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Old 03-24-2011, 12:05 PM
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I'm still in pursuit of the root cause on the engine noise. I thought I had it slam dunked when I found that the spark plugs were loose - all 4 of them! Weird, but I was going to change them out and discovered that each was loose. One was just barely wrench tight, and the worst was 1/4 turn from finger tight.
I went ahead and replaced them...I keep two sets and change them out every month or two when the car gets hard to start. I suspect the carb is worn out and its running rich. The "Bugspray" carburator has no adjustments or re-jetting capability, so it's just a seal replacement in the rebuild kit.
Anyway, replaced the plugs, and the knock and backfiring on decel are still there. So, the only other thing I could think to do at the time was to change the timing. I loosened the distributor and twisted a bit this way and that, but it didn't have any affect on rev-up, only on idle speed. WILD !! If I didn't know it could do better, I'd give up
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Old 03-24-2011, 12:22 PM
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The backfiring is still an exhaust leak. All your seals should have a metal donut on them, including the seals to the engine. The knock is a little more troublesome. Does it sound "deep", like inside the case, or more "to the surface", like a ping or rocker noise? Have you done the basics as described earlier in the thread? Have you adjusted all your valves to spec?

The Bugspray carb... well... they were never the best to begin with. If it's running lean, you'll experience the knocking that you might be hearing. Personally, I'd ditch it and find a nice used Weber.
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Old 03-26-2011, 08:28 AM
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Yes, I did all of the tests/check described. No discernable leaks were detected around the manifold, or the couplings to the heater box. I put the towel over the exhaust as well, and the engine did not accelerate but just a little, and the noise was still there. It seems to eminate from the exhaust tip; at least its the loudest when right behind the car. Moving forward, it gets quieter.
One thing is that its mellower that it originally was. If I wasn't in tune with the issue, I might not notice. Maybe the glasspack is moving around. They are kind of cheap; the paint is already off and they are rusting through the chrome. I'm sure the guts arent any better.
I'm learning my way around the bugspray carb as issues arrise. I'd love the dual downdraft Kadrons I had on the Speedster; reliable, adjustable, reliable, simple, AND reliable....Not sure the budget can support them at the moment: Dual college payments coming in the fall!! I might even have to sell the project in favor of a car that could survive the college 'experience' and the (aHem; unfavorable...) attention this car would bring
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