Super rough running - cause?

 Created by: spectre1275
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 Posted: Apr 11, 2019 04:47AM
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US
1.75" Carb?  HS6?

It could be the fuel delivery to the carb is insufficient, the float bowl level could be way too low, the air filter could be plugged, or yes... maybe even the coil could be bad.  Go through the basics.  Set the valves on the engine when cold.  Tune the ignition system.  Save the fuel system for last.  You said this is a car with Pertronix.  At least temporarily refit points and condenser.  

Make one change at a time and test drive between each subsequent change so you can tell what the problem really is.

Doug L.
 Posted: Apr 11, 2019 04:19AM
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"....I've not yet taken a closer look, but thought y'all might give me some "check this first" ideas.

 - float bowl?
 - coil?
 - Petronix kaput?
 - fuel delivery?

It's the idling fine thing that's got me stumped..."

Float bowl? .... unlikely ..you'd notice the overflow ...and easy to check if empty  (the float bowl is not the problem)

Coil?  .. my pick - BTDT.... a couple to times... clean the points, optimise timing etc and things go fine ..until you ask bit more and then things start to break down.  The engine will run without (or with low) load but the compromised spark just doesn't cut it with a richer mixture....  I had  a Volvo that ran fine with a sick coil  ...until you tried to pass a 
truck.  At about 4K in top ... just about when you drew level with the cab .... it would die in the bum. Coil tested fine; eventually we ran out of ideas and tried a replacement .... VOILA ... as the Froggies say.. 

Petronix Kaput... also BTDT... its obvious .. nothing happens...

Fuel delivery . possible... pull the fuel line and check flow.  

Cheers, Ian

 Posted: Apr 10, 2019 01:37PM
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Hey all,

'68 mini has been running fine, (though smells a little rich).  1275, 1.75 carb, electronic ignition and fuel pump.

Last week on the way home, it started losing power, and sounding like it was running on 3 cylinders. 

I pulled over for a quick look - Oil pressure & level were fine, water temp fine.

Normally I'd suspect either an air leak, ignition issue or fuel problem, BUT it idles fine.  It's just when I put it in gear and try to drive away, I'd say I'm down power by 70%, and can barely limp along at 20mph in 2nd gear.

I've not yet taken a closer look, but thought y'all might give me some "check this first" ideas.

 - float bowl?
 - coil?
 - Petronix kaput?
 - fuel delivery?

It's the idling fine thing that's got me stumped.

Thanks!

Scott

New Zealand - The only place where a kiwi can mean a fruit, bird or mini owner...

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