Posted by Ddd [108.162.237.19] on Tuesday, March 20, 2018 at 08:59:56 :
Trying to diagnose this issue.
Background: rebuilt and installed a 218 engine in my WC about 500 or so miles ago. Can't rember but it's at least 500 miles run time now is my guess
Symptoms: first start up, truck runs good. Nice clean even exhaust at the muffler end of things. Engine smooth.
As it warms up I notice it begins to "burble" or miss.
Very quickly say within a minute or two this happens.
Sounds almost like a miss but it's not the best explanation. More or a "burbling" at the exhaust.
Thought it was the carb. I installed a brand new reconditioned unit when the truck was rebuilt at the same time the engine was installed.
Rebuilt /reconditioned / cleaned carb just the other day. Again! No change. Thought maybe I missed a passsagewsy or something so replaced this with a NOS rebuilt unit I had stored away.
No change with new carb.
Pulled plugs and regapped to 0.025". No change.
Pulled plugs again and tried 0.030". No change.
Adjusted timing even though it was good . No change.
Never did any valve adjusting since the engine was installed so thinking as it's now breaking In and an adjustment is what's required here.
Before I pull off the fender and other accessories to adjust, tell me your thoughts. Is this what's the likely culprit causing the "burbling" at idle?
Maybe the valve to tappet gap too tight so as engine warms up the gap closes up, not allowing valves to fully seat letting gasses by? This the "burbling" tones I hear maybe?
Another thing I noticed is the carb air mix screw. Usually I have always run it about 3-5 turns out from full seated in.
I noticed I can get the "burbling" to calm down by turning it in nearly to full seat! Well within 1/2 turn out from full seat
I know that's not where it should be at nearly fully seated in. That's too rich.
Any other ideas where to look?
I'm running a mechanical advance distro with points and condenser ; i.e. Not electronic setup.
This burbling happens at idle. Revingbit up it seems to go away but not entirely sure. I'll check that again.
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