Could use some immediate help on cam timing

66furys

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Often wonder where my brain has retired to. Old 66 383, think that I need to replace timing set and damper. So, before beginning, open distributor and get rotor on no. 1 cylinder, then bring damper around to TDC. Now that I am looking at the cam gear, it is out 180, time mark on top. Also the cam dowel is at 1100 and should be about 4 oclock. So, I think I am safe to just rotate to get old time marks aligned, turn cam 180, and replace. But, WTH is going on that when the marks are aligned, my rotor will be at opposite cylinder, not 1. Any thoughts appreciated as I have now lost what hair I had left. thanks
 
Often wonder where my brain has retired to. Old 66 383, think that I need to replace timing set and damper. So, before beginning, open distributor and get rotor on no. 1 cylinder, then bring damper around to TDC. Now that I am looking at the cam gear, it is out 180, time mark on top. Also the cam dowel is at 1100 and should be about 4 oclock. So, I think I am safe to just rotate to get old time marks aligned, turn cam 180, and replace. But, WTH is going on that when the marks are aligned, my rotor will be at opposite cylinder, not 1. Any thoughts appreciated as I have now lost what hair I had left. thanks
You have to remember that the crank revolves twice for every one time the cam does. Same for the distributor.

So... You could turn the crank another turn and the cam will turn a half turn and everything will align like it should.
 
John, that is right for the cam gear, but will no longer be on no. 1 cyl TDC.....and I have always thought this was how you set them up.....all on No. 1 TDC. I have now done as you say, turned and aligned both for the new gears.....but no longer on No. 1. Drivin me nutz??
 
I have never seen this much play in a TC. I have not pulled the plastic gear, which may be where most of the wear came from....note spacing on plastic teeth to chain not too hot. But, timing mark is at top, and dowel can be seen at about 11 oclock. New gear needs to have the dowel at 4 oclock to line up the dots, as here. But again, not on No. 1 after I did the align for both new and old gears.

timing gears.jpg
 
In the world of Chevy V-8 engines, from 1955 forward, plus the later 60-degree V-6 engines, when the dots are together, that is the "180 degrees out" cylinder firing. When #1 cylinder fires, the dots are at 12Noon. In the case of those earlier Chevy V-8s, the "180 degrees out" cylinder is #6, as it is for Chrysler B/RB engines.

When my late machine shop operative mentioned this quirk and kink in things, that was the first time I'd ever heard of such, for any engine. I'd always consider timing sprockets being "dot-to-dot" was #1 firing. Yet, I found documentation of such in Chevy service manuals. Prior to that investigation, I had not seen it in print, but then the print service manuals I had read were usually aftermarket or Chrysler factory service manuals. Timing marks at 12Noon, #1 fires, timing marks "dot-to-dot", #6 fires. At the time, I was only considering that Chevy V-type engines were that way, but possibly not? ONLY in the Chevy service manuals was this detailed!

The great thing is that if the engine was running, you just position the crankshaft to reflect a particular position of the timing marks, then duplicate that with the new components. For camshaft replacement, follow Chrysler factory assembly directions as to camshaft and intermediate shaft positions. Then rejoice in the bottom of the distributor shaft having a tang which indexes with a slot in the intermediate shaft . . . either correct or 180 degrees out, and easy to correct if wrong.

The "cylinder firing" can be observed in valve train action, too. When #1 is on the compression stroke, #6 is not, and vice versa. Same thing if you remove #1 spark plug, too.

Enjoy!
CBODY67
 
Related to "timing chain slack", things can look much worse than they really are, as to accurate cam timing. I recently saw where somebody actually measured the actual cam timing versus the observed slack and discovered that what appeared to be "too much", only affected cam timing by 1 degree.

I know there are methods to check such without taking things apart, which usually result in many degrees of rotation before the distributor rotor moves. When running, the driver's side of the chain will be tight and the other side will not be. As long as the tight side is within specs, that is all that really matters. As long as the loose side does not flop around too much and maybe wear a hole in the passenger side of the timing cover, all is usually well. Not unlike observing the tension side of a fan belt and its non-tension side. You never see the tension side of the dual belts on a Chrysler a/c compressor and alternator belt flopping around at certain rpm levels, typically. On the "long-run" timing chains of OHC motors, "guides" and "tensioners on such" keep the timing chains in their place. Similar on some cam-in-block V-8s,too, but usually without the hydraulic tensioners.

Enjoy!
CBODY67
 
John, that is right for the cam gear, but will no longer be on no. 1 cyl TDC.....and I have always thought this was how you set them up.....all on No. 1 TDC. I have now done as you say, turned and aligned both for the new gears.....but no longer on No. 1. Drivin me nutz??
The piston will be at TDC twice for each revolution of the camshaft. So, one turn should bring that pin to 4:00 and the piston at TDC.

BTW, that's actually missing a tooth of the plastic gear. So good timing (pun intended) on the change.
cam gear.jpg
 
Thanks for confusing the crap out of me Old Man.....but I hear you. Am going to pull the old one, and replace with new with no engine movement...and pray. Should work. I am going to have to keep my eye out for more on this No 6 thing and see if I can understand. And, John, as you said on the dampers before, there are at least 17 chrysler designs and this engine had the wrong one.....I am not sure I will survive this job mentally. I want to add one photo of the plastic gear after out. Thanks guys.
 
All is normal, proceed to line up the marks and replace timing set.

When marks are as instructions say the engine is not ready to fire #1, it is firing on #6.
 
Thanks 413.....I think I got it....makes no sense, but things are no longer as clear as they used to be.

plastic time gear.jpg


new timing gears.jpg
 
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