Compression: Look. Could there be a problem?

sortkaffekop

sortkaffekop

Senior Member
1: 80
2: 75
3: 90
4: 100
5: 90
6: 90
7: 95
8: 85

This is warm, with no oil.
Tried oil in 1: 100 psi

My problem is: Misfire at high revs.

All ignition componets new or checked. Timing at 2 degrees, checked. New fuelpump. New fuellline

Sticking valve?? Rings ??

Please put in your experience and knowhow.

Christian
 
This is a 60 2.2 litre french flathead 1953. High revs is flat out. Idle bit uneven but ok - acellerating ok. Strangely when closing the points gap to a minimum - engine will run quite better.
 
Closing the points a bit will do few things.

1, it will retard the ignition marginally.
2, it will decrease the dwell time of the coil.
3, the physical movement of the points will be less.

1, I don't know what the effect of retarding the timing would be relative to your problem, unless it is indicating it is too far advanced.
2, I'm pretty sure reducing dwell time would be a retrograde step regarding coil saturation, unless the coil voltage is too high??? Sort of out on a limb with this one.
3, Maybe moving the points less is helping because you are getting points bounce? I would be tempted to try a new set of quality points carefully set up on a proper distributor timing fixture.

Hope this helps, I'm sort of thinking it through from first principles.

Mart.
 
Actually reducing point gap will INCREASE saturation time. This might indicate the ignition system is weak. If you have a primary resistor try by-passing it for a short run.
 
^^ Ha ha, yeah, JWL of course you're right. I didn't think that one through properly. Good call that.

Mart.
 
Have discovered a (weak) short cut else where - giving a vaque constant current in the ignition system - and also through the coil. Could that have weakened the (2 week old) coil??
 
Modern manufacture of the old breaker type ignition systems components leaves a lot to be desired. A coil can only be tested with equipment made to do so. The most problematic item in the breaker ignition is the capacitor (condenser). You have to purchase three of them now days to get one half way decent one. If the condenser is bad, the points will burn and the performance of the system suffers. If a coil gets very hot during use, it can be damaged. Accidentally leaving the ignition on while the points are closed can melt stuff inside. A misaligned set of breaker points will not last long with a bad condenser. A person has to adjust them by hand with pliers to correct a misalignment.

For the old 6-volt systems of the late 40s & early 50s and many of the early 12-volt systems, they used the same basic can type coil design with 1.5 Ohm primary winding. On 12-volts, they used a 1.3 to 1.5 Ohm external ballast resistor to reduce voltage and control current. On 6-volt systems, they didn't use a ballast and it worked just fine.
 
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