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Mysterious spark plug debris
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Author:  Tim_K [ Sat Nov 03, 2001 9:01 am ]
Post subject:  Mysterious spark plug debris

I've finally got my new /6 engine running good.It ran 16.30 @ 84.4 a couple days ago, pulling a 3330 pound 1971 Valiant with me in it. Works out to 168 net hp, although I was hoping for 200. The final carb set up specs are:

450 holley mechanical secondary, #62 primary jets, #9 metering plate in the rear, the equivalent of #67 jets. 8.5 power valve, pink pump cam, #31 shooter for accelerator pump.

I'd been jetting down the carb gradually from #66 primary jets, and had black spark plugs within 50 miles a lot. #62 jets were just enough to get rid of most of the black carbon, but I saw that #3 plug (Autolite 26) had a bunch of teeny tiny shiny specks all over the insulator. Is that something to be concerned about? No other plugs had any shiny powder on them.

Author:  Doctor Dodge (Doug Dutra) [ Sat Nov 03, 2001 9:10 am ]
Post subject:  Re: Mysterious spark plug debris

Quote:
: I've finally got my new /6 engine running
: good.It ran 16.30 @ 84.4 a couple days ago,
: pulling a 3330 pound 1971 Valiant with me in
: it. Works out to 168 net hp, although I was
: hoping for 200. The final carb set up specs
: are: 450 holley mechanical secondary, #62
: primary jets, #9 metering plate in the rear,
: the equivalent of #67 jets. 8.5 power valve,
: pink pump cam, #31 shooter for accelerator
: pump.
: I'd been jetting down the carb gradually from
: #66 primary jets, and had black spark plugs
: within 50 miles a lot. #62 jets were just
: enough to get rid of most of the black
: carbon, but I saw that #3 plug (Autolite 26)
: had a bunch of teeny tiny shiny specks all
: over the insulator. Is that something to be
: concerned about? No other plugs had any
: shiny powder on them.


How is the over-all color on that plug, tan or "bone white"?
Clean the plug (or replace it) and keep an eye on that cylinder. The smallest piece of "crud" going through the combustion process (with high cylunder pressures like yours) will "pepper" a plug fast, this is not a big deal, as long it is not an on-going condition. (it could be a real lean hole and over time, that will "burn" a piston)
DD

Author:  Tim_K [ Sat Nov 03, 2001 9:22 am ]
Post subject:  Re: Mysterious spark plug debris

Quote:
: How is the over-all color on that plug, tan or
: "bone white"?
: Clean the plug (or replace it) and keep an eye
: on that cylinder. The smallest piece of
: "crud" going through the
: combustion process (with high cylunder
: pressures like yours) will
: "pepper" a plug fast, this is not
: a big deal, as long it is not an on-going
: condition. (it could be a real lean hole and
: over time, that will "burn" a
: piston)
: DD


The plug colors are tan to dark tan. I didn't want to go much leaner. I figure better to be a little rich than lean. Compression test showed 190-200 psi in all cylinders. I'll have to check the plugs again tomorrow and see how they're doing.

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