Cam Alignment Tolerance

[Mashermoto]

I've read the cam chain tip and followed the manual procedure for aligning the cams. The alignment mark on the exhaust cam lags behind about a degree or two. My question is if I'm in tolerance.


I've found top center using a degree wheel and piston stop.


I've aligned the indicator with the the T mark.


After following the manual procedure for aligning the cams and setting the chain tensioner the intake cam marks align very close.


The exhaust cam marks lag a few degrees.

Do I have more work to do here?

[Ivan]

Those marks are usually "close enough" to get the cams in proper synch. To find out where they really are, you need to use a travel indicator and find the degree at which the designated lift is achieved. Most cams will say Xº at .020" lift.

[petejw]

HeyMashemoto,
Those cam dots need to align,
looks like it might be a tooth off at the crank,
play with it carefully and see if you can get them to line up.

[Mashermoto]

I was able to get the exhaust to move one tooth to the right. Here are the results


This is the intake.


This is the exhaust. It is now leading a little bit

They are much closer, but still more work? I'm not sure how to get it to adjust any more

[petejw]

Looks better, but Ive always been able to have
mine line up, is that with the tensioner in place
and adjusted?

[Mashermoto]

Pete,

Yes, that is with the tensioner in place. I re-read your first reply about my chain maybe being a tooth off. The above setting was made by moving the exhaust cam one tooth. Tonight I'll try to move the chain on the crankshaft and see if that will help.

I guess the correct setting is for the two dots to align spot on with the arrows

[Ivan]

I guess the correct setting is for the two dots to align spot on with the arrows

Mine don't line up spot on. It can't be too critical, since the arrows on the caps are from the casting process, which isn't very accurate at all.

[trbig]

I think the first spot you had it in would be correct. (In the first pic) If you were to put it there and slightly advance the crank, it will show a SLIGHT advancement on intake and a SLIGHT retard on exhaust. All this means is that your cam chain is slightly stretched. Once they do this, it makes the links in between the two cams a little further apart over time.. but it will still run just fine.

Besides a bit of performance, this is another reason I'd like to have slotted cam sprockets. You could adjust them to get them exact each time.


Tod

[Ivan]

Besides a bit of performance, this is another reason I'd like to have slotted cam sprockets. You could adjust them to get them exact each time.


Tod

I am workin on it man, give me time...

[Mashermoto]

I agree TR. The distance between the intake sprocket and exhaust sprocket is going to determine how much the exhaust lags or leads the exhaust. The crank pulls the intake, and the intake pulls the exhaust. So any slack between the intake and exhaust is how much the the exhaust will lag behind.

And yes, slotted cam sprockets would make this thread a moot point Even with a streached chain you could still adjust the cams alignments spot on

What confuses me is that the intake aligns very close. With the distance between the two cams being much less than the distance from the intake to the crank, it just seems like the exhaust should align better than it is. I'll keep messing with it. In the meantime I'll check back to see what folks have to say.

Later.

[skids]

I think the later of the two is more correct. It is less than half a chain link from perfect, right?

[trbig]

I think the later of the two is more correct.

Why?


Tod

[TADracer]

Check those cams!

Since you have your degree wheel mounted and TDC found, why dont you try and get ahold of a 1" travel dial indicator and mount it on the head with the probe on the top of the valve bucket to measure the cam lobe centers and be sure. Factory lobe centers should be 101 degrees for both intake and exhaust. Checking height should be around .040" (which is about 1mm).

The procedure is to zero the dial indicator then rotate in direction of running until dial indicator measures .040" and record that number from the degree wheel. Then rotate until valve opens and then closes again to .040" and record that number. The formula is opening # + closing # + 180 /2 and subtract the smallest number.

If you have in fact moved the exhaust cam one tooth off then you will come up with a crazy lobe centerline for that cam and you will actually be off many degrees at the crank. Plenty enough to cause a collision between valve and piston. While your degree wheel is mounted, check for piston/valve clearance at TDC, 5, 10 and 15 degrees before and after TDC.

I have been using slotted cam sprockets for years. There is no big horsepower gains to be had but it does increase tuneability alot. But it is a bit more work if you ever remove your cams as you must degree them in every time.

[trbig]

But it is a bit more work if you ever remove your cams as you must degree them in every time.

Why wouldn't it be EASIER? Leave the sprocket bolts loose, put the cams exactly on the dots and tighten up the sprocket bolts.


Now, if you were timing them each time to get them at a 5 degree advance or whatever.. then yeah, I can see that. But to have them to keep the engine timing stock.. seems like it would be much easier.


Tod

[Mashermoto]

TAD,

You mean like this


The short answer is it is a pain in the asprins It would be much simpler to just follow the instructions, but it's turning out to not be that simple.

I probably will use your suggestion, just to find out the truth and sleep a little better at night

101 degree seperation is real tight Are you sure about those factory specks