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By Lanny White - 2 Years Ago
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I have made several posts regarding my rough running 1954 stock Merc and am wondering if it could be a timing chain issue. I have zero experience with timing chains but have a basic understanding on the function. The engine was running good, I lugged it out in second gear as I was pulling into my driveway, killed the motor and it sort of "humped up" like they do when stalled. I have diagnosed and repaired/replaced all of the normal tune-up stuff.
What are the symptoms of a jumped chain? And, more importantly, how can it be checked without an actual tear-down visual? I have a good, old-timey, mechanic working on it now but he has limited experience with Y Blocks. My pea brain says to crank to #1 TDC and then look at # 1 intake and exhaust rocker arms. Please don't laff - I've never been in this territory! Car has been down for over a year and my frustration level is to the moon...
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By Florida_Phil - 2 Years Ago
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Man! You are bringing back some old memories for me. When I was a kid the timing chain jumped on my '56 Ford Victoria. This happened when I was revving the engine and my "Coat Hanger" throttle linkage stuck wide open. I was making $1.10 an hour bagging groceries and I had to pay a mechanic to fix it. Yikes!
My advice is to seek help from an experienced mechanic. All V8 engines work pretty much the same. As you know, you first must find TDC in cylinder number one. You could use the timing mark, but you don't know if it's correct as the damper may be wrong as well. A mechanic will use a piston stop. When the piston is at the top and both intake and exhaust valves are loose, you are at TDC of the compression stroke. At this point, the distributor rotor should be roughly pointing to ignition terminal one. It is possible someone could have installed the distributor out of position. If not, the front of the engine must come off to verify the timing chain condition.
A jumped timing chain is fairly rare on a street car unless it's been abused like mine was. If the motor has a bunch of miles, it is most likely stretched and worn. I would start with a timing light to see what's happening. You could have anything from bad timing, bad wires, an out of phase distributor, vacumn advance problems, carb problems or ignition problems. All hard to diagnose without working on the car itself. I understand your frustration.
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By Hoosier Hurricane - 2 Years Ago
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A quick and easy way to check the chain is this: take off a valve cover. Turn the engine by hand and watch #1 or #6 exhaust valve (depending on which cover you removed). Watch as the valve closes, and when it is almost closed, the intake valve of the same cylinder will start to open. When both valves are equally open, verified with a straight edge across the valve spring retainers, the timing pointer should be within about 10 degrees of TDC or 0. If off more than 10 degrees, there is a problem with the timing chain.
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By Lanny White - 2 Years Ago
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How do I search the forum for info on setting up the timing chain on the gears? I remember previously reading that there is a specific number of chain link pins between the marks.
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By stuey - 2 Years Ago
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This is on Ted Eatons website
https://eatonbalancing.com/wp-content/uploads/2015/09/Rollmaster-timing-set.jpg
stuey
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By Lanny White - 2 Years Ago
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stuey, thanks for the link. Just what I needed. Yesterday, with the help of a good, old-timey mechanic, we reinstalled the newly rebuilt '55 4V carb after a minor tear down, inspection, and air blowout, re-installed the fuel pump after a bench test, re-set the low-speed jets and timing, started the engine and it ran like crap, as before. Much exhaust popping and blowback at the carb. Loosened the dizzy hold-down and advanced the distributor nearly 50 degrees! Ran like a top!!
Timing chain inspection next... More later.
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By DryLakesRacer - 2 Years Ago
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Perhaps the timing mark on the damper has moved.. That happened to me. The outer ring moved..
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By Lanny White - 2 Years Ago
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Thanks again for the input, previously checked all indicators for timing - dizzy properly set with rotor pointing to #1 on the cap, #1 cyl. at TDC on compression (finger in the plug hole trick), timing pointer pointing at 4 degrees, #1 cyl. valves closed (visual at rocker arms). Pulled the front of the engine off to inspect the timing chain and gears. With the engine set up as above, the crank gear mark is at approx. 3 o'clock (there are nor corresponding marks on the chain anywhere) and the cam gear mark is at approx 9 o'clock. The repair manual says that the marks on the crank and cam gears should align with the respective marks on the chain, which, as I just stated, doesn't have any marks whatsoever. The manual also states that there should be about 1/2 inch side play on the chain, which there is.
the motor has about 3,000 miles on it since major rebuild, don't know if the chain/gears were replaced as the rebuild was about 35 years ago and tthe motor kept in storage until 2013.
Looks like I should rotate the cam gear to to 3 o'clock, remove the chain, rotate the crank gear to 3 o'clock, and re- set the chain at 12 link pins of separation. OR maybe I should buy new gears and chain, assuming that they will have the proper markings, and install at 12 pins. Probably, with a worn chain and gears, it might just jump again (assuming that it has jumped). Would the motor even run if it jumped 90 degrees? Keep in mind that I had to advance the dizzy about 50 degrees to get it to run correctly...
More help please!
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By peeeot - 2 Years Ago
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If your cam timing is correct it should be possible to get the gear marks to line up with 12 pins in between like shown in the earlier link. I am not certain whether that would happen with #1 at TDC on compression or not. I would suggest rotating the crank until the crank and cam marks are both near 3 o’clock and verifying the 12 pins before removing the chain—this way you can know for sure whether your timing jumped.
Before teardown, did you check compression? Valve lash? If the engine likes really advanced timing that suggests a very slow-burning mixture (lean, possibly?)
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By Ted - 2 Years Ago
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Stating the obvious here but have you checked the valve lash yet?
With only a ½” of slack in the chain, it’s unlikely that the chain has slipped a tooth. A cranking compression test on the engine would help to also verify that the cam timing is correct and at the same time give a quick indication if the engine is suddenly having issues on a particular cylinder. For the 256 engine, I would be looking for at least 130 psi for the cranking compression give or take 10 psi.
