Question on Timing Marks on 440


Active Member
Dec 7, 2011
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Winnipeg, Manitoba
I installed the comp cams #2104 double roller timing chain set on my 440 and being like 40 years since rebuilding engines, I jumped the conclusion that the two circle dots have to match when installed. Well, this set, while it came with instructions that I must have not read, has two sets of indicators for 3 different timing settings. I picked what used to be the circles on the inside of the tooth ring which according to the instructions are wrong. I have reset to factory settings as per intructions and am trying to confirm proper timing. I popped the left side valve cover off to watch #1 cylinder valve movement as I turn the engine over (clockwise from front of engine). Intake opens shortly after moving off the timing mark. If TDC is top of compression stroke, shouldn't the exhaust valve be opening first?
Your at the beginning of the four stroke cycle. No, because exhaust valve is not supposed to open when piston is moving downward. It should not start opening until after piston moves down, after ignition occurs and pushes it down, then as it comes upward, that is when exhaust should open.
Here's the relevant portion of the instructions from Comp Cams.

I've installed dozens of cams over the decades and performed the full "degreeing" procedure, using a degree wheel and dial indicator, so I have a little experience here.

I'm not sure I understand your question, so let me ask:

1) You have the timing set on the engine, but it's all buttoned up now and you don't know what degree mark you used (the O, Triangle or Square)? If that's the case, I highly doubt you'll be able to determine if you're 4 degrees advanced or retarded by watching a rocker. Gotta pull the cover to make sure.

2) Same thing, but you're not sure you put the two circles (or Tri or Sq) marks opposite each other, such that the cam mark is at the bottom and the crank mark is at the top as per the (famous!) pic, below? If that's the case, you'll soon know because valves will hit pistons and your rocker vs. piston motion will be all out of whack.

3) Or, I guessed wrong and I'm of no help at all. :(

I reread your question. It seems like you believe you put the circle marks together correctly, and you're just wanting to confirm that it's all good.

In that case, the previous replies are pointing you in the right direction. You're a little confused because you're at "overlap" and 180* away from the "real" TDC with both valves closed.

Seems to me you've got it licked.
Is it possible I am 180 out? I was sure I did some checks before buttoning it all up. I do remember now getting a backfire on initial startup. Instead of adjusting the timing on the distributor, I moved #1 across opposite to what I though was correct thinking I did something wrong. I think that was a mistake. Will the engine run being 180 out?
Will the engine run being 180 out?

No. Nada. Nyet.

Let me regroup.

Thus far, you've run the engine, as in idling at 800 rpm or somesuch? Yes?

If so, your camshaft situation is not a situation, particularly so if you have your "O" marks aligned (instead of the Advance or Retard marks). If you're 180 out on the timing marks the engine will not run and you'll be bending valves against the pistons.

As I said above, I think you're fine.
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Your distributor would be the only thing out 180°. Those dots alternate (aligned on top or aligned on bottom) every other revolution. As long as aligned 6o'clock or 12 o'clock on the top gear it is good.
Ok, that latest changes things, a little. Here’s what I have so far. I lined the “0”‘S on both using the outside marls, not the key way and realized tonight why. The keyway “0” does not let the be piston rise to tdc. The outside “0” does.

(Photos might be mixed up. Hard to do this on a phone)

You can see the marks I used. However the instructions say to use the Keyway “0”. Anyway I had the car running snd did my break-in. Car ran seemingly ok at 2500-3000 rpm but idled rough. The exhaust would make your eyes water. Burning gas like crazy. Took the plugs out, all black, looked like running rich for a thousand miles. Blamed it on the carbs. Went through 4 carbs, all with same results. That’s when I decided to check the timing. With the timing marks aligned, here is my distributor with #1 at top right corner. Second picture is with cap off where the rotor is pointing at #1. It’s opposite. Again, as if it’s 180 out or as the second last post indicates, the marks could be be 6 or 12 o’clock.

Being the 180 off or whatever that issue is, I can live with since it was running. I think I understand that now. However, unless I am missing something, the instructions seem to wrong re standard or factor marks. 2. if the factor marks are off on the crank sprocket, is the cam gear where it should be or is it three teeth off. 3. if I use the keyway “0”, the dampener markings are will not line up with the timing tag.

I tried calling Comp Cams but they are near impossible to get through and have not responded to my email from last week questioning these things.

I'm not an expert and there are plenty more knowledgeable members but I'll try my best.

Yes, use the outer mark on the crank sprocket for lining up your timing chain. If you're using the "O" marks this will point the cranksprocket keyway roughly to 2 o'clock.

Lining up timing gears can be done two ways. Dot-to-dot is what my FSM says, this will have rotor point to #6 cylinder. If you line up both marks to 12 o'clock on the timing gears rotor will point to #1 cylinder. This is where the "180 degrees out" comes from.

Also, your #1 location on the distributor is different from stock, that would be more around 5 o'clock if I'm not mistaken. Could be that initial timing is way off, but can only check with a timing light.

Hope this helps!
I'm mostly paraphrasing the same thing as @thethee with what I'm about to say. I just went through this as I'm presently installing a cam.

On the crank gear, the "inner O" is for which Woodruff key slot to use. The "outer O" is the one that should line-up with the cam gear.

I have determined that the usual cam installation instructions to point the "O" dots on crank and cam gears at each other actually result in the cam being installed with the cam 180* off, which is to say piston #1 is at TDC at the end of the exhaust stroke, not the end of the compression stroke.

If you installed your distributor in the engine at that point, you'd want the rotor tip to point to the tower for #6, since that is the plug that would be firing at that time. Or rotate the crank through one full 360* revolution and the engine will now be at TDC with #1 firing.

EDIT: I noticed you also said something about the damper marks not lining-up with the marks on the timing tab if you use a certain keyway. That has nothing to do with how you installed the cam or timing set. The damper only keys onto the crankshaft one way. If your timing marks are off when piston #1 is at TDC as measured some other way, then that is a different problem! Possibly you need a new damper because the outer ring has become unbonded from the rubber insulator and rotated.
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Mike66 is spot on with his comments.

Look at this pic from the FSM again. You can see the crank key is about 20* clockwise from the crank O mark, just like your pic of your crank gear. So you're good.

As Mike66 mentioned, as for your damper's TDC mark not aligning with the timing cover mark whey you are SURE that #1 is at TDC (or #6 at TDC, for that matter), there is indeed a very good chance that the damper outer ring has unbonded from the inner hub and rotated somewhat, usually to a retarded "setting". Since your damper is off, give it a magnifying glass inspection to see if you can determine it has failed. Sometimes you can wobble the ring, but usually the bond sorta "re-bonds" once it has moved. No fix other than a new damper.
Thanks to all. The pics helped a lot and i was able to get through to the Comp help line and it took the tech some time to figure it out as well. I have reset as per pics and marks and reassembling. Will see what happens in next few days.