Too much gear w/c4?

ols0051 · 07-21-2005, 04:20 PM

I was thinking that my 4.10's are going to be too much for my c4 and 26 inch tall M/T's. I was going to run a 5spd but changed my mind after putting in the 4.10's. I want to keep around 6k at the finish line. Would going to a 28inch tall tire help that much? I guess I just need to run it a little then figure it out. just curious though. tfs trackheats,tfs stage2, victor jr, 650carb etc.....

Capri306 · 07-21-2005, 06:45 PM

I would figure out how much horsepower you're making with the engine first, consider ~17% loss through the drivetrain, then calculate your approximate trap speed. From there it's easy to figure out what RPM you'll be turning, and should let you know the limits on the gear ratio.

On pure guessing, estimating around 400 horsepower, it'd be safe. BTW, 6000 RPM isn't really that high. She'll take it.

Unit 5302 · 07-21-2005, 09:20 PM

You'll see approximately 7.5% less RPM with a 28" vs a 26" tire. With 4.10 gearing on a 26" tire, you'll hit 6000rpm at 113mph in 3rd. With a 28" tire, you'll be running at 122mph at 6000rpm in 3rd.

Jeff Chambers · 07-22-2005, 07:06 AM

Remember that you'll have additional RPM gain because of the converter. You'll need to know what the approximate slip of the converter is at the TOP end of the RPM range. I agree with Capri, since you're carbureted I'd spin that sucker to the moon.

ols0051 · 07-23-2005, 04:29 AM

Looks like i'll be doing some testing soon. Now RPM really plays a factor with all this. How high could I spin this thing. the shortblock is stock. I did the usual rod bearings,main bearings, arp rod bolts,rings etc..but it's still a stock crank, rods, pistons. I did however put on a ATI damper to help out with harmonics. But that is not going to save the world.

82 GT · 07-24-2005, 04:14 AM

Your max rpm is going to depend on your cam specs and provided you have the correct valve springs and such to match.

07-21-2005, 04:20 PM	#1
ols0051 Registered Member Join Date: Sep 2002 Location: cent.wis Posts: 203	Too much gear w/c4? I was thinking that my 4.10's are going to be too much for my c4 and 26 inch tall M/T's. I was going to run a 5spd but changed my mind after putting in the 4.10's. I want to keep around 6k at the finish line. Would going to a 28inch tall tire help that much? I guess I just need to run it a little then figure it out. just curious though. tfs trackheats,tfs stage2, victor jr, 650carb etc.....

07-21-2005, 06:45 PM	#2
Capri306 Moderator Join Date: Sep 1998 Location: Grand Rapids, Michigan, USA Posts: 1,001	Re: Too much gear w/c4? I would figure out how much horsepower you're making with the engine first, consider ~17% loss through the drivetrain, then calculate your approximate trap speed. From there it's easy to figure out what RPM you'll be turning, and should let you know the limits on the gear ratio. On pure guessing, estimating around 400 horsepower, it'd be safe. BTW, 6000 RPM isn't really that high. She'll take it. __________________ Capri306, Moderator The Mustang Works Online 1979 Mercury Capri 1987 5.0L Mustang LX Notchback 1993 5.8L Eddie Bauer Bronco

07-21-2005, 09:20 PM	#3
Unit 5302 Registered Member Join Date: May 1999 Posts: 5,246	Re: Too much gear w/c4? You'll see approximately 7.5% less RPM with a 28" vs a 26" tire. With 4.10 gearing on a 26" tire, you'll hit 6000rpm at 113mph in 3rd. With a 28" tire, you'll be running at 122mph at 6000rpm in 3rd.

07-22-2005, 07:06 AM	#4
Jeff Chambers Moderator Join Date: Aug 2000 Location: Milan, OH Posts: 2,699	Re: Too much gear w/c4? Remember that you'll have additional RPM gain because of the converter. You'll need to know what the approximate slip of the converter is at the TOP end of the RPM range. I agree with Capri, since you're carbureted I'd spin that sucker to the moon. __________________ Jeff Chambers 1990 Mustang GT 10.032 Seconds / 137.5 MPH 14-time Street Warrior World Record Setter CRT Performance 2001 Tropic Green Mustang GT - 12.181 / 113.2 MPH 2002 Ford F-250 Crew Cab 7.3l Power Stroke - 17.41@77.2 "There's nothing boring about a small block automatic shifting gears at 9400 rpm!"

07-23-2005, 04:29 AM	#5
ols0051 Registered Member Join Date: Sep 2002 Location: cent.wis Posts: 203	Re: Too much gear w/c4? Looks like i'll be doing some testing soon. Now RPM really plays a factor with all this. How high could I spin this thing. the shortblock is stock. I did the usual rod bearings,main bearings, arp rod bolts,rings etc..but it's still a stock crank, rods, pistons. I did however put on a ATI damper to help out with harmonics. But that is not going to save the world.

07-24-2005, 04:14 AM	#6
82 GT Import Slayer Join Date: May 1999 Posts: 2,241	Re: Too much gear w/c4? Your max rpm is going to depend on your cam specs and provided you have the correct valve springs and such to match. __________________ '82 GT 351W (.060)Comp Cams 274* Extreme Energy cam, ported & polished heads w/ 1.94/1.60 valves 10.3:1 flat top pistons,stealth intake, Mallory dizzy,Holley 750dp carb, BBK shorties,Flowmaster exhaust,C-4 with 3700 stall converter, B&M pro shifter,8.8 rear, 4:10's, subframes, electric fan, powermaster alternator, 4 core radiator.

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