What are most of you turning on the highway with 3.50 gears? I know my tire height is about 25" tall. I don't know what the original tire height was on 1967 Shelbys.
-Keith
Automatic or Manual trans?
Quote from: 1967 eight barrel on August 20, 2018, 02:58:20 AM
I know my tire height is about 25" tall. I don't know what the original tire height was on 1967 Shelbys. -Keith
The Speedway 350's, were approximately, 26.75" in diameter.
Doug
Manual... Would be 1:1 in 3rd Auto 4th Manual.
255-40-17. 25.02 tire height
-Keith
My guess is 3000RPM but someone that is running with the set up you have will need to report what they see.
I was curious too. An FE turning 3K at 55MPH gets on your nerves quick.
-Keith
Here's a simple calculation tool if you know the gear ratio, tire height, trans high gear ratio and MPH: http://www.csgnetwork.com/multirpmcalc.html
About 3800 rpm at 70 mph. 3:50 rear. I love the sound! Only fear in back of my mind is that the engine might blow up but it hasn't yet. And I recall zray saying that the revs are fine and no fears. I'm going with that line of thinking and if the engine blows so be it. Will then put a four bolt main svo block in her.
At 55 I believe the revs are around 2800 maybe a tad more.
Quote from: 1967 eight barrel on August 20, 2018, 10:47:42 AM
I was curious too. An FE turning 3K at 55MPH gets on your nerves quick.
-Keith
The 427 in my Fairlane has 3:89 gears with a 4 speed and runs 4K at 70 which scares me to death so I stopped doing that :)
I wish that Hone overdrive company would actually make and sell overdrives.
http://hone-o-drive.com/hone-o-drive/
Anyone live near Branson able to peek in?
I came up with 3K too, but it seems to be a bit over that. I am considering 3.25 or even a bit numerically lower.
Keith,
Bowling & Grippo program gives 2586 rpm at 55 MPH with tire diameter 25.02 "
Texas Swede
Thank you! Some ask the final transmission output, which with any four speed I know of is 1:1. The calculator I used showed about 3000 rpm. It seems I am turning more than that. The tach was rebuilt and calibrated, so I don't think that's the issue.
-Keith
Tire diameter is somewhat vague, circumference is what really counts. More or less air pressure could affect the circumference, which in turn determines RPM. Also, if you're not 100% sure of the gear ratio jack it up and turn the driveshaft so that the tires make one complete revolution (turning the tire and counting driveshaft rotation could be affected by the diff).
Quote from: 1967 eight barrel on August 20, 2018, 06:56:15 PM
Thank you! Some ask the final transmission output, which with any four speed I know of is 1:1. The calculator I used showed about 3000 rpm. It seems I am turning more than that. The tach was rebuilt and calibrated, so I don't think that's the issue.
-Keith
Unless they installed the wrong gears, they are 3.50s. I went by the tire manufacturer's information on diameter. I used the calculator to confirm the speedometer driven gear. It just seems a bit steep for 3.50's. I appreciate the input.
-Keith
Took a ride this morning and remembered to check this out. Richmond 5-speed (5th is 1:1), 3.50 rear, 235-60R15 tires. Tach showed about 2600 RPM at 55 MPH. That's about 150 more RPM than the calculator says it should be. The speedometer checks to be fairly accurate with my phone's GPS app. The hardest part was slowing down to 55. ::)
Quote from: kjspeed on August 21, 2018, 11:01:48 AM
Took a ride this morning and remembered to check this out. Richmond 5-speed (5th is 1:1), 3.50 rear, 235-60R15 tires. Tach showed about 2600 RPM at 55 MPH. That's about 150 more RPM than the calculator says it should be. The speedometer checks to be fairly accurate with my phone's GPS app. The hardest part was slowing down to 55. ::)
So if he is running a 4 speed, 3000RPM at 55 is probably an accurate reading.
You're about an inch taller than I am according to the tire chart.
-Keith
Quote from: Greg on August 21, 2018, 12:06:03 PM
Quote from: kjspeed on August 21, 2018, 11:01:48 AM
Took a ride this morning and remembered to check this out. Richmond 5-speed (5th is 1:1), 3.50 rear, 235-60R15 tires. Tach showed about 2600 RPM at 55 MPH. That's about 150 more RPM than the calculator says it should be. The speedometer checks to be fairly accurate with my phone's GPS app. The hardest part was slowing down to 55. ::)
So if he is running a 4 speed, 3000RPM at 55 is probably an accurate reading.
He should be closer to 2700-2800 all things being equal even though the calculations indicate it would be 2586 or so. My combination calculates to 2478 @55MPH but actually reads 2600 on the tach. I've got a stagger gauge somewhere so I'll have to check actual tire dimensions or check the circumference with a tape. BTW my 5th gear is 1:1 the same as 4th gear in a 4-speed. 1st through 4th is like running a 4-speed with a 5.00 rear gear.