Timing question

[Patch]

So I pulled the timing cover today. The aluminum cam gear and nylon teeth are indeed still in there. I have a double roller replacement to go in. Here's where I start getting a little confused. My stock timing chain set up is 12 and 12. Cam index hole to the left. The double roller replacement is set up for 12 and 6 with the cam index hole to the right. I have the right valve cover off to help verify TDC. I am at TDC and both marks are at 12&12. Distributor rotor is point at #6. What am I missing? I've always assumed on new timing sets, pips went to pips.....but for this to bolt on, I'm going to have to keep 12 & 12 on the new set.....the rotor pointing at 6 is what's throwing me off....I thought it should be pointing towards #1? Am I over thinking this?

[jocko]

Can you describe what you mean by "my stock timing chain set-up is 12 and 12"? With 1 rotation of the crank, it would be at 6 and 12, the proper place for R&I of the timing chain. I can't really see the cam dot anywhere(?)

12 and 12 is #1 firing position. This is where you want to be when setting ignition timing, but not where you want to be when setting valve timing.

To set valve timing (by installing the timing chain), you want the cam dot at 6 o'clock and aligned with the crank dot at 12 o'clock before you install the chain.

[AussieinNC]

Simple answer

12...12 will point dist at cyl 6

12...6 timing will point dist at cyl 1....

If the new double row needs the engine to be 12...6, 12 on crank...6 on cam gear...

Assuming you havent taken off the cam gear and chain yet,,,just manually turn engine crank one full revolution...

You will then have the 12...crank and 6...on cam positions...and the dist should be pointing at Cyl 1...

If you had set Cyl 1 to TDC on compression before dismantling...it would be at 12...6...
Remember to use thread locker on those cam bolts...

Have fun ...

[GASoline71]

Even your stock timing setup was at 12 o'clock on the crank gear and 6 o'clock on the cam gear from the factory. Then rotate the crank one full turn and they are now 12 and 12 with the engine set to be at TDC on the #1 cylinder. Install your double roller the exact same way.

Gary

[Patch]

The dot in the circle is the only spot on the 1969 OEM cam timing gear that I can find. With it at the 12 o'clock position, the engine is TDC on #1 and the dist rotor is pointing where you see it in the picture. This timing chain is the loosest chain I have ever come across and although it wouldn't surprise me if it has jumped, if it did, the marks still line up and no nylon teeth are broken off.
If I were to put the new Edlebrock timing chain on with the dot at the 6 o'clock position, the index pin on the new cam gear will be 180 out. If I were to install the new cam gear with the pip at the 12 o'clock position, it would line up with the index pin on the cam.

[Patch]

Originally Posted by GASoline71

Even your stock timing setup was at 12 o'clock on the crank gear and 6 o'clock on the cam gear from the factory. Then rotate the crank one full turn and they are now 12 and 12 with the engine set to be at TDC on the #1 cylinder. Install your double roller the exact same way.

Gary

The way it sits in the picture it is currently on TDC for #1. Cam gear mark at 12 and crank gear mark at 12.....this is why I am confused.

[AussieinNC]

If you dont want to turn the engine, just install the cam gear with its index mark at 12, the cam pin will be at 9 as it is now and the crank gear will have its mark at 12...

It really doesnt make a difference in that the cam is currently set for cyl 6 to fire at TDC...instead of the way most books tell you to run 6..on the cam and 12 on the crank...making the dots closer visually...less chance of being one tooth off...

Cylinder 1 as pictured would be on overlap...cyl 1 piston would be at TDC on overlap...exhaust closing and inlet opening...

[AussieinNC]

If you turn the crank one full turn, cyl 1 will come back to TDC and the gear set will read 6...12 6 on cam...12 on crank...

[GASoline71]

Originally Posted by Patch

The way it sits in the picture it is currently on TDC for #1. Cam gear mark at 12 and crank gear mark at 12.....this is why I am confused.

After 40 years of prior owners... it looks like it was set 180 out and then the plug wires moved around the cap. If you turn that engine over one full turn, you will have the cam gear at 6 oclock and the crank gear at 12 oclock. It will then be on TDC #1.

Gary

[Patch]

Originally Posted by AussieinNC

If you dont want to turn the engine, just install the cam gear with its index mark at 12, the cam pin will be at 9 as it is now and the crank gear will have its mark at 12...

It really doesnt make a difference in that the cam is currently set for cyl 6 to fire at TDC...instead of the way most books tell you to run 6..on the cam and 12 on the crank...making the dots closer visually...less chance of being one tooth off...

