Gradually running rougher, And tailpipe popping Options

[jeffdon]

So, My carbed, cammed, malloried 2056 has been steller for about 6k miles. Then on a run up to Santa Rosa it started feeling less "crisp" on acceleration, and is popping out the tailpipe when cruising along. Not loud bangs, kinda softly doing it. Getting also a bit of snorting out the carbs on start up. Going to crawl under today and check for exhaust leaks (SS exchangers).

What else should I check?

Valves?
Timing?
Ignition circuit?

Also, as an engine wears in and you start putting some miles on it, can it change in such a way that would require re-evaluating your jetting?

[jmill]

Valves
Timing
Sync/tune carbs
Check for exhaust leaks

Did you not check/adjust any of those in the first 6k miles of a fresh rebuild?

[jeffdon]

Valves
Timing
Sync/tune carbs
Check for exhaust leaks

Did you not check/adjust any of those in the first 6k miles of a fresh rebuild?

Been into the valves three times at regular intevals. Timing a couple, its been solid. Carbs have been synched and I have felt pretty dialed in on the jetting. Leaks, I think I have been good, at least I have not seen or felt any when under the car. That being said, I suppose something could have been knocked out of whack at some point. The car rides rough on poor roads, and thats a lot of jarring about.

[jmill]

What type of linkage do you have? I gave up on the cheap ones due to movement. At a minimum you want the hex bar with cast arms and carb plates for the ends.

On a side note, carbs are putzy. I played with them at every oil change.

[jeffdon]

What type of linkage do you have? I gave up on the cheap ones due to movement. At a minimum you want the hex bar with cast arms and carb plates for the ends.

On a side note, carbs are putzy. I played with them at every oil change.

Its a home brew bell crank my dad fabbed up around '85. Its actually been dependable over the years, and on a couple different engines.

This is the closest i have now for a pic, but I think it gives the general idea (NOT attached to the carbs in this pic)

[914.SBC]

Mine did exactly what you are describing (keep in mind I have a v8) but it turned out to be an exhuast leak.

[jeffdon]

Mine did exactly what you are describing (keep in mind I have a v8) but it turned out to be an exhuast leak.

Interesting that a V8 would behave the same way.

[mrholland2]

Mine did exactly what you are describing (keep in mind I have a v8) but it turned out to be an exhuast leak.

Interesting that a V8 would behave the same way.

Not sure this is even germane, but a coworker of mine had this happen in a late 70's/early 80's Cadillac. Turned out it was because of low oil pressure not pumping up the lifters. Is your 2.0 hydraulic lifters? Low oil pressure? Unlikely, but every idea might lead to another. (IMG:style_emoticons/default/idea.gif)

[jeffdon]

Mine did exactly what you are describing (keep in mind I have a v8) but it turned out to be an exhuast leak.

Interesting that a V8 would behave the same way.

Not sure this is even germane, but a coworker of mine had this happen in a late 70's/early 80's Cadillac. Turned out it was because of low oil pressure not pumping up the lifters. Is your 2.0 hydraulic lifters? Low oil pressure? Unlikely, but every idea might lead to another. (IMG:style_emoticons/default/idea.gif)

Mechanical, and my OP is right where it should be.

[TheCabinetmaker]

gradual deterioration of power would point me towards a dirty carb, decreasing fuel pressure (maybe due to a dirty filter), weakening spark, or worse, losing compression. did you do a compression check when fresh? If so, do another one and compare.

[jeffdon]

gradual deterioration of power would point me towards a dirty carb, decreasing fuel pressure (maybe due to a dirty filter), weakening spark, or worse, losing compression. did you do a compression check when fresh? If so, do another one and compare.

You know, I was having hot start problems (cranking, no firing) and found that moving my coil (bosch blue) to the firewall solved it. Perhaps its breaking down.

As a complete aside, yesteday morning, I had a belt squeeling, and found I had lost the Alt. adjuster bolt. No gen light warning. I fixed that, and was hoping that maybe i was running rough due to voltage dropping gradually. After running for half an hour, it made no difference.

[TheCabinetmaker]

Ha! that would definitely cause a weak spark

[jeffdon]

Turned in the idle mixture screws, and it seems to have its old crispness back.

Plugs at idle look like this....what say all yee ole plug reading pros?

[TheCabinetmaker]

Electrode is kinda hard to see, but doesn't look rich. Is that oil on the threads?

[struckn]

Ha! that would definitely cause a weak spark

Look for arcing from the plug wires and the connection from Coil to Dizzy and plugs also. If you have electronic ignition (i.e. pertronix) Gap your plugs .040 - .050.

[jeffdon]

Electrode is kinda hard to see, but doesn't look rich. Is that oil on the threads?

No its not oil. Electrode color is reddish brown to whitish red.

[jmill]

I'd be happy with that plug. Looks to be #9.

[Porschef]

[/quote]
Look for arcing from the plug wires and the connection from Coil to Dizzy and plugs also. If you have electronic ignition (i.e. pertronix) Gap your plugs .040 - .050.
[/quote]

I swapped out to Pertronix, but didn't read any mention of changing the gap. Is this your experience to find it to run better with the .040-.050 setting?

Thanks

[jeffdon]

[quote name='Porschef' date='Feb 12 2012, 11:02 AM' post='1623529']
[/quote]
Look for arcing from the plug wires and the connection from Coil to Dizzy and plugs also. If you have electronic ignition (i.e. pertronix) Gap your plugs .040 - .050.
[/quote]

I swapped out to Pertronix, but didn't read any mention of changing the gap. Is this your experience to find it to run better with the .040-.050 setting?

Thanks
[/quote]
(IMG:style_emoticons/default/agree.gif)

[jeffdon]

I'd be happy with that plug. Looks to be #9.

Kind of a cross between 9 amd 14, which makes me happy