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Urgent cam degreeing help needed- Erson RV10 cam profile
https://slantsix.org/forum/viewtopic.php?t=38469		 Page 1 of 1
Author:  Reed [ Thu Dec 31, 2009 11:11 am ]
Post subject:  Urgent cam degreeing help needed- Erson RV10 cam profile
Well, I thought I was smart enough to figure this all out, but I think I messed up the math badly.

I had a stock 1964 225 cam reground to the Erson RV10 profile.

The cam shop gave me the following specs only:

Duration @ .050 lift = 212 intake and exhaust
valve lift = .435 intake and exhaust
valve lash is .012 intake and .012 exhaust

According to the Erson catalog, the RV10 cam has the following specs:

Duration = 254
Duration at .050 = 210
Gross lift = .435
Lobe center = 111
Advance = 4 degrees
Valve lash = .022

These are fairly close to what the cam grinder told me, so I assumed that the lobe center and duration figures from the Erson catalog match what I have.

I calculated the valve events at 0.00 inches of lift to be:

16 degrees of lobe overlap ([254/2]-111)
Intake opens at 246 degrees BTDC (254-[16/2])
Intake closes 8 degrees ATDC
Exhaust opens 8 BTDC
Exhaust closes 246 ATDC

And I calculated these events @.050 liftto be:

-6 degrees valve overlap ( [(210/2)-111])
Intake opens at 213 degrees BTDC (210-[-3])
Intake closes at 3 BTDC
Exhaust opens at 3 ATDC
Exhaust closes at 213 ATDC


So I got the degree wheel installed at TDC using a piston stop (I am 90% sure I did this right). When I installed the dial gauge and noted the valve events, this is what I got (the following are not measured at .050 lift):

Intake starts opening at 15 degrees before TDC
Intake fully open 114 degrees after TDC
Intake fully closed 59 degrees after BottomDC (121 BTDC)
Exhaust starts opening 38 degrees 142 after TDC
Exhaust fully open at 102 BTDC
Exhaust fully closed at 15 degrees ATDC

Also, I am measuring .235 total lift, far less that the .435 lift the cam is supposed to be ground to.

If you have followed my lousy measurements, you see my initial math was WAY off. Somewhere I royally messed up my math. I am totally lost and clueless. Please help.

Thanks!
Author:  slantzilla [ Thu Dec 31, 2009 12:13 pm ]
Post subject: 
Reed, couple questions:

How exactly did you use the stop to mount the degree wheel at 0?

What surface are you placing the dial indicator against to get your readings?

Cam lift for .435 gross should be around .290". (.290X1.5=.435)
Author:  Reed [ Thu Dec 31, 2009 12:30 pm ]
Post subject: 
Dennis- Thanks, but Josh was kind enough to call me and walk me through it.

Turns out that everything is actually perfect as is. The old MP double roller timing set I am using is manufactured with a four degree cam advance in the cam gear, so the intake centerline is 106.5 degrees, right where I wanted it.

But to answer your questions, I found TDC using the stop by bolting the degree wheel on roughly where I thought TDC was, attaching a pointer, putting in the stop tool, rotating the motor one way and then the other marking where the pointer was at each stop, then splitting the difference between the stops and adjusting the degree wheel accordingly.

The dial indicator was megnatized to the head and the tip was on the top of the adjuster nut on the rocker arm. Josh told me the error of my ways, and I then removed the rockers and put the dial gauge on the top of the pushrod (head is on and motor is in the van).

Josh is a fine human being and very kind.

Thanks! I now can put this whole mess back together.
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