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Discussion Starter #1
Ignition man,

I am hoping you could give me some advice on my situation. I am getting a pinging when I drive the car above 2500 rpms. Let me tell you what I have done so you can hopefully correct me on something.

I have set the initial timing at 8 degrees btdc with the vaccuum advance disconnected(stock point distributor). Once that was set up I buttoned down the distributor and connected the vaccuum line to the full vaccuum sourse(driver side of an edelbrock#1406 carb)my total advance is 33 [email protected] rpms. I checked how much the mechanical advance actually advances: 15 [email protected] rpms. I dont know when the stock vaccuum advance drops off.

At these setting I am getting a pinging at 2500-2700 rpms when the vehicle is driving.

please help- this is driving me nuts!
 

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I know I'm not the IGNITION MAN, but I have to add my two cents. Try an advance can with a lower amount and a heavier spring. Mabey sonething around 10 degrees. Most stock distributors come with a can that is from 15 to 18 degrees and comes in too easily for todays premium.

[This message has been edited by mutant 68 (edited 09-03-2000).]
 

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Discussion Starter #3
thank you mutant. i've been thinking of doing just what you've suggested but the thing that is bugging me is I cant imagine I cant get rid of the ping no matter if I retard or advance the timing. I just feel something is wrong. it is a brand new distributor so i dont think anything is worn. I have a friend with a chevelle with an almost mirror image setup as mine and he doesnt get any pinging. so that leads me to believe something is amiss. please help with some troubleshooting tips. thanx
 

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This may be something you already tried.
Try runing it with the advance disconected and the vavume port pluged. This will tell you if you have a problem with the advance can or not. If you have to much of a freeway flyer gear(2.73)it will be much more of a load against the motor(it has to work harder).You cant run as much with that type of a set up.



[This message has been edited by mutant 68 (edited 09-03-2000).]
 

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Discussion Starter #5
mutant- it is a 2.73 gear in the rear end(at least that is what the original gear would be
for this camaro)what steps can I take to rule the gear ratio out of the equation? I guess I'm still stuck on the thought that I see tons of older cars with original distributors high, gear ratios, in obvios worse condition than this car, but are able to drive on the freeway without sounding like a diesel engine. any steps someone can give me to walk through would be more than appreciated. thanx
 

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If it were me I'd slow down the advance curve and take a couple of degrees out of the mechanicle(so you do'nt get more than 36 at full advance without the vacuume advance). Full advance at 3200 or thereabouts and try that. Curve kits are avalable everywhere.



[This message has been edited by mutant 68 (edited 09-03-2000).]
 

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As a generalization, because we don't actually know the engine or performance level it was built to, you could do the kinda-sorta universal default fix-curves.

Mutant is right on many points.

I'd use a Crane 99601-1 adjustable vacuum advance and the spring set that comes with it (the part number listed is for the stock GM points tyoe distributors, an HEI takes a different Crane part number).

The vacuum advance should be set to add 10 crankshaft degrees total. Set it up on full manifold vacuum after you set the initial timing to 12 or so initial degrees at the lowest idle the engine will go to.

As far as curve for the mechanical advance, start with the blue and silver spring each.

Pull the distributor and set the end play to .010/.015, then look at the underside of the point cam. You will see a pin protruding through the slot in the plate. If there isn't a bushing on the pin, you may need one to close the total amount of mechanical advance movement. NAPA has the bushings available, DP101, and the dealer should be able to get them if they don't already stock one.

Now comes the tricky part without a distributor machine. You need to mark the balancer with three more lines, so place the balancer in the tdc position, make a mark at the 10 degree line, move the balancer to put the mark you just made on tdc, make another mark on 10, etc. Three extra lines will be 20, 30, 40 degrees as the curve comes up, and the lines will read the individual lines on the plate, IE, line 3 plus 6 is 36 total at whatever rpm it gets there at. Read this again a few times, it will become clearer. Makes a stock balancer into a poor man's degreed one. Timing tape does same thing, only easier.

I would start the mechanical curve at 900 or so rpms, and limit it at 2,800 to 3,000 rpms for a stock engine. There should be 24 crankshaft degrees of mechanical curve.

What you should end up with is something like this for a start. Initial timing of 12 degrees, 24 degrees added to the initial as total initial and mechanical (no vacuum advance connected) for 36 degrees. There should be a 10 degree rise in idle initial timing with the addition of the vacuum advance from the Crane unit when itn is connected to full vacuum at idle, giving a total idle advance of 22 degrees.

If you have a distributor machine available and somebody who knoes how to use it, that way is the easiest to do the mods.

Please post the particulars of your engine/drivetrain and useage, and we can alter the above to maybe fit better.

As mutant surmized, you now have too much mechanical degrees of advance, getting there too fast, which makes the initial want to be lower than it really likes, and a vacuum advance that has too many degrees in it to help also.




[This message has been edited by IgnitionMan (edited 09-04-2000).]
 

