help l20b adjustable cam sprocket

[tycot1]

i am trying to help a friend get his l20b fired and i have discovered the timing is totally out. we pulled the cover and everything is set up wrong. i was looking at all of the markings and quickly discovered that i could not see the "v" and "dash" markings due to what looks like an adjustable cam sprocket. it looks like the inside of the sprocket has been machined out and the outside has had four holes drilled so it can be bolted up to the plate that has been added behind the sprocket. why would this be here? there are no longer markings to see where i am at. can it be removed and have a normal gear put back in? it has a 780 shadbolt cam and does not have any cam tower shims (may not be important). any thoughts. the plate on the left is showing the back side in this pic

[Sealik]

Pics.....780 Shadbolt cam...?

[Sealik]

I would probably get the engine at TDC...wedge the chain and pull that crap off.

 

 

Hold on......... pics!

[tycot1]

i say 780 shadbolt cam only because this is what he has written on an engine parts list that came with the car. this is the plate from the side before removal. fuel pump drive not important.

[datzenmike]

Judging how thin the lobe bottom is, it's likely a regrind.

 

[Xander_42]

I'll take it if you guys don't want it. :P

[banzai510(hainz)]

OK I see the cam is NOT at TDC. as the dowel will be pretty close to the 12 o clock position.Some body FUCKED UP here

 

so this means the crank is where you took the chain off? You have to put it back to exactly how you took it off.

 

I alwasy take the sprock chain off after I dial the motor to TDC.

 

If you try to dial it to TDC you might hit a valve when turnning the crank with out the chain .YOull need to put the chain loosly back on and turn it to close to TOP DEAD CENTER so the crank and cam move as one. so the valves dont jam up

 

I cant tell if tyou got the fron cover on or not as I guess this might help,as I cant see the chain.

 

People who use these sprockets are more knowlegable on cam timming and use a degree wheels and a height gauge

 

Buy a 4 hole jap sprocket and set to # 3 position ,thats about the best I can do.

byron 510 up there in BC can get this going if he lives close by or another realm memeber

 

watch this.

[DanielC]

This is a picture of a OEM Nissan "racing" cam sprocket

This sprocket allows the cam to be set at 0, 3, 6, 9 degrees advanced, and 3, 6, 9, and 12 degrees retarded from the stock position. The stock sprocket allows 0, 4, and 8 degrees advanced.

[HRH]

Here's a link to an adjustable cam gear. Similar to what you have. Not a bad thing, just needs to be degreed in correctly.

 

http://www.rhdjapan.com/kameari-cam-sprocket-gear-slot-type-l4-l18-l6-l20-l28-57820

[HRH]

The other thing you can do is find a machinist who has a copy of the Nismo cam gear, and have him make you a number 4 hole. That's what I did with my 510. Not nearly as good as fully adjustable, but certainly cheaper.

[banzai510(hainz)]

I was thinking if you dont hsve the chain on slowly turn the cam and rotate the the crank a little clockwise at a time till its at TDC. (if from cover is off)

 

then place from cover on to get close to TDC on timming mark and then get a New chain with the brite links and you could put it on that way should be close enought to start. Put chain on dimple. Pick say Number 3 then turn can left to tighten it then tighten all the cam setting bolts you got.

[DanielC]

If you carefully turn the crank pulley by hand, you can feel TDC on a four cylinder because when two pistons are at TDC, the other two are at BDC. At that point, the pistons are changing directions, and essentially not moving. There will be a slight reduction in the force needed to turn the crankshaft.

[tycot1]

thanks for the help guys, the cover is off. the guy tried to do this himself and mixed things up bad. i have a new timing set for it but it is not jap. is there any reason why i could not just eliminate the adjustable cam gear? i have watched your videos and they are very helpful. i have done this job 5-6 times in my time but things have never been this mixed up when i started before. so i want to turn the crank and cam at the same time without the chain to get it close, put the chain on, rotate to the left a bit, tighten cam bolt, instal cover to check for tdc on the arrow and v and dash marks. when setting tdc i want to get it when the piston is going up and not down, right. when these things are set up i will do a rotation on the engine to be sure everything lines up still. one thing i was lost on is the correct way to set up the guide and tensioner. i should leave the two guide bolts finger tight, instal tensioner and squeeze closed, push the top of the guide to the drivers side of the car, where do i set the bottom of the guide?, then tighten the guide at the top then bottom. do another rotation and instal the cover again to be sure it all lines up. once this is correct set the oil pump up and instal loosely, i done understand exactly what the top drive gear should look like. what is the 11.28 in reference to, the two bolts? the dist is electronic too if that is going to matter.