3-Keyway Timing Sets

1. ## 3-Keyway Timing Sets

I have a Comp Cams #2110 timing set, which has a 3-keyway crank sprocket.

In order to ask the question I am going to thoroughly explain the facts as I know them in order to make the question easy to understand.

The below timing mark explanations are worded in a way that assumes the cam is ground "straight up" (no advance or retard).

The keyway for the "O" timing mark is for "straight up".

The instructions say that the triangle shaped keyway is for 4* advance.

The instructions say that the square shaped keyway is for 4* retard.

My question is:

According to the instructions, the triangle shaped keyway is for 4* advance. Does this refer to 4* CAM advance or 4* CRANK advance? Does this mean that if I use the triangle shaped keyway that it will advance the CRANK 4*, which in effect will retard the CAM 2* since the cam spins at half the crank speed?

Or will the triangle shaped mark retard the CRANK 4* to advance the CAM 2*?

2.

3. "Advanced" indicates cam advanced, you can get an "Offset keyway" that will buy you more-less depending on what way it's installed, I recommend using a degree wheel and double checking the cam timing for what you want, 4* IMO is a lot if you dont have a starting point, my freind who is an automotive machine shop teacher always uses a Jesel belt system to dyno tune the valve timing then goes back to the chain, set for the findings... Good luck!

GT

4. Degrees are degrees read on a degree wheel.

They are always crankshaft degrees.

But you always check them. Can't tell you how many Comp sets I have checked that were off.

5.

6. Originally Posted by Infomaniac
Degrees are degrees read on a degree wheel.

They are always crankshaft degrees.

But you always check them. Can't tell you how many Comp sets I have checked that were off.
OK so by changing the cam timing by 2* of camshaft rotation , that will actually move the timing events by 4* of crankshaft rotation. In other words, the cam only has to advance 2* of cam rotation to move the intake centerline from 110* to 106* (difference of 4*) of crank rotation. Am I correct in saying this?

Also, according to my instructions, the "triangle" keyway is the 4* advance keyway while the "square" keyway is the 4* retard keyway. Does this mean that if I use the "triangle" symbol that it will advance the CAM? Or will using the "triangle" symbol advance the CRANK instead?

7. Originally Posted by Jetaholic
OK so by changing the cam timing by 2* of camshaft rotation , that will actually move the timing events by 4* of crankshaft rotation. In other words, the cam only has to advance 2* of cam rotation to move the intake centerline from 110* to 106* (difference of 4*) of crank rotation. Am I correct in saying this?

Also, according to my instructions, the "triangle" keyway is the 4* advance keyway while the "square" keyway is the 4* retard keyway. Does this mean that if I use the "triangle" symbol that it will advance the CAM? Or will using the "triangle" symbol advance the CRANK instead?
It will move the valve timing events by that many degrees. But degrees are crankshaft degrees. The valves open and close relative to crankshaft position.

For example if the intake opens 12 degrees before top center as ground. It should open 16 degrees BTC by advancing or using the triangle keyway.

All measured on a degree wheel. Connected to the crankshaft.

But there is no guarantee. You really need to measure it straight up (by the gears) before doing anything. And why advance or retard it?

8. Originally Posted by Infomaniac
It will move the valve timing events by that many degrees. But degrees are crankshaft degrees. The valves open and close relative to crankshaft position.

For example if the intake opens 12 degrees before top center as ground. It should open 16 degrees BTC by advancing or using the triangle keyway.

All measured on a degree wheel. Connected to the crankshaft.

But there is no guarantee. You really need to measure it straight up before doing anything. And why advance or retard it?

"Advance" in my post was used merely as an example to help explain my question.

The cam I have is ground 2* advanced (112* LSA installed on 110* intake centerline). This will put the intake at 110* ATDC and the exhaust centerline at 114* BTDC when installed on the "O" mark on the crank gear. On a jet boat application I don't see any reason to advance the cam at all since the motor doesn't really see much of a load below 4000 RPM anyway, so I was hoping to retard it 2* so that the cam would be installed "straight up" (112* ATDC intake centerline and 112* BTDC exhaust centerline). In order to do this it's looking like I'm gonna need a different crank gear to make it happen.

9. Originally Posted by Jetaholic
"Advance" in my post was used merely as an example to help explain my question.

The cam I have is ground 2* advanced (112* LSA installed on 110* intake centerline). This will put the intake at 110* ATDC and the exhaust centerline at 114* BTDC when installed on the "O" mark on the crank gear. On a jet boat application I don't see any reason to advance the cam at all since the motor doesn't really see much of a load below 4000 RPM anyway, so I was hoping to retard it 2* so that the cam would be installed "straight up" (112* ATDC intake centerline and 112* BTDC exhaust centerline). In order to do this it's looking like I'm gonna need a different crank gear to make it happen.
Yep and advance is just used as an example by me also.

I guess what I am really trying to say is get the degree wheel out and measure it as is in the straight up (by the gear) position before brain fukin yourself to death on what to do. Chances are it will not degree out as printed on the card regardless of what it is supposed to be.

You might get lucky and it fall 2* retarded, you might buy some degree bushings drill the cam gear and jack with it until you get it where you want it or you might buy the slightly fancier timing set with the adjustable bushing to put it right where you want it the fast way.

10. And maybe we went about it the long way. Retarding it 2* will put it back to where you want it. (The true straight up position)

And the cam bushing method is the way I see you going about it. Again if it degrees in where it is supposed to.

The issue with some Comp sets I have had is the dots do not line up when they are supposed to. It's very disturbing. I set the degree wheel up with a piston stop. Line up the dots, go back and look at the dots when the wheel says exact TDC and they are off. Not only off but can't physically line them up when the engine is at TDC.

11. Originally Posted by Infomaniac
Not only off but can't physically line them up when the engine is at TDC.
I ran into this with a Crane set. Also, the gears wouldn't line up with a straight edge. I ended up using one gear from the new set and one from the old set to get it right. Never seen anything like that before.

Tim

12. ## 2 words

Chain Stretch............Get a gear drive, degree it in, and forget about it....Ray

13. Originally Posted by River Rat 005
I ran into this with a Crane set. Also, the gears wouldn't line up with a straight edge. I ended up using one gear from the new set and one from the old set to get it right. Never seen anything like that before.

Tim
Yea I just put the crank and cam in the correct position and make my own dot.

14. ## 1 word

Originally Posted by Moneypit
Chain Stretch............Get a gear drive, degree it in, and forget about it....Ray
Jesel!! It's sitting here waiting to go in. Also have a Pete Jackson in the box I used for a couple years. Between a chain or gear I'd go gear. Jesel seems to be the the drive of choice now. We'll see how it works out.

Tim

15. Originally Posted by Infomaniac
Yea I just put the crank and cam in the correct position and make my own dot.
Ya know I had thought about doing that exact same thing. Finding TDC, then rotating the crank so that it's 7* before TDC (that's the intake opens 0.050" on my particular cam) or 5* BTDC if I plan to retard it 2* as mentioned above, then rotating the cam by hand until the dial gauge indicates 0.050" on the intake lobe, then removing the cam sprocket and installing the chain at this point. I'm thinking if the camshaft doesn't move when I pull the cam gear off to install the chain it should work?

16. I think I would degree it in straight up to see where it's at. Then use an off set key or bushing to set it where you want it.

Tim

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