A verification of the cam timing can come from observing that the intake and exhaust valves on any given cylinder at TDC on the overlap cycle are equally open. With the exhaust valve coming up and closing while the intake valve is going down and opening, the retainers for those two valves should be level with each other at TDC for the cam timing to be in the ballpark. If the damper ring has slipped, then the damper will be misleading if using that TDC mark as an indicator. If your particular engine does not have a rubber mounted damper ring, then the TDC mark on the belt pulley should be adequate for this check.
You don’t mention what ignition setup you have but that’s a good place to start once you have verified that the timing chain is indeed not the problem. If you haven't performed a cranking compression test yet, this would be a good time to do so.
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By Lanny White - 2 Years Ago
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Thanks for the input, Ted. Yes, 2 compression tests have been done, one by me and the other by my mechanic. Both tests were within a couple of pounds of each other with 7 cylinders at 120 and #2 at 110. #2 is really hard to check due to obstructions of the generator and battery tray and the heater blower. Possibly it would test higher if I could get my old hands down there easier. Valves were adjusted about 1,500 miles ago.
As stated above, the crank gear mark is at 3 o'clock (TDC compression stroke) but the cam gear mark is at 9 o'clock. What is the solution to get both gear markings to be aligned at 3 o'clock so I can check the number of chain link pins between the two marks. Also, as stated above, I am unable to find any marking on the chain to align with the gear marks.
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By Stiggy - 2 Years Ago
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There is no markings on the chain ~ to get the crank and cam marks to their 3 o'clock (and a bit) position,
you will have to remove the cam gear. Then get the crank and cam gears in position with 12 links between
marks. Also, watch this video ~ https://www.youtube.com/watch?v=b1Z2L9pgMXU I'm sure it will help..
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By Ted - 2 Years Ago
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Lanny White (7/13/2022)
As stated above, the crank gear mark is at 3 o'clock (TDC compression stroke) but the cam gear mark is at 9 o'clock. What is the solution to get both gear markings to be aligned at 3 o'clock so I can check the number of chain link pins between the two marks. Also, as stated above, I am unable to find any marking on the chain to align with the gear marks.
To get both gears so that the marks are at the three o’clock position, you just need to rotate the engine another complete revolution.
The timing marks are in position when the #6 cylinder is at TDC and on its compression stroke. The #1 cylinder would be at TDC but the valves would be at their overlap cycle.
Most timing chains made now for the Y do not have the off-colored links to facilitate locating the chain on the marks. You simply need to count the pins between the marks and ensure that it is twelve pins between the marks. Be sure that you count 'pins' and not 'links'.
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By Lanny White - 2 Years Ago
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Well, here I am again. Ugh!! Tore the timing cover off, removed the chain and gears, no problems found upon inspection, reinstalled using the proper alignment as previously described, started the engine, no change.
Bought a new (made in USA) timing chain and gears, removed the old and installed the new using the proper alignment, started the engine, ran fine for a few minutes. Shut it off to make minor adjustments, started it again and it began misfiring out the exhaust just like before.
Pulled the newly rebuilt carb apart for another inspection, blew out the passages, reassembled and installed, put in a new USA rotor just for grins. Started the engine and it ran fine for about 10 minutes. Thought we had it, finally! Shut it off for minor adjustments and restarted. Misfiring as before. Same as it has been for over a year.
Distributor is a rebuilt, engine was running perfectly before this mess started a year ago. I have no way to check the dizzy to see if the problem is with it. I have had it out many times and inspected it until I am blue in the face. Any suggestions on a dizzy guru with some old-time fancy equipment that can give me an Rx to see if its dead and then make it well? Any suggestions on where to locate a 1954 rebuilt dizzy? I'm pulling my hair out!!!!
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By Florida_Phil - 2 Years Ago
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I know how frustrating those problems can be as I just got through a similar one myself. I suspect you have an ignition problem as it sounds like you have checked everything else. Are you running points and a condenser? If so, there are a bunch of junk Chinese parts out there. Go to a NAPA store and buy good quality parts and try again. Change the points, condenser, rotor and cap. Make sure all the internal wires are good and tight. What coil are you running? You can check your coil with a multi meter. Are your ignition wires good? Especially check the coil wire as it can cause all kinds of intermittent problems. You will not be able to time the engine with a timing light until you verify your timing mark, but you can get it close by hand. Keep looking and you will find the problem.
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By Robs36Ford - 2 Years Ago
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You mention in a previous post about a vacuum reading fluctuating and in another post you were going to look for leaks but I find no results of that.
Did you and also what was your vacuum reading at idle and when you try to rev up ?
Reading the vacuum gauge can tell you where to look:
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By Lanny White - 2 Years Ago
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This has been quite a rodeo. Thank you all for your help.
It appears that the culprit was a distributor shaft that is slightly undersized in diameter causing the rotor to not seat firmly. Yes, the spring clip was/is in place. I tried several new rotors, some of which were NOS, and all were slightly sloppy on the shaft with movement left and right and rocking up and down. I hadn't noticed the rocking until last week. A friend gave me a 1954 dizzy that is in good shape and all of the rotors fit snugly on it. A quick clean-up, points, and condenser and she fired right up. No more cackling!
I believe that when the engine was cold the rotor had been a little more snug but as it warmed then it started flopping around a bit more, thus running quite well for a few minutes and then beginning the crazy misfiring.
Got it running on Friday, fifty mile round trip to a car show on Saturday. I will run some Seafoam thru it, reset the low speed mixture and timing with the vacuum gauge, and I think I am good to go!
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