Engine Leans Out At Cruising / Light Throttle

[Geoff 2]

45-55* at cruise is usually ideal. Low compression engines need more timing. This is a very simple & quick test: retard the timing about 5* by turning the dist. Might idle rough etc,
but test drive, cruising, to see if problem improves or is eliminated.

 

[Charlie Brown]

45-55* at cruise is usually ideal. Low compression engines need more timing. This is a very simple & quick test: retard the timing about 5* by turning the dist. Might idle rough etc,
but test drive, cruising, to see if problem improves or is eliminated.

Ok, tried this and no real change. This issue is becomming very frustrating for me. I've tried all the suggestions from members as well as many of my own. For sure I'm missing something here. Upon reseal, I did remove the camshaft to get at the rear cam plug, so maybe the cam sprockets are off, but I doubt it. I'm prety meticulous about such things. Not quite sure what my next step will be.

 

[gtxrt]

Ok, tried this and no real change. This issue is becomming very frustrating for me. I've tried all the suggestions from members as well as many of my own. For sure I'm missing something here. Upon reseal, I did remove the camshaft to get at the rear cam plug, so maybe the cam sprockets are off, but I doubt it. I'm prety meticulous about such things. Not quite sure what my next step will be.

check your float levels again. try another carb

 

[furious70]

Are you sure it's not more than lean surge, is it actually an electrical miss under other circumstances? Don't happen to know anyone with an old fashioned scope?

 

[Charlie Brown]

Are you sure it's not more than lean surge, is it actually an electrical miss under other circumstances? Don't happen to know anyone with an old fashioned scope?

Yes I suppose that's possible. Something to consider for sure. I was able to get my hands on another similar carb (AVS) to try and will do this first. The weather though, is making it a bit of a challange to test the car lately. It's been raining stedy for the last 4 days and calls for the same well into next week. Thanks for the tip.

 

[Charlie Brown]

Update - decided to remove the carb and strip it down again. The intent was to go over all the tiny passages again to make sure they were clean. After I tackled that, I put lots of air to all the parts / passages. After one last visual to make sure I didn't miss any parts, I spied this - see photo. I saw that one of the primary boosters was missing the welch plug. While I'm not sure if this was a pre existing condition or something that just happened while blasting air at all the parts, it still needs to be fixed. I fabbed a plug and tomorrow I'll get some fuel proof epoxy to make sure they don't come out again. I'm hoping this was my initial problem. Stay tuned.

 

[Geoff 2]

Great catch!!!

That will definitely cause surging because it is a giant air bleed that is leaning the mixture.

 

[Charlie Brown]

So after all the chasing of my issue, it seems that the culprit was the missing welch plug on the one of the primary boosters. Took the car for a decent rip today and all seems good. Thanks to all who offered great advice.

 

[BSB67]

If the car ran perfect before the reseal, then you need to look closely at everything you touched since then.

Post 27, 49, and 61.