Galled drum valve?

[Terry Keeley]

In no way am I bad mouthing CMB, in fact I think they're doing a great job and have had zero issues running their 21's, 45's, 67's, 80's and the new VAC 90.

Stu mentioned a while back some were having issues with the new billet drum housing and to either drill an oil hole or cut a groove in the face, my 90's came with the groove, the new 67's didn't have it so I drilled a hole.

Was I just unlucky or is the groove bettter? Maybe an oil groove in the bushing the whole way around?

VAC 90:

Hole I put in my new 67 drum:

 

[Joe Warren]

Terry I would really be looking at Crankshaft end play. when a drum valve sees heat....... Flywheel collet worn? bearings worn? Square drive that does limit shaft end play? or Collet drive that does not control crankshaft thrust loads??? & percent of Oils and type of oil in fuel? what does the drum drive pin hole look like?Does the engine have CMB OE needles in the rod? Some local needles that appear to be the same Pin size are fractionally longer and cause a problem thrusting the crank into the drum. But normally that shows up on the drum as a RING. if you use local brg house needles they must be the same size and exact LENGTH...... as the OE needles. & I have see this be a problem before with this same engine????????

 

[Terry Keeley]

Terry I would really be looking at Crankshaft end play. when a drum valve sees heat....... Flywheel collet worn? bearings worn? Square drive that does limit shaft end play? or Collet drive that does not control crankshaft thrust loads??? & percent of Oils and type of oil in fuel? what does the drum drive pin hole look like?

Thanks Joe, first thing I looked at, drum had some end play (didn't measure, was enough).

Motor was new, went on the 12th easy break in run. Lots of oil for break in (18%). No square drive for me...

 

[Joe Warren]

I`am sure you are aware of min & maxs in machining. But if the drum did not have end play the crank shaft will thrust load it & make heat & it will heat the end of the bushing first........ same end you had a failure... This was a problem many times with the Picco 67/80 too. But we stacked case gaskets in them to space the drum hsg & drum away from the crankshaft drive pin. It never seemed to be a problem on the west coast cause most ran square drive shafts that limited flexshaft travel & did not push on the crank the same as a Collet type set up......... even with stk crank end play.The drum should have end play while the crank is being trusted hard forward in the case. Rod Needle length can effect this quickly.... & the drum intake valve normally shows this if it is a thrust type problem?? it would show the parts are getting pressed into the drum while running and show a pattern of what parts are rubbing..... may or may not be your problem?? Just .....Food for thought.....

 

[Tim_Duggan]

Is it feasible / possible that whilst running the hole is actually drawing oil away from the immediate area of the drum, rather than forcing it in?It is in the area of an airflow and could be acting like a venturi tube.

 

[Rick Pirrone]

i was thinking that the hole had to be drilled parallel and not down through the brass sleeve

so it would come out were the grove is on the vac 91s ??????????

i too want to do this to my 67

cheers rick

 

[DON MAHER]

Terry,

Just did the same thing to my new 67 cmb drum. Looks same as yours, but I did not drill or notch. I think the problem with MY drum was that the clearance for the drum to bushing was to close. After cleaning up the drum & bushing it was only .0005 yes that is 1/2 thou. On all of the 67/80 motors with cast back plates that I have (8) the clearance is .002-.004 thousands. My fault for not checking before running. I Just reset to .002 thou, will see if this will work on the new back plates without drilling and notching, will let you know.

Don

ps end play was/is fine.

 

[Tim Kish]

Terry,

Just did the same thing to my new 67 cmb drum. Looks same as yours, but I did not drill or notch. I think the problem with MY drum was that the clearance for the drum to bushing was to close. After cleaning up the drum & bushing it was only .0005 yes that is 1/2 thou. On all of the 67/80 motors with cast back plates that I have (8) the clearance is .002-.004 thousands. My fault for not checking before running. I Just reset to .002 thou, will see if this will work on the new back plates without drilling and notching, will let you know.

Don

ps end play was/is fine.

At .0005 clearance is crazy tight , depending on surface finish you need min .0004 clearance just to fit the two parts.

No room for oil that tight .

Maybe flared out or a small bur from drilling ?

Tim

 

[SayMikey]

If its a 67 take a hard look at the flywheel cone big end that goes against the bearing. If it has some wear on it replace it and make a stainless washer to go between the bearing and cone.

 

[Tim Kish]

Water and air temp still very cold , was the engine getting warm enough , especially being new and breaking in.

