CB/CL 350 Ball Bearing Cam Step by Step

Boomer343

Boomer343

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https://www.vintagehondatwins.com/forums/index.php?threads/4484

Thanks to Connor1 and Bob Foist from the linked thread I set out to do this modification. Their numbers gave me a starting point and proof it was a doable and desirable modification.

NTN 6004 ball bearings were used, the side covers will be removed before final assembly. 20mm x 42mm x 12mm are the bearings stated dimensions.

The cam has to be machined down to 20mm from its original 22mm.

Note .... Actual measurements are different, the inner diameter of the bearing was measured with a bore gauge and micrometer. Outer diameter of cam was turned to match but give a slip fit as measured with a micrometer.

I changed the mounting screws to allen head fasteners with washers. I also used a torque wrench set to 75 inch/pounds to tighten the fasteners.

The gaskets are new and their thickness needs to be taken into consideration. Mine measured .57 mm

For those just wanting the numbers this is what my next one will use.

Points side: Leave 6mm as measured from machined rub face. On cam cover leave 5mm lip to be sized to approx 4mm. Dish the lip to give clearance to the bearing, leave an outer ring.

Tach side : Leave 7mm as measured from the machined rub face. On cam cover leave 5mm lip to be sized to approx 4mm. Dish the lip to give clearance to the bearing leave an outer ring.

End play to be adjusted to .005" .... sorry for the measurement cross over, my dial indicator is Imperial. I was able to get .006" which could be changed by choosing a thinner gasket.

Start on one side and centre the cam gear in the case, measure only from the outside machined surfaces of the case. Size the lip on the cam cover to achieve the cam gear being centred.

Complete the other side to achieve the desired end play. The bearings twist easily and can give false readings. I found moving the bearing on the shaft slightly before each test gave the best results.

I made a mistake on the points side cutting the cam to 5.5 mm and then doubling down by cutting too much off the cam cover lip. A shim was required.

Pictures following.
 
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So starting at the end. The cam rolls so smoothly and I can see benefits in longevity, heat reduction and valve clearance accuracy.



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Tach side. This is with the correct 7mm left on the cam. Bearing sits slightly proud of the case but the actual outer load surface of the bearing is in contact with the cam case.


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Points side with 5.5 mm instead of 6mm being left on the cam. I also modified the case to allow oil flow to flow from the top and over the bearing. Small drilled holes were a brain fart.


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Centring the cam. It was easiest to measure as shown, then repeat in same way on the other side. I confirmed on the OE set up that the cam is centred in the case. Measure only using the outer machined surface.
 
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I used my buffing wheel and compound to polish the seal running surface and the cam lobes. Getting a slip fit is tricky, at least for me. I can do press on fits without problem. I have one that is not as tight as I would like so will be doing some remedial work on it to correct that. Hours spent rebuilding equipment pays off.

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Points side with the shim of shame. Note the dishing of the cam cover to give clearance to the bearing. This also makes it easier to size the lip. The shim is made to clear the oil drain hole in the cover. This a how not to do it picture.

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And the tach side done as it should be. The lip ended up being 3.90mm. Each set up will be different.
 
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This was my set up to cut the cam covers down on the lathe. It worked but in the future I will simply cut with a hacksaw and file/sand down to size. Lots of porosity in the metal.

Seals were sourced form a local specialty supplier, 35 x 20 x 6 double lip seal. They lack the directional ribbing of the OE but they will not be dealing with the same amount of oil.
 
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Well the shim of shame is gone. Decided that if this gets put on my CL350 I would like better cosmetics on the parts. Also figured out a better way to measure the lip. Used the measurements from the first post. Cut with a good hacksaw then filed to size. Went quite quickly especially compared to the first set.
4 plus thou for end play.
Now do I really want to pull that motor .... this set up is worth it I believe.
 
teebo said:
This is beyond what I could do, but I'm curious as to the benefit.
Click to expand...

The ball bearings reduce the friction and therefore heat by a large factor. Connor1 and Bob Foist both report much cooler running. Ball bearings require very little in the way of lubrication and the weak point of the 350 engine is top end lubrication.

The ball bearing set up is far more accurate in centring the cam in the cam case both horizontally and vertically for the timing chain. I believe this will allow more accuracy when setting valve clearances and keep the timing chain running true.

I put together a good cam and a set of OE cam covers all within factory spec to check the set up and verify a few things. I had forgotten the large clearances and slop built into the OE set up. No wonder the 350 engine sounds like a sewing machine.

In my case I had one of the nicest cams I have come across but that had been damaged by someone doing a seal change. Now the cam is usable and should have a long life.
 
No wonder the 350 engine sounds like a sewing machine
Click to expand...

That made me laugh

...but seriously, I will be following your progress on this endeavor.
 
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Update ..... finally got to put the ball bearing set up into my engine. Didn't document install but it is much simpler than the OE since the rockers and pins get installed after the camshaft is is place and in time.

I must say the engine is quieter and smoother. There is much less resistance in turning the engine over using the rotor bolt. Looking forward to taking it for a ride.

I would do this conversion again especially after figuring out to do it.
 
Decided to a second conversion and perhaps a third as well.

One item to note on the 6004 bearing .... should be a C3 designation to allow for the temperature fluctuations and they are more forgiving of slight misalignment.

I tried a different way to size the end caps using my variable speed router set to its lowest rpm and a 1/4 solid carbide bit.
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Cut a 2" hole into a piece of melamine and screwed the cover to it. (piece had been rough cut with a hacksaw) Light cuts but it went very quickly and quite accurately. Will finish by hand once I'm into assembly.

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