Timing

Timing

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By Lanny White - 7 Years Ago

Stock 1954 Mercury - To preface, I'm just an old-time shade tree mechanic and it doesn't take too much to stump me. The engine has been progressively running rougher (missing) for the past several hundred (700-800) miles and last week I peeked inside the distributor cap to check for cracked or broken pieces. Oh, the engine has about 2,000 miles since rebuild. It appears that its firing well in advance, as at each brass electrode inside of the cap (each plug wire) the flat surface surrounding the electrode on the leading edge (counter-clockwise rotation) is blown or melted away in a tight vee pattern to a depth of about 3/32". Timing is set at 3 degrees BTDC
at 500 rpm. Also, the rotor cap electrode firing end is black (dusty carbon) only on the leading edge instead of the middle of its face.
The points, set at .015, appear to be opening correctly.

The engines starts immediately, idles a little rough, and then begins to protest when I let the clutch out. What gives? ? ?

By Tedster - 7 Years Ago

It almost sounds like "rotor phasing" is off, but I'm not sure how that would happen in a stock setup. Maybe if the distributor was stabbed wrong? edit: That can't be it.

Obviously need a new cap and rotor. This is where an ignition scope would come in handy, if you know someone who has one. They take all the guess and by golly out.

By miker - 7 Years Ago

I know a guy who does a lot of dyno tuning and electronic point conversions. He keeps a stack of common distributor caps and rotors. The caps have as big a window as he can make between the coil post and number 1 cylinder. The rotors have a painted white line center to the cylinder contact. After he sets the timing, he put the light on the cap, and sees that the rotor contact is pointed at #1 when it fires. Now, if it isn’t I don’t know how you fix it, but it seems along the same lines as what your talking about. Maybe the points bolt in and fit, but are a bit off, rubbing block too worn or too tall to begin with? I’m sure someone will know.

By Hoosier Hurricane - 7 Years Ago

On my '57 with an electronic conversion kit, the reluctor slips over the original cam. This caused the rotor to not seat fully on the shaft causing a crash between the rotor and the cap. I had to grind a little off the bottom of the rotor so that it would seat fully. A friend of mine had the same problem on his car at the drags, I gave him my spare ground-off rotor and got him going.

By GREENBIRD56 - 7 Years Ago

This has been too many years back for me to be coherent - but using a "windowed" cap or (in the case of my high zoot tuner friends - clear) - you use a timing light to look at the position of the rotor relative to the cap terminal. What you want is for the engine spark to jump just ahead of the terminal at idle - and then as you progress to full advance, move to a better fit at full throttle. The modified cap is rigged for adjusting the fit. The cap you are going to run on the engine is then altered to mimic the positioning of the test cap. The worst one I can remember was on my buddies '69 340 Dart and we had to do a good bit of "Dremel" work on the Mopar cap to get it shifted to a better firing location.

By Lanny White - 7 Years Ago

This is all good info but it doesn't answer the question or address the problem. The distributor cap is being destroyed as it appears that it is firing early. The timing is set correctly as are the points. Has anyone ever seen a dist. cap getting wrecked like this and, if so, what was wrong and what is the remedy.

By stuey - 7 Years Ago

Hi Lanny. First I am a novice at this but this struck me. You say "It appears that its firing well in advance, " but go on to say "Timing is set at 3 degrees BTDC "
I thought Y- blocks needed 6 to 12 degrees. Maybe its a timing issue. Others will jump in and put me right then we all learn

Re: rotor phasing MSD has a good video on you tube

stuey

By GREENBIRD56 - 7 Years Ago

So the point cam - and the rotor drive are mechanically fixed. The cap is securely locked into its slot. So that part of this is verifiably correct.
Is the spark advance working? This is a purely vacuum controlled advance system and so far as Y-blocks go, the initial 3º is severely retarded. Is it simply staying at 3º as the engine accelerates?

By Lanny White - 7 Years Ago

Stuey and Greenbird, I will verify 3 degrees timing with the Merc repair manual but I have never known how to check if the advance is working properly. More help?

By 57RancheroJim - 7 Years Ago

Was the dampner replaced or rebuilt when the engine was done? I'm just assuming they were like the Fords and if the ring has slipped you won't know exactly where your timing is. Have you checked the point dwell?
Every cap I have seen shows it arcs on the leading edge and the rotor.
Has this car been converted to 12V?

By Tedster - 7 Years Ago

Jim brings up a really good point. The balancer/damper should have been rebuilt or replaced as part of any basic overhaul.

