Tall deck timing chain.

I’m convinced when they design a motor the first thing they do is the timing chain. Talk about restrictive.

SN005 is building a tall deck motor so I needed to work out what we were doing on the timing chain. I was hoping that my normal KA setup would work with a redesigned pivot for the tensioner arm.

Using my normal method of mocking up substituting plastic for metal. 

Actually worked out better than the normal setup. It looks like the extra height on the head will allow the arm to clear the timing cover without modifying the cover.

It uses all the stuff from a KA24 timing chain kit except the bottom chain needs to be a 94 link instead of the 92.

I was trying to get the arm closer to the tensioner but this is the best I’m going to get. Each full link you add or subtract shortens or lengthens the chain by 5/8” so the adjustment is pretty coarse.  The guides are stock out of the box Nissan KA24. The jumper brackets on the tension side are temporary. I’ll design something a little better.

I’m happy with the angle on the top tensioner. The upper brackets should start to become a standard item at this point. I changed the way the cam cores are being produced. I’m bringing the cams to length after heat treating and then shipping them to Schnieder for OD turning. This is giving me a lot more control.

This is what I settled on. A sub plate for the idler and a sub plate for the pivot guide and tensioner.

Then a spacer plate to bring the tensioner into the correct position.

I drilled the top gears so that they have 2.5 degrees adjustment and the cams are doweled to break that into 1.25 degree increments.

 

Bottom gear is new. It is a triplex 06P sprocket from Martin Sprocket with the teeth case hardened. I then bored, reamed and honed it out to 35mm.

Before and after.

The idea is that the inner and outer sprockets will provide strength to the middle driving set. This is way better than what I was running on the prototype. There is 3.5mm of adjustment front to rear via shim packs. This will make setting up the chains a lot easier.

 

 

Came together just fine.

 

Hopefully I’ll be able to get this kind of fit on the regular height blocks.

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