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E: Engine Comet Engine Assembly

craig

Well Known and Active Website User
VOC Member
Comet engine came apart for a variety of reasons, Oil fouling plug, too much vibration at tour speeds, needs electric start, oil leaks from all sources,
Decided, due to main shaft damage, 60 year old rod assembly, and bearing fits, to purchase a new crank assembly.
New barrel fitted to new muff and returned to standard bore.
Fitted new oil pump. Centered crank using slip on inner races - needed a 0.025 shim on drive side.

20211130_CaseHalvesReady1.jpg

Flipped timing side over, heated case half to about 225F, knocked tall spindles down using a nut and brass hammer, slide hammered low spindles up using a G72 long nut. Slide hammer threaded 5/16BSF.
Replacing OEM steel E212 steady plate with new alloy version. Replaced slightly worn followers with new. Finalized exhaust lifter setting and bent the cotter key after this photo.

20211208_StudsLevelShims1.jpg

My sealant is Threebond 1184, applied a small bead, assembled case halves.
20211208_Threebond1184BoltUp1.jpg

Now centering Alton, measuring to decide on crank pinion
 
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Martyn Goodwin

Well Known and Active Website User
VOC Member
Do NOT seal the alton to the case with anything. Fit a garter seal as detailed in attached. Also to address oil leaks first make sure the breather has been correctly set up as described by Irving in 'tuning for speed'.

With all you are doing it may be worthwhile checking the condition of the bore and the piston rings before you go much further plus why not fit 'proper' valve stem seals - this trio of details should eliminate almost all oil leaks.
 

Attachments

  • ALTON COMET SEALa.pdf
    443.2 KB · Views: 23
  • Heavy Breathing Part 1.pdf
    200.3 KB · Views: 16
  • Harmony.pdf
    192.2 KB · Views: 16

craig

Well Known and Active Website User
VOC Member
Tried two methods of measuring shaft to shaft to determine pinion.
$7 calipers and $200 micrometer, neither produced anything reliable.........having a set of pinions seems best.
+4 or +6 look to be solution for best fit

20211208_171743.jpg


20211208_182100.jpg
 

craig

Well Known and Active Website User
VOC Member
Thank you Martyn, I will incorporate this tech advice into this project.
I do have 18-35-7 seal in stock.
Any photos of the breather piping? tubing? catch tank?
Banjo A48/A22? or A61AS/A22? or?

"I then timed the breather so that it was closing at or just after 4 degrees AFTER bottom dead centre; on my Comet this meant it was opening at around 24 degrees after top dead centre. I ran-in the rebuilt motor with considerable care and can report, now with over 10,000 miles on the rebuilt motor it remains oil tight and oil consumption is so low as to be almost impossible to measure. As to the breather hose – I followed Phil’s’ advise about a large bore hose running from the breather outlet banjo upwards till it touched the bottom of the fuel tank, then it arches downwards, behind the battery where it exits into my home made catch tank (made from a small discarded plastic juice bottle)."
 
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greg brillus

Well Known and Active Website User
VOC Member
Craig, I've seen a couple of Alton's used on Comet engines were they become very noisy, the shaft bearings gone........this was almost certainly due to the gear meshing being too tight........It can be tricky as the magnets in the Altons are very strong and perhaps the back lash check is not done correctly because of this.......Given this issue, you should avoid using too large a crank gear, as this will ultimately lift the large idler assembly further up, this will take away any clearance for the meshing of gears including the Alton........had one do this recently and the Alton was brand new less than 12 months ago........ Cheers.
 

Martyn Goodwin

Well Known and Active Website User
VOC Member
Thank you Martyn, I will incorporate this tech advice into this project.
I do have 18-35-7 seal in stock.
Any photos of the breather piping? tubing? catch tank?
Banjo A48/A22? or A61AS/A22? or?

"I then timed the breather so that it was closing at or just after 4 degrees AFTER bottom dead centre; on my Comet this meant it was opening at around 24 degrees after top dead centre. I ran-in the rebuilt motor with considerable care and can report, now with over 10,000 miles on the rebuilt motor it remains oil tight and oil consumption is so low as to be almost impossible to measure. As to the breather hose – I followed Phil’s’ advise about a large bore hose running from the breather outlet banjo upwards till it touched the bottom of the fuel tank, then it arches downwards, behind the battery where it exits into my home made catch tank (made from a small discarded plastic juice bottle)."
Here is the best photo - sorry about quality. I used large bore oil hose and with epoxy as glue and sealer fitted a copper pipe cut-off sleeve to the banjo so increasing the OD to be a snug fit in the bore of the hose. The 'catch tank' was a small discarded plastic drink bottle that I painted black on the outside but leaving a clear vertical window so I could see any contents. That is held to the oil feed hose A65/2AS at the back of the F106 with thin black cable ties. When you want to empty/clean the 'catch tank' just cut the cable ties - fitting new ones after cleaning is done.

M
Screen Shot 12-09-21 at 04.39 PM.JPG
 

craig

Well Known and Active Website User
VOC Member
I was not happy with the original steel E212 fit.
Replacement in alloy sounded like an upgrade for thermal expansion.
20211209_E212Weights.jpg

Installed 18x35x7 seal for Alton shaft spacer. Installed Alton from outside to visually center in new seal. Using the spacer simply positioned (not installed) from inside to visually check seal lip sealing OD against spacer OD, I satisfied the centering of the Alton.
20211209_AltonCenterSeal.jpg


Went to fit Alton gear and could not get it to fit.
Loosened ET51AS Idler gear shaft and moved idler gear.
I am not happy with the big gear/cam fit at this time, but the Alton gear fits fine.
 
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craig

Well Known and Active Website User
VOC Member
Loosened ET51AS idler gear shaft and tapped the big gear around with a small 3oz brass hammer.
achieved best cam fit , best Alton fit, and breather seems okay but looser fit than I had initially fit without Alton.
So now I will fit a -6 half time pinion and have a nice fit for all.

20211209_HalfTimeFit.jpg
 
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