Tim

 

[Terry Keeley]

Terry,

Just did the same thing to my new 67 cmb drum. Looks same as yours, but I did not drill or notch. I think the problem with MY drum was that the clearance for the drum to bushing was to close. After cleaning up the drum & bushing it was only .0005 yes that is 1/2 thou. On all of the 67/80 motors with cast back plates that I have (8) the clearance is .002-.004 thousands. My fault for not checking before running. I Just reset to .002 thou, will see if this will work on the new back plates without drilling and notching, will let you know.

Don

ps end play was/is fine.

Never checked it but will have a look. Tim's right, a couple thou needed at least.

Maybe flared out or a small bur from drilling

Tim

Thought that too, went in and de-burred the inside of the hole with the dremel, used a sharp drill and don't think I pushed the bushing in.

If its a 67 take a hard look at the flywheel cone big end that goes against the bearing. If it has some wear on it replace it and make a stainless washer to go between the bearing and cone.

Not sure how that would do it but collets are in good shape, no flywheel rubbing on case.

Water and air temp still very cold , was the engine getting warm enough , especially being new and breaking in.

Tim

Ya, water was like ice, had to use an 0.015" restrictor to get enough heat!

 

[Mark Bullard]

I think a little to tight like Don says. The hole taking fuel/oil away also like Tim says.

I would not loseen it up to much. This small diameter would work good at 0.0010. What you need is a small radius trough or ditch the same lenght as the rotor opening on the other side of the opening of the housing. This will allow fuel to puddle in the bottom of the housing to lub the rotor as it turns. This will also push the fuel out to the ends of the rotor where the rotor sees the most out of balance dynamic frequency.

 

[Tom Foley]

I'm thinking set it up vertically in the mill ( or the lathe horizontally ) and internally bore a shallow groove that coincides with the hole to allow the oil to have someplace to go . Fuel / oil mix is both cooling and lubrication . I loosened up the fit as per Jerry Crowthers advice and so far , so good .

 

[Terry Keeley]

Measured drums and housings off my two new 67's. Both drums were 0.7088", the housing that galled after 12 runs was 0.7096" and the other one that didn't (9 runs) was 0.7098". Less than one thou. clearance is a little tight IMHO. :unsure:

Think I'm gonna bore an oil groove all the way around and connect it with the hole.

 

[Mark Bullard]

Measured drums and housings off my two new 67's. Both drums were 0.7088", the drum that galled after 12 runs was 0.7096" and the other one that didn't (9 runs) was 0.7098". Less than one thou. clearance is a little tight IMHO. :unsure:

Think I'm gonna bore an oil groove all the way around and connect it with the hole.

This is what I am talking about. This was done on the first K 45's.

 

[Terry Keeley]

Measured drums and housings off my two new 67's. Both drums were 0.7088", the drum that galled after 12 runs was 0.7096" and the other one that didn't (9 runs) was 0.7098". Less than one thou. clearance is a little tight IMHO. :unsure:

Think I'm gonna bore an oil groove all the way around and connect it with the hole.

This is what I am talking about. This was done on the first K 45's.

View attachment 47253 View attachment 47254

"A picture's worth a thousand words", thanks!

 

[ALLAN YUEN]

Look at my Picco 45R drum bottom galled 1.5 degree drum value

 

[NITROSNIFER]

Allan you should put that drum in the for sale section. You'd call it " like new only used back up". and ask at least 200.00

 

[Mark Stein]

Terry, cant quite tell from the picture. Is there a smooth break on the drilled hole where it comes thru the brass or a chamfer. I prefer a smooth break in place of a chamfer. I would recommend a radiused edge on the housing at the exit. The sharper the edge the more shear you will have. A smooth radiused edge will make it easier for a film to form and transfer on the surfaces.

Although the groove in the face of the housing must work some I would bet the drum is acting as a flinger.

Just a thought

 

[Terry Keeley]

Terry, cant quite tell from the picture. Is there a smooth break on the drilled hole where it comes thru the brass or a chamfer. I prefer a smooth break in place of a chamfer. I would recommend a radiused edge on the housing at the exit. The sharper the edge the more shear you will have. A smooth radiused edge will make it easier for a film to form and transfer on the surfaces.

Although the groove in the face of the housing must work some I would bet the drum is acting as a flinger.

Just a thought

I just de-burred the hole where it came through, nothing fancy. Looks like they counterbored the end of the bushing 45*.

Really think it's just fit a little tight, and maybe some way to get oil to the area. I'm gonna check my 90's when I get a chance...