Engine Help...

Freddie · 01-03-2008, 08:37 PM

Sorry: I am using full length BBK headers, they are 1 5/8 tube with a 3" collector... I am thinking of putting a pair of flowmasters on it and running a real short system..

Would I be better off jst putting a shorter tire on it rather than change the gear? I also have a pair of 26x10 drag radials..

Moparteacher · 01-03-2008, 09:02 PM

A shorter tire doesn't have the same effect as a gear change. The gears multiply torque. 3.73 to 1 multiplies the rotational force by 3.73 times. 4.30's multiply by 4.3 times. So lets say the the driveshaft is applying 400 ft.lbs of torque. (400x3.73) divided by two. Two tires right? this equals 1492/2=746ft.lbs at each wheel.
(400x4.3)/2=860 ft.lbs of torque applied to each wheel.

A shorter tire will not multiply torque. A taller tire will allow for a taller gear and a greater torque multiplication. The only time you would want to move to a shorter tire is when you are in-between optimum gear ratios. Even then the change is minor.

Run the 28x10 only if you can't fit an even taller tire, and then calculate the optimum gear for shift rpm and mph.

greg fulk · 01-04-2008, 08:14 PM

Freddie a shorter tire also has a smaller footprint! I think that's the last thing you need with a trans brake. Are you running Hoosiers or M/T ? I know with some playing you can get a 28x10.5 M/T under one of those cars........of course if ya already have the 26x10's give them a try......on Dad's 6 cyl nova stocker the 24x9 M&H's are good for about .05 in the 1/8th over 26x 8.5 M/T. good luck & don't forget to play with lots of differant air pressures.........

Freddie · 01-04-2008, 08:56 PM

Greg: I have a set of 26x10 M/T drag radials a little worn but still workable... the 28x10's are also M/T's but these are slicks..

alot of guys I know are running close to the same car, mine is a little lighter, they are using the 28x10's and most are running a 4.10 gear, but also they all run a glide instead of the 3 speed..

greg fulk · 01-04-2008, 09:19 PM

yea a glide wouldn't "hit" the tires like that 3 speed. my neighbor/buddy has an 86 Capri (with an 88 mustang frontend) he had a 306 roller motor that ran 10.40's . it has 29.5 x 12.5 slicks & he left the line @ 5200rpms! with a C4! good luck! oh p.s. he has a 347 in the car now (alum head motor) it runs 9.30's!

Chris1529 · 01-04-2008, 09:25 PM

You need to run the lowest gear you can. I think 430 to 456 would be a good start. From my experience, I think you will see that the guys running the 4.10's have a power adder such as nitrous or a supercharger. What RPM are you expecting it to run?

Freddie · 01-04-2008, 10:08 PM

I would like to shift the car at 6500.. and run through the traps at no higher than 6800-7000 tops.. since I dont have high dollar rods in this motor, I dont think over 7000 is wise.. I dont use stock rods either..

most of the guys running glides around here are all motor.. one of them has a big ole 437 small block in his, so I know I cant use any info he gives..

just trying to get this combination solidly into the 10's so I can run S/ST this year..

I took the car to test it the other weekend.. didnt go so well... my Converter ended up being a junk piece ( broken sprag) no stall at all.. on the brake could only get to 1400 rpm.. then I found out I put the wrong box of springs on these heads.. motor was stumbling at 5500... yet the car still managed to run a 8.45 in the 1/8th.. with a 2.47 60'..

New converter is here from TCI no used junk this time.. and new springs came in today...

01-03-2008, 08:37 PM	#1
Freddie Member Join Date: Jul 2005 Location: Tampa Fla / Anderson SC Posts: 334 Likes: 12 Liked 3 Times in 2 Posts	Re: Engine Help... Sorry: I am using full length BBK headers, they are 1 5/8 tube with a 3" collector... I am thinking of putting a pair of flowmasters on it and running a real short system.. Would I be better off jst putting a shorter tire on it rather than change the gear? I also have a pair of 26x10 drag radials..

