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Unread 11-11-2013, 07:10 AM   #91
Matt1981CJ7
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Then you should be good.

Connecting the vac advance to manifold adds around 8* of advance to the idle, which is desirable.

Without it, your initial is probably around 10*, which is a normal amount of initial.

Matt

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Unread 11-11-2013, 07:20 AM   #92
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Quote:
Originally Posted by Matt1981CJ7 View Post
Then you should be good.
SWEET!

Finally something goes smoothly with this thing.

Gotta say though, with that thing at 3000 rpm with no load on it, it sounded like it was going to take of for the International Space Station.....
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Unread 11-11-2013, 07:28 AM   #93
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Gotta say though, with that thing at 3000 rpm with no load on it, it sounded like it was going to take of for the International Space Station.....
I hear you, especially when your face is about 6" from the fan blades as you try to read timing and work the throttle at the same time.

Did you happen to notice at what RPM your centrifugal kicks in?

Matt
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Unread 11-11-2013, 07:32 AM   #94
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Originally Posted by Matt1981CJ7 View Post
Did you happen to notice at what RPM your centrifugal kicks in?

Matt
I didn't.
Was kind of short on time so I didn't take the time to do any plotting.
I will next time I go to the garage. Probably Wednesday.

Damn life and it's commitments are interfering with my garage time...
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Unread 11-11-2013, 08:18 AM   #95
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This thread reminded me how much I miss Facebook........
You said it right there, brother. Nothing like having vodka oozing out of your pores and spending an hour deleting all of your posts from yesterday


Shawn
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Unread 11-11-2013, 09:27 AM   #96
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Now I have a question. If the timing is set to a specific advance at 3000 rpm w/o the vacuum advance connected won't the advance at 3000 rpm be higher once the vacuum advance is hooked up again? Is that taken into account with the target 3000 advance?
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Unread 11-11-2013, 11:07 AM   #97
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Lee,

Yes, manifold vac will add advance at 3000 RPM, just as ported vac would, when just revving the engine in the garage.

But, the engine will never see that much advance in any load situation.

Matt
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Unread 11-11-2013, 11:19 AM   #98
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So using 2Xtreme's example he will actually be seeing more than 31* advance if there were a situation where he could drive along at that rpm and be getting enough vacuum, right? I understand about no or little vacuum under load. In fact, I understand almost all of this, I am just looking for confirmation.
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Unread 11-11-2013, 11:40 AM   #99
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Originally Posted by ScroungerLee View Post
So using 2Xtreme's example he will actually be seeing more than 31* advance if there were a situation where he could drive along at that rpm and be getting enough vacuum, right? I understand about no or little vacuum under load. In fact, I understand almost all of this, I am just looking for confirmation.
The only time his engine will see more than 31* at 3000 is under no load situations.

For example, coasting down a hill his engine may pull 25" Hg of vacuum at 3000 RPM, perhaps slightly higher. Since high vacuum leans out the air/fuel ratio, and a lean charge needs the spark to happen faster, that's exactly when the additional vac advance is needed.

Matt
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Unread 11-11-2013, 02:08 PM   #100
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Originally Posted by Matt1981CJ7 View Post
2X,

DO NOT set initial timing to the highest vacuum reading. It's likely to result in far too much advance. Use the vacuum gauge for setting the mixture. Use a timing light for timing.

Here's what I recommend. The total timing (initial and centrifugal) at the upper RPM ranges is what I've found to be the most critical for performance. IMO, you should strive for 30-35 degrees total at around 3000 RPM. Once you achieve that, then let the initial land where it lands. My 258 ended up around 11 BTDC initial.

Then hook your vac advance up to manifold vac, set your idle around 700 RPM and dial in the mixture, and enjoy.

Matt



Hi Matt...I have been trying to get an optimal setting for my DUI hei and the motorcraft 2100 combo and found on the DUI engraved on the bottom, 24* at 3000 rpm... Is the 30-35* at 3k that you recommend more for a standard AMC distributor or ?
Thanks...
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Unread 11-11-2013, 02:41 PM   #101
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dres,

I would start at what's recommended by DUI, then creep it up in small increments, testing driving each time.

Every engine is going to be slightly different. From my research, the 30-35* at 3000 RPM benchmark was fairly common in many stock applications, even with some SBCs.

Matt
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Unread 11-11-2013, 06:05 PM   #102
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Bought your digital gun today. Unfortunately ran into those same other responsibilities that 2x mentioned. With 12 years in and 3 'conflicts' fought, my Veteran's Day lasts two days so I will be getting some numbers tomorrow. Thanks for the thread Vince and your time Matt and Shawn! Never did plot this thing. Anxious to see how my ear is calibrated!
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Unread 11-12-2013, 06:15 AM   #103
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With manifold vacuum connected Grammys CJ sits at 23 to 25 at idle. No problems.

At least you didn't have the 6r head and set it at 30@3000rpm and have mid 20's at idle with no vac advance.

Matt the only distributor I've ever ran across with 20* of mechanical built into it was a stock HEI.

If the 13r is truly meaning 13* mechanical he should fall into the mid teens initial without any vacuum on the can. He should make sure he's not sitting close to 20 at idle with vacuum disconnected. 30-13=17

Remember if you flip your advance head to the 18r side your rotor will now be 180 out since the notch the rotor sits in follows the advance head flipping. Your going to need to pull your distributor and rotate it 180* and drop it back in.
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Unread 11-12-2013, 06:56 AM   #104
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86,

What I've found is the advance slot labels (13r, 18r, etc...) don't necessarily reflect the actual maximum degrees of advance on a Motorcraft.

For example, on the 18r slot, mine gave me nearly 24* of centrifugal. At 35*/3000 RPM, my initial (without vac advance) was at 11*.

There was a bit of discussion about this on my thread, but never a definitive answer. I attributed the discrepancy to the slots not being cut accurately. Also, the little tab, that stops the weights from opening any further, had a plastic covering. I took that off on a recommendation from Terry (Mcmud). I believe that gave me a few extra degrees.

Matt
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Unread 11-12-2013, 07:18 AM   #105
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Quote:
Originally Posted by Matt1981CJ7
86, What I've found is the advance slot labels (13r, 18r, etc...) don't necessarily reflect the actual maximum degrees of advance on a Motorcraft. For example, on the 18r slot, mine gave me nearly 24* of centrifugal. At 35*/3000 RPM, my initial (without vac advance) was at 11*. There was a bit of discussion about this on my thread, but never a definitive answer. I attributed the discrepancy to the slots not being cut accurately. Also, the little tab, that stops the weights from opening any further, had a plastic covering. I took that off on a recommendation from Terry (Mcmud). I believe that gave me a few extra degrees. Matt
Good enough.

I know Grammys CJ isn't anywhere near 30* with initial set to 9 ish.
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