The Ford Barn

scooder · 12-13-2014, 11:49 AM

Ian, to answer your question how high does a stock flathead rev. Much more than 4000, 5000 easy, much more and the stock valve springs can't keep up. Built in limiter if you like.
Look up the Elgin race 1933 or 34. These were stock mechanically, were down shifted at north of 80mph into second gear on down hill parts. The engine braking helped them.
I try to tell folk that flatheads arnt made of chocolate, and they definitely arnt fragile.
Martin.

1935coupe · 12-13-2014, 12:04 PM

I was looking into Mitchell and found $2750 through Mac, though I would call direct and ask a few questions before ordering and wow I am glad I did. She gave me a lot of information, I did not know there were 3 shift options stick on the floor, no not enough room, under the dash, ok but when she told me about the on the shifter option that was it. nothing but a switch on the shifter handle. then the price 2400 a lot better then 2750

Tony, NY · 12-13-2014, 12:25 PM

Quote:

Originally Posted by Ianrhall

Ok, where could I get those gears?
Ian

http://www.joblotauto.com/specials.a...currRecord=37#
Joblot Automotive for your needs. They show 3:54 gears.

Ianrhall · 12-13-2014, 01:36 PM

Looks good, not exactly sure which parts on that link I would need for a 40,s truck.
Been told it "probably" has either 4.11 or 3.78 as standard
Ian

Tony, NY · 12-13-2014, 04:56 PM

Sorry, forgot you're truck is 42-47. Those gears are not for that. Joblot did have a set of gears for 42-47 pickup when I called a couple years ago. Don't know what ratio they were. Maybe, give them a call.

JSeery · 12-13-2014, 05:24 PM

Sponsored Links (Register now to hide all advertisements)

Quote:

Originally Posted by Ianrhall

Looks good, not exactly sure which parts on that link I would need for a 40,s truck.
Been told it "probably" has either 4.11 or 3.78 as standard
Ian

It is fairly easy to check, I would start there.

dean333 · 01-16-2015, 12:30 PM

Ok, I have P215-70 R16's with a 4:11 rear. What tire size to I need on the back to effectively mimic a 3:78 ratio?

JM 35 Sedan · 01-16-2015, 01:04 PM

Quote:

Originally Posted by dean333

Ok, I have P215-70 R16's with a 4:11 rear. What tire size to I need on the back to effectively mimic a 3:78 ratio?

This might help....

http://www.flatheadv8.org/formula1.htm

or maybe this....

http://www.btc-bci.com/~billben/rpmtire.htm

dean333 · 01-16-2015, 01:18 PM

Thanks John, didn't help me though.

Ken Arms · 01-16-2015, 01:22 PM

I looked hard at Mitchel for my 34, after some measuring it looks like the floor pan would need to be altered for clearance, I decided to go 354.

JM 35 Sedan · 01-16-2015, 01:37 PM

Quote:

Originally Posted by dean333

Thanks John, didn't help me though.

I had 750 x 16 Diamondback radials on the back of my '35 fordor sedan when it had 4.11:1 rear gears. I believe I (or someone) calculated this to be close to 3.78. I have since installed 3.78 gears and gone back to 600 x 16 Coker radials and the car seems to run about the same as the previous setup.

dean333 · 01-16-2015, 02:51 PM

Sounds good JM but your missing a number, that's what's confusing me. For RADIALS P750-??/R16's?

JSeery · 01-16-2015, 02:53 PM

Johns formula should help:

MPH = RPM * Tire Diameter / Gear Ratio * 336

then

Tire Diameter should = (MPH X Gear Ratio X 336) / RPM

If you want to drive say 65 MPH and you have a 4:11 and cruise at say 2200 to 2400 RPM it will give you the required tire diameter.

TD = 89762.4 / 2200 or 40.8

TD = 89762.4 / 2400 or 37.4

So a tire diameter or 37 to 41 should get you between 2200 and 2400 RPM at 65 MPH. Someone with the larger tires will have to check and see if this came out correct.

Note: just checked mine and this sounds to big, my rear tires measure about 29. So that would be:

TD = 89762.4 / 3100 or 28.96

So, with 29 inch tires it would run about 3100 RPM, not that bad for a 4:11 gear.

scooder · 01-16-2015, 02:54 PM

Quote:

Originally Posted by dean333

Ok, I have P215-70 R16's with a 4:11 rear. What tire size to I need on the back to effectively mimic a 3:78 ratio?

Just had a play on a tyre gear ratio program. Looks like you need to go to 235-80-R16.
These are a tadge big but close.
This is the info I got.
Your 215-70-R16 are 27.8" tall. At 70 mph in direct drive with 3.78 would be revving at approx 3198 rpm.
At the same rpm with 4.11 rear and 30.8" tyre (235-80-R16) the speed would be about 71mph.
This was using an online program.
Hope this helps.
Martin.

scooder · 01-16-2015, 02:57 PM

Typing at the same time.
Did you say 37-41" tyre !!!!! I think some numbers are muddled.
Martin.

Brendan · 01-16-2015, 07:29 PM

John, how was stopping your car with the 750s ?

