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Timing stock l20b with no marks on cam sprocket


BOZO

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Building an l20b. I ordered a jap timing set and thought all was good until I went to put the cam sprocket on and found there were no marks on the sprocket to give me an idea where I am at. I would set it with a degree wheel but I do not know the valve events on a stock 1978 l20b cam. It is currently set up by which dowel it slid on best with the engine at tdc and the cam just guessed at for 10 and 2. I have searched extensively and all information just talks about the v notch (which I do not have) lining up with the cam plate mark. I have successfully built a few l series motors so I am familiar with what to do normally. I may have to order another cam sprocket. Anybody have any info to help degree in a stock l20 cam?

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Pictures of the cam sprocket?

 

 

If you set the front cam lobs at 10 and 2, that gets you in the ball park. There are three holes on the sprocket, use the middle one. 

 

Do you have the old sprocket by chance? 

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Cam sprocket is currently on engine on the engine stand so it is hard to tell anything, but using my old sprocket to get things lined up is a good idea! Then I could just replace it with my new one. Sometimes the answers are so simple they just elude me. THANK YOU

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Use your old sprockets to transfer the two timing DOTs to the new sprockets. Set engine to TDC. Cam dowel in the #2 or middle hole on the cam sprocket. Count the double links between these two DOTs should be 38??? (I'll check when I get home so hold off on this, maybe 42 or something but I have it marked down)

 

With new chain and sprockets, this is the factory L20B setting.

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The timing dots are there on the teeth. What's missing is the v notch on the backside that lines up with the cam retainer plate marker. I bought this timing kit just because it was from Japan so I could trust it being right. Can't tell you the brand right now because I am at work, but it was one of the more reputable brands.

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thats weird most jap made ones have the V notch.

Tsubaki sold thru importrp.com could get them but I dont know where else to buy them unless buy chance.  I just cked and they dont have any on importrp.com.

 

There was a few guys on here that found the good sets. My OSK is OK has the marks but sprocket on dowl is a little loose(like hole a little to big )

 

If you have the 1 2 3 on the spocket you just have to go buy that and assume its good.

 

My Hainz L series adtsun  vid is on youtube  if that can help

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Also, my block has been decked .018 and my head .004 so I just can't guess at what is right. Using my old sprocket to check alignment then replacing it with my new one will solve the issue I believe. Y'all keep posting specifications on things like chain lengths and such. Every time I come across things like that, I cut and paste to my own database and it is there when I need it. Thanks to all and especially Draker for mentioning my old sprocket. Now if I can just find it.

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Decking the block or head moves the sprockets closer together same as if the chain was stretched.

 

The cure for this is to add 0.020" shims under the cam towers. This keeps the cam and crank sprockets the same distance apart... OR move the cam dowel to the next highest number on the cam sprocket. I agree it would be nice to have the little V notch. Can you transfer the old notch location to the new sprocket? Notch with as file?

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You can go to this page, go close to the bottom.  Down load the Nissan L-20-B service manual.

http://www.davidcmurphy.com/olddat/620tech.htm

Page 12 in the manual has a cam timing diagram.

 

From TDC, firing stroke,

Exhaust opens 54 degrees before BDC.

Intake opens 6 degrees before TDC.

Exhaust closes 14 degrees after TDC.

Intake closes 52 degrees after BDC.

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Concerning cam tower shims, at the moment, my chain guide has plenty of adjustment and the tensioner is where it should be. Also my wipe patterns on my rocker arms are correct. My head was not warped. I only had material removed from the head to give me a good sealing surface. If the cam does not time out correctly with the standard sprocket, my next step will be to obtain an aftermarket sprocket with more adjustment.

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Each hole is 4 degrees, or about half a tooth of adjustment on the cam. The deciding factor is the position of the V notch under the horizontal etch line on the cam thrust plate. As long is it is under, or slightly to the right as viewed from the front you are correctly timed. Period.

 

 

Set this up and check the V location. It's easier to move to the #3 hole than shimming the cam which may mess with the wipe pattern. Most likely with new chain and sprockets it will be fine as it is on the #2

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