48 Lincoln Continental won't rev over 2,800 rpm

[MattMudBall]

Hi,  I'm working on this 48 Lincoln Continental convertible V12 and she won't rev over about 2,800 rpm once warmed up. Runs great at idle, even though it's having high rpm problems. Sometimes when the

engine is cold it will rev up just fine until it is warmed up or by the time i pull out of the driveway. The problem is present with or without a load. Can drive around but won't go over 40 mph once warmed up.

 

I've rebuilt 2 different carbs, It as an electric fuel pump pushing from the tank and has 5 psi at the carb. Gasoline is fresh.

 

New points, condensers, ballast resistors, spark plugs, spark plug wires, fuel filter. I made my own coil plate to accept 2 universal 6 volt coils. I've tried old points and old condensers before the distributor was sent out for overhaul and points setup. I've tried bypassing the ballast resistors. Spark plugs are gapped at 28 thou and are a nice tan color. Nice blue spark will jump a 1/4" gap.

 

 Vacuum advance is working according to a mark I made on the crank pulley and using a timing light while revving the motor.  I've pulled the timing cover off to make sure the marks were lined up. At full throttle, vacuum gauge with exhaust disconnected shows 5" and at idle the gauge bounces slowly from 15.5"- 16.5" (this variation could be from points slightly out of sync, but problem still existed when points were in sync). Brand new optima 6v battery. Can't find a vacuum leak. No valve ticking. No smoke, no oil burning. All cylinders have 100-110 psi. Hope someone can help.     

[38ShortopConv.]

If you are sure your timing is correct and the carb jets not  too small,  # 52s,  maybe you have a loose baffle in the muffler blocking as the exhaust gas flow increases.  

[MattMudBall]

The original jets are #57. I have tried smaller and larger jets to no avail.  No blockage in exhaust manifolds and I put a drain snake through the pipes. I've been testing with and without a muffler.

[Mssr. Bwatoe]

I would get a good stock ignition coil, have skip haney rebuild it---

no reason for cobbled coils---The same problem with old and new dist??

--chk plug wire location firing order---make certain hot blue spark on both sides,

all cylinders---you describe a v-12 running on six---maybe a condenser is gounding out when hot

[MattMudBall]

As off right now the stock coils are on. Yes, same problem with old and new distributor. I know its running on all 12 cyl, I will double check.  I have 3 sets of good condensers and have tried them all. 

[Ray500]

You might want to send your distributor to Jake Fleming down in Dallas to make sure it's working properly.  I do like Skip Haney in Florida for rebuilding with new coils in the ignition coil.  You can't accurately time the engine with the distributor on the the motor.  Lots of variables that have to be investigated one by one to find the problem.  Vacuum advance is important in the distributor with increase in RPMs, Jake can test the distributor for that.  I would also trace each of the 12 plug wires to make sure they are connected properly, it's sometimes easy to get them mixed up as they are very tightly crowded in the distributor area.  I have labels on mine that plug into the distributor plates.  (labeled white shrink tubing from my label machine) Keep looking, you'll find the problem.  As Btwatoe mentioned it does sound like you're running on 6 cylinders!

Edited June 26, 2018 by Ray500 (see edit history)

[MattMudBall]

While using my coil adapter plate, I put 12v coils on the car and a 12v battery, start it up and it runs perfectly! This tells me there is a current draw or a voltage drop somewhere in the system. I believe the reason for this is because 12 volts require less current. With a 6 volt system, having thick healthy wires are critical because lower voltage requires higher current. In my case, as the wires warm up it is creating even more resistance. There is no need to convert everything to 12 volts. A new wiring harness should fix my problem.

 

P.S. Most aircraft operate on 28 volts

[Ray500]

The  voltage at the connection point on top of the distributor/coil should read about 2-3 VDC using a 6 volt battery on each side running.  If it's not there then the resistors on the regulator board mounted on the firewall inside the car might have to be changed.  You can also measure the voltage on each side of the resistors and make sure you have a fully charged battery.  Wiring or corrosion could be an issue, with mine I replaced the entire wiring harness some time back to eliminate any wiring issues and because it was 70+ years old.  Don't forget to make sure you have solid good grounds from the battery to the engine/body.  

[MattMudBall]

Voltage to the coils is 2.2 volts. The resistors on the firewall inside are new and checked. Battery connections and ground wires were cleaned. Having a set of coils rebuilt was one of the first things done to fix this problem months ago. I really think a new wiring harness is the answer.

[19tom40]

The input voltage to both coils should not be the same. One coil input will be lower voltage because the points are closed and current is flowing through the resister, the other coil input should be above 4 volts, because there is no current flowing through the resister.

 

The first thing that I would do is get the engine to operating temperature and check the spark from each coil (cyl 1 & 2) for a good blue spark at least 1/2" long. If you have this, the ignition is in good condition. If not check the condenser for the side that has the weak spark. If both sides show a weak spark, check the input to the ignition resisters, it should be at least 6.3 Volts. Also check the dwell if you have a dwell meter. It should be 36 degrees on the 6 cylinder scale.