01-03-2008, 09:02 PM	#2
Moparteacher Junior Member Join Date: Nov 2007 Location: Boise Posts: 49 Likes: 0 Liked 0 Times in 0 Posts	Re: Engine Help... A shorter tire doesn't have the same effect as a gear change. The gears multiply torque. 3.73 to 1 multiplies the rotational force by 3.73 times. 4.30's multiply by 4.3 times. So lets say the the driveshaft is applying 400 ft.lbs of torque. (400x3.73) divided by two. Two tires right? this equals 1492/2=746ft.lbs at each wheel. (400x4.3)/2=860 ft.lbs of torque applied to each wheel. A shorter tire will not multiply torque. A taller tire will allow for a taller gear and a greater torque multiplication. The only time you would want to move to a shorter tire is when you are in-between optimum gear ratios. Even then the change is minor. Run the 28x10 only if you can't fit an even taller tire, and then calculate the optimum gear for shift rpm and mph. __________________ Gary Weaver Moparteacher@yahoo.com

01-04-2008, 08:14 PM	#3
greg fulk VIP Member Join Date: Jan 2003 Location: jackson Posts: 1,165 Likes: 0 Liked 5 Times in 3 Posts	Re: Engine Help... Freddie a shorter tire also has a smaller footprint! I think that's the last thing you need with a trans brake. Are you running Hoosiers or M/T ? I know with some playing you can get a 28x10.5 M/T under one of those cars........of course if ya already have the 26x10's give them a try......on Dad's 6 cyl nova stocker the 24x9 M&H's are good for about .05 in the 1/8th over 26x 8.5 M/T. good luck & don't forget to play with lots of differant air pressures......... __________________ Greg Fulk 308 308X P/SA "ALL AMERICAN"

01-04-2008, 08:56 PM	#4
Freddie Member Join Date: Jul 2005 Location: Tampa Fla / Anderson SC Posts: 334 Likes: 12 Liked 3 Times in 2 Posts	Re: Engine Help... Greg: I have a set of 26x10 M/T drag radials a little worn but still workable... the 28x10's are also M/T's but these are slicks.. alot of guys I know are running close to the same car, mine is a little lighter, they are using the 28x10's and most are running a 4.10 gear, but also they all run a glide instead of the 3 speed..

01-04-2008, 09:19 PM	#5
greg fulk VIP Member Join Date: Jan 2003 Location: jackson Posts: 1,165 Likes: 0 Liked 5 Times in 3 Posts	Re: Engine Help... yea a glide wouldn't "hit" the tires like that 3 speed. my neighbor/buddy has an 86 Capri (with an 88 mustang frontend) he had a 306 roller motor that ran 10.40's . it has 29.5 x 12.5 slicks & he left the line @ 5200rpms! with a C4! good luck! oh p.s. he has a 347 in the car now (alum head motor) it runs 9.30's! __________________ Greg Fulk 308 308X P/SA "ALL AMERICAN"

01-04-2008, 09:25 PM	#6
Chris1529 VIP Member Join Date: Dec 2006 Location: West Virginia Posts: 1,366 Likes: 6 Liked 70 Times in 29 Posts	Re: Engine Help... You need to run the lowest gear you can. I think 430 to 456 would be a good start. From my experience, I think you will see that the guys running the 4.10's have a power adder such as nitrous or a supercharger. What RPM are you expecting it to run? __________________ Chris Bowman The Mountain State Mustang 1984 Mustang GT350

01-04-2008, 10:08 PM	#7
Freddie Member Join Date: Jul 2005 Location: Tampa Fla / Anderson SC Posts: 334 Likes: 12 Liked 3 Times in 2 Posts	Re: Engine Help... I would like to shift the car at 6500.. and run through the traps at no higher than 6800-7000 tops.. since I dont have high dollar rods in this motor, I dont think over 7000 is wise.. I dont use stock rods either.. most of the guys running glides around here are all motor.. one of them has a big ole 437 small block in his, so I know I cant use any info he gives.. just trying to get this combination solidly into the 10's so I can run S/ST this year.. I took the car to test it the other weekend.. didnt go so well... my Converter ended up being a junk piece ( broken sprag) no stall at all.. on the brake could only get to 1400 rpm.. then I found out I put the wrong box of springs on these heads.. motor was stumbling at 5500... yet the car still managed to run a 8.45 in the 1/8th.. with a 2.47 60'.. New converter is here from TCI no used junk this time.. and new springs came in today...