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WOW, advance spring difference

400 views 6 replies 2 participants last post by  unhumen 
G
#1 ·
Well, after reading all the threads I could find and asking a couple of questions I finally took the plunge and tackled the daunting task(or so I thought) of putting the lighter advance springs in. Wow, what a difference on acceleration! And, what an easy job to put in. I thought I might have to pull the distributor(which Ive never done b4) and risk screwing something up, but other than using a small gear puller for the trigger wheel it just took popping off the cap, taking the rotor off, undoing 2 screws on the plate, and there they were! Sorry if this seems silly to you veteran ignition gurus, but electrical ain't my bag. Anyways, I haven't tried it out at freeway speeds yet, since I just put them in, but I get much quicker acceleration and response than b4. I highly recommend this simple modification!!

donnerparty
 
#2 ·
I understand your enthusiasm, but don't try to sell this as a home game just yet!!

You must make sure you are not having detonation now that you have changed the ignition curve (bringing in the centrifugal advance sooner in the RPM range by using lighter springs).

Bringing in the advance sooner will make the engine much more responsive, but you must listen closely for 'Pinging', 'Knocking', 'Spark Clatter', .... You know, Detonation...

You can also keep an eye on your spark plugs, look for little 'Balls', especially if they are purple.
Look for cracked or broken porcelain around the electrode.
Look for any mis shaping of the center electrode.
Look for any mis shaping of the 'Ground' electrode, including bending, won't hold proper gap, little pieces 'melted' or 'gouged' out, and watch for the square edges to be rounding off.

These are all signs of detonation, and the problem must be corrected immediately!
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So many cats, so few recipes...
 
G
#3 ·
Thanks Aaron, the pinging I'm listening for. I'll keep an eye on the rest of it also. I'm going to be experimenting with the timing and plan on retarding it just below where the pinging starts. Does that sound about right? Thanks again, Ritch

donnerparty
 
#4 ·
Depending on when the detonation happens....

If it happens during low RPM (under 3,000 RPM) acceleration, with no heavy loads, try installing one spring a little heavier than what you have now.
If the pinging happens under low RPM cruse, (highway speeds, around 2,200 to 2,800 RPM in high gear) it's a load thing, and you will need to experiment with timing curve to eliminate it.
Load, RPM and vacuum readings are everything when doing a timing curve.

The general rule is...
Take the timing up until you start to get 'Knock'....
Back the timing off until the knock is eliminated, then back off 4 more degrees.

The reason for the extra 4 degrees of retard is there is detonation going on you can't hear, all things being even, this should eliminate it.
One of those $75 dash mounted knock sensors is a wonderful thing when you are recurving an ignition for the first time...
(Just like a $100 Rich/Lean Dash mounted indicator is a wonderful thing when you are tuning a carb, worth it's weight in gold!!)

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http://www.jegs.com

So many cats, so few recipes...
 
#5 ·
Hey TR good to see you back
I have a slight knock in my 258 with the motorcraft distributer that is driveing me nuts.I did the TFI upgrade without the MSD although I have one sitting in my project box.I am not blameing this knock on the TFI just giving as much info as I can.
the knock does not start untill the temperature hits about 140* and the CTO switches from manifold to ported vacume,and it does not knock at Idle appx.750 RPM the knock starts at about 1000 RPM after the ported vacume kicks in .It goes away at higher rpms, but will do it when it hits about 1000 RPM during acceleration.
I have tried regapping the plugs,retarding the timeing,I have not tried changeing the springs yet but have considered it,I also discovered a slight leak around the Accelerator shaft on the carb.but right now I am chaseing my tail trynig to figure this out it has been going on for a while.I don't know that it is or is not a rod knock,or the carb or the ignition.
Well if you see this any info would be appreciated.
TIA


Ray
Learn to let go of what does not serve you ,but forces you to serve it
why does everyone ask if I am gonna paint it ?
 
#6 ·
Look for vacuum leaks before you go any further.
Sounds like you may have a vacuum leak in transition that is overcome in higher RPM.

Other wise, your guess is as good as mine....?

So many cats, so few recipes...
 
#7 ·
Thanks TR
I am looking into another carb ,The overall manifold Vacume is pretty good .So I am thinking the Accelerator shaft ,I have yet to check it thoroughly just going around in circles .

Ray
Learn to let go of what does not serve you ,but forces you to serve it
why does everyone ask if I am gonna paint it ?
 
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