Valve gap/timing question

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xbartx
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Valve gap/timing question

Postby xbartx » Sat Oct 10, 2020 8:43 pm

In adjusting my valves, I noticed that the # 1, 2, 3 & 5 valves gaps are not at its widest at top dead center? It get a little wider rotating the crankshaft 5-10 degrees. What am I doing wrong? I assume this is not right.

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MiCarl
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Re: Valve gap/timing question

Postby MiCarl » Sat Oct 10, 2020 10:30 pm

Boy, it's been awhile since I did mine and my manuals are packed away because we're in the middle of a move. Set them according to the manual. If it says TDC then use TDC.

Your maximum clearance isn't necessarily at TDC and they will likely be different between odd and even numbers of revolutions because the cam turns at half the speed of the engine.

I suspect the manual says TDC of the compression stroke. This is where both valves are 1/2 revolution from being about to open or just closed. TDC of the exhaust stroke both clearances will be nearly 0.
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Glen
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Re: Valve gap/timing question

Postby Glen » Sat Oct 10, 2020 10:54 pm

Hi,
Turn the engine so each valve lifter is fully down, before setting the clearance.

Below is a page from the 1949 Cub operator's manual, telling about adjusting the valve clearance. :)

http://farmallcub.com/rudi_cub/www.clea ... age-39.jpg

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Re: Valve gap/timing question

Postby inairam » Sun Oct 11, 2020 7:13 am

you can set several values at a time see below.

The manaul says .013 but I have seen a number of member suggesting 0.015 which is what I have been using. Maybe it is becuased they noticed this as well. I personally did not notice this but will look next time.
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Valve Lash Adjusting Procedure.jpg
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Re: Valve gap/timing question

Postby Gary Dotson » Sun Oct 11, 2020 7:19 am

You're not saying that you have that situation on all four of those valves, are you? That wouldn't be possible. At top dead center, cyl. #1. those four valve lifters are all on the camshaft base circle, hence maximum clearance. If you have that situation on only 1 valve, it would be an indicator of camshaft timing set a tooth off. It's also possible that your timing mark is not where it's supposed to be. (I've only seen this on number series with starter/ generator) If none of this applies to your case, it's simply error on your part. Are you sure you're on TDC #1?

xbartx
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Re: Valve gap/timing question

Postby xbartx » Sun Oct 11, 2020 9:51 am

Gary Dotson wrote:You're not saying that you have that situation on all four of those valves, are you? That wouldn't be possible. At top dead center, cyl. #1. those four valve lifters are all on the camshaft base circle, hence maximum clearance. If you have that situation on only 1 valve, it would be an indicator of camshaft timing set a tooth off. It's also possible that your timing mark is not where it's supposed to be. (I've only seen this on number series with starter/ generator) If none of this applies to your case, it's simply error on your part. Are you sure you're on TDC #1?

I think it was the case in all of the valves. I originally adjusted the valves at the TDC and then going back and double checking is where I noticed that the gab would increase when moved off of TDC. I will recheck the valves and see what I come up with, I'm a bit stumped.

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Re: Valve gap/timing question

Postby Jim Becker » Sun Oct 11, 2020 11:26 am

One thought, are you sure you are at TDC? If your front pulley has 2 notches, you need to be aligned at the second one. If you only found one notch, make sure there isn't a second one currently filled with paint, dirt, etc.

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Re: Valve gap/timing question

Postby xbartx » Tue Oct 13, 2020 5:14 pm

Looking at this with a fresh set of eyes, I believe I got the valve clearance sorted out. Thanks for the help!

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Re: Valve gap/timing question

Postby Jim Becker » Tue Oct 13, 2020 9:01 pm

???

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Re: Valve gap/timing question

Postby outdoors4evr » Thu Oct 15, 2020 11:39 am

What was the issue?
Wear on the front pulley keyway?
Was the cam off by one tooth?
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xbartx
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Re: Valve gap/timing question

Postby xbartx » Sat Oct 17, 2020 8:48 am

outdoors4evr wrote:What was the issue?
Wear on the front pulley keyway?
Was the cam off by one tooth?

The issue was a inexperienced mechanic.
I'm not sure what I did wrong exactly, but the next morning after rereading the manual I started over and got the desired results.
-Brad

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Re: Valve gap/timing question

Postby Jim Becker » Sat Oct 17, 2020 8:57 am

Glad you got it straightened out with minimal effort. Time spent in the manuals is usually time well spent.

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Re: Valve gap/timing question

Postby Gary Dotson » Sat Oct 17, 2020 9:30 pm

Believe me, it's ok to make mistakes, once in a while. I watched, just this afternoon, as an experienced Cubber got a little off key on a valve adjustment, it just happens some times. We all get tripped up from time to time, but we're not trying to feed our families, playing with Cub tractors, so it's ok!


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