Timing marks on cam sprocket

[troublemaker]

So here's one for you. I rebuilt a 73 440 about 2 years ago. Mild rebuild. I nstalled a Edelbrock double roller timing chain set.
With #1 @TDC and #1 valves closed(as they should be) the marks on the cam sprocket and crank sprocket did not line up. I was 180 off on the cam sprocket. Mark on sprocket on the top. The crank keyway was at 2 o'clock and the crank sprocket was lined up with the 0 timing mark on top. So I lined up # 1 and ran my firing order and had no problems. The car ran fine for a year or so with the only problem being my wires are 180 off at the distributor. All was good. I just put a new single bolt cam in and thought I would look at it again. I can't figure out why the timing marks don't go head to head. My harmonic balancer is in 0 and I'm at TDC on #1 and my cam gear is still lining up 180 off. Any ideas?

 

[kiwigtx]

Seen that before - the cam is made by a different company to the timing gear set.

 

[troublemaker]

So I'm thinking about just running it. Mopar cam and edlbrock set.
Thanks for the reply

 

[kiwigtx]

Mine was 180 out like you said - Comp Cams and a Cloyes gear set.

 

[troublemaker]

Good to know I'm not the only one. I couldn't figure out what I was doing wrong
Thanks again. I knew i could count on you guys for an answer

 

[Hemirunner]

The cam turns 1 revolution for every two of the crank. Rotate the crank one revolution and the marks will line up.

 

[Lionized]

The cam turns 1 revolution for every two of the crank. Rotate the crank one revolution and the marks will line up.

^^This^^

 

[troublemaker]

So let me understand this correctly with the timing gear and chain installed and on number one cylinder top dead center rotate the whole crankshaft one full turn and that will line up the marks and I will still be at top dead center on number one cylinder

 

[troublemaker]

How can that even work?

 

[Lionized]

Compression stroke and power stroke.

 

[multimopes]

Not sure and probably wrong but I think they mean with the timing chain off, then re-install?!?

 

[mopar 3 B]

Yea a pain in the a** but if you had just lined the marks up timing would have not been 180 off.

 

[bm02tj]

compression stroke only concerned for installing distributor

 

[Hemirunner]

So let me understand this correctly with the timing gear and chain installed and on number one cylinder top dead center rotate the whole crankshaft one full turn and that will line up the marks and I will still be at top dead center on number one cylinder

Yes. TDC is TDC regardless of what stroke you’re on. It works because the cam turns 1/2 revolution for each revolution of the crank. Notice the size difference of those gears?

 

[dvw]

A piston at TDC is the on exhaust stroke or the compression stroke. Each cylinder at TDC compression has an opposite cylinder at TDC exhaust. Standard Mopar firing order, 18436572 would be 1/6,8/5,4/7,3/2,6/1,5/8,7/4,2/3 . If a cylinder is at TDC exhaust the distributor rotor will point 180 degrees from it's plug location. So when the dots on the timing gears are lined up, #1 will either be at TDC compression or 180 out at TDC exhaust. If it's on TDC exhaust (both valves on that cylinder opened equally) rotate the ENGINE one turn. The CAM has now rotated a 1/2 turn and is on TDC compression (both valves closed). Dropping the distributor in at TDC compression will allow the normal factory distributor location and wiring.
Doug

 

[troublemaker]

Just for everybody's info the old timing gear and the new one are the same diameter. The difference between old and new is the old one had two holes 180 apart so you could actually rotate the sprocket 180 to align the marks. The new one has a slot, and as a novice I would have thought that TDC was located with #1 at the top of the compression stroke with both valves in the closed position. STUPID ME. Anyway FYI I did rotate the crank 360 and aligned the marks and the valve trane .did not move on #1. Valves still remained closed. Just sayin', what do I know. I would have never figured it. LOL

 

[troublemaker]

Hey Doug, very good explanation. Thanks, that is just what happened. The original builder set it up 180 off on the exhaust and wired in the distributor to match. I was screwed from the start. Leave it to a Chevy guy working on a Mopar.
Thanks

 

[Hemirunner]

Just for everybody's info the old timing gear and the new one are the same diameter.

Just for the sake of clarification, I was referring to the cam gear vs the crank gear when I asked about diameter. Hence the 2:1 ratio.

 

[lewtot184]

with the marks lined up at the sprockets the #1 intake valve should be opening an #6 firing; IIRC.

 

[451Mopar]

So here's one for you. I rebuilt a 73 440 about 2 years ago. Mild rebuild. I nstalled a Edelbrock double roller timing chain set.
With #1 @TDC and #1 valves closed(as they should be) the marks on the cam sprocket and crank sprocket did not line up. I was 180 off on the cam sprocket. Mark on sprocket on the top. The crank keyway was at 2 o'clock and the crank sprocket was lined up with the 0 timing mark on top. So I lined up # 1 and ran my firing order and had no problems. The car ran fine for a year or so with the only problem being my wires are 180 off at the distributor. All was good. I just put a new single bolt cam in and thought I would look at it again. I can't figure out why the timing marks don't go head to head. My harmonic balancer is in 0 and I'm at TDC on #1 and my cam gear is still lining up 180 off. Any ideas?

That's normal. When the timing mark is at the "6" O-clock position that is TDC overlap where both intake and exhaust are slightly open.
At the "12" O-clock position, TDC compression for ignition/spark.