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Discussion Starter #8
here are the particulars on my engine/trans.

307 v-8
600 cfm electric choke edelbrok carb
performer manifold
1 5/8"headers into dual 2"pipes to glasspacks
stock point distributor
th350 trans
stock converter
2.73 gear ratio
autolite#24 spark plugs(2 heat ranges colder)
stock camshaft/lifters/rockers

i hope this info is helpful. thank you
 

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I performed the mods as spec'ed by IgnitionMan several months ago. It works. The car is much more responsive, idles significantly better, and not a hint of detonation.

I still have one question concerning the manifold vacuum source. Is vacuum from the manifold port (typically the #8 cylinder) acceptable or is it best to connect to the carb baseplate?

Thanks IgnitionMan

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Click here to see see my car and hear 5-speeds. http://www.geocities.com/casanoc
 

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Dwell for all GM window type point distributors is, and always has been, 30 degrees.

I would want to see the vacuum for advance purposes, taken as close to the throttle butterflys in the primary side of the carb as possible. Lets the diaphragm in the vacuum advance see throttle position change just that much quicker, so the reaction is as fast as possible.

If you simply cannot find a source on the carb base, then the single runner take-off will do fairly well also..
 

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Discussion Starter #12
i'll have to get my hands on a vacuum gauge as soon as possible. i've got the crane adjustable canister&kit on order so i will be doing this work as soon as i get the parts. please keep watching for responses from me i will be in touch daily. thank you
 

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Actually, I make the small body original point distributors into a hybrid HEI, (not a PerTronix disaster), but a dedicated HEI, with point type cap, appearance and clearances, 4 prong HEI module and Ford/MSD pickup. Then, I don't have to worry about points "wearing" anything in, down, out or whatever.

Seems to me that if you let the points "wear in down to 30 degrees", you will have to reset the timing once the points stop acting up. If the dwell is set properly, at 30 degrees, and the timing is also set properly, the dwell could be restored by resetting the dwell while using a timing light to confirm proper timing. Another way to do it is if the dwell and timing is set correctly from the start, all one needs to do to reset the timing back to the initial position after the points wear in is to simply set the dwell back to 30 degrees, and the timing will come back in to its proper place.

I know this to be true, both methods, because that's the way points ignition systems and dwell works.

Anyone want pics of my HEI or MSD Trigger Pickup conversions, post your e/mail address here and I'll forward three pics to you directly, for your inspection. This is what I do for a living.
 

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Send me one too.

[email protected]

Question, can I use any big block points distributor or do I have to use my original one? I'm thinking about your conversion, but I'd like to set my original distributor aside.

Thanks


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'69 RS SS 396 375hp L78 Convertible, M22, 3.31 posi, deluxe interior, gauges, rosewood wheel, AM-FM,fold down seat, tilt wheel, SS wheels, console mounted 8 track player, chambered exhaust
 

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Ignitionman:
Please send me the pics of the HEI / MSD conversions.

[email protected]

I have been following all of this. Very interesting and informative. I have not had any problems to speak of with my '69 Camaro with 396 BB, but I'm about ready to get out the 'ol timing light and take a look at my ignition and timing setup.

Recently I did experience a little "pinging" or "clattering" noise under heavy throttle at about 3,000 on the freeway. I was thinking it was timing. But then I remembered that I had not been adding lead additive to my gas as I usually do. My motor is a '66 396 from a Chevelle. It has been built up a little by the previous owner and has DUI HEI ignition, 8mm silicon wires, Edelbrock RPM 750 cfm with electric choke and vacuum secondaries, and roller rockers. I don't know what the cam is. It's running the original iron Chevy heads that came with this motor.

Anyway, my "pinging" went away after I added lead additive to the gas. It seems to run fine now. But, after following these posts, I think I should check out my timing and ignition and total advance, etc.

Also, I am interested in your ignition mods and conversions.

Thanks. I enjoy your posts and information.
Jim
 

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I'm just going to take a stab at this, and I could be WAY off base. It seems to me, if you don't think retarding the timing will help much, because I'm guessing you've tried this, maybe you have mated the wrong timing cover and balancer. In other words, 0 degrees on your balancer's timing tab is not actually TDC for #1. I've heard of people having this problem before. I don't know what year this changed, but someone who does (I-man?) might be able to tell whether this is possible or not. Anyway, seems like maybe your timing is either WAY off, your compression is WAY up there (which I don't think is the problem), or the gas your using is HORRIBLE. Just my 2 cents. Take care.

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69 SSRS Frame-off Resto
81 Z-28 377ci Drag Car
 

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IgnitionMan, why do you refer to the Pertronix as a disaster? Is there something about their setup that you don't like? I've used it on a couple of cars in the past and they ran nice and smooth and no dwell changes to worry about.

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Jeff H - 93 Indy 500 Pace Car(supercharged), Hugger Orange 69 Z28 with JL8 brakes & crossram
 
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