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Setting up timing case

redbloke1956

Well Known and Active Forum Website User
Non-VOC Member
Hi to all, I have recently set all spindles (Comet) to the correct height, I have a brand new Large idler spindle, Cam spindle, Cam, Large idler pinion etc.
I have puchased 2 sets of shims ET173/1 and thrust washers/shims ET173, (In my view ET173 is being used as a thrust washer?) *both ET173's are .065" thick

So Looking at drawing MO13a.5 if I put an ET173/1 on both ET51 spindles and then an ET173 on both spindles I will end up with around .065" end float on all other spindles or a very warped steady plate? or are ET98/1 shims supposed to be .065" thick as well.
Can anyone tell me what I am doing wrong or what I am missing please?

yours in confusion
Kevin
 

A-BCD

Well Known and Active Forum Website User
VOC Member
MO13 has some omissions, there should be 1/2" washer E95 inside the breather pinion and a 5/16" outside. Some Comet small idlers have enough end-float for a thin E173/1 on the inside as well as the thick E173 on the outside.
Have you got a steel or alloy idler ? Alloy idler requires E173/1 on the inside, not needed on steel idler. You should fit a thick E173 on the outside. Cam followers require a 3/8" washer ET98 on the inside.
What was the 'correct height' measurement you used on the spindles ?
Hope this helps !!
 

davidd

Well Known and Active Forum Website User
VOC Member
I do not think that you can set the spindles to the Factory specified height. I should say that you can, but you will have to do a lot of shimming to get the steady plate level.

I think that your instincts are correct. The ET 173s are very thick and will keep the steady plate quite high. What I did was to measure to the top of ET173 on the large idler. This is the only spindle that cannot be changed in height. Add in the specified clearance and this will be the height of the back side of the steady plate on all spindles. On the last engine I did it was .455" above the mating surface. I set the rest of the spindles to this accounting for the clearances and shims.

Once you have done all this careful work, the gears are installed and they must be aligned with shims for the best tooth engagement. Additionally, the cam followers and cams may need shimming so that the followers are tracking on the center of the lobe. This may change the tooth engagement and you have to go back and forth. Finally, you have to shim up from the spindle to give the correct end float. The steady plate will be dead flat. Unfortunately, you will need a large assortment of different sized shims to accomplish this. These are available from industrial supply houses, but not the Club.

One spindle may be a problem. The rear most cam follower spindle intersects with the clylinder stud. When installed it sat .50" above the mating line so it had to be removed and ground. This may be a problem based on the supplier, so it may not be an issue in all cases.

The Comet timing chest drawing that you cite I believe is the most recent revision. I found a mistake in it last year and it was revised.

David
Just measured my ET173 and it is 0.071" thick.
 
Last edited:

Howard

Well Known and Active Forum Website User
VOC Member
Hi Kevin, what you're doing wrong, is confusing a 1940s engine design with 21st century technology. Your poor old engine was built from parts made by real people to tolerances, then it's suffered many years of use ( misuse?) ......... you can't rebuild them to a drawing and parts list, it's a fitting job, not an assembly job.

Follow David's lead, get a large assortment of shims, and spend some quality time lining up gear teeth to gear teeth, and cams to followers. Don't rush it, and if you're not satisfied with the result, start again - it's worth geting right.

H
 
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