5 Bearing Cam?

[jeepguy1948]

I just purchased a number of parts and one of the items is a 5 bearing Model A camshaft. Well, call me stupid but I had never heard of such a thing before the Burtz engine came along. If anybody can enlighten me, that would be great. Thanks!

[Joe K]

Covered in Steve Plucker's seminal study available at http://www.plucks329s.org/pdf/engine...ESCRIPTION.pdf

Change from 5 bearings to 3 done around Oct. 6, 1928.

ANYTHING Steve is worth reading.

Joe K

[Smokedtires]

Originally Posted by Joe K

ANYTHING Steve is worth reading.

Joe K

Great site Joe. Thanks for the link.

[Jim Brierley]

There were 3 different 5 brg. cams. First had all 5 brgs. ground to the same size. Next were ground, but undersize to allow quicker installation in the 3 brg. blocks. Last they were rough turned on a lathe. The first can be used in the Burtz block, but not the last two.

[JayJay]

Originally Posted by Jim Brierley

There were 3 different 5 brg. cams. First had all 5 brgs. ground to the same size. Next were ground, but undersize to allow quicker installation in the 3 brg. blocks. Last they were rough turned on a lathe. The first can be used in the Burtz block, but not the last two.

Jim, wasn't there an issue with the oil groove in the Model A five-bearing cam journals allowing pressurized oil to spew out of the bearings? The oil groove on the Burtz cam does not extend to the periphery of the journal.

[Pete]

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We turned a lot of 3's into 5's back in the olden dayz.

[Bruce of MN]

Originally Posted by Pete

We turned a lot of 3's into 5's back in the olden dayz.

Pardon my ignorance, but how did you add metal to the cam to make journals and add metal to the block for the bearing surfaces there?

[johnneilson]

Lots of welding and bolts

Been making billet cam blanks when needed up to 1.75 dia

J

[Jim Brierley]

Originally Posted by JayJay

Jim, wasn't there an issue with the oil groove in the Model A five-bearing cam journals allowing pressurized oil to spew out of the bearings? The oil groove on the Burtz cam does not extend to the periphery of the journal.

Not that I know of, in fact the A's had no pressure, to anywhere.

I've made supports to go under a 3-brg. cam when running high spring pressure in race engines, such as at Bonneville.

[JayJay]

Originally Posted by Jim Brierley

Not that I know of, in fact the A's had no pressure, to anywhere.

I've made supports to go under a 3-brg. cam when running high spring pressure in race engines, such as at Bonneville.

Sorry, I wasn't clear. I was talking about using an A five-bearing cam in a Burtz with pressurized oil to the cam bearings.

[johnneilson]

Jay
It should not be a problem
If you are really concerned then adding a restriction in the galley that supplies oil to that bearing is possible
I don’t have any problems with 0.030 restriction and this is done in all B motors I put together
Understand that I provide min 20 psi to motor

J

[Pete]

Originally Posted by Bruce of MN

Pardon my ignorance, but how did you add metal to the cam to make journals and add metal to the block for the bearing surfaces there?

Here are pics of the intermediate bearing blocks. They are bolted in and then align bored.

The cam is the one that won the Antique Nationals vintage 4 cyl. top fuel class several years ago. .550+ lift.

The machining operation is boring the lifter holes oversize for the radius lifters.

[Bruce of MN]

Originally Posted by Pete

Here are pics of the intermediate bearing blocks. They are bolted in and then align bored.

The cam is the one that won the Antique Nationals vintage 4 cyl. top fuel class several years ago. .550+ lift.

The machining operation is boring the lifter holes oversize for the radius lifters.

Thanks, that clarifies. I'll have to look at my engine and visualize where those blocks and bolts would go. I am too stock oriented and don't visualize possibilities like you innovators do.

[Pete]

Originally Posted by Bruce of MN

Thanks, that clarifies. I'll have to look at my engine and visualize where those blocks and bolts would go. I am too stock oriented and don't visualize possibilities like you innovators do.

A flat spot is machined on the block where the aluminum housing sits. The aluminum housing is doweled to the block besides being bolted.
The cam runs directly in the aluminum housing. No insert bearing.
Everything is pressure oiled at 90 lb.

Actually, this was a fairly conservative engine compared to some Bonneville engines. This was even a wet sump engine.

[Pete]

Bruce, I forgot to answer one of your questions.
The intermediate bearings were made in 2 pieces and welded to the cam core.
The original journals were sleeved to get up to the required size.
The lobes were welded for the required added size.
The whole build a core operation cost about half of what a steel billet would have cost.

[Bruce of MN]

Question in red

Originally Posted by Pete

Bruce, I forgot to answer one of your questions.
The intermediate bearings were made in 2 pieces and welded to the cam core.
The original journals were sleeved to get up to the required size.

Did you grind the lobes down to be able to get sleeves with some wall thickness?

The lobes were welded for the required added size.
The whole build a core operation cost about half of what a steel billet would have cost.

[Jim Brierley]

Originally Posted by JayJay

Sorry, I wasn't clear. I was talking about using an A five-bearing cam in a Burtz with pressurized oil to the cam bearings.

The Burtz block is made with no oil holes drilled in #2 & 4 cam brgs., you need to drill a hole in them when running a 5 brg. cam. If you keep the hole small enough, you will have oil while not loosing pressure. I drilled mine to .040", and think .030" would be just fine. I'm going to run an original 5 brg. Model A cam.

[Pete]

Originally Posted by Bruce of MN

Question in red

Did you grind the lobes down to be able to get sleeves with some wall thickness?

I made the cam sleeves from steel tubing. The lobes were finished at the design diameter. As I recall the journals ended up about .250 larger than stock.
The cam bearing set used was a Federal Mogul 1253 M STD.