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Old 07-27-2020, 12:15 PM   #8
DRG-ler's Avatar
Join Date: Dec 2018
Location: Berlin / Germany
Posts: 88
Default Re: Backfire in overrun mode (load change)

Originally Posted by 30 Closed Cab PU View Post
I was just trying to throw some easy things at you, hoping that it would get the discussion started.
If am off base, my apologies.
Everything okay, I didn't get it wrong. Everything is good. You don't have to apologize for wanting to solve my problems either. The Tip with the valves is not wrong in itself, but it is the most complex and expensive problem, so I don't want to think about it yet. I want to exclude the cheap alternatives before I take the step and disassemble the engine block.

Lean conditions cause back fire through the carburetor throat. Some folks refer to an after fire condition as back fire but it doesn't fit the definition very well. When the exhaust was mentioned, I could tell the meaning though.
No, the misfire does not come from the carburetor. That would make the noise louder, I think. It's hard to describe now, but chinacrackers in a tin can do it pretty well.

So actually I see the problem myself more in sucked false air (leaking manifold / carburetor seals) or actually in poorly closing valves.

I have to see if I can find someone with an endoscope who can look at the valves without taking my head off.
If there were clear deposits of oilcoal, the problem would have been found.

Greetings Andy

Last edited by DRG-ler; 07-27-2020 at 12:20 PM.
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