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ET: Engine (Twin) Series ‘D’ Breather


Cyborg

Well Known and Active Website User
VOC Member
Me too! In my die cast C motor 10545. Bush seized onto the spindle, well tight! Had to split it longitudinally with a hacksaw blade. Polished the spindle & fitted the the pinion from my '48 B motor which has what appears to be a cast iron? sleeve. The inside of that sleeve had plenty of natural lubrication grooves, it gave the distinct impression of having been drilled in manufacture, not bored, and certainly never honed!
So is there a preference for sleeve material?
I need to make a new bush to replace the alloy one, I am leaning towards cast iron, an old sash window weight could be good?
There is a note in Instruction sheet 6 "The Timing Gear" page 3 under breather valves. It says the one piece cast iron type ET141/1 was found to be unsatisfactory under racing conditions and if fitted, should be replaced with one or the other of the composite pattern ET141/1AS which has a bronze sleeve or ET141/3AS which has a cast iron or light alloy sleeve.
Not sure why the one with the cast iron sleeve is preferable to the one piece cast iron one.

Mine has a bronze bushing and the gear is stamped ET49/1, so a !/@ time pinion, but no keyways.
 

Pushrod Twin

Well Known and Active Website User
VOC Member
yes, when I first got my hands on them, I was admiring the new and improved casting. Less chance of my gearbox and case turning into chutney.
So did your castings have any porosities in them? My die cast cases look like volcanic rock, more holes than alloy, around the mains bearings. I had to sleeve the bearing bores to rectify the wear & mis-alignment anyway, so have good seats for the bearings. Then they mysteriously leaked oil from below the rear barrel. Fixed that by riding until it was hot, laying it on it's side, and my son laid into it with the TIG until it stopped bubbling!
 

Attachments

Bill Thomas

Well Known and Active Website User
VOC Member
I found the spindle, I just wondered if the pinion was wider, But I think it's a half time pinion,
The photos can mislead you ?.
Was trying to see what the tube was made of, They also say the "C" one was for a Comet, But I think it's the same for a Twin ?. All too tricky for me !.
 

Pushrod Twin

Well Known and Active Website User
VOC Member
There is a note in Instruction sheet 6 "The Timing Gear" page 3 under breather valves. It says the one piece cast iron type ET141/1 was found to be unsatisfactory under racing conditions and if fitted, should be replaced with one or the other of the composite pattern ET141/1AS which has a bronze sleeve or ET141/3AS which has a cast iron or light alloy sleeve.
Not sure why the one with the cast iron sleeve is preferable to the one piece cast iron one.

Mine has a bronze bushing and the gear is stamped ET49/1, so a !/@ time pinion, but no keyways.
Thanks Cyborg, I had forgotten about the bronze sleeve version, clearly that's the best option.

Here is a pic of the leak stopping weld. There is a lot of metal in that part of the case so I was not concerned about distortion of the barrel throat.
 

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Cyborg

Well Known and Active Website User
VOC Member
The only porosity I have found is on the timing side case where the front cylinder liner resides and it doesn't look like it would cause any problems. There is one other tiny spot around where a push rod tube ET104 seal would sit, but it too is minor and a pinhead sized drop or two of Devcon would seal it and not be visible. They look like very nice cases, so barring any surprises as they get assembled...... like perhaps finding out why a set of NOS cases were sitting on the shelf collecting dust for 65 yrs.
 

Cyborg

Well Known and Active Website User
VOC Member
I found the spindle, I just wondered if the pinion was wider, But I think it's a half time pinion,
The photos can mislead you ?.
Was trying to see what the tube was made of, They also say the "C" one was for a Comet, But I think it's the same for a Twin ?. All too tricky for me !.
Yes its a 1/2 time pinion. I've seen them with and without the keyways.
 

John Cone

Well Known and Active Website User
VOC Member
On the VOC Spares site, the photo of the D spindle part number ET159/1 (or the later parts book MO13) shows the flat. I have an NOS one here in the photo, but didn't want to use it due to some pitting from corrosion, although the pits might help hold oil.
Based on your responses (thank you) I decided to go dig out the idler that mounts on it and there are two oil holes in the bush that line up with the flat, so now it becomes obvious that they put the flat there to hold whatever oil mist should find its way in. I recall looking at this pinion previously and wondering if it was OEM or something that was just made up by someone.... but now looking at a later (D era) MO13, it shows the oil hole in the bushing. As for indexing, I'm assuming the flat should be towards the top in order to hold more oil while hopefully keep it away from the cam and mag pinions because of the aforementioned reduced bearing area. If anyone can confirm my assumption on the indexing, it would be appreciated.
View attachment 32107View attachment 32108
Not long ago i had to remove my timing side for some thing else and found a nut laying in the bottom of the timing chest. This had the end off the spindle still in the nut. I notice that it had sheared off the Idler spindle that drove the distributor gear. After taking the steady plate off i found that the idler was seized to the spindle which in turn had been spinning in the crankcase. I replaced the spindle, slightly oversized, supplied by Maughans and fitted it with the flat upper most hoping that oil would get into the new idler bush.
 

