads and more cam, something that makes power till 6000rpm. If your current one isnt big enough. What are the specs?

JADIII35

The following in the information I have on my cam. I personally don't know what to make of it, but I went with whatever the machine shop recommended.
Crane Cams
Hydraulic roller special compucam 2010
Lift: intake @ cam 256 @ valve 384
exhaust @ cam 271 @ valve 407
1.5 rocker arm ratio
Cam Timing: intake opens 14*ATDC, closes 18*ABDC, max lift
106*ATDC, duration 184*
exhaust opens 23*BBDC, closes 9*BTDC, max lift
106*BTDC, duration 194*

I have to keep the car smog leagle, so the most to the intake I probably can do is large tube runners and large port intake.

Thanks for the advice,
Jim

FndmntlsOfPimpn

off topic sorry but they have smog laws in ohio?

FndmntlsOfPimpn

off topic sorry but they have smog laws in ohio?

JADIII35

Oh yes they do!!! Not all counties, but mine sure does and they are pretty tough

nsimmons

Thats your problem right there..thats a teeny weeny smaller than stock, made for tow trucks cam. Swap that puppy out for a compu cam 2040 or 2050 if your feeling adventurous. The 2010 cams power band is idle to just over 4000 rpm, right where your hp dies. A larger cam will give you strong power to at least 5000rpm

The car will pass emissions no problem with either of those cams, Im running much larger cam than that and my emissions are cleaner than stock. C0 was 0.03 max allowable 0.98.

Thats the problem right there, no arguments about it. Steeper gears will be a huge mismatch. Do a 2040 cam, and then 3.73 gears and you'll think you have a different car.