SBF Gear Recommendation Please

[Sean Marconette]

Dale,

The issue I ran into with street gears in my 8.8 stick stocker was stress fractures of the pinion teeth. Your engine will make quite a bit more power and not be as violent as a stick car, I would run a Pro gear if available.

Sean

[pmrphil]

With an automatic car that runs 12's (or even 11's) a pro gear seems unnecessary. Don't forget that the pro gear will wear much quicker than a standard gear, and while we're at it, needing a pro gear when using only 31 spline axles is kinda overkill as I see it.

[FireSale]

Thanks for the info. Forgot to mention that the trans is a C4. Current converter stall is 3500 (I drive it to the track). That will be replaced with 4500 or above as part of the differential upgrade.

Index for GT/MA is 11.75. Looking for 11 flat or better to be competitive around here.

Dale

[Lou Jeffery]

Standard gears will be more than sufficient. I ran a 8 inch rear axle in my Maverick going 11.30s, only upgraded to a 8.8 for more ratio options.

[HR9121]

I would also think the standard gears would be fine also and I would think you would need the 4.56 to get you up in rpm power range also.
I ran a 302 in a fox body bracket car, it was only 2950# but ran a 30" radial like stockers run and ran a 4.88. It ran 10.50-10.60 and would trap at 6900-7200. With those little motors rpm's are your friend.

[Chris1529]

what kind of RPM do think its going to run? I'd look at a 4.86 at least.
probably lean toward 5.14

[FireSale]

Originally Posted by Chris1529

what kind of RPM do think its going to run? I'd look at a 4.86 at least.
probably lean toward 5.14

The Comp Cam that is giving me the mid 12's at 105 ish is a solid roller with a 3000-65000 power band. It's on the way out for another solid roller that will give me at least 7000 in the traps. I'm currently maxing out at 5500 when I hit the lights so I'm not using the power I have on tap. According to AFR the AFR 1399 heads I have will take up to a .600 lift cam. Looking at Crowers that are rated at 4000-8000 and 3000-7000 and Lunatis rated at 4400-7500 and 4400-7200. The Dynamic Compression Ratio from the Crower cams would be 8.9 and 9:1 respectively and the Lunati cams clock with a DCR of 8.6:1.

My block is the Ford Racing M-6010 BOSS302 4 bolt main rig. My machinist went nuts over it. Rods are forged Crower Sportsman from the Accepted Products list and the crank is a forged Eagle. I pulled the heads recently after a season of driving to the track and bracket racing and everything looks brand new.

The bottom end is underused.

I used gear calculators based on 7000rpm and 28 inch tires to determine speeds for gearing. I know it doesn't factor weight and HP, but it was all I could find to mess with. 4.56 gave me 128 and 4.29 gave 136. 136? OOPs too fast, scratch that. 4.86 yields 120 and 5.14 is good for 113.

Dale