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Rebuild for mileage and emissions
https://slantsix.org/forum/viewtopic.php?t=64507		 Page 11 of 12
Author:  SlantSixDan [ Thu Aug 06, 2020 8:34 am ]
Post subject:  Re: Rebuild for mileage and emissions
Plugs still running too hot. Keep working on fuel mixture (richer) and plug heat range (colder, like a № 7). They shouldn't be bright white like that; they should accumulate a tan-to-brown coating.
Author:  rich006 [ Thu Aug 06, 2020 10:21 am ]
Post subject:  Re: Rebuild for mileage and emissions
Quote:
Plugs still running too hot. Keep working on fuel mixture (richer) and plug heat range (colder, like a № 7). They shouldn't be bright white like that; they should accumulate a tan-to-brown coating.
OK, so I'm already running a 64 jet and I have the float setting higher than it was (it's now at spec, level with the gasket surface). Would it be reasonable to try an even larger jet and/or higher float? What else can I do to enrich the mixture?

The exhaust is still stock by the way, 2" all the way back. You asked about that previously.
Author:  SlantSixDan [ Thu Aug 06, 2020 11:19 am ]
Post subject:  Re: Rebuild for mileage and emissions
I think at this point I'd be trying to put some eyes on the actual mixture "as received" (in the cylinders) across a range of engine speeds and loads, preferably with exhaust analysis on a dyno—no idea how easy or hard it is to find such a facility these days—or at least with a see-thru spark plug.

Reason I asked about the exhaust is that exhaust restriction (such as in the muffler) can easily cause ping in an engine that otherwise wouldn't do so.
Author:  Jase [ Thu Aug 06, 2020 11:40 am ]
Post subject:  Re: Rebuild for mileage and emissions
Quote:
Plugs still running too hot. Keep working on fuel mixture (richer) and plug heat range (colder, like a № 7). They shouldn't be bright white like that; they should accumulate a tan-to-brown coating.
And the ground strap looks discolored, due to heat.



My uninformed question (maybe directed to those who spend time at the race track) is as follows:
Does a compression test give any additional information at this point to help with tuning?
Author:  volaredon [ Thu Aug 06, 2020 4:52 pm ]
Post subject:  Re: Rebuild for mileage and emissions
How long should plugs be run in an engine to get an accurate plug reading? Maybe his are still bright white because it hasn't been run long enough?
Author:  matv91 [ Thu Aug 06, 2020 5:02 pm ]
Post subject:  Re: Rebuild for mileage and emissions
http://www.slantsix.org/forum/viewtopic ... 19&t=63479
Author:  matv91 [ Thu Aug 06, 2020 5:47 pm ]
Post subject:  Re: Rebuild for mileage and emissions
http://www.slantsix.org/forum/viewtopic ... 6&start=15 at the bottom of this page 2 pictures main well air bleed holes look for the green dot 25/32 actual fuel level should be right at that green dot. Preferably in your case towards the top of that hole or just covered. In this case warm car up, take top off,measure fuel level not float level. In an air bleed carb the the fuel level in relationship to those holes is really important. The 74 fsm on page 14-12 fig 5 shows fuel level line with power valve vacuum piston in up position.Also on that same page the power valve channel restriction is mentioned and shown in fig 5
Author:  matv91 [ Thu Aug 06, 2020 5:57 pm ]
Post subject:  Re: Rebuild for mileage and emissions
Here is a very short film, about how an air bleed carb works. https://www.youtube.com/watch?v=aJMXh5F6ncE
Author:  SlantSixDan [ Thu Aug 06, 2020 7:04 pm ]
Post subject:  Re: Rebuild for mileage and emissions
Quote:
How long should plugs be run in an engine to get an accurate plug reading? Maybe his are still bright white because it hasn't been run long enough?
Go for a drive including suspected problem conditions (around town, on the highway, where/whenever it's suspected the engine isn't getting a proper air/fuel mix), return to the shop/garage/driveway, pull the plugs and read. It is not necessary to go for dozens or hundreds or thousands of miles.
Author:  Charrlie_S [ Fri Aug 07, 2020 3:12 am ]
Post subject:  Re: Rebuild for mileage and emissions
This is just a personal opinion, and I have nothing to back it up. If it were me, I would try a set of the stock (or one heat range colder) NGK short (stock) reach plugs. Never did like the idea of that long ground electrode, in an engine not designed for it.
Author:  SlantSixDan [ Fri Aug 07, 2020 10:20 am ]
Post subject:  Re: Rebuild for mileage and emissions
The one-range-colder plugs he's now trying have the stock-length electrodes, not the extra-long ones.
Author:  rich006 [ Wed Aug 12, 2020 3:42 pm ]
Post subject:  Re: Rebuild for mileage and emissions
Somehow I got unsubscribed from notifications for this thread, so I didn't see the last few posts (my fault for not reading the forum regularly, right?). In the meantime I installed some NGK BKR7E plugs, heat range 7, electrodes shorter than the ZFR6GP which were in turn shorter than the ZFR5N. The detonation may be slightly better now but not a lot better. The color after a 10-mile drive is if anything even lighter than the heat range 6 plugs (#2 cylinder plugs shown below).

Matv91, thanks for the documentation and links. I understand your suggestion is that the float level may be too low and thus the air holes may be exposed too early, causing too much air to mix with the fuel. I'll try that in-car float adjustment when I get a chance. I think I'll also try a new fuel filter, which probably I should have replaced when I put the motor back together. It's only a few years old but it's easy to replace.

Cooler, shorter plug side by side with hotter medium length plug:
Image
Author:  Dart270 [ Wed Aug 12, 2020 5:54 pm ]
Post subject:  Re: Rebuild for mileage and emissions
What is your cranking compression psi? What fuel grade are you using?

Lou
Author:  SlantSixDan [ Wed Aug 12, 2020 6:01 pm ]
Post subject:  Re: Rebuild for mileage and emissions
Yeah, there is definitely something awry if you can run plugs that much cooler and still have 'em running hot like that.

Don't throw away your 6s and 5s; you may wind up returning to one or the other after you get the cause found and solved!
Author:  rich006 [ Wed Aug 12, 2020 6:10 pm ]
Post subject:  Re: Rebuild for mileage and emissions
Quote:
What is your cranking compression psi? What fuel grade are you using?

Lou
A few weeks ago I had these compression results, after 5 engine rotations:
1 - 160
2 - 160
3 - 170
4 - 170
5 - 175
6 - 180

I was considering running the test again in case I didn't turn the engine enough times, but haven't gotten around to it.

I'm running Shell 87 octane; I burned through all my old February fuel and refilled with new recently.
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