Vacuum advance


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Post Sun Dec 04, 2016 12:38 pm

Re: Vacuum advance

You fellows explaining it and how it works and is put together will help others down the road. Thanks Guys!

Golden Jubilee
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Post Sun Dec 04, 2016 1:04 pm

Re: Vacuum advance

Great information here. After playing with the distributor on my 49 KB1 ( cleaning,lubing etc) and spending time finding why it didn't advance I replaced a hold-down bolt that had it locked down through the advance slot. I found a small washer and bolt that fit through , locked the bottom plate and all is good now BUT after reading this thread I'm going to find a shoulder bolt, spring and a ribbed,dished washer ( if I can ) and maybe it will be even better. I assume that the need for the spring is to keep the washer off of the slotted plate ?
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Golden Jubilee
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Post Sun Dec 04, 2016 1:47 pm

Re: Vacuum advance

the stepped washers job is to hold the distributor clamp plate down so no up or down motion while allowing rotation for vacuum advance,

the engineers at IHC came up with this set up early on, I Think D series motors have this set up, I know SD and BD motors into the 50s use the same set up,

if the hold down washer isn't used, then it is possible for distributor to crawl up ward during operation and lose contact with drive tang on oil pump, and truck stops dead.

the spring maintains washer contact with plate to hold it down while still allowing rotation,

as 1949\kb-3 mentioned you need to make sure washer goes up over shoulder on hold down bolt, or the whole thing binds up,

pretty simple yet complicated system,
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Golden Jubilee
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Post Sun Dec 04, 2016 2:05 pm

Re: Vacuum advance

More distributor pictures from the IHC R parts book MT 221A
Attachments
DISTRIBUTOR PARTS.jpg
DISTRIBUTOR BRACKETS.jpg
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Yard Art
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Post Mon Dec 05, 2016 9:20 am

Re: Vacuum advance

bedrockjon wrote:the stepped washers job is to hold the distributor clamp plate down so no up or down motion while allowing rotation for vacuum advance,

the engineers at IHC came up with this set up early on, I Think D series motors have this set up, I know SD and BD motors into the 50s use the same set up,

if the hold down washer isn't used, then it is possible for distributor to crawl up ward during operation and lose contact with drive tang on oil pump, and truck stops dead.

the spring maintains washer contact with plate to hold it down while still allowing rotation,

as 1949\kb-3 mentioned you need to make sure washer goes up over shoulder on hold down bolt, or the whole thing binds up,

pretty simple yet complicated system,


I agree with this.
The shoulder bolt along with the small washer, that resides in the clamp plate slot, holds down the advance/retard plate and pointer plate tight against the block. The spring and stepped washer on the shoulder bolt apply pressure to the clamp plate to hold down the distributor. But it is in my opinion that the stepped washer should have the raised section against the spring. This would allow more clearance between the small washer in the clamp plate slot and the stepped washer. Therefore, guaranteeing the stepped washer is applying pressure against the clamp plate and not the small washer. If the raised portion of the stepped washer was facing down, it could contact the small washer in the clamp plate slot and not apply pressure to the clamp plate. That is, until the distributor would walk up. But it could function either way, just depends if the small washer is higher than the clamp plate.

Golden Jubilee
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Post Mon Dec 05, 2016 9:58 am

Re: Vacuum advance

Thanks for the detailed explanations.

But we still have a little disagreement on the stepped washer position?

Bedrockjon says the stepped washer should have the raised side facing down. After playing with it in different positions I thought it went this way too.
Badbubba says it should go the opposite way. He has a good point about the clearance under the stepped washer.

I can understand both ways and I have assembled mine in both positions and the distributor still seems to move properly. What I don't know is how it will hold up when the engine is running since mine has not run yet.
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Golden Jubilee
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Post Mon Dec 05, 2016 10:14 am

Re: Vacuum advance

Thank you Nikkinutshop for posting the manual pages.

They bring up a small point I noticed but did not ask about?
There appears to be two different styles of the advance plate that clamps to the distributor body. They even show a different number of washers.

Here is what I have on my 49 KB3 and my parts manual has the same layout.

Image

Here is the one Nikkinutshop posted.

Image

Note the different number of washers. My diagram shows nothing under the stepped washer but the posted diagram has 2 small washers under the stepped washer.

When I took my distributor out it matched my parts catalog diagram BUT had two small washers under the stepped washer. Until that other diagram was posted I thought maybe I had two additional washers that should not be in there?

Does the position of the side clamp mean anything? I know mine is right up against the block and is not that easy to get to.
Maybe a improvement for ease of service?
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Attachments
Advance exploded diagram.JPG
Vacuum advance mine.JPG
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Golden Jubilee
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Post Mon Dec 05, 2016 1:33 pm

Re: Vacuum advance

Yes, when SD motor was introduced in late 1949 or 1950 (depending on who wants to argue it) one of the "improvements" was relocating clamp bolt orientation for easier access, the rest of the set up works the same, I THINK the Vac diaphragm is slightly different body wise but connects up and has same "pull"

International didn't always get it right, but they did learn and Listen,,,,,I have stacks of Service Bulletins that explain to mechanics how to address/fix/replace problems reported by drivers/owners of trucks, so moving the bolt location was one of these,

by the way, you can swap your hold down plate on a KB with the SD one for easier bolt access,

oh, and like I said, every truck/motor I've dealt with that wasn't bogdered too much, the step washer faces down,,,,,,but like I also said, I could care less which way someone else wants to put it, seems to work either way,
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Rookie
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Post Thu Jan 18, 2018 3:29 pm

Re: Vacuum advance

Folks, that was an extremely helpful explanation and I need to get on my lathe and make one of those washers. And, I have one more question. The arm on my vacuum advance canister retracts when vacuum is applied but it does not return when the vacuum is released. Am I missing a spring somewhere or is my canister malfunctioning ?

Rusty Driver
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Post Fri Jan 19, 2018 9:45 pm

Re: Vacuum advance

RisingSunRanch wrote:Folks, that was an extremely helpful explanation and I need to get on my lathe and make one of those washers. And, I have one more question. The arm on my vacuum advance canister retracts when vacuum is applied but it does not return when the vacuum is released. Am I missing a spring somewhere or is my canister malfunctioning ?


RisingSun, Parts book for the R series with sd engine shows a spring in the canister under the fitting. Yours could be missing or broken.
Just looks like a common coil spring in the pic.
I am kind of in the same situation as you with the advance system on my R150. This thread has been very informative.
Dennis
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