model b engine cm gear

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dave hummell

Member
Today a good friend gave me a late b model block and crank and some other parts to the engine. Does the b have an aluminum cam gear from the factory?
 
Or you can go with bronze. There is an inherent chatter, Ford used fiber to quiet it down. Problem with fiber is it wears, altering valve timing and sloughing off fibers which clogs the oil pump pickup screen. The chatter doesn't occur under load, only at idle.
 

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Chris Haynes said:
What is different about a Late B Block?
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The early B engines didn't have a counter balanced crank shaft. Later, they did and when an early one came in for rebuild, weights were added. Later again, B engines were used in agricultural equipment and all sort of machinery, even after production for cars stopped. Those engines can be readily identified by a small diamond cast on the side of the block just under the water pump (in front of the side cover) on the RHS. They are referred to as a "Diamond B" engine. As to just the block itself, I am not aware of there being any difference - it was the internals that were different. Others might confirm or correct that.
 
Model B engines had a pressurized oiling system to the main bearings. This is why the valve side cover is about 1" taller, the extra area covers the pressurized oil galley. If you check with A & B engine rebuilders most will say that re-machining the B blocks is challenging. They seem to be thinner castings and are easy to machine through where you do not want to. The Diamond B blocks are much better. The castings are thicker and they make great engines when rebuilt and put in an A.... That is what I have in my 31 W/B PU.
 
They generally crack from the exh valve to the cylinder.. sleeve, seat and pinning fixes it (the picture is a diamond block). Late B blocks don't have the clutch servo pad on the left side,an idea ford scrapped before production but the early blocks has the pad. B engines use a positive flow lubrication system as opposed to the A's gravity lubrication for main and cam bearings.

Diamond casting mark means it wasn't cast at the Rouge. No one has yet to identify the foundry that used that mark. Other than having the latest revisions to design, there is no proof that the diamond blocks are superior to Rouge cast ones.
 

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Not true about Diamond blocks being thicker. I have both and see no difference. The Diamond is an aftermarket casting house's trademark.
 
Bob Bidonde said:
Not true about Diamond blocks being thicker. I have both and see no difference. The Diamond is an aftermarket casting house's trademark.
Click to expand...

Hey Bob,
Not to ‘split hairs’…diamond block not being of thicker block metal.. say than a model A block.
Yeah, comparing a nos A block to a nos B diamond block, you statement may be dead on.
However, chances of finding nos A is improbable. A blocks are older than B blocks. Logic says that the older rusted A block will weigh less than a B block.
Taking this a step further, since diamond blocks were made after B, would they stand a better chance of their metal being even better ( heavier) condition !
Now, Ive just obtained a LATE diamond (1937). The metal in this Diamond B is beautiful shape. No faults, cracks etc.

This may be considered flimsy evidence by some. But if choice, Ill say Diamond B
Will be my first choice to check out for a build !
 
Interesting article, have seen it before.

If you will indulge me, a pressurized system must have some form of pressure regulator or relief in the system. Not saying that your car doesn't have one, can you please point out the pressure reg/relief on a stock "B" model engine?

Best, John
 
The pressure relief system is that the oilpump drive is held down by the spring . When excess pressure occurs the drive lifts slightly against the spring pressure enough to regulate as the oil spills out at the bottom into the valve chest .

John in the longest day of the year Suffolk County England .
 
The hole is to lubricate the timing wheel and dipper tray as there is no hole in the casting like a Model A engine . The oil pump has a capacity to pressure feed the main bearings and lubricate the timing wheel and dipper tray at the same time. In my view the mains are pressure fed not gravity like a model A . The drive would lift a few thou if the system pressure reached a certain point high revs and cold oil . The proof of the pudding is someone somewhere has a pressure gauge on the gallery ,I bet it reads more than zero .

John in same place same weather .
 
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My stock B engine was rebuilt in 1989 with 20,000 miles on it now.

Oil pressure with hot engine has always been 2 lbs at idle with 20 W50 and 8 at 45 mph to 10 at 65.

The oil pump was rebuilt to Ford specs for Model B oil pumps.

There is a difference between A and B oil pumps

The B pump from the factory was modified for more volume.

I have posted this information in the past and was told by "experts" that there is no difference between A and B and that I did not know what I was talking about.

The differences are spelled out in Nov 1932 service bulletins with specific warnings to NOT use certain parts from A pump in the B pump.

The large hole (5/16ths as I remember) in front of the galley MUST not be reduced in size. Doing so will starve the rod bearings of oil.

The purpose of the changes to the oil pump volume are to insure that enough oil is delivered to the dipper tray for the rod bearings.

The stock Model A engine gets horsepower at 2200 the B at 2800 RPM so more volume is needed to keep dipper tray from running low on oil.
 
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Thanks Benson, yes the "B" pumps are different.

One of the changes had to do with the thru bore in the housing and the diameter of the shaft, allowing for more volume. The feed hole out the front of the galley is for feeding the tray, for my purposes, it is always plugged. But I do not run dipper rods.

My statement about the system not being pressurized comes from the fact that the feed hole into the galley from the pump is the same size as the front hole where the oil exits for the dipper tray. That being said, it is not a pressurized system, it has oil directed to the bearings. I am really surprised to hear your motor has 8-10 psi at speed, I would not have expected that. The last stocker I ran had so much clearance it made no pressure.

The picture shows a moderately built "B" motor, good for street and hill climbs approx 180 hp.

Best, John
 

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