Labman2000

I want to thank all information/ help in advance. Here is my problem, i have been battling finding the source of this fairly constant small miss i can feel in my 1965 200 6 cyl. 3 speed For quite some time and cant seem to nail it down so far.. here is what i have done to this point, and what i know of the engine prior to my owning it.. im going to try to cover all and appoligise if to long.
Rebuilt autolite 1100 carb.
New fuel tank, pickup assembly and line.
New fuel pump and filters
Petronix igniter 1 w/constant 12v source.
Flame thrower coil
Complete new plugs gapped .045
Wires,rotor.cap
Manifold vacuum at 600rpm idle 19-20
New reman. Dist.
Timing adjusted all from 6-12 BTD
Compression checked cylinders.. all good and within i believe 5-10psi
I do not remember exact numbers.
Engine was supposed to have been recently rebuilt, and i have confirmed pistons are .040 over.
And nothing i have done has touched the miss.
The car, starts, idles, and accelerates fine, but does start missing at around 2200rpm and then at any speed holding constant it has a fairly constant miss i can feel.
The last thing i have done is install the distributor and did notice that when set at 6 degrees BTD. when i run the idle up to 1600rpm, the advance is off the scale at about 12oclock. I would guess about 35-40 advance this seemed high. Again sorry so long thanks

Gun Jam

Start with the simple stuff and move up...

0) When did it last run right? I get the feeling the answer is never...???

1) Check for vac leaks around the carb base and intake gaskets...This is most commonly done with carb cleaner with engine at idle. If you spray around carb and you notice a drop in RPM there is a leak at that location.

2) Check for spark leak...You can do this by running the engine at idle in a dark ish room and using a spray bottle with water...Set it to mist and spray around the ignition system and see if you can see any spark jumps from a plug wire or such...you'll want to check from cap to plug end and to coil.

3) The ignition system is highly suspect here...a bit more tricky to check into but could indeed be an issue...How are you checking timing? Do you have a timing light?
40deg is not excessive with a vac advance system. First you'll want to check base timing. you MUST disconnect any vac lines going to the distributor FIRST. If you dont you maybe looking at vac advance and not base timing. With vac lines off is it still at 12 deg? Or is it -3deg TDC. With VAC line off it should advance to 32deg about. So 12 initial, 20 deg advance all in by 2,500 rpm for a total of 32. Then with the vac line connected (which is probably ported vac) you should see 12 initial still, + 20 advance + 10 vac advance all in by 2,500 rpm for 42 total. Under load vac drops off an should retard timing 10 deg back to 32 max under load.

If you dont have a timing light go get one.

If all that checks out

then

The carb could be running lean at part throttle you could try increasing idle mix volume by backing out the idle mix screw(s) this would increasing idle richness, decrease idle rpm (probably) and increase part throttle cruise mix and may eliminate the stumble.

If none of that works maybe replace the pertonix system...They fail often from my experience.

Gun Jam

Oh yeah for what its worth I had the exact same issue...its was a burned intake gasket...the heads had a port for exhaust cross over but the intake did not...I did not block off the x over port proper and over time it burned through the intake gasket and cylinder 2,3 and 6,7 started to suck wind and it created exactly what you were taking about...Carb cleaner would have found the issue but I saw exhaust smoke on the heads first between the union of the intake and heads....BUT lots of other stuff can cause the same issue as well

Labman2000

I have checked for vacuum leaks with that method and have found nothing, i can do again more carefully. I have also searched for spark leak in the dark but with no water. I will try this as well. I am checking the timing with a light at 600rpm. Idle and vacuum from the carb to the distributer off and plugged and set at 6 degrees then hooked back up it stays the same 6 degrees then when running up the idle to 1600rpm. The advance runs up to approx. 40 degrees with the vacuum gain at the higher rpm. This is a 1965 200 6 cyl. It had no intake gasket due to the manifold is one piece with the head, also on these distributers it was my understanding that the advance was to gain with an increase in vacuum from the carb as acceleration. Maybe im missing something. My vacuum gains from the carb upon acelleration not decreasing engine speeds.

Gun Jam

Okay
Im not totally clear on your advance curve

At idle its 6deg no vac right?

With vac still disconnected from the distributor what is the timing reading at:

1000 rpm

1,500 rpm

2,000 rpm

2,500 rpm

3,000 rpm

With vac connected what does it read at those same RPMs

-Gun

Labman2000

With timing set to 6degrees and vacuum disconnected from dist. And plugged. The timing will remain at 6 degrees throught all rpm ranges, due to no vacuum draw attached. This to my understanding a 100% vacuum advance, "load-o-matic distributer and has no machanical advance systems at all.
I will have to go check and collect that data as to where the advance rises to at each rpm with the vacuum attached. Thanks

Labman2000

Here are the readings with all hooked up, engine warm in netural at 600rpm =6 degrees
800rpm = 6 degrees
950rpm = 10 degrees
1000rpm = 14 degrees
1100rpm = 16 (scale stops at 14) rest is best estimate based on scale
1150rpm = 18 degrees
1250rpm = 20+ degrees
1400 rpm = 28 degrees
And at 55mph the car runs 2500 rpm so based on this pattern it would be very high at this point depending on what the limit of advance rotation in the dist. Allowes before it hits its stopping point.

Gun Jam

Well thats half the data....the damper wheel really only goes to 14 deg?

Yes a working dizzy should follow a linear curve (well most do) Maybe you could find out what the diameter of the damper wheel is and buy some timing tape that will read from -10 to 90 deg or something with reasonable numbers....I know my fairly high performance v8 has no issues with 40 deg advance at part throttle cruise.

So its not a pertonix system just the ignitor? This ignitor is physically place inside this goofy *** vac only advance system?....I tried to read about it but is says they quit making them in 57....sounds like they hate any changes...and Im not sure you even have one due to the end date production (but I see here that it was offered on i6 into 60s so perhaps it is)

When did it last run right?

The load o matic sounds like a pile I would personally dump it directly for a system that actually functions proper with counter weights and electronic ignition. I have zero experience with the load o matic systems...I still think you have an ignition problem (which is now possibly also a carb issue thanks to the load o matic) I dont have enough experience with that particular system to provide any further reasonable assistance out side of "get rid of it" you'll have to deffer to an i6 pro thats messed with that ignition system.
Sorry

-Gun

Labman2000

Not a problem. Thank you for trying to help me! All infomation helps.