B 4 cyl. into a 30' A
- Thread starter mollydog
- Start date
pat in Santa Cruz
Well-known member
In addition to the adapter kit, you will need:
(easiest) a B oil pan with the rear trans mount part cut off and an A flywheel housing.
( not as easy, but no float o motors and more trans options) Or a B transmission and 32 B fly housing to mount to the B pan. You will also have to modify the A motor mounts to fit the 32 fly housing, or use float o motors. The advantage is you can use stock B gears with their primitive synchromesh and better 2nd gear ratio or stuff a set of "39 gears" V8 gears into the box and have the best synchromesh and higher 2nd gear. You will also need to find a double loader top shifter to do this..If you choose to use stock B transmission, you should re build it and be sure to set up the main shaft backlash to factory spec (.004-008). They commonly have more backlash, which causes popping out of gear. If you choose this route, you will find more assistance on the HAMB than here.
See here for housing differences:
http://www.fordgarage.com/pages/flywheelhousings.htm
If you have an intact B pan, search for a cutoff one before destroying a good B pan.
(easiest) a B oil pan with the rear trans mount part cut off and an A flywheel housing.
( not as easy, but no float o motors and more trans options) Or a B transmission and 32 B fly housing to mount to the B pan. You will also have to modify the A motor mounts to fit the 32 fly housing, or use float o motors. The advantage is you can use stock B gears with their primitive synchromesh and better 2nd gear ratio or stuff a set of "39 gears" V8 gears into the box and have the best synchromesh and higher 2nd gear. You will also need to find a double loader top shifter to do this..If you choose to use stock B transmission, you should re build it and be sure to set up the main shaft backlash to factory spec (.004-008). They commonly have more backlash, which causes popping out of gear. If you choose this route, you will find more assistance on the HAMB than here.
See here for housing differences:
http://www.fordgarage.com/pages/flywheelhousings.htm
If you have an intact B pan, search for a cutoff one before destroying a good B pan.
Charlie Stephens
Well-known member
I went the "easiest" route with mine and am very happy with it in my '31 RDPU.
Charlie Stephens
Charlie Stephens
Jim Brierley
Well-known member
contact me at jimb4e4@gmail.com and i will send you the chapter of my book that i wrote on such a swap.
Additional info here:
ratios of B and V-8 transmissions:
http://www.vanpeltsales.com/FH_web/flathead_trans-gearratios.htm
Model A ratios are 3.12 1st, 1.85 2nd and of course 1:1 in 3rd.
Note that there are two popular versions of the V8 ratios:
The V8-60 ratios are another animal and I did not examine them.
1. One V8 with almost same same 1st gear (3.11) and a slightly higher 2nd (1.773 vs 1.85 on stock A).
2. Second one with 2.820 first and a 1.604 2nd gear. This is close to the Mitchell (15% 1st - 15% 2nd version).
The Lincoln-Zephyr gears are too tall for A model A when used with 3.78 and the .411 also.
Even with a V8 engine, Paul Garrigan told me that he found the taller of the Zephyr gear sets to be too much for his hopped up V8. 296 CU with two 97's, Offy heads. 4. 0 inch Mercury crank and .250 over bored (yes 1/4 inch over bore- 3 7/16ths).
He removed the tall LZ gear set and installed the lower ratio of the two L.Z. gear sets.
3. Mac Van Pelt's book can be found on his website ... VERY good info on building V8 / B transmissions and what gear sets fit what cases and which interchange.
Also explains why the 39 and later synchronizers are better.
Paul's comment when I asked about putting a B or 32 to 38 V8 transmission in the Coupe was: "They are only slightly better than a Model A transmission and only IF you double clutch them!"
Also that the side loader (40 to 48 as I remember) gears will fit the top loader cases. Assuming that you have a "double loader", 3 inch top shifter that Pat in Santa Cruz talks about above.
Lots of good stuff!
ratios of B and V-8 transmissions:
http://www.vanpeltsales.com/FH_web/flathead_trans-gearratios.htm
Model A ratios are 3.12 1st, 1.85 2nd and of course 1:1 in 3rd.
Note that there are two popular versions of the V8 ratios:
The V8-60 ratios are another animal and I did not examine them.
1. One V8 with almost same same 1st gear (3.11) and a slightly higher 2nd (1.773 vs 1.85 on stock A).
2. Second one with 2.820 first and a 1.604 2nd gear. This is close to the Mitchell (15% 1st - 15% 2nd version).
The Lincoln-Zephyr gears are too tall for A model A when used with 3.78 and the .411 also.
Even with a V8 engine, Paul Garrigan told me that he found the taller of the Zephyr gear sets to be too much for his hopped up V8. 296 CU with two 97's, Offy heads. 4. 0 inch Mercury crank and .250 over bored (yes 1/4 inch over bore- 3 7/16ths).
He removed the tall LZ gear set and installed the lower ratio of the two L.Z. gear sets.
3. Mac Van Pelt's book can be found on his website ... VERY good info on building V8 / B transmissions and what gear sets fit what cases and which interchange.
Also explains why the 39 and later synchronizers are better.
Paul's comment when I asked about putting a B or 32 to 38 V8 transmission in the Coupe was: "They are only slightly better than a Model A transmission and only IF you double clutch them!"
Also that the side loader (40 to 48 as I remember) gears will fit the top loader cases. Assuming that you have a "double loader", 3 inch top shifter that Pat in Santa Cruz talks about above.
Lots of good stuff!
Last edited:
Bob Bidonde
Well-known member
The Model "B" engine is far superior to the Model "A" engine. Somebody at Ford finally realized that bearing stress is a function of the projected area of the babbitt and its lubrication, so the Model "B" has larger bearings and pressurized main bearings.
john charlton
Well-known member
The easiest setup is to stay with the stock A trans . All you have to do is cut off the bottom steel flywheel guard off the oil pan and modify the "C" semi circular plate to suit the larger rear main bearing setup then bolt to the stock A flywheel housing , The A flywheel housing bolts straight onto the back of the B motor .
John in rainy evening Suffolk County England.
John in rainy evening Suffolk County England.