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Unread 11-10-2013, 01:21 PM   #76
2Xtreme
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Quote:
Originally Posted by ScroungerLee View Post
With or without the vacuum advance? Hopefully with it
Now that you mention it, I'm not sure......

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Unread 11-10-2013, 01:28 PM   #77
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Quote:
Originally Posted by 2Xtreme View Post
Set timing to 31* @ 3000 rpm
Landed at 17.7* @ 700 rpm
Yep, that's what I'd expect from a 13R advance slot on the head. That's too much initial, IMO.

Your choices are:

1. Dial it back to about 23* total/10* initial and run a rather lazy advance curve. It will look something like the second curve below.

2. Turn the advance head over to the 18R side. That should produce an advance curve similar to the first curve below.

Disregard the pink curve. That's irrelevant to this discussion, for now.

Matt
advance-curve-5.jpg  
advance-curve-1.png

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Unread 11-10-2013, 01:33 PM   #78
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Originally Posted by 2Xtreme View Post
PERFECT!
I know the feeling!

It's not that big of a deal. Just set aside an afternoon, get a 12 pack of your favorite "soda" and be methodical.

Just don't lose the damn pin!


Shawn
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Unread 11-10-2013, 01:36 PM   #79
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WOW! I don't know what to say... Clearly the Centrifugal is coming 'In' at 1,200 on the first graph, and the second it's a little slower.

I don't know how flipping to 18 degrees on the advance head is going to delay the centrifugal in the second graph since that's not how it works...

Where are the vacuum readings for this vehicle UNDER LOAD?

Are you just tuning it to sit and idle at no load in the driveway, or just to rev up without loading/driving it?
If you want an ACCURATE advance curve map, then you might consider getting some vacuum readings at the distributor so you know what you are ACTUALLY working with when driving... Just a thought...
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Unread 11-10-2013, 01:41 PM   #80
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Hammer,

I agree, the advance under load and varying vacuum pressure is important. I was going there in time.

I was also going to get to messing with spring weights to adjust when the centrifugal comes in and how quickly it rises, if the OP desires that info.

My graphs were only for example purposes. I had to lighten the springs considerably to speed up the timing of the centrifugal "coming in".

Matt
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Unread 11-10-2013, 02:10 PM   #81
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Shawn,

This thread has reminded me how much I miss Terry (McMud).

It was fun having you two walk me thru this stuff.... concisely.

OK, Vince, where were we?

Matt
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Unread 11-10-2013, 02:17 PM   #82
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Quote:
Originally Posted by Matt1981CJ7 View Post
Shawn,

This thread has reminded me how much I miss Terry (McMud).

It was fun having you two walk me thru this stuff.... concisely.

OK, Vince, where were we?

Matt
I miss Terry, too. I really wish he'd had shared the fact that he was battling cancer and the meds were making him "off".

What can ya do...


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Unread 11-10-2013, 02:21 PM   #83
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Quote:
Originally Posted by swatson454 View Post
But I thought the centrifugal advance was supposed to be all in by 1,200, as per the self-imposed expert. Doesn't look to me like your stock curve even started to move until 1,600. What gives?
Yep, the stock curve was a joke. But, let's just stick with Vince's situation, for now. The results will speak for themselves.

For further clarification, the graphs above are the before and after results of flipping the advance head and lighter springs....and about 4 variations in-between.

Below is a video after I got the timing and carb dialed in.

Matt

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Unread 11-10-2013, 04:19 PM   #84
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Matt,

I don't suppose you still have my curve on file, do you? I lost everything last year when my computer died. Just curious...


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Unread 11-10-2013, 04:33 PM   #85
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Quote:
Originally Posted by swatson454 View Post
Matt,

I don't suppose you still have my curve on file, do you? I lost everything last year when my computer died. Just curious...


Shawn
I'm afraid it may have been purged. Sorry.

I do recall our final curves were remarkably similar, even though you were running an HEI and I a Motorcraft.

Matt
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Unread 11-10-2013, 04:44 PM   #86
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Awe, no sweat.

I remember the curves being pretty darn close as well. I've got a dinky photobucket graph that's probably too small to look at and "somebody" was drinking and was off a few degrees towards the top end but hey, what can I say, right

As long as it's all in by 1,200 rpm. And we all know that those carb boosters flow at 800 rpm.
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Unread 11-10-2013, 04:49 PM   #87
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I think this is close to being right but scotch may have another opinion. I know you made a larger version for my dumb arse but it's gone now. Either way, it sure isn't all in by 1,200

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Unread 11-11-2013, 05:15 AM   #88
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....This thread has reminded me how much I miss Terry (McMud).
This thread reminded me how much I miss Facebook........
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Unread 11-11-2013, 05:21 AM   #89
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Vince,

If the timing numbers you posted were with the vac advance connected to manifold vac, then you may be fine at those settings.

If the vac advance was disconnected and plugged, then you still have some work to do.

Matt
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Unread 11-11-2013, 06:03 AM   #90
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Quote:
Originally Posted by Matt1981CJ7 View Post
Vince,

If the timing numbers you posted were with the vac advance connected to manifold vac, then you may be fine at those settings.

If the vac advance was disconnected and plugged, then you still have some work to do.

Matt
I'm sure the 3000 rpm was set with vac advance disconnected and plugged.
I think the 700 was with it connected to manifold.

I say this because I followed your advice here:

Quote:
Originally Posted by Matt1981CJ7 View Post
....IMO, you should strive for 30-35 degrees total at around 3000 RPM.....

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

Matt
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