Anyone remember how to degree a cam?

[craig32]

Hi again all,
I just changed the distributor in my project to a dual point, but after 20+ years, I forgot how to degree a cam. :eyerole If I remember right, it was something like 38 degrees before. The new dual point is mechanical advance, where the old one is vacuum. Anything special I need to know about that? I changed the distributor ok, just need to know where the timing should be. Oh btw, I tried to post a pic of it earlier, but it didn't go - you all know what a small block with headers and 2 fours looks like anyway, right? Thanks in advance.


Craig

 

[SPANISHVETTS]

Last time I did it I used the info from here.

 

[Jack]

The info at crane cam degree link is good ... BUT ... If you've simply swapped distributors, you don't need to degree your camshaft.
JACK:gap

 

[craig32]

Jack,
I have no timing marks, so I'm not sure where to set the distributor. When I did it before, I never made marks, just set it. I wasn't really planning on 25 years elapsing, or changing the distributor but I recently realized I never put a dual point in it and the original 2 X 4's had them. Thanks again.
Craig

 

[JohnZ]

Unless you have some pressing need for the dual-point non-vacuum advance distributor (don't know what your project is), the dual point distributor is a step backwards in terms of idle cooling, throttle response, and fuel economy. If you're going to do it anyway, with a GM distributor, you set the dwell independently for each set of points, with the other set disabled; set each one for 29* dwell, and when you're done, with both sets working, you should show 34* dwell.

 

[craig32]

Sounds like I should put the old one back in then? I'm not having much luck with the timing, so it sounds probable. My project is a tractor - 327 with gear driven roller cam and 2 four barrels. The original 283 - 2 X 4's had a dual point, so I got one. I need to get a radiator hooked up to it so I can run it longer than half a minute and get it all adjusted right. I hadn't touched it in like 10 years, all it needed to start was a new coil. I figured last year when I bought the Vette (that needed work) that buying parts for it would help inspire me to fabricate the parts I need to finish my lifelong 'project' Thanks again.

Craig

 

[Jack]

Sounds like you need to find TDC & mark it on the balancer. #1 cyl is on left side of motor, all the way at front of motor. Pull left valve cover so you can see both #1 I&E valves. Pull #1 sp plug. Bring #1 piston up to top when BOTH #1 I&E valves are fully CLOSED ... that's TDC ... mark it on balancer and at an adjacent non-rotating part ... don't move the crank anymore. Put the distributor in and make sure rotor tip ends up pointing toward #1 cylinder. Fire it up & Set the rest of timing with a timing light/your ear and set the gaps (as JOHNZ said) with dwell meter. Rev it to 2800-3K where total timing should end up about 38*.
JACK:gap

 

[craig32]

Jack, I have the mark on the balancer, just no other mark to correspond with using a light. Apparently I have the terminology wrong concerning 'degreeing' The cam came with papers, way back when, which told where it should be and how to mark it. What I wanted to know was if anyone was familiar with that process. Sorry for the comfusion.
Craig

 

[OldCorvetteFan]

Craig -

I think what you're asking is setting initial and total timing. Degreeing a camshaft is a process to ensure that the Intake and Exhaust lobes of the cam open and close at the right time with respect to crankshaft travel.

Back in the old days, when I had to set initial timing on engines with missing timing tabs on the camshaft cover, I used the following process:

1. Fabricate or purchase something you can use as a timing tab. Install it on the engine.
2. Remove the coil wire.
3. Remove the valve cover.
4. Observe the valve train for #1 cylinder, and look for the engine to begin it's compression stroke. I had a fabricated threaded insert that I used to place a hard mechanical stop near TDC.
5. Manually rotate the engine until you reach the mechanical stop, and make a mark on the harmonic balancer.
6. Rotate the engine in the opposite direction (should be the ONLY direction you can go!), until you hit the stop again. Make a second mark on the harmonic balancer.
7. The point halfway between the marks (they should be pretty close to each other) is TDC, or zero degrees.

Initial timing should be between 10 and 20 degrees BTDC, and should begin advancing at about 1200 RPM. Total timing advance should be about 36 degrees, and should occur at about 3000 RPM.

Good Luck!

Steven

Hey! I think this is my first post! I hope you find this helpful!

 

[grapeknutz]

Craig -

I think what you're asking is setting initial and total timing. Degreeing a camshaft is a process to ensure that the Intake and Exhaust lobes of the cam open and close at the right time with respect to crankshaft travel.

Back in the old days, when I had to set initial timing on engines with missing timing tabs on the camshaft cover, I used the following process:

1. Fabricate or purchase something you can use as a timing tab. Install it on the engine.
2. Remove the coil wire.
3. Remove the valve cover.
4. Observe the valve train for #1 cylinder, and look for the engine to begin it's compression stroke. I had a fabricated threaded insert that I used to place a hard mechanical stop near TDC.
5. Manually rotate the engine until you reach the mechanical stop, and make a mark on the harmonic balancer.
6. Rotate the engine in the opposite direction (should be the ONLY direction you can go!), until you hit the stop again. Make a second mark on the harmonic balancer.
7. The point halfway between the marks (they should be pretty close to each other) is TDC, or zero degrees.

Initial timing should be between 10 and 20 degrees BTDC, and should begin advancing at about 1200 RPM. Total timing advance should be about 36 degrees, and should occur at about 3000 RPM.

Good Luck!

Steven

Hey! I think this is my first post! I hope you find this helpful!

One of the best explanations yet! Oh yeah welcome to

 

[OldCorvetteFan]

One of the best explanations yet! Oh yeah welcome to

Thanks for the kind welcome! I've been lurking here for quite a while, and decided after the 2005 Bloomington Show that it was time to get actively involved again. My wife and I have decided its time for another Vette in the family, so I'm working my way back into the Corvette Lifestyle.

Steven