Pushrod Twin

Well Known and Active Website User
VOC Member
The only porosity I have found is on the timing side case where the front cylinder liner resides and it doesn't look like it would cause any problems. There is one other tiny spot around where a push rod tube ET104 seal would sit, but it too is minor and a pinhead sized drop or two of Devcon would seal it and not be visible. They look like very nice cases, so barring any surprises as they get assembled...... like perhaps finding out why a set of NOS cases were sitting on the shelf collecting dust for 65 yrs.
Lucky! I guess they improved as the foundrymen improved their techniques. The push rod tube seats on mine are riddled with porosities, needed plenty of RTV sealant around them.:)
 

Pushrod Twin

Well Known and Active Website User
VOC Member
Not long ago i had to remove my timing side for some thing else and found a nut laying in the bottom of the timing chest. This had the end off the spindle still in the nut. I notice that it had sheared off the Idler spindle that drove the distributor gear. After taking the steady plate off i found that the idler was seized to the spindle which in turn had been spinning in the crankcase. I replaced the spindle, slightly oversized, supplied by Maughans and fitted it with the flat upper most hoping that oil would get into the new idler bush.
Was the idler bush aluminium?
 

Cyborg

Well Known and Active Website User
VOC Member
Lucky! I guess they improved as the foundrymen improved their techniques. The push rod tube seats on mine are riddled with porosities, needed plenty of RTV sealant around them.:)
I am debating whether or not to paint the cases and suppose porosity would be a good argument (supported by the factory according to that bannanaman) for doing so.
 

MartynG

Well Known and Active Website User
VOC Member
The spares company show an alloy type for a Comet, I think it's the same for a " C" Twin.
I think you just have to make sure more clearance and more end float.
The breather sleeve is aluminium while the spindle it is on is steel. Aluminium expands at around twice the rate of steel so if there is insufficient end float it WILL seize. Happened to me. To ensure it does not happen set it up with at least 0.015" end float. See MPH 852,page 23, point 1.
 

Robert Watson

Well Known and Active Website User
VOC Member
I just hate it when aluminum expands at twice the rate of --- well ---- aluminum. :);)

Never read the contents just the grammar and the logic! Once a proof reader is a habit hard to break....
 

greg brillus

Well Known and Active Website User
VOC Member
Cyborg, your cases were probably left on the shelf due to the bearing bores being under size, any more than 0.0015" interference and the bearings will be too tight. I would be taking your time and double checking everything. If the outer races on the timing side are too tight, the inner races will either not fit or be too tight. The small race can be honed out quite easily to fix this, but the larger inner will spell the end for that bearing, as removal will most likely destroy it. Do not over heat the cases, an actual 200 deg Celsius is too hot, the metal will start to become annealed, about 170 to 180 max. Remember to install the small outer first, then the oil pump sleeve, inner large race last. Good luck with it.
 

Pushrod Twin

Well Known and Active Website User
VOC Member
The breather sleeve is aluminium while the spindle it is on is steel. Aluminium expands at around twice the rate of steel so if there is insufficient end float it WILL seize. Happened to me. To ensure it does not happen set it up with at least 0.015" end float. See MPH 852,page 23, point 1.
Yes, it is the expansion of the aluminium that I am wary of. It wasnt longitudinal expansion that caused mine to bite, I believe it was simply a lack of diametral clearance in the area where it was an interference in the pinion.
I suspect that the bushes may have been press fitted to the pinion then put on the shelf for later assembly without the bore being re-sized. This would leave the bore in the pinion area a few tenths or even a thou undersize, maybe not enough for the engine assembler guy to notice, if it slides on and turns, its good, right? Probably 90% were good enough. Mine had a new spindle, .001" over size, enough to compromise the clearance when the alloy expanded.

I'll make the replacement bush from bronze, only 1/2 thou tight but loctite it, then hone the bore to finished size.
 

MartynG

Well Known and Active Website User
VOC Member
I just hate it when aluminum expands at twice the rate of --- well ---- aluminum. :);)

Never read the contents just the grammar and the logic! Once a proof reader is a habit hard to break....
Like to take the credit - but it was an eagle eyed forum admin that made the fix.
 

Cyborg

Well Known and Active Website User
VOC Member
Cyborg, your cases were probably left on the shelf due to the bearing bores being under size, any more than 0.0015" interference and the bearings will be too tight. I would be taking your time and double checking everything. If the outer races on the timing side are too tight, the inner races will either not fit or be too tight. The small race can be honed out quite easily to fix this, but the larger inner will spell the end for that bearing, as removal will most likely destroy it. Do not over heat the cases, an actual 200 deg Celsius is too hot, the metal will start to become annealed, about 170 to 180 max. Remember to install the small outer first, then the oil pump sleeve, inner large race last. Good luck with it.
Thanks Greg. The cases are a bit of a mystery in that they were not a matched set and the mating numbers suggest that the drive side was machined prior to Harper and the timing side was done after Harper took over.
I have a mill and it is large enough to get the cases in, but then no room left to stuff anything into the quill. I formulated a plan of attack, but wanted to bounce it off the master, just to make sure I was headed in the right direction. Long story short, he took pity on me and removed the luck factor. I have machined a few precious things like Norton cam boxes, but these were a daunting task, so happy I caught him waiting for the rain to stop. Definitely above my pay grade. Mains on both sides were undersize (which strikes me as odd given the mating #’s) as were the bores for the G14 and G15. The G14,15 bores were also tapered, but there was enough meat there to straighten them out. Some of the spindle bores were undersize as well. I had 2 new ET30/3 and the smaller of the 2 is a very snug fit in the bore. The breather spindle went in with the flat up, so hopefully it’ll retain a bit of oil. One of the new E91 bearings didn’t pass muster, because it had too much runout and I was instructed to tell the vendor to stick it.
The ET92 and ET94 races were lapped to size and the decks came out to less than .001” over 10 inches, so I now have a (quote) “ beautiful set of cases”.
 

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