Lincoln mark IV 1973 made in 1972

[brunoffrance]

Hi the community,

As the title indicates you, I'm a proud owner of a Mark IV "73" but the Marti Auto report indicates that , from the ordering to the release of this car is from November 17 to December 29 1972 .
Even if this marvelous car is tagged 73 ( serial number 3Y89A852240 ), I wondered if I have to consider 72 or 73 spécifications as it's the same engine 460. I try to adjust the ignition timing so I don't know which data in degrees to take ( 73: 14), 72: 10° and finally 72 california : 6° ).
my car comes from at first from Honolulu , HI so the DSO is certainly from California ...

I've red there was a decal somewhere on the car to indicate me the exact year ... The one I've found is inside the driver door as Marti copy. but no indications on ignition timing .

Thank you in advance to help me in this search.

3Y89A852240_dlxrpt.pdf

(337.11 KiB) Downloaded 9 times

[RMAENV]

It is a 73 model year and 1973 specifications. Years ago, we all anticipated the new model year which they usually unveiled in September of the previous year. i.e. The 73 model year cars were released beginning in September of 1972.

[brunoffrance]

thank you for your reply .... i'm going to make adjustments with 73 specifications as the document loaded indicates to do ...
Hope it'll be right as the engine is wrong when accelerating ....

[Dan Szwarc]

Hope it'll be right as the engine is wrong when accelerating ....

The decal is on the drivers door.

If the VIN starts with a 3, it’s a 73. There is nothing else to question.

[Lee]

Bruno, if I understand, you think the engine does not accelerate properly? I will warn you, those early 70s cars have some oddball emissions parts on the distributor that rarely function after 50 years, and are no longer manufactured. The EGR system also tends to foul easily, and when they stick (they all eventually do), you’ll have a terrible idle, because raw exhaust leaks into the fuel-air charge.

I would counsel you to look carefully at the vacuum hose routings, to see whether a previous owner has already bypassed (or tried to bypass) those items. If not, I would consider doing that.

Here is an overview of the 1973 system, and the items that can fail (in addition to IMCO specific parts):

When I was a young man, I bought quite a few of these early emissions cars, often very cheaply, because the owner had given up on trying to make them run correctly. Pre-engine computer days, it was pretty easy to just remove that stuff, and plumb them like a pre-emissions engine.

[ContiFan]

As the title indicates you, I'm a proud owner of a Mark IV "73" but the Marti Auto report indicates that , from the ordering to the release of this car is from November 17 to December 29 1972 .
Even if this marvelous car is tagged 73 ( serial number 3Y89A852240 ), I wondered if I have to consider 72 or 73 spécifications as it's the same engine 460. I try to adjust the ignition timing so I don't know which data in degrees to take ( 73: 14), 72: 10° and finally 72 california : 6° ).
my car comes from at first from Honolulu , HI so the DSO is certainly from California ...

I've red there was a decal somewhere on the car to indicate me the exact year ... The one I've found is inside the driver door as Marti copy. but no indications on ignition timing .

"Model years" have differed from "calendar years" in the U.S. for ages. Model years typically run from September to August e.g., the 1973 model year may have gone from September 1972 to August 1973. However, there have also been many times when new models have come out before September (e.g., a 1973 model coming out in July 1972 or even earlier) or after September (e.g., a 1973 model not coming out until December 1972 or later).

Also, it's not unusual for features or options (including engines and transmissions) to vary during a model year as sometimes these things are added/modified or removed during that year.

[brunoffrance]

Thank you for your explanations;
this week-end , I've spent hours to make the right adjustments with my strobe light.... I've found on the engine carter, the "famous decal" where it's well written the ignition timing with 14 degrees at 650 rpm in Drive position .... No good result .
Nothing to loose, I've tried to change to 72 specifications California ( as my car came from Hawaii ) : 6 degrees at 625 rpm D. No better but not worse.
i ve noted at slow speed, the engine turn right but when I accelerate, it's really not progressive , lack of power and moving car .

I'm going to replace the ignition pressure valve ( 50 year old ) and all the complete ignition circuit until sparkles ( wires, distributor ... ) .

Step by step , I'll find the solution ...

[Lee]

Bruno, if you have not already done so, here are a few other things to check that might assist you:

Are the points new or filed, and gapped to 0.17” (0.43mm)? Are you getting a strong spark? Do the spark plugs look good?

When you first checked your timing, was it very retarded? I ask the question, because the timing chain could be bad and have slipped a tooth, and that would be a tell-tale sign. Often engines will continue to run (badly) with the cam out of time. Do you have a vacuum gauge, to check manifold vacuum? That is another tool that can help diagnose a problem.

