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Old 08-04-2013, 08:42 PM
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350 timing marks when replacing chain and gear

I know this has been covered, but it seems people have two different opinions.

Should the marks on the cam gear and crank face each other, or both be at 12 oclock? Summit says facing each other, other people say both at 12.

Back story.....

350 in a 85 Cutlass, from a 79 G20 van, bought car for my son, never ran quite right.

tried tuning it up, replaced points(don't know why they didn't leave the 85 HEI in), cap, rotor, plugs, wires etc, tried timing it. I kinda had to guess since the genius left the timing tab off when he put a chrome timing cover on it.

The vacuum advance hit the manifold, so I suspected the distributor a tooth off, so I pulled the dist and moved it a tooth, still wouldn't time, tried moving the plug wires over one place, still wouldn't time.

Finally got pissed, took the distributor out, took the valve cover off, took the plug out and put it on TDC, marked the timing cover, and the balancer and put the distributor back in, started it and tried timing it with a light and a vacuum guage. Still didn't run right.

So I figured, who knows what the van went through in its life, maybe a flat cam, or bad dist or timing chain jumped.

So I bought all new timing set, cam, lifters and HEI distributor.

Took the engine out and tore it apart and found what looks like the cam is a tooth off, the chain seems tight, so evidentally the timing chain may have been replaced before, PICS Below

So before I tore it apart, I thought I would clarify what position the marks should be. Right now they are facing each other (1tooth off) and I believe its on TDC on NO 1.

I rotated it in the firing order and watched 2, 1, 8 move, then went back to where the push rods on No 1 were both rotatable. NO IDEA WHY THE IMAGE OF THE MARKS WONT POST
http://i572.photobucket.com/albums/s...psc4030f2b.jpg




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Last edited by rp23g7; 08-04-2013 at 08:50 PM.
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Old 08-04-2013, 08:57 PM
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It can be done either way. The cam is 1/2 speed of engine. So the timing marks can be together or both up. Both up leaves engine at TDC and both together is 180 out. Just turn engine one revolution and timing marks are both up.
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Old 08-04-2013, 09:05 PM
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Do what the cam manufacturer tells you don't follow the herd!


#1 piston at TDC and dots together! cant go wrong here now the reason they put them at 12 is for a fast fire up but its going to move when you spin the engine to set your valve train. So just line up the dots and leave it at that. plus its easier to use a strait edge this way to check to make sure they are inline with the crank and cam
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Old 08-05-2013, 04:44 AM
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It appears by the photo that you just need to turn the crank clockwise a tooth for the marks to line up, does not look a tooth off.

When both marks are together, you are at the #6 firing position. When both marks are at 12 o'clock, you are at #1 firing position.

It is best to align marks together for a good visual, then turn crank 360 to be at #1 firing position and drop distributor in with rotor pointing at #1.

You can leave marks together, just be sure to drop distributor in with rotor pointing at #6
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Old 08-05-2013, 09:07 AM
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Quote:
Originally Posted by GMC boogie View Post
It appears by the photo that you just need to turn the crank clockwise a tooth for the marks to line up, does not look a tooth off.

When both marks are together, you are at the #6 firing position. When both marks are at 12 o'clock, you are at #1 firing position.

It is best to align marks together for a good visual, then turn crank 360 to be at #1 firing position and drop distributor in with rotor pointing at #1.

You can leave marks together, just be sure to drop distributor in with rotor pointing at #6
Nah, I think its actually a tooth off, it wouldn't time no matter what I did, think I am going to pull it out to see what is going on, but I will follow your instructions, thanks
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Old 08-05-2013, 03:59 PM
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Quote:
Originally Posted by rp23g7 View Post
I know this has been covered, but it seems people have two different opinions.

Should the marks on the cam gear and crank face each other, or both be at 12 oclock? Summit says facing each other, other people say both at 12.

Back story.....

350 in a 85 Cutlass, from a 79 G20 van, bought car for my son, never ran quite right.

tried tuning it up, replaced points(don't know why they didn't leave the 85 HEI in), cap, rotor, plugs, wires etc, tried timing it. I kinda had to guess since the genius left the timing tab off when he put a chrome timing cover on it.

The vacuum advance hit the manifold, so I suspected the distributor a tooth off, so I pulled the dist and moved it a tooth, still wouldn't time, tried moving the plug wires over one place, still wouldn't time.

Finally got pissed, took the distributor out, took the valve cover off, took the plug out and put it on TDC, marked the timing cover, and the balancer and put the distributor back in, started it and tried timing it with a light and a vacuum guage. Still didn't run right.

So I figured, who knows what the van went through in its life, maybe a flat cam, or bad dist or timing chain jumped.

So I bought all new timing set, cam, lifters and HEI distributor.