A mechanic's vacuum gauge connected to manifold will tell the tale on your general setup. A healthy stock engine in good tune should pull about 20" steady needle hand at Sea level. "Slow" or late (retarded) ignition timing, poor compression, valve lash too tight, misadjusted carburetion, exhaust restriction, they are a very good yet inexpensive diagnostic tool.

By Lanny White - 7 Years Ago

Tedster and '57 Rancherojim, the engine is a 256 cid and I suspect that the dampner has been properly installed inasmuch as the engine was balanced. It is still 6 volt and I confirmed from the repair manual that the initial timing is 3 degrees BTDC. The manual also describes various distributor tests that would have been done with various shop test equipment back in the day (which I don't have). However, I do have a vacuum gage and can check that reading. Assuming the vacuum is adequate, how can I test to see if the dizzy is advancing properly? Valves were adjusted about 1,000 miles ago. Teapot carb has been rebuilt and adjusted and seems to be working well. Have not checked compression yet but it seems that the timing issue needs to be corrected first.

By Sandbird - 7 Years Ago

Just wondering if you disconnected the vacuum line to the distributor before setting the initial advance?

By Tedster - 7 Years Ago

Your engine has (I think) what's called a Load-o-Matic style distributor, so there is no mechanical advance whatsoever, engine ignition advance is derived solely through engine vacuum from two different sources, "venturi vacuum" being one of them. I have no idea how to check this, I'll look in my manuals and see if there is something that can be performed without special or proprietary test gear.

Still, now that I think about it, the testing with a conventional distributor is simply to spool up the RPM and watch where the ignition advance ends up at. I'd think it would be very similar with the LOM distributor. You'll need a tach and a timing light.

One bit to keep in mind though, don't take anything for granted when troubleshooting. A compression test is not a bad idea for a couple different reasons.

One is there's a recorded baseline for future reference. Verifying or checking for true TDC (using a piston stop tool) you know for certain whether the timing marks on the damper are accurate or not. If the balancer/damper was not renewed as part of the overhaul, a new one needs to be fitted. Basically what I'm getting at is you can't make any assumptions, don't guess, measure. Low engine or venturi vacuum would cause big trouble with a LOM, because all of the advance is derived from there.

By KULTULZ - 7 Years Ago

LOM timing is 3 degrees STD and 6 degrees AUTO factory tune. Curb idle has to be at spec to set initial timing..

To check timing advance, watch whether the marks on the balancer advance when reving the engine. This will only give an indication as to whether the advance system is functioning. You would need either a DIST MACHINE or TACH and timing tape to verify the correct timing advance curve whether OEM or modified.

Take verifying #1 TDC as the first step to heart. Beyond that is just guessing/assuming.

By Kahuna - 7 Years Ago

If you still have the original Load-a-Matic distributor, the diaphram may be bad,
not allowing the correct advance.
Just a thought
Jim

By Lanny White - 7 Years Ago

Kahuna and Tedster, more diagnostics today and find that there is NO vacuum at the carb vacuum advance port, let alone at the dist. Rather than take the teapot apart again to see if there is a blockage to that vacuum port, I will re-route the vacuum line from a manifold location using a tee block and then retest for advance. Yikes!

By Sandbird - 7 Years Ago

If you connect a loadamatic distributor to intake vacuum it will go to full advance immediately. They only need about 3 in vacuum for max advance may damage an old diaphragm if you hit it with
15 to 20 inches of vacuum. Get a hand operated vacuum pump to check your distributor advance. If you get no vacuum from the carb when you rev it a bit the carb is at fault. Not too familiar with a 54 Tpot if it has a spark control valve you can change it other than that it may have to come back apart.

By miker - 7 Years Ago

Along with what Sandbird mentions, unless your vacuum guage reads real low, you might not see a reading, especially at idle and just above. It’s a very weak signal, more in the manometer range than an automotive vacuum guage.

By Lanny White - 7 Years Ago

Miker and Sandbird, thanks for your replies. . . . Just came back from from NAPA with the same info on low vacuum, so I will not hook up to the manifold and will recheck my gauge to see if it reads low enough - probably not. The teapot does have a spark control valve and I will look further at the repair manual for clues. . . . . . . . . .

By GREENBIRD56 - 7 Years Ago

Once upon a time my father - who was coaching my friend and I about tuning multiple side draft carbs ('67 Triumph Spitfire) - proceeded to give us a shopping list that included clear aquarium tubing. He promptly fastened it on a plywood backer in a deep "U" (dunno the details nearly 50 years later) and poured some distilled water in there. Basically created a backyard manometer, read with a tape measure. Such an approach is probably still available today if you want to try it out - there must be something on Google....
The last time I used such a device it was called a "slack tube" and I borrowed it from a local Detroit Diesel distributor.