JM 35 Sedan · 01-16-2015, 08:07 PM

Quote:

Originally Posted by Brendan

John, how was stopping your car with the 750s ?

Brendan, did not seem to be any difference in stopping between the 750Rx16 versus the 600Rx16 to me. The floaters work great once I got them totally tuned in.

Brendan · 01-17-2015, 12:39 AM

Kool I was wondering how it would stop.

12-13-2014, 11:49 AM	#41
scooder Senior Member Join Date: Jul 2010 Posts: 2,593	Re: gearing up to go faster questions Ian, to answer your question how high does a stock flathead rev. Much more than 4000, 5000 easy, much more and the stock valve springs can't keep up. Built in limiter if you like. Look up the Elgin race 1933 or 34. These were stock mechanically, were down shifted at north of 80mph into second gear on down hill parts. The engine braking helped them. I try to tell folk that flatheads arnt made of chocolate, and they definitely arnt fragile. Martin.

12-13-2014, 12:04 PM	#42
1935coupe Member Join Date: Sep 2014 Location: maryland Posts: 46	Re: gearing up to go faster questions I was looking into Mitchell and found $2750 through Mac, though I would call direct and ask a few questions before ordering and wow I am glad I did. She gave me a lot of information, I did not know there were 3 shift options stick on the floor, no not enough room, under the dash, ok but when she told me about the on the shifter option that was it. nothing but a switch on the shifter handle. then the price 2400 a lot better then 2750

12-13-2014, 01:36 PM	#44
Ianrhall Senior Member Join Date: Apr 2014 Posts: 253	Re: gearing up to go faster questions Looks good, not exactly sure which parts on that link I would need for a 40,s truck. Been told it "probably" has either 4.11 or 3.78 as standard Ian

12-13-2014, 04:56 PM	#45
Tony, NY Senior Member Join Date: May 2010 Location: Capital of Corruption , NY Posts: 811	Re: gearing up to go faster questions Sorry, forgot you're truck is 42-47. Those gears are not for that. Joblot did have a set of gears for 42-47 pickup when I called a couple years ago. Don't know what ratio they were. Maybe, give them a call.

01-16-2015, 12:30 PM	#47
dean333 Senior Member Join Date: Jun 2012 Location: Shorewood Illinois Posts: 861	Re: gearing up to go faster questions Ok, I have P215-70 R16's with a 4:11 rear. What tire size to I need on the back to effectively mimic a 3:78 ratio? __________________ Tim Carlig

01-16-2015, 01:18 PM	#49
dean333 Senior Member Join Date: Jun 2012 Location: Shorewood Illinois Posts: 861	Re: gearing up to go faster questions Thanks John, didn't help me though. __________________ Tim Carlig

01-16-2015, 01:22 PM	#50
Ken Arms Senior Member Join Date: May 2010 Location: Essex Vermont Posts: 599	Re: gearing up to go faster questions I looked hard at Mitchel for my 34, after some measuring it looks like the floor pan would need to be altered for clearance, I decided to go 354.

01-16-2015, 02:51 PM	#52
dean333 Senior Member Join Date: Jun 2012 Location: Shorewood Illinois Posts: 861	Re: gearing up to go faster questions Sounds good JM but your missing a number, that's what's confusing me. For RADIALS P750-??/R16's? __________________ Tim Carlig

01-16-2015, 02:53 PM	#53
JSeery Member Emeritus Join Date: Nov 2012 Location: Wichita KS Posts: 16,132	Re: gearing up to go faster questions Johns formula should help: MPH = RPM * Tire Diameter / Gear Ratio * 336 then Tire Diameter should = (MPH X Gear Ratio X 336) / RPM If you want to drive say 65 MPH and you have a 4:11 and cruise at say 2200 to 2400 RPM it will give you the required tire diameter. TD = 89762.4 / 2200 or 40.8 TD = 89762.4 / 2400 or 37.4 So a tire diameter or 37 to 41 should get you between 2200 and 2400 RPM at 65 MPH. Someone with the larger tires will have to check and see if this came out correct. Note: just checked mine and this sounds to big, my rear tires measure about 29. So that would be: TD = 89762.4 / 3100 or 28.96 So, with 29 inch tires it would run about 3100 RPM, not that bad for a 4:11 gear. Last edited by JSeery; 01-16-2015 at 03:00 PM.

01-16-2015, 02:57 PM	#55
scooder Senior Member Join Date: Jul 2010 Posts: 2,593	Re: gearing up to go faster questions Typing at the same time. Did you say 37-41" tyre !!!!! I think some numbers are muddled. Martin.

01-16-2015, 07:29 PM	#56
Brendan Senior Member Join Date: May 2010 Location: At my kitchen table in Santa Rosa, Ca Posts: 2,903	Re: gearing up to go faster questions John, how was stopping your car with the 750s ? __________________ If it would have been a snake it would have bit ya! i can't spell my way out of a paper bag!

01-17-2015, 12:39 AM	#58
Brendan Senior Member Join Date: May 2010 Location: At my kitchen table in Santa Rosa, Ca Posts: 2,903	Re: gearing up to go faster questions Kool I was wondering how it would stop. __________________ If it would have been a snake it would have bit ya! i can't spell my way out of a paper bag!