72 Chrysler 55 Hp, Timing

[Blue Bird]

Hello all, new to this site, and needing a little help.
I have a 72 55 horse, and am trying to smooth out its performance, I have a manual and I am mechanically inclined but havent worked on out boards.
My main question is because my motor does not have timing marks (the manual confirms some dont) I evidentally must use a special tool refered to as (T-2937) which screws into the number one cylinder and has a rod (with marks) on it which are used to find 28 degrees BTDC. I dont have one and cant find one so I decided to make one easy enough but I need to know the placement of the marks at the 40 horse end of the rod.
If any of you have one could you please measure the placement of the first and second mark on the rod from the end.
THe motor runs well but idles rough, compression is 140lbs, and it is my understanding it was stored much of its life, none of the bolts have been turned i.e. the paint is still perfect, so I read earlier that I can get a Fuel pump and Carb kit from NAPA so I will do that but I want to ensure that the timing and all linkages are correct, and, apperently to do that I need this tool (T-2937).
If anyone has any info, or suggestions please respond. Thank you and good boating.

 

[Frank Acampora]

Re: 72 Chrysler 55 Hp, Timing

The reason for the tool is because the crank can move a degree or two at TDC without moving the piston, so the piston is measured at 28 degrees (36 0n the bigger engines). Since you don't have marks on the flywheel, it is moot unless you are setting the points with the flywheel off and use the piston to determine closing of the points.

If you can make the tool, fine! If you can find an Intertech manual it gives the actual measurement while most others dont.

However, If you work accurately, you can feel TDC through the top plug hole and then mark the flywheel gear and the block for 0 degrees. You will not be off by more than a degree. NOW: you count the gear teeth and divide 360 by that number. This gives the number of degrees in a tooth spacing (If I remember correctly it is 4.5) thus you can use the teeth to determine the timing setting you want. --6 teeth to the right of 0 will give 27 and 7 will give 31.5 advance. That's how I do it on my 1967 55.

 

[Blue Bird]

Re: 72 Chrysler 55 Hp, Timing

Thank you Frank, that makes alot of sense, I do want to set everything from the points to the carb linkage. And yes I can feel the slop at TDC, was thinking just backing up to take up the slop but your info makes alot more sense.
I will be trying this on Thur/Fri, I will let you know how it turns out. Let me ask you this, while working on this engine i got stranded thought I lost spark tried everything finally I reversed the plug wires (to see if I could get a backfire or something) the dam thing fired right up and actually ran great for awhile then stalled again I switched the wires back and she fired right up again, got any ideas how this could happen, this is why I am concerned about the timing.

Thanks again Frank.

 

[Turn4fun]

Re: 72 Chrysler 55 Hp, Timing

I made the timing gauge too. Mine is pictured below. Here's how I arrived at the measurement on the rod. Since there is a bit of play at TDC, I installed the gauge and positioned the #1 close to TDC. Then I set up a dial indicator on the end of the rod and turned the flywheel to the point where the piston stopped rising. I placed a mark on the flywheel and block and then another at the point where the piston began to withdraw. I split the difference between the marks and made this my TDC mark. Once I established the exact TDC I scored a mark on the rod. To get the degree of advance I followed a procedure outlined in my Seloc manual. You need to get a very accurate measurement of the circumference of the flywheel. The manual recommended using a fabric sewing tape measure but I did not feel that was best since sewing tapes aren't all that accurate and can stretch. I used an adhesive backed foil duct tape because it is paper thin, very flat and does not stretch. I wrapped it around the flywheel (backing not peeled off of course) making sure the edge sat flush on top of the ring gear. I overlapped the tape making sure it was tight and then scored through it with a razor blade. I then laid the tape out flat on a table and measured the distance between the score marks. You could probably use paper instead of tape, just make sure your measurement is accurate and convert any fraction of an inch into decimal form. The formula to get 28? advance is 28 ? 360 X flywheel circumference. So if your flywheel measured 28?" then 28 ? 360 = .077, and 28.250" X .077 = 2.175" which is how far clockwise from the TDC mark your BTDC mark needs to be. Once the BTDC mark was established and set I scored another mark on the gauge rod. Be sure to measure your flywheel because the circumference mentioned above is a made up measurement for illustrative purposes. On my gauge rod, the distance between the marks is .250"
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[Blue Bird]

Re: 72 Chrysler 55 Hp, Timing

Thanks Turn4Fun, Both responses I have recieved make sense yours allows me to easily make my tool.
I'm sure I can get this motor running right now will let everyone know Thr/Fri again thanks for your help.

 

[Turn4fun]

Re: 72 Chrysler 55 Hp, Timing

One thing worth mentioning, I'm not convinced that 28? is correct. When I first came to the forums someone said that the correct timing for this engine is 30? even though my manual says 28?. I timed mine at 28? but it would not run quite right, click here to read my last thread about the problem. Since it would not work right I began to second guess that I had made my gauge right. So I got out a compass, a protractor and some card stock and made a degree wheel. I took the flywheel off and replaced it with the degree wheel. Then I used my gauge to set TDC, lined up the degree wheel and snugged up the flywheel nut to hold it in place. I rotated the crank a few revolutions to make sure the degree wheel didn't creep. Then I rotated it to 28? BTDC and checked the gauge rod. Sure enough, it was correct. So I then rotated to 30? BTDC and scored a new mark on the rod and retimed the engine. I took it out yesterday and it worked much better, still not exactly right but close.

 

[Blue Bird]

Re: 72 Chrysler 55 Hp, Timing

Going to try 30 degree's today to start, do some fishing, I will let you know. Thanks

 

[Blue Bird]

Re: 72 Chrysler 55 Hp, Timing

well I'm back, I went to take the flywheel off to set the points and low and behold the sheer key was broke, must have been that way for weeks. That explains how the motor would run with the plug wires backwards. I knew it was a timing problem.
Now its a parts problem I cant find the key anywhere, I couldent even find it on this sits parts list, anybody have any suggestions I know the part number is 28-F92498 dont know the maker or whose number it is but thats what the guy that looked it up told me.
So it appears thats all I need, to get to the fish.

 

[Blue Bird]

Re: 72 Chrysler 55 Hp, Timing

Found the new key way, rebuilt the carb, fired it up and she ran smooth as silk went fishing last night went 5 for 5. I appreciate all the help from you guys im back in the water, happy and loving life.