Cylinder 1 as pictured would be on overlap...cyl 1 piston would be at TDC on overlap...exhaust closing and inlet opening...

I understand everything you're telling me....I promise I do. When I spin the crank 1 revolution(I just went out and verified) and the marks are pointing at each other, cylinder 1 is in overlap....(closing and opening of exhaust and intake) when I spin it back around to 12 and 12....#1 is in TDC firing.

[AussieinNC]

Cylinder # 1 is at TDC twice for every single full revolution of the cam...

Once on compression, with cam index dot at 6 and crank index at 12...
Once on overlap on cyl #1...

The original photo shows me the engine is at TDC on compression on cyl #6...

It is not 180 out...

It is simply on compression on cyl 6

Half way thru the firing order of 1843 6572...

Just turn the engine one full crank revolution and the dots will line up 6...12

[Patch]

Originally Posted by GASoline71

After 40 years of prior owners... it looks like it was set 180 out and then the plug wires moved around the cap. If you turn that engine over one full turn, you will have the cam gear at 6 oclock and the crank gear at 12 oclock. It will then be on TDC #1.

Gary

Hi Gary....just did that a few minutes ago. With the engine 180 out from that photo, it is not in TDC for #1. It's in overlap....exhaust closing and intake opening. When it is in overlap, the timing marks are pointing at each other. I'm not trying to be difficult to all who are trying to help, but I have been fighting this and scratching my head about it all damn day. This is something I have not seen before.

[Patch]

Originally Posted by AussieinNC

Cylinder # 1 is at TDC twice for every single full revolution of the cam...

Once on compression, with cam index dot at 6 and crank index at 12...
Once on overlap on cyl #1...

The original photo shows me the engine is at TDC on compression on cyl #6...

It is not 180 out...

It is simply on compression on cyl 6

Half way thru the firing order of 1843 6572...

Just turn the engine one full crank revolution and the dots will line up 6...12

Right before I stopped at that position, I wa building compression on cylinder #1, when I try it your way, I have zero compression on 1. Like I said, I agree with and hear what you're saying, but it's not matching up to what the engine is doing on my end. I've rebuilt small blocks, big blocks, Chevy and Chrysler, pretty much the only thing that scares me is automatic transmissions. Retired Navy jet mechanic.....so I'm listening to ya...but unless I'm just not seeing something..... AND.....I appreciate the hell out of ya'lls help....but something not jiving on my end

[AussieinNC]

Just line the dots up dot to dot...

If you have turned the engine now so the dots are close to dot to dot...swap the gears est out...

I have seen some engines that did not come to TDC when dot to dot...

When you then have the cam cover on, set cyl #1 TDC on compression and set dist to cyl #1...

[AussieinNC]

That chain looks so stretched it is likely retarded cam phasing, that will usually result in loss of pressure thru late closing points...

Put the dots to dots...put the chain on and bolts etc...then turn the engine by hand and you will feel cyl 1 will then build compression as it should...

[AussieinNC]

Forget where dist is pointing until you get the cam gear set on...

then bring cyl 1 to TDC on compression...

check rotor position...you can either "move the wires around"...if necessary....

or better is lift the dist and reset to where it should be...

IF its a HEI dist, the #1 cyl post if left of opening in cap....

If its a standard points dist...cyl 1 is right of points adjust window...

[Patch]

Originally Posted by AussieinNC

That chain looks so stretched it is likely retarded cam phasing, that will usually result in loss of pressure thru late closing points...

Put the dots to dots...put the chain on and bolts etc...then turn the engine by hand and you will feel cyl 1 will then build compression as it should...

That chain is wasted for sure....cracks all throughout the nylon teeth on the cam gear.

[AussieinNC]

Yep...standard for the era...

Double row is better, so long as its not a chinese chain...

I usually use Cloyes sets...

Dont forget thread locking compound on the bolts that attach the cam gear...

[Patch]

I would like to apologize!! Got wrapped up in cam timing vs. ignition timing.....So much wasted time over nothing! I appreciate all of your help greatly!!! I was wrong.....you were right.......ugh...that hurt a little..... Got it all swapped out......good Lord I messed myself up.......

[AussieinNC]

Yay!!!

Another Chevy lives again...

Glad the forum was able to help ya out...

[garyd1961]

The way I always do it is to set the chain at 12 and 6, turn the crank one revolution then set the distributor to #1.

[Patch]

I'm not sure why I was getting hung up on the issue of at 6 and 12 I wasn't on TDC for # 1......But after I do the HEI swap, I will drop the distro in and move it over to the normal drivers side cylinder 1-ish position.