Classic Mustangs List Archive

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Mail From: ffacker (Fred Facker)

After all the backfires through the carburetor earlier
in the month, I replaced the coil on my '66 289, c-4,
600 cfm Holley, with an Epoxy Pertronix coil. The car
runs well at low speeds, and has not backfired through
the carb since I swapped the coils again. (Although,
the wire did pop off the new coil within the first 10
minutes I had it on the car, which caused some major
backfired through the tail pipe, but that was my own
fault for not making sure the wire was on well.)
However, once I hit 60-65 mph if I push the gas pedal
more than about a quarter of the way down, I start
getting the "clackity clackity clackity" of the
knocking/pinging. I can maintain speed or accelerate
slowly above 60-65, but forget about just putting the
pedal down and going.

Does this sound like I need to:
a) retard the timing
b) turn down the vacuum advance
c) increase the size of my secondary jets
d) other

I'm really liking where the timing is set at low
speeds because the car is running so smooth when I hit
the brake I worried the engine has died because it's
not bouncing around like it had been, which makes me
think maybe I'm just getting too much advance at high
speeds?
Also, if it sounds like the jets, how do I identify
what size the stock jets are, so that I can buy the
next size up?

I'm so close to fixing this thing, but it's causing me
major headaches.

This read-only message was archived from a public mail list.
Mail From: RFedd ((email redacted))


sounds like a lean condition. Either back off the timing a couple of degrees
or ad some more fuel.

Ron

In a message dated 9/30/2004 12:30:45 PM Pacific Standard Time,
(email redacted) writes:

I'm so close to fixing this thing, but it's causing me
major headaches.




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Mail From: kennethsteinbach ((email redacted))

I haven't read all the messages in this thread so I don't know exactly what you've done as far as timing, but the general rules of thumb regarding timing are as follows: What you really need is a custom timing curve. The original advance curves back in those days generally had too little initial advance, too slow an advance rate, either too little or, in some cases, too much total centrifugal advance, and too little or too much vacuum advance. A bandaid to perk up the bottom end is to advance initial timing, but this of course increases total centrifugal advance and you end up with high speed/load preignition. A typical performance advance curve would have about 12 degrees initial advance and 36 degrees total all in by 2500-3000 rpm. Added to this would be maybe 6-10 degrees of vacuum advance. A typical factory curve is 8 degrees initial, 30-34 degrees total, all in at 4500 rpm, and as much as 15-20 degrees vacuum advance. The solution is either to have the distributor curved by a pro, install an adjustable aftermarket distibutor, or install an advance kit in the one you have. The kits consist of different tension centrifugal advance springs, different distributor advance weights, and an advance limiter so that you can run more initial advance without overadvancing on the topend. OR you could do what I've been doing the last three years on my Supra Turbo, go 21st century and do all this stuff via your laptop.

-------------- Original message --------------

> After all the backfires through the carburetor earlier
> in the month, I replaced the coil on my '66 289, c-4,
> 600 cfm Holley, with an Epoxy Pertronix coil. The car
> runs well at low speeds, and has not backfired through
> the carb since I swapped the coils again. (Although,
> the wire did pop off the new coil within the first 10
> minutes I had it on the car, which caused some major
> backfired through the tail pipe, but that was my own
> fault for not making sure the wire was on well.)
> However, once I hit 60-65 mph if I push the gas pedal
> more than about a quarter of the way down, I start
> getting the "clackity clackity clackity" of the
> knocking/pinging. I can maintain speed or accelerate
> slowly above 60-65, but forget about just putting the
> pedal down and going.
>
> Does this sound like I need to:
> a) retard the timing
> b) turn down the vacuum advance
> c) increase the size of my secondary jets
> d) other
>
> I'm really liking where the timing is set at low
> speeds because the car is running so smooth when I hit
> the brake I worried the engine has died because it's
> not bouncing around like it had been, which makes me
> think maybe I'm just getting too much advance at high
> speeds?
> Also, if it sounds like the jets, how do I identify
> what size the stock jets are, so that I can buy the
> next size up?
>
> I'm so close to fixing this thing, but it's causing me
> major headaches.
> _______________________________________________
> Classic-mustangs mailing list
> (email redacted)
> lists.twistedpair.ca/mailman/listinfo.cgi/classic-mustangs
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Mail From: W427 (David)

Your vac advance should decrease timing when you add more throttle and
the vac drops. Disconnect and plug your vac line and test. If it does
not ping on cruise accel like before, you have the line on the wrong vac
source and it's working backwards. Otherwise you may have incorrect
total timing or incorrect power valve (lean) or lean jets. If it was a
lean jet problem you should have felt slight surging at stable cruise
before now.

I would not turn down the vac advance because you weren't pinging at
stable cruise where it gave you max advance; but be sure it's on a
ported vacuum source or if it's a dual diaphragm or leads to a vac tree
that the hose routing is correct.

If you do a Google search you can find sites that get very involved with
ignition timing, distributor advances, etc. Good luck Fred.

Fred Facker wrote:
> After all the backfires through the carburetor earlier
> in the month, I replaced the coil on my '66 289, c-4,
> 600 cfm Holley, with an Epoxy Pertronix coil. The car
> runs well at low speeds, and has not backfired through
> the carb since I swapped the coils again. (Although,
> the wire did pop off the new coil within the first 10
> minutes I had it on the car, which caused some major
> backfired through the tail pipe, but that was my own
> fault for not making sure the wire was on well.)
> However, once I hit 60-65 mph if I push the gas pedal
> more than about a quarter of the way down, I start
> getting the "clackity clackity clackity" of the
> knocking/pinging. I can maintain speed or accelerate
> slowly above 60-65, but forget about just putting the
> pedal down and going.
>
> Does this sound like I need to:
> a) retard the timing
> b) turn down the vacuum advance
> c) increase the size of my secondary jets
> d) other
>
> I'm really liking where the timing is set at low
> speeds because the car is running so smooth when I hit
> the brake I worried the engine has died because it's
> not bouncing around like it had been, which makes me
> think maybe I'm just getting too much advance at high
> speeds?
> Also, if it sounds like the jets, how do I identify
> what size the stock jets are, so that I can buy the
> next size up?
>
> I'm so close to fixing this thing, but it's causing me
> major headaches.
> _______________________________________________
> Classic-mustangs mailing list
> (email redacted)
> lists.twistedpair.ca/mailman/listinfo.cgi/classic-mustangs
>

This read-only message was archived from a public mail list.
Mail From: ffacker (Fred Facker)

Kenneth, thank you so much for explaining the timing
curve. I've sat and read my 66 manual, but still had
no real understanding how the centrifugal and vacuum
advance all tied together. I thought the vacuum
advance was increasing advance as speed increased, but
I see that's the opposite, so I'm glad I didn't go
adding washers or bending springs before I consulted
the list.

I am getting slight surging while cruising at about 60
mph. I guess that means I should up the jets one or
two sizes.

When I order the jets, will they come with
instructions or do I need to go buy a Holley book to
learn to change them out?