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  #1   IP: 66.235.22.17
Old 05-10-2018, 01:05 AM
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Hows she sound?

I've now run the freshly rebuilt A4 a few times. Sounds decent to me, but I'm not sure how a perfectly running unmuffled A4 should sound. I'm hoping some of you with more experience can advise me.

Here it is running at idle. I assume the slight sputtering is just because it's unmuffled.

Running at idle

Here it is running a bit faster, maybe around typical cruising speed. Sounds a little rough to me. Is that because it's unloaded, and if it were loaded up with a prop it would be smoother?

Running at Cruise

In general, does this sound good? Or do you hear anything of concern?

Thanks
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Old 05-10-2018, 06:13 AM
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Old 05-10-2018, 06:16 AM
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Wink Hemi?

Sounds pretty good to me. Although the exhaust is loud she's running decent...no smoke, no knocks that I can tell. Always a little valve train noise in these engines...I think you've got it. Did you time it with a timing light?

PS: "Has it got a Hemi"?
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Old 05-10-2018, 03:32 PM
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Thanks Mo. I timed it by sound/smoothness, but I plan to do the timing light thing.

... and the A4 is about as opposite of a Hemi as you can get!
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Old 05-10-2018, 07:51 PM
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Wrist, This provides a great opportunity to do the tuning before dropping that pretty A4 back into your boat. I prefer using timing marks rather than the "seat of the pants" method of setting the timing. For the carb screw idle mixture adjustment, 1-3/8 turns out has worked well for me. I feel that timing should be set with a timing light, at about 700 rpm and set at tdc or a couple of degrees before tdc. In your case, I would increase the rpm's from idle and watch for the timing to advance as the R's increase, which is a good way to see if the distributor is advancing as it should. I have worked with others, using this method, and the results have been very similar, with a smooth running engine with minimal blow-by. By the way, a small dab of white fingernail polish on the flywheel rolled pin will make make reading the timing light much easier.
Tom
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Old 05-10-2018, 09:31 PM
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Thanks Thatch, I do plan to hit it with the timing light, but I wasn't sure where the timing marks were. I'd expect them on the rim of the flywheel. But the roll pin makes more sense, especially because the flywheel is hidden when the cover is installed.

Regarding advance, I assume there's some sort of mechanical advance in the distributor? There's no vacuum connection, at least not on either of my A4s.
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Old 05-10-2018, 10:38 PM
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Timing marks on an A4 can be considered one of it's weak points. Mechanical advance is listed at 17 degrees and should be achieved under 2000 rpm. Moyer's replacement springs do a good job of advancing the spark at the correct time and are certainly worth the investment. As a side note, the two best changes I have made to my A4 are the addition of electronic ignition and fresh water cooling.
Tom
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