can't get rid of pinging - Team Camaro Tech
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post #1 of 14 (permalink) Old May 11th, 00, 12:29 PM Thread Starter
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Hi Everyone, I have a '68 RS convt. with a 350(mid '70's), HEI, edel.600 carb., stock exhaust, cam, and turbo 350. First off, I don't have a timing light or access to one at the present moment. Problem is car pings under WOT or under a load. If I retard it where it doesn't ping, then it won't start like its out of gas. Advance base timing(dist) and it starts fine but pings like crazy. The best I have been able to get it is with light weights in the dist. with the heaviest springs I could find. Starts like timing is retarded(spits back through carb sometimes with white smoke) and bangs out about 4500 rpm. If I advance the timing where it doesn't bang out, pinging sounds like its coming through the hood. I have read every post on timing on this page and can't figure it out. Have I overlooked something simple or has anyone heard of this? Thanks for your help

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post #2 of 14 (permalink) Old May 11th, 00, 12:48 PM
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I had a similar problem with my 355 sb. Pinging at WOT under load. I tried all kinds of weight/spring combos and adjusting the base timing. Had to go all the way to TDC to get it to soften up. Then the car wouldn't run worth a crap at idle.

Turned out to be the bushings in the disributor. Timing was jumping 6-8 deg at higher RPM's. I ended up boxing up the orig. dist. and went with a R-to-R MSD billet distributor. NO more pinging. Plus..no more points and a fully adjustible curve (and limit).

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post #3 of 14 (permalink) Old May 11th, 00, 02:56 PM
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Rick,
Are you using a vacuum advance distributor ? If not, you probably should be. With a strictly mechanical distributor I do not think you can get enough low rpm / low load timing for good power without having too much advance at cruise rpm / high load conditions. Without a timing light, you are just wasting your time trying to properly set the ignition up. You can get a fairly decent one at Sears for $30 bucks or so.
Maybe Ignition Man can add more info to the problem.

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post #4 of 14 (permalink) Old May 11th, 00, 06:36 PM Thread Starter
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It is definately a vacuum advance dist. I even went and bought a brand new advance canister with only 10 degree advance. I understand about the timing light but my belief was that if you set the distributor where the engine cranks over fine every time even when hot, you are pretty darn close. I do plan to borrow a timing light today to be safe. But get this, me and the wife just went for a ride in it. Air temp is 73 degree, beautiful night, punched it going about 60 mph and it kicked down in 2nd with just a little ping and was hauling ***. Stopped and filled up with gas and when I took off and punched it, it started banging out about 4000rpm!!! And it did that all the way home. Sounds like something is sticking or not working all the time doesn't it? Thanks for your advice.

Richard
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post #5 of 14 (permalink) Old May 11th, 00, 06:48 PM
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rickelo - can you discribe what you mean by "banging out"? Is it a loud popping and loss of power at 4000? Could be a valve train problem!

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post #6 of 14 (permalink) Old May 11th, 00, 07:03 PM Thread Starter
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more like a backfire through the carb...if i get out and advance the distributor, it doesn't bang out but pinging is worse, i guess because of too much advance timing. when i retard the distributor to rid the pinging, i can rev it up in the yard and soon as the 4-barrel starts to open, it starts backfireing. at first i thought it was a worn lobe on camshaft, but it seems if that was the case, it would bang out all the time. i know this is weird but hope it helps.
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post #7 of 14 (permalink) Old May 11th, 00, 08:58 PM
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OK, teen-agers, here is the classic HEI over-advancing/vacuum advance on ported vacuum source ping thing.

Start by having the mechanical curve set up to give 12 degrees in the distributor/24 degrees crankshaft mechanical advance. Shoiuld start about 900 rpms, limit at about 2500/2800 rpms.

Your 10 degree vacuum cannister is OK, but you need it connected tro full maniflod vacuum, not ported. Ported vacuum advance will add timing to the top end rpms, just where you don't need it. full manifold vacuum will draw the vac advance in at idle to help stabilize the idle pull against a torque converter, will drop off when the throittle is opened.

With all this done, set the initial idle timing at 12 degrees, then when done, connect the vacuum advance.

Your total mechanical degrees will be:12 initial, 24 added mechanical = 36 degrees.

Iintial idle timing is 12 degrees plus the supplemental vacuum advance of 10 = 22 degrees, just fine for an early 350 engine.

HEIs will over advance big time if not recurved, and if the vacuum advance is connected to ported source, then watch the ping monster take over the engine.

Give it a shot, should keep the detonation meanies away.

[This message has been edited by IgnitionMan (edited 05-12-2000).]
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post #8 of 14 (permalink) Old May 12th, 00, 11:33 AM
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Is this also true for a non HEI distributor?
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post #9 of 14 (permalink) Old May 12th, 00, 02:43 PM
 
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<BLOCKQUOTE>quote:</font><HR>Originally posted by rickelco:
Hi Everyone, I have a '68 RS convt. with a 350(mid '70's), HEI, edel.600 carb., stock exhaust, cam, and turbo 350. First off, I don't have a timing light or access to one at the present moment. Problem is car pings under WOT or under a load. If I retard it where it doesn't ping, then it won't start like its out of gas. Advance base timing(dist) and it starts fine but pings like crazy. The best I have been able to get it is with light weights in the dist. with the heaviest springs I could find. Starts like timing is retarded(spits back through carb sometimes with white smoke) and bangs out about 4500 rpm. If I advance the timing where it doesn't bang out, pinging sounds like its coming through the hood. I have read every post on timing on this page and can't figure it out. Have I overlooked something simple or has anyone heard of this? Thanks for your help

rickelco
<HR></BLOCKQUOTE>

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post #10 of 14 (permalink) Old May 12th, 00, 03:55 PM Thread Starter
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It is connected to manifold port now. I'm pretty sure its the port on the left side of the edelbrock 600 if standing in front of the car. When I connect it to the right side, it pings even worse. The first dist. I had put in it had a stuck advance which I found when I pulled it out. Are the weights supposed to pull back in tight against the stops when you pull them out by hand or are they still a little loose? I'm beginning to wonder if the bushings in this dist. aren't worn. Right now it starts fine, but pings on WOT. Plus, besides the pinging, it bangs out, like spitting back through the carb about 4000 rpm. If I advance the dist.(base timing) a couple of degrees, its harder to turn over, pinging is worse, but it doesn't bang out and hauls ***. But I don't like that pinging and I know it is harmful to the engine. I have a set of heavier weights....should I try those?
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post #11 of 14 (permalink) Old May 12th, 00, 04:37 PM
 
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hope you dont "BANG OUT" a pushrod or a worse yet valve. keep up the huntin youll find it good luck
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post #12 of 14 (permalink) Old May 12th, 00, 05:11 PM
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Hey IgnitionMan, do you have a shop that we LA locals can patronize?



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post #13 of 14 (permalink) Old May 13th, 00, 12:05 PM
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I'm wondering if this is running way to lean. Maybe a vacuum leak under the carb base or something. Lean mixture will really raise hell causing this type of problem sometimes.
These Edelbrock carbs are jetted pretty lean out of the box too.
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post #14 of 14 (permalink) Old May 13th, 00, 02:28 PM Thread Starter
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I did change the springs in the top of the carb to the next hardest ones. Not sure, but I think that is supposed to make it leaner. It was smutting up the rear valance panel out of both pipes so I figured it was running rich. You could smell it also. The spring change seemed to help that problem but that was before the pinging

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