3 vs 5 cam bearings

A

acenewman

Member
Can anyone fill me in on the 5 bearing cams vs 3 bearing cams? The eingine that came out of my car is a mid 29 motor and it has three cam bearins. I started tearing down another motor I am building for the car with is a mid 28 motor and it has 5 cam bearings. Is it as simple as they started with 5 and two got dropped at some point? Crank looks to be a much beefier forging in the 28 motor as well. Quite different from the 29 crank. Just thinking out load. Appreciate any feeback that can be provided.
 
Early Model A engines used a 5 bearing camshaft and a crankshaft that had a "Diamond" shape to it.
Attached is a photo that shows the early style on the right and the later style crank on the left.
If you are building up a 5 bearing camshaft engine you either need to use 5 bearing cam or you should plug the two spare bearing lube holes if you use a 3 bearing cam.

Darryl in Fairbanks
 

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d.j. moordigian said:
The blocks that I've seen/have with 5 cam bearings don't have lube holes @ the
#2 and #4 journal.

Dudley
Click to expand...
Even if they did, you don't need to plug the holes. Ford had drain holes in the floor of the T and B engine. The A didn't have these holes but needed them because he added the down tube and that didn't work completely. A little more oil drainage wouldn't hurt. MHO.
 
so it sounds like I could run the three bearing B cam I have in a 5 bearing block? Interesting collection of parts I have. Seems that my 29 block had the older crank in it and the 28 motor had the newer crank style. You never know what your geting till you tear it apart.
 
You can use a Model B camshaft in any Model A engine regardless of the number of cam bearings in the block. Some people thought the the early Diamond Crankshafts were superior to the later crankshafts. Frontenac would modify them for Model T's:
http://www.nwvs.org/Technical/MTFCA/Articles/1204Frontenac.pdf
page 26

According to this article it was a lighter and stronger crank.
At least it sounds like you have some good parts to choose from.
Good Luck with your project.

Darryl in Fairbanks
 
There were actually 3 different 5-bearing cams, I think it went progressively like this; first it came with all 5 brgs. ground to the same size, next came all 5 ground but #2 & #4 were undersize, then came the cam with #2 & #4 rough-turned to a smaller diameter. I believe this was because they quit using the 5-brg. block before the cams were used up and it was quicker and easier to insert the cam into a block without fighting the cam through with all 5 bearings full size. The first version is often used in the Donovan block today.
 
Here you go...the change happened between these numbers:

5 OR 3 CAMSHAFT BEARINGS

5 # 481,204 OCTOBER 03, 1928
3 # 492,408 OCTOBER 06, 1928 (11,204)
(SEE FORD SERVICE BULLETIN: JANUARY, 1929)
(CONTINUED THROUGH END OF PRODUCTION)

THE “RELEASE” INFORMATION OF SEPTEMBER 28, 1928, INDICATED:
· “REMOVED SECOND AND FOURTH CAMSHAFT BEARINGS”.

Pluck
 
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