Took the engine out and tore it apart and found what looks like the cam is a tooth off, the chain seems tight, so evidentally the timing chain may have been replaced before, PICS Below

So before I tore it apart, I thought I would clarify what position the marks should be. Right now they are facing each other (1tooth off) and I believe its on TDC on NO 1.

I rotated it in the firing order and watched 2, 1, 8 move, then went back to where the push rods on No 1 were both rotatable. NO IDEA WHY THE IMAGE OF THE MARKS WONT POST
http://i572.photobucket.com/albums/s...psc4030f2b.jpg



Both positions are correct but you've got to keep track of where the in the firing order these positions are at to properly align the distributor.

With both the crank and cam gear in the 12 o'clock position the number 1 cylinder is ready to fire the power stroke and number 6 is ending its exhaust stroke.

With the crank gear at the 12 o'clock position and the cam gear at 6 o'clock the pip marks face each other making them easy to line up, however, number 6 is now ready to fire the power stroke and number 1 is ending its exhaust stroke.

To make my life simpler I always bring the number one cylinder and the distributor to number 1 firing before removing the distributor. For installation of the timing set I always pull the crank around to the pip mark facing the 12 o'clock position with the cam gear and chain installed with the pip mark in the 6 o'clock position, this makes it easy to see that you've got alignmnet between the gears. Once everything the gear alignment is verified and all the bolts are run in to hold the gear, I rotate the engine 360 degrees which brings the assembly back ready to fire number one with crank and cam gear in the 12 o'clock position so the distributor can be reinstalled exactly where it came from.

A little hint here, the distributor gear does a 1 tooth rotation toward the retarded position as the distributor is removed. This usually takes the oil pump drive with it. When you put the distributor back in if it just drops in place it's probably a tooth off so when you remove the distributor take a long screw driver or an oil pump assembly pressurization tool (essentially a distributor without a gear) and give the oil pump drive shaft a litte advancing twist (clockwise rotation). That way when you align the distributor to your removal datum point and the rotor to the number one firing position on the distributor housing it ends up right where it fires number 1 on TDC.

The datum marks are to align the housing with a easily identifiable object that aligns it's orientaion to the rest of the engine. While in that position you also mark the housing with where the rotor is when it's ready to fire number 1. Normal installtions usually have some fudge space so if your off a tooth you can rotate the distributor to regain the number 1 alignment with rotor and cap. But with space constrained installtions like a V8 planted into an S10/15 or Vega/Monza there often isn't any space to align the distributor other than how it was so it's important to mark off repeatable locations for alignment of the distributor on these type things.

Bogie

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Old 08-05-2013, 08:03 PM
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Here ya go (actually looks right from here if the cam was turned CW a bit more):

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Old 08-06-2013, 09:10 AM
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Quote:
Originally Posted by oldbogie View Post
Both positions are correct but you've got to keep track of where the in the firing order these positions are at to properly align the distributor.

With both the crank and cam gear in the 12 o'clock position the number 1 cylinder is ready to fire the power stroke and number 6 is ending its exhaust stroke.

With the crank gear at the 12 o'clock position and the cam gear at 6 o'clock the pip marks face each other making them easy to line up, however, number 6 is now ready to fire the power stroke and number 1 is ending its exhaust stroke.

To make my life simpler I always bring the number one cylinder and the distributor to number 1 firing before removing the distributor. For installation of the timing set I always pull the crank around to the pip mark facing the 12 o'clock position with the cam gear and chain installed with the pip mark in the 6 o'clock position, this makes it easy to see that you've got alignmnet between the gears. Once everything the gear alignment is verified and all the bolts are run in to hold the gear, I rotate the engine 360 degrees which brings the assembly back ready to fire number one with crank and cam gear in the 12 o'clock position so the distributor can be reinstalled exactly where it came from.

A little hint here, the distributor gear does a 1 tooth rotation toward the retarded position as the distributor is removed. This usually takes the oil pump drive with it. When you put the distributor back in if it just drops in place it's probably a tooth off so when you remove the distributor take a long screw driver or an oil pump assembly pressurization tool (essentially a distributor without a gear) and give the oil pump drive shaft a litte advancing twist (clockwise rotation). That way when you align the distributor to your removal datum point and the rotor to the number one firing position on the distributor housing it ends up right where it fires number 1 on TDC.

The datum marks are to align the housing with a easily identifiable object that aligns it's orientaion to the rest of the engine. While in that position you also mark the housing with where the rotor is when it's ready to fire number 1. Normal installtions usually have some fudge space so if your off a tooth you can rotate the distributor to regain the number 1 alignment with rotor and cap. But with space constrained installtions like a V8 planted into an S10/15 or Vega/Monza there often isn't any space to align the distributor other than how it was so it's important to mark off repeatable locations for alignment of the distributor on these type things.

Bogie

Bogie
great info, thanks
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