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Another urgent cry for help from MattyBrown
https://slantsix.org/forum/viewtopic.php?t=44876		 Page 1 of 1
Author:  MattyBrown [ Sat May 07, 2011 7:17 pm ]
Post subject:  Another urgent cry for help from MattyBrown
Okay, so tonight I was determined I would finally figure out if my cam is in time.

I set up a dial gauge above my open valve cover. Ran a coat hanger down to the little cups that sit on the cam (where the pushrods go).

I marked on a a degree wheel the exact moments that my intake should open and close. Lined TDC on the wheel up with TDC on my damper.

Turn the damper until intake should open. Start to get readings on the dial about 10 degrees BEFORE that spot. Hmm, is my cam advanced?

Check the spot where the valve is supposed to be closed. Get reading on the dial between 10-20 degrees AFTER when it is supposed to be closed. Hmm, WTF?

What's up with that? I decided it must be movement on the cam that makes up for valve lash. So I repositioned my dial gauge so that it is touching only the base of the valve springs. Check to see where it starts to move. The results were still very similar to the results I noted above.

So is this a completely inaccurate way of checking my cam timing?

I decided to find the point on the degree wheel that would be exactly half way between Intake Open and Close (according to factory spec). Sure enough, when I hit this mark, my dial gauge says the cam has hit the highest point.

So is this an acceptable confirmation my cam position or is this some sort of fluke? Is the absolute highest point on the cam supposed to be halfway between intake open and close (spec)? Why am I getting so much movement on my gauge before and after the other events?

If you've got the knowledge, please help clarify this insanity for me! I just want this to be over!!!

THANK YOU!

-Matt
Author:  ceej [ Sat May 07, 2011 7:26 pm ]
Post subject: 
Try this:

Set your dial indicator to zero at the very top of the intake lobe's lift.

Back the engine off counter-clockwise 'till it reads 0.100" lower than peak lift. Rotate it clockwise again until it reads 0.050" lower than peak lift. Write that number down.

Rotate the engine clockwise, normal rotation, past the zero (Max lift) point and on until it reaches 0.050" less than peak lift. Write that number down.

take the difference, divide by 2, and add the result to the first number. That's your Lobe Center. :D

CJ

OH! PS: The lash ramps will start in before the advertised duration in most cases, so seeing numbers different from the stated open and close is normal. Remember there is lash to pick up.
Author:  MattyBrown [ Sat May 07, 2011 7:32 pm ]
Post subject: 
Hey Ceej, thanks for that info. I will go try it. But, could you tell me this:

Once I have the lobe center number you speak of, how do I use it confirm that my cam is in the correct position?

Thanks!

-Matt
Author:  MattyBrown [ Sat May 07, 2011 7:42 pm ]
Post subject: 
Ceej, forgive me, I thought I understood your instructions, but the bit that confuses me is:

"take the difference, divide by 2, and add the result to the first number."

Could you dumb that down a step for me? Sorry, I'm fried.

-Matt
Author:  ceej [ Sat May 07, 2011 7:47 pm ]
Post subject: 
Write the numbers down. However many degrees the crank is at when those events occur. The difference between those numbers will be how many degrees between -.050" of max lift. When you divide by two, you find out how many degrees you need to add to the lower number to find the center of the lobe when compared to the crank rotation.

Intake Center should come out somewhere around 106°

Clear as mud? :lol: Tell us what the numbers are and we'll help!

CJ

PS: I'm fried too. The Hooptie is all back together and in the deep need for a post cam run-in oil change. :wink:
Author:  MattyBrown [ Sat May 07, 2011 8:13 pm ]
Post subject: 
Okay thanks Ceej. I'm about to do the test now. Praying for something in the 106 region. I'll be back with the results soon.

-Matt
Author:  ceej [ Sat May 07, 2011 8:16 pm ]
Post subject: 
You have a PM.

CJ
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