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AIShelby

L 16 Chain Guide options

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Has anyone used a different chain guide (tension side) to take up slack in timing chain? Had to have head milled and looking for option other than tower shims or head gasket.

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There is an adjustment on the timing chain tensioner side guide, but you would have to take the front timing chain cover off to do the adjustment, if you take it that far apart I would just put a new timing chain kit on it.

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guides are slotted/

partsgeek.com has shims and Silver Seal has them also.

 

I don't think tension side can be adjusted its just a straight shot down.  so cam tower shims are needed

 

Slack side the guide is slotted.

 

 

YouTUBE  . hainz L series Datsun

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How much was the head milled? It might not need shimmed..

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Not sure until get head back from machine shop. I have heard that a Z24 or similar tension side guide has more curve and will take up the slack and then no need to shim cam towers. Has anyone heard about this or done this .

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If it's still at the machine shop.. why not just have the job done right? If they need to take off too much material... then they need to shim the towers. If they are a reputable shop, they will let you know.

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Can a napZ head even be shimmed?

The L head has a tower for the cam, the napZ head doesn't have a tower, all it has is a cap.

Looks to me like it would need a thicker headgasket, but I don't work on napZ engines.

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Can a napZ head even be shimmed?

The L head has a tower for the cam, the napZ head doesn't have a tower, all it has is a cap.

Looks to me like it would need a thicker headgasket, but I don't work on napZ engines.

 

this is on an L16 head. He mentioned using a Z guide on the L to take up the slack.

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this is on an L16 head. He mentioned using a Z guide on the L to take up the slack.

 

ahh, I see that now, the L block guide is adjustable/slotted on the chain tensioner side, but unless the chain is making a lot of noise I would not worry about it, they are loose to start with when new if you turn the crank the right way.

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OEM chain guides are thicker steel than some aftermarket guides, which allows them to be slotted even more than the factory slots. Just file them out a hair (curved guide only).

 

There's a thread here from a couple years ago where we discussed proper timing chain geometry. You should look that thread up.

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Thanks for the responses. I am getting ready to rebuild a L 16 road race motor the blew the Head gasket. I do not know how the chain is going to line up until I start reassembly. I am looking for a solution if slotting stock guide will not not rake up slack. Do not want to lower compression with thicker head gasket, shim towers and do the lash pad exercise. Could not find timing chain geometry thread. If I find a solution with alternative guides I will post with pictures.

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Not sure until get head back from machine shop. I have heard that a Z24 or similar tension side guide has more curve and will take up the slack and then no need to shim cam towers. Has anyone heard about this or done this .

 

 

The tension side is on the left and there is no slack to take up. The chain is straight between the cam sprocket and the crank sprocket that pulls down on it against the valve springs. The tension side guide has no curve in it and merely prevents the chain from vibrating like a plucked guitar string.

 

All slack is collected on the right side where the tensioner is. This guide is curved slightly and the mounting bolt holes are slotted and can be slotted even more. 

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What MIke just said I just said.

 

 

I think you worrying about nothing. get cam shims. AND IF HEAD MILLED ALOT fAR AS i KNWO ONE CAN GO 3 SHIMS AT. 015 EACH

 

sound like you need A MUTIPLE HOLE SPROCKET TO GET WAHT TIMMING YOU WANT DIALED IN

 

putting tension on the tight side chain dont make sense. If any chain arch is applied it will stress out the bolts and wear the chain guide out very quickey. I dont see a fix for this on the tight side. Like Mike said it to keep it from vibrating

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There is another reason to setting up the chain geometry just right. The wear points on the curved guide and on the tensioner get worn really fast if not properly aligned. Not such a big problem on a street engine, but on a race motor, this can lead to broken guides or premature wear resulting in chain slack and sloppy variable cam timing (not the good kind of variable cam timing).

 

The curve at the meeting point of the tensioner and the curved guide should be a smooth transition. Sometimes stacking up two of the rubber washers behind the tensioner plunger does the trick, sometimes slotting the holes in the guide, usually it's a combination of both.

 

As others have said, use cam tower shims as needed to restore the cam to its proper height and to make sure the rocker geometry doesn't suffer.

 

Also, if it's a race motor, cut the tensioner spring in half. This makes head removal easier in that you don't have to worry about the plunger popping out and costing you valuable time during at the track repair sessions. It also cuts down on tensioner wear.

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You can just about get your cam timing right on if you just play around a bit. If your cam gets retarded and your on number 3 or 4, jump a tooth and go back to number one...

 

I wouldnt bother shimming it of you took .015 off the head. Maybe even up to .050"... More than that start shimming? I havint had one that was rebuilt 6000 times, the ones ive had have been stock or had a cleanup done to it.

 

I did see an l6 head bent that bad.. Close to .100"

We heated it up till the seats fell out and pressed it allmost straight again. Took about .020 off the face and the top to get it straight again. How the cam turned before is a mystery to me, cause bolting the cam towers on after i milled it the cam went in like butter :)

 

If you set your timing by degreeing it in you could put the cam gear in an arbitrary spot and drill a new dowel hole...

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Cam timing can be fine tuned by drilling the hole in the sprocket to accept the offset cam degree bushings. Comp Cams, Mr Gasket, etc make them and are sold in a variety pack - https://www.summitracing.com/search/part-type/camshaft-degree-bushings/engine-type/v8?N=4294943508%2B4294951399&SortBy=BestKeywordMatch&SortOrder=Ascending

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Cam timing can be fine tuned by drilling the hole in the sprocket to accept the offset cam degree bushings. Comp Cams, Mr Gasket, etc make them and are sold in a variety pack - https://www.summitracing.com/search/part-type/camshaft-degree-bushings/engine-type/v8?N=4294943508%2B4294951399&SortBy=BestKeywordMatch&SortOrder=Ascending

I forgot about these! These are great for racing classes that state "must run a stock timing gear" and for dialing a cam in. Slower than having an adjustable gear but cheap and works!

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When I had my '76 L20B head off it was on the wrong hole. It was set on the #1 but only has 50K original on it (got 60K now) Can't see why the head would have been off before this, but whatever. I put it back together on the #2 hole. Stock engine... absolutely NO difference noticed. Drove 3K road trip to Canby last year and got 27-28MPG US MPG average with 4:11 differential. I realize that a 'built' engine would probably show differences. 

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Here is a visual of the slack side guide with bolt notches.

BA0240747-1.jpg

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When I had my '76 L20B head off it was on the wrong hole. It was set on the #1 but only has 50K original on it (got 60K now) Can't see why the head would have been off before this, but whatever. I put it back together on the #2 hole. Stock engine... absolutely NO difference noticed. Drove 3K road trip to Canby last year and got 27-28MPG US MPG average with 4:11 differential. I realize that a 'built' engine would probably show differences. 

Right is right. Setting the cam for optimal power at the right RPM is something you do only once. That is, unless you change the cam.

 

On a stock L20B, you'd be lucky to feel the 3-5 HP gain. If the cam timing was vastly off, you'd definitely feel the difference.

 

Adjustable cam gears are a waste of money.

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