Greetings!!

Thanks to the Cap'n... I finally found the correct distributor cap for my car. I installed it yesterday, and the car rund PERFECT... I couldn't ask for better....

Until, of course.... I get to around 4200 RPMs.

First off, there is no hesitation... no backfiring... nothing... all the way up to 4200RPMs... the car runs just as good as my new cars.

But right at that point..... it starts to "miss" pretty violently. The car actually starts "bucking"

Not sure how to put it into text other than....

GRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR (4200 rpm) RR...RRRR....RRRRR....RRRRR.

Again, no coughing, no backfiring or popping... just a bad "miss" or "hesitation".

I "THINK" it might be electrical, because at the same time.... my tachometer starts going all screwy, and flopping all over the place. Plus, it has a brand new fuel filter in it, so I don't think it's that.

I've also put a brand new coil in it recently as well.

Any ideas?????

pinched fuel line or dwell on distributor (but that should have been set by your mechanic).

Sounds like a weak spring on the points, bouncing at high rpm. Get new points or
a good optical trigger. Dimitri

Here are my 3 guesses with no other information provided:

1. Points (dirty, bad or whatever)
2. Condensor
3. Weak or failing ignition coil.



just my $0.02

I'd start with dwell then timing.

OR

rev limiter spring broken,
m ike

Rev limiter will go ba ba ba ba ba ba very quickly.
Know I used to hit the rev limiter in my 009 dizzy all the time while on course.

I would look at fuel line crimp.
or what was the last thing you changed before it started doing this? Well that's the thing to look at 1st

I would change your points and sence your there the condenser tho when

the condenser goes it will usually miss all the way through the RPM's.

I'm having a similar problem with low rpm. Accelerating....no worries at all, however when maintaining a speed at low rpm I get the grrrrr hiccup grrr hiccup

If it has a points plate and grounding jump wire is loose/off/missing the two plates can still make contact with each other as they rub together metal to metal, but at high rpm vibration will be strong enough to make plates have intermittent contact and give symptoms you have.

Throttle valve sensor a/k/a throttle position sensor.

Man.. so many suggestions... I don't even know where to start. It has NEVER done this before.... So I have no idea.

History:

Car wouldn't stay running, so I bought a new coil.. that fixed that problem.

Car was running rough..... so I bought a cap, rotor, plugs, and points off ebay.

Rotor didn't fit, so I just changed cap and points... still ran rough.

Took car in to have carbs adjusted, discovered that it was the wrong cap. Mechanic was able to tune it nicely anyway.. excepted it hesitated at high rpms.

I figured the correct cap (050) would solve the problem.... it didn't.

Are the points different on the original distributor than on an 050? Could that be the problem? They fit.. so I figured they were correct.

Points are points. but the advance plates might be a nice place to start.

Be careful of the little Jesus clips and spring thinys when you take the dizzy apart.

a Jesus clip is: anything that goes sproing! and you say "jesus where did that go"?

Listen, investigate the fuel system first. Take a flashlight and look down your tank filler to see if there is a bunch of rust at the pickup fittings. That is classic that everything works fine at low RPM then once more fuel is needed the car starts to shut down. How old is the gas in your tank?

If it were me I would find someone with an O2 sensor or meter that can be put in the exhaust to see what is happening with the mixture. If that is not possibble, go somewhere that you could drive fast for a mile or so, put in a new set of spark plugs and then fire it up and go like hell until you get the miss. Immediately shut it off, coast to a stop and pull the plugs and look at them with a magnifying glass to see if they are all the same, etc. You could take them to your mechanic to see what he sez. The last choice is to put it on a analyzer machine that can read everything such as voltage to the plugs a/f mixture, etc. Good luck.