By Tedster - 7 Years Ago

I've read (some) conflicting information, claims that the LOM was actually a very fine distributor advance system when setup and operating correctly. Perhaps not for performance applications, for general use. I've also read they had excellent fuel economy.

I don't know enough about them to say my opinion, other than there are generally plenty of obsolete automotive components that work very, very well for their intended purpose when understood and adjusted correctly. It wouldn't surprise me a bit if that statement about LOM distributors were true, put it that way. Sometimes it's just the nut behind the wheel that's the problem! Usually what happens is somebody swaps out the carburetor, and the head-scratching begins.

Btw, a "ported" source of engine vacuum (above carburetor throttle plates) will not have any vacuum at idle RPM. If you start swapping hoses around with out a clear understanding that isn't going to help the issue. Odds are they were correct or only install one way? I would never install a LOM system but I'm stubborn enough if it had one I'd want to understand it and make it work as advertised. Maybe acquire a post '57 distributor and start setting that up too.

Take it one thing at a time. You have the manual, that will help a great deal.

By Lanny White - 7 Years Ago

Thanks again for all of the information - sure wish I had a Sun Tune-up machine. . . . . . My car is a stock 1954 Sun Valley and I suspect all of you know it is quite valuable. Because of that, I do not want to make any modifications (except minor) that would have an impact on its value. I know that changing out the rebuilt teapot to a more modern carb with corresponding intake and distributor would probably make a good fix. However, as above stated,and the fact that I too am stubborn, I want to make it run like it is supposed to. I'll check the compression today to rule out any associated internal problems and then pull the carb again for re-inspection and repair (if necessary) in the spark control and the secondary throttle vacuum assembly, both of which probably have an impact on distributor vacuum. Please bear with me - with the combined knowledge of all you Y-Blockers, we can get this ol' beauty back at the car shows again!

By Tedster - 7 Years Ago

There's nothing that says the engine can't be converted back to the teapot carb and LOM distributor upon resale. Still, I "get" that you want to keep it original configuration and get it running right.

Did you get a manifold vacuum measurement with a gauge yet? This is a quick and easy way to determine basic internal mechanical engine health and setup. Compression, valve adjustment and ignition timing. Run the engine at a normal idle RPM. At Sea level you're looking for a steady needle at 18" to 20", if you snap the throttle it should drop to around 5" and rebound to 25" or so before returning to 18" to 20", this means the compression is reasonably good. It doesn't replace an actual compression test, but it's pretty accurate. And saves wear and tear on battery and starter and is a lot easier. There are several charts available for download on reading a vacuum gauge, the amount of info that can be gleaned is extensive in the hands of a competent mechanic.

By Lanny White - 7 Years Ago

Thank God and all you Y-Blockers, especially Tedster for yesterday's post. I learned more today about a vacuum gauge than I have over the last 60 years of bending wrenches. My old gauge, complete with original use instructions, led me to minor adjustments to the idle screws and to the timing. Gauge read 18 - 20 at idle, down to 5 and up to 25 with a snap of the throttle, and back to 20 at idle. Took it for a spin and didn't feel or hear any misses and came up the hill to the house in 2nd gear with no hiccups or hesitations. Looks like I'm back on the road again!

By oldcarmark - 7 Years Ago

Tedster (8/3/2018)

I certainly understand your Opinion on this Post. However as I am sure you are aware in 1957 Ford went to the "Dual Advance" Distributor which are far more responsive to Load (Vacuum advance) and Engine Speed (Centrifugal Advance) at the same Time the Holley 4150 Carb. was added. The Combination of the 2 really woke up the Performance of the Y Block. Even upgrading only the Distributor to the dual Advance type makes a big difference in the way these Engines perform even retaining the Teapot Carb. The recommended initial Timing Specs using the Loadomatic were also very Conservative. There's not a lot U can do to improve the the Stock Loadomatic Distributor Characteristics. I have converted 3 1956 Y Blocks to the 4160 Holley and 57+ Distributors. 2 of my Own and a Buddies 56 that had a rebuilt Engine installed and it ran like a Dog until I convinced Him to spend a little more and convert it to the better Setup. Nothing that can't be reversed but personally I don't see myself ever reverting to Stock Setup. I like to drive My Cars and enjoy them as well as I think improved reliability and not having to worry about under hood Fires. Just my own Opinion and I don't knock anyone who stays Stock.