Galled drum valve?

[Derret]

One of the services that I offered while in the model parts business was bushing(rebushing) drum rotors like this- mainly Rossi & Picco parts of all sizes.

On the drum valves that I rebuilt & honed to size I used approx. .0013-.0015 running clearance-

I believed in lots of break in time on motors to get things happy inside the motor-

Your parts had .0008/.001"- a bit tight I think-

Keeping the fit to a miminmum helps (a lot) to seal base compression of the motor.

Read Mark Bullard's post again on correct thinking on this also-

I would add the drum may not have enough side clearance in the motor-

I wanted minimum usually- about .004/.005 to start with-

Prob. in these motors also is the loose rod rollers tend to be pushed sideways in the motor as it runs & will force the rotor back tightly against the drum face- not allowing much clearance for oil to flow properly-

Hope this is useful-

Dave Richardson

RPM Inc(Ret)

 

[Terry Keeley]

One of the services that I offered while in the model parts business was bushing(rebushing) drum rotors like this- mainly Rossi & Picco parts of all sizes.

On the drum valves that I rebuilt & honed to size I used approx. .0013-.0015 running clearance-

I believed in lots of break in time on motors to get things happy inside the motor-

Your parts had .0008/.001"- a bit tight I think-

Keeping the fit to a miminmum helps (a lot) to seal base compression of the motor.

Read Mark Bullard's post again on correct thinking on this also-

I would add the drum may not have enough side clearance in the motor-

I wanted minimum usually- about .004/.005 to start with-

Prob. in these motors also is the loose rod rollers tend to be pushed sideways in the motor as it runs & will force the rotor back tightly against the drum face- not allowing much clearance for oil to flow properly-

Hope this is useful-

Dave Richardson

RPM Inc(Ret)

Thanks for the reply Dave, yup 1.3 to 1.5 thou would be better I think, more like a rod bushing. Again, I'm gonna cut on oil groove all around right in that area, that should help also.

BTW, what alloy did you use for the bushing?

 

[Tim Kish]

I just checked both of my VAC 91's and they have .0015/.0021 clearance.

The housing are both out of round by .0005/.0006.

Tim

 

[Derret]

Terry- I used Free cutting UNS-C54400 Phos bronze for the bushings : ASTM B139 , Alloy 544

Federal QQ-B750

SAE CA544

This material is common thru metal supliers at an affordable cost.

It machines very well, is durable, wears well IF the right amount of running clearance is used to flow oil thru the bushing.

I think the higher lead content in this material made it well suited for this application-

Hope this helps-

Dave Richardson

RPM Inc (Ret)

 

[Terry Keeley]

Again Dave, thanks for sharing your experience and expertise!

 

[DON MAHER]

Guys,

Just finished running 2 gal. thru the drum with .002 thou clearance, no holes or slots. ALL GOOD!!!

Don

 

[stan simpson iv]

Just deburr the SHILLZ out of it and run it...I had one stick a LONG ways back,just did not clean her out,now I have not had a problem with them after I deburr them REALLY good. Anything under .002 is too tight...deburr or stick some paper in there not enough room for good oil as was said earlier in this thread. I used to bush the Rossi 45's for years also...we used bronze boat shafts my dad brought home from work for our bushings...they lasted for ever. (just my .02 cents)

 

[Terry Keeley]

Thanks for all the suggestions guys, also Rick via pm.

I decided just to open the clnc up a bit to about 1.5 thou, nothing fancy, just some 400 grit wrapped around some 5/8" tubing for a tight fit in the housing, couple turns and wala.

Checking them again seems mine were about 3 tenths out of round, looks like they honed them after the window was cut.

Stand by for further updates...

 

[Tom Foley]

I just measured my new engine and man its tight

.0005 is all it has . Yes 1/2 of 1 thou

The drum is even firm to push into the housing

What is the best way to improve the clearance

Light Oil (WD 40 ), 400 paper to start on your pinkie , work it around as concentric as possible , wash in soapy water , check , repeat . Do the drum valve as well leaving all corners radiused , clean repeat .Should take abut a case of beer to get it right !

 

[dwilfong]

Clover 400 grit lapping compound then finish with 1200 grit garnet dose both at the same time.

Fit it the same way you do a piston.

I removed .125 off the back of the drum and housing on my VAC .91 intake and opened it up to .625 on the inside.

 

[David Bryant]

is this galling issue responsible for failure of other parts (ie. crank-pin breakage, rod breakage, crank-shaft breakage)?

 

[Tom Foley]

It could be , things stop in a hurry !

 

[Joe Warren]

I just measured my new engine and man its tight

.0005 is all it has . Yes 1/2 of 1 thou

The drum is even firm to push into the housing

What is the best way to improve the clearance

Light Oil (WD 40 ), 400 paper to start on your pinkie , work it around as concentric as possible , wash in soapy water , check , repeat . Do the drum valve as well leaving all corners radiused , clean repeat .Should take abut a case of beer to get it right !

:lol: :lol: depends on how fast you drank

 

[Joe Warren]

I just measured my new engine and man its tight

.0005 is all it has . Yes 1/2 of 1 thou

The drum is even firm to push into the housing

What is the best way to improve the clearance

Light Oil (WD 40 ), 400 paper to start on your pinkie , work it around as concentric as possible , wash in soapy water , check , repeat . Do the drum valve as well leaving all corners radiused , clean repeat .Should take abut a case of beer to get it right !

Tom does your fingers get bigger after a case?...... :huh:

 

[Tom Foley]

I just measured my new engine and man its tight

.0005 is all it has . Yes 1/2 of 1 thou

The drum is even firm to push into the housing

What is the best way to improve the clearance

Light Oil (WD 40 ), 400 paper to start on your pinkie , work it around as concentric as possible , wash in soapy water , check , repeat . Do the drum valve as well leaving all corners radiused , clean repeat .Should take abut a case of beer to get it right !

:lol: :lol: depends on how fast you drank

Figure of speech calculated by a beer every 7 minutes . :lol: :lol: :lol:

 

[Terry Keeley]

Put another gallon of fuel (8 runs) on the drum that galled, all good.

Think just opening it up slightly plus the oil hole has solved the problem.

 

[Tim Kish]

Put another gallon of fuel (8 runs) on the drum that galled, all good.

Think just opening it up slightly plus the oil hole has solved the problem.

Ran almost two gallons through the twin testerday and both motors look perfect and are wearing in nicely. B)

Tim

 

[Thomas Hulbert]

Put another gallon of fuel (8 runs) on the drum that galled, all good.

Think just opening it up slightly plus the oil hole has solved the problem.

Ran almost two gallons through the twin testerday and both motors look perfect and are wearing in nicely. B)

Tim

Tim you might need a breathalizer test if you went threw that much. You may not be up to the task of driving the boat properly let alone parking it. Your walking was a little off after as well. Better have a look at the parking job again on the tape from the guard.

:angry:

 

[Tim Kish]

I just opened up a new 67 , it only had .0005 clearance .

No wonder it stuck first run .

Tim