You mention trouble accelerating…but does it idle well, and then cruise well at steady speed? I ask, because a bad accelerator pump and/or power valve in the carburetor would give you those symptoms.

We have several members here who are skilled at diagnosing problems with Lincolns, and the more details you can give us, the better our chances are of helping you. I know the language difference does not help matters.

[brunoffrance]

hi lee; Thank you one more time for your constructive advices .

yes, technical English is not easy to talk about as it's not my native language so I try to do my best.

I havent check the point gap so it'll be replaced by a new one, with a new distributor and rotor ( thank you rock auto ) .
i'll replace wires too and sparks , the original ones : Champion RV17YC !

initially, the timing was not in the good value ( 14 degrees) as the mechanic guy did nt know the value to adjust ( ... ).
seems all sparks works well but some times faults in accelerate : sparks or other ? in doubt, I'll change sparks with original ones even if the are not the best one ( copper versus iridium ).
About the vacuum valve on the distributor, it'll be changed too to be reassure that the problem does not come from there.

I'll re adjust the 73 specifications with all these new pieces in place .... i cross fingers

[Lee]

Bruno, be aware those RV17YC plugs are one heat range hotter than the factory spark plugs. That may be fine, but when you do pull them out, see how the look, maybe take some pictures. You can tell from their appearance if they are in the right heat range. Also make sure to check the gap (0.034”). Often, new plugs are made to fit multiple vehicles, and the gap you get might be 0.44” or even larger. If the person who last installed plugs in the car didn’t know that…that could also lead to the problem you describe.

[brunoffrance]

hi again lee,
i've taken sparks informations from the Haynes repair manual where they say for my 1973 : Champion RV17YC or equivalent / 0,O35 inch .
I prefer this manual to the serie of black books from Ford ( I've bought, of course ) where I never find the good information in measure as the famous 14 degrees @ 650 or so .
have the Champion RV17YC a bad reputation ? if yes, what do you advice ...

[Lee]

Bruno, I personally don’t like the Haynes manuals, but they are better than nothing.
There has been a lot of part number consolidation when it comes to finding the right heat range for an older car. The original plug number was Motorcraft ARF-42, and that correlates to RV15YC in the copper core (which is all the originals were). Even the Champion website says so. If you choose a platinum plug, that changes to a “17” heat range part number, probably because they do not have a platinum plug in the proper 15 heat range. And a 17 may be fine, it will depend on their appearance after using them for a while.

[brunoffrance]

all is replaced ( sparks, distributor cover, rotor, wires ) except the valve timing that was not exactly the same but the old one was tested in blowing inside after dismounted.There are always problems in accelerate driving.
last adjustment is this valve timing on the distributor : you have to tight inside the valve , introducing an allen key . There was originally 1,5 tour . I've search on Haynes and shop manual to get the number of tour to do but nothing precise is given ... you have to adjust on road .
Do you have the number of tour(s) usually done for a MK IV 73 ?

thank you one more time.

[Lee]

When you say “valve timing”, do you mean the vacuum control on the distributor?:

If so, I can only tell you that the factory specification is about 23-24 degrees at the crank. You or your mechanic will have to use a timing light to get the the correct number of turns (tours?) with the Allen wrench.

With the way these were plumbed for emission control, you may not be getting any vacuum at all to the canister at any time. I would check that. If adjusting the vacuum canister Allen key to either extreme does not change how the car runs…that is very likely the case.

If it were mine…
I would set initial timing at about 10 degrees. Turn the Allen screw fully clockwise for maximum vacuum advance, then I would run a new vacuum line with full time vacuum to the canister. Readjust the idle as necessary, then take if for a test drive and see if things are improved. If there is “pinging” under acceleration you may need to reduce the vacuum and/or initial timing.

If none of that improved the running, I’d look elsewhere for your acceleration problem. Like the carburetor.

You may need to find a mechanic who is old enough to remember when Charles de Gaulle was President to help you. Somebody like that should understand the principles of mechanically controlled ignition and carburetors, regardless of the country of manufacture.

[brunoffrance]

hi Lee , one more time,

yes i've used inappropriate terms with valve timing for vacuum control and tour for turn .....

i've tried different adjustments as full Allenscrew to contact and the Allen unscrew to 3 turns from the contact and always bad in accelerate.

In your document ( valve specification and small 2 ) , they specify 1 turn down after contact .... Even if that 'll not change the situation, may be I have to do it .

So I agree with you, the problem is more situated around the carburetor .... My mechanic has cleaned it and the problem is now, certainly at this level and not in the new timing system . Yes he knows Charles de Gaulle, only in picture or on Youtube .... All the mechanics I know are from Chirac or Sarkosy génération and pretend to be specialists .... they aren't !

Thank you for your help.