Does anybody have a good "how to?" I've watched a couple videos on YT, but most are for cheby v8 and I really need to get this right.
Thanks.
Degree in a cam.
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datzenmike
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- Joined: 24 May 2006 12:40
- Location: Van. Isle.
Re: Degree in a cam.
With the engine precisely at TDC look through the top hole on the cam sprocket. If it timed correctly you should see this...
Note that the notch on the cam sprocket is below and just slightly to the right of the horizontal etched line above it on the cam thrust plate. This is perfectly timed.
L16/18s are set at the factory on the #1 position, L20Bs on the #2 position but chain and cam wear will see the notch slowly move to the left. When this happens the sprocket can be moved to the #2 hole (#3 hole on the L20B) and this corrects the cam timing events by removing about 4 degrees or the length of the etched line.
Note that the notch on the cam sprocket is below and just slightly to the right of the horizontal etched line above it on the cam thrust plate. This is perfectly timed.
L16/18s are set at the factory on the #1 position, L20Bs on the #2 position but chain and cam wear will see the notch slowly move to the left. When this happens the sprocket can be moved to the #2 hole (#3 hole on the L20B) and this corrects the cam timing events by removing about 4 degrees or the length of the etched line.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs
Re: Degree in a cam.
Thanks, I know this part. I mean with a degree wheel. It's a regrind cam, I need to get it dialed in properly so it works as intended.
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datzenmike
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- Posts: 6081
- Joined: 24 May 2006 12:40
- Location: Van. Isle.
Re: Degree in a cam.
There is no way to adjust the cam timing other than the three adjustment settings. You would need an adjustable sprocket for that. It's be close enough.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs
Re: Degree in a cam.
My opinion. You need the specs from the "cam grinder" You need a degree wheel, and pointer. You need a dial indicator and a "mount" for the indicator. NOTE a magnetic base doesn't work on the NISSAN aluminum head.
Assemble the engine per the "book". Including crank position, cam chain installation, etc, etc. Carefully roll the crank back and forth and observe on the dial indicator where the events are occurring and compare to what the cam grinder says the specs are. You can change the "events" by 4 degrees either way by selecting different holes in the upper cam chain gear. One of the 3 holes should get you the cam grinders specs for the "events" Opening and closing. Takes a while on fresh components
Regards
DAVE KING
'
Assemble the engine per the "book". Including crank position, cam chain installation, etc, etc. Carefully roll the crank back and forth and observe on the dial indicator where the events are occurring and compare to what the cam grinder says the specs are. You can change the "events" by 4 degrees either way by selecting different holes in the upper cam chain gear. One of the 3 holes should get you the cam grinders specs for the "events" Opening and closing. Takes a while on fresh components
Regards
DAVE KING
'
Re: Degree in a cam.
I'm assuming that you already have weak mushy mock-up valve springs installed instead of the fancy valve springs...
Stick a dial indicator into the spark plug hole, make note of TDC and use that to zero your crank-mounted degree wheel.
Stick a dial indicator tip onto the valve or the spring keeper or whatever piece up there makes sense to take a measurement from (with the indicator's axis of travel mostly aligned with the axis of the valve's travel), then start measuring valve displacement (with respect to base circle) vs crank angle...
Are you worried that you will have a valve-to-piston collision? If so, rotate the crank by 5°, then push the valve down, make note of the clearance room as a displacement:collision difference value. Do that through the entire crank rotation if you want, but it only really matters around the tip of the cam lobe and just after. Make sure you have some clearance. I don't think you would want the valves & pistons getting much closer than 0.050" at worst.
Stick a dial indicator into the spark plug hole, make note of TDC and use that to zero your crank-mounted degree wheel.
Stick a dial indicator tip onto the valve or the spring keeper or whatever piece up there makes sense to take a measurement from (with the indicator's axis of travel mostly aligned with the axis of the valve's travel), then start measuring valve displacement (with respect to base circle) vs crank angle...
Are you worried that you will have a valve-to-piston collision? If so, rotate the crank by 5°, then push the valve down, make note of the clearance room as a displacement:collision difference value. Do that through the entire crank rotation if you want, but it only really matters around the tip of the cam lobe and just after. Make sure you have some clearance. I don't think you would want the valves & pistons getting much closer than 0.050" at worst.