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Discussion Starter #1
My initial advance is set to 15 deg. with the vacuum adv. disconnected and the carb. port blocked off. At 3000 rpm the advance is 46 deg. Does this seem too high? If I try to bring the initial advance down any lower the engine knocks, or if I drop the idle rpm down much below 800 I get a knock. It seems that total advance should be in the mid 30s with an initial of around 10 or below. Am I off base here?
MSD pro dist., AFR 195 heads 72 cc, 10:1 comp., Ext. Energy 268, Dommed forged TRW pistons. 170 psi.
 

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I can't even begin to take a guess as to why your mill knocks when you reduce the timing or lower the idle. When you say knock are you refering to run-on or detonation (pinging) or? Can you go into more detail, rpm this happens at, when under a load or when shutting it off?

As for your distributor it has 31 degs mechanical built into it (46 total minus 15 initial). Sounds like it's been played with and needs to be played with some more and limited to about 20 degs of mechanical movement.
 

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Discussion Starter #3
It knocks when the rpm drops below 700,either because I have tried to retard the initial advance below 15 or because I drop the curb idle below 700. This is under a no load condition. How do I change the built in advance of the dist. The dist. is brand new. Ther is no detonation when I turn the ignition off.
 

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I am imagining that your statement of 170psi is that of the engines cylinder pressure.

You are getting to the ragged edge of being able to run pump without detonation (a 170psi with poor timing control is a bad thing). I would say it is paramount to get the timing issues resolved. I agree with Dennis, it sounds like the mechanical advance springs might be the first place you should screwtinize. Pop the cap and rotor and use the MSD supplied chart for configuring the springs, for the amount of and rate of advance.

But 15-16 initial is right about where you want to be.....
 

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Discussion Starter #5
I'll look at the chart your speaking of. and get the timeing problem fixed first. I;m running 91 oct. now. Do you think I should add some octane booster to that?
 

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If you get the timing dialed in, you should be OK.....but precise timing control is going to be the key in your engines longevity. I see that you stated an MSD distributor, this is a good thing, as they are pretty soild in maintaining accurate timing.

You wont really know if you will require an additive or not until you get the timing rock solid. Maybe.....maybe not..... tough to say without 'seeing' the total package.

But I will say that 180-185 is the upper limit on 91 pump gas and that is with using MSD's Digital 7 Programmable......My last power plant was a small block making 600+ish HP on 91 pump and the only wat I got it to live was with the Digital 7 Pro. on 91 R/M octane without additives.
 

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Have you checked to see that the proper advance stop bushing is in place. MSD gives you several bushing thicknesses to control the total amount of advance. Sounds like your bushing may be missing.
 

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Some timing lights won't work right with an MSD.
I think the dial back type are worse in some cases.

I like a plain timing light with timing tape or degeed balancer.
David

Here is a quote from the MSD website:


Timing Fluctuations
<http://www.msdignition.com/images/5pixspa.gif> If your timing seems to be jumping all over the place, check the following items:

* What kind of timing light are you using? Many lights have trouble reading the MSD's capacitive discharge multiple sparks. Dial back timing lights are not recommended. Try another non-adjustable light and check the timing again. MSD offers a Timing Light, PN 8990.
* Make sure you are not using Solid Core wires.
* Inspect the routing of the Magnetic Pickup Harness. It should be routed clear of the coil primary wires and plug wires. It is best to route it along a ground plain such as the firewall, frame or engine block to form a shield around it.
* Check the polarity of the magnetic pickup wires of the distributor. Reverse the connectors and check the timing again. The correct polarity is whichever connection gives the most retarded timing.
* On Chevrolet engines, if the timing is retarding 10 - 20 degrees inspect for cam-walk. This is especially prevalent on engines with a chrome or stock timing chain cover that is actually bowing forward allowing the cam to "walk".
 

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Make sure your H/B didn't spin.When the keeper is at 12 oclock. 0 is at 11.Or check it with #1 cylinder.Mr. :cool: Nick
 

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Discussion Starter #12
Thanks for all the advice:
I did have some arcing on my plug wires to the MSD primary coil wires. After I cleared that problem up I was able to get a good timeing base line set up. I;m using a Craftsman timeing light with a variable timeing dial. At 3000 rpm now I get 38 deg. of advance at 3000 rpm.
 

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Discussion Starter #13
I'm kind of new to "The Team Camaro" site but I appreciate the responces I got for my questions about my timeing problems.
 

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I've heard it here enough times, plus seen it myself with a friend setting timing with a dial back light, - couldn't do it.

Make sure the plug wires are the spiral core type when using an MSD unit.
David
 
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