Stupid ignition timing thing!

[82LTDQS]

Yeah, Im usuing an HEI what unknown weights and settings.

[sly]

That never stopped any CVN members.

go figure... I'm not a CVN member.

[GM_Guy]

Retard your timing until the ping (which is what I assume you mean when you say knock - shaking pebbles in a can type noise) goes away. Ignore the timing light for now. After the ping is gone, or only comes back occasionally under specific conditions, get out the timing light and see where things are. If you can't find any mark, or it seems to be an impossible number the outer ring of your balancer has probably walked which is causing you to set your timing to a value other than what you think you are setting it at.

Now, if you actually mean knocking, you may be looking at a bad bearing somewhere.

That hole is for a fancy-ass timing light with a pickup that drops in the hole

Alex.

[82LTDQS]

Thanks GM Guy. I like that, Home grown Instructions. Thats what working on cars is about. Will do.

I did mean ping. Not knock.

[gadget73]

I have actually seen cases where the only way a motor will stop pinging is to set the timing to some stupidly late value, and it wasn't a spun balancer. Grossly wrong carb jets will make for a lean fuel mix, which will make things ping. Its gotta be pretty bad for that to happen though. An engine that runs extremely hot will also be inclined to ping, but if you aren't running over 220 degrees, thats likely not a factor.

[import convert]

when i used the proform HEI i couldnt have it set past 6* base with 93 octane. i had a rich holley 600 and a ford E cam on the motor. it sucked but with a stock distributor with sinlge vacume advance and an explorer cam ive been fine with 89 octane and like 9* base. i think the HEi dizzy advances too quick and/or has more advance built into it then stock dizzy does

[1987cp]

Um, not to belabor the obvious, but those two setups are liable to perform like completely different engines!

Your distributor will have the advance curve YOU give it. If you don't like it, get some recurve supplies and try something else. Or hire someone who knows more than you do and ask him to do it. Either way.

Many stock-spec Duraspark distributors seem to have came equipped with HEAVY advance springs, which means a SLOW advance curve. I haven't studied exhaustively, but it seems we're usually advised that this is a BAD thing from both performance and economy perspectives. So my tentative conclusion at this point is that when tuning with a Duraspark distributor, two important things to do are to (a) know your total advance (which may not be the same as someone else's engine likes) and (b) get some lighter advance springs.

[import convert]

yea i figured that out eventually. after i read that the vacume advance can be tuned to youre setup i figured that the vacume advance on the HEI distributor was set with too quick of an advance or too much advance. the car was great at full throttle but partial throttle itd ping. i got nothing like that on the duraspark distributor

[1987cp]

I was talking about centrifugal advance, not vacuum advance. My approach has become to usually disconnect the vacuum advance and leave it that way.

[gadget73]

The centrifugal advance is more important overall, vac advance is mostly there to give a little bit of part throttle economy. It can screw things up though so you have to be careful with it, or limit how much additional timing can be added with the vacuum can. Or just leave it unhooked if screws things up too much. The mechanical curve has to be approximately right though. The stock Duraspark curve is probably exceptionally conservative for durability reasons. Not quite enough timing costs you horsepower, not pistons like too much timing will.

[1987cp]

I tried screwing with a couple of vacuum advance canisters a few months back. Tried both of them on the same engine without changing anything else. It seemed weird to me at the time that the two canisters' adjustment ranges didn't seem to overlap, and that they seemed to respond at very different vacuum levels. After deciding that I had lots more to learn about spark timing and vacuum advance's relation to varying vacuum levels (ported or manifold, depending on where you choose to hook yours up), I decided that it didn't really drive any worse with it disconnected and finally gave it up entirely.

[gadget73]

yeah there is a lot of variation in those cans. Unfortunately their characteristics seem to be very poorly documented so I have absolutely no idea how you even pick one unless its a case of randomly finding one that works properly for you.

[91waggin]

Efi ftw

[Gsmagnum]

I am not sure how your distributor is set up, but on a Mopar, there are slots that generally need welding up to limit the mechanical/centrifugal advance. It might be money well spent to take your distributor to a shop that does recurving.
I think that part of the issue is that the ignition on 70's and 80's cars is so retarded, that they add way too much advance for having the initial timing bumped into the 8-12* advanced range.
Not an expert here, but I am thinking that you should either take it in to have it curved for your specific application or do some searching to find more info to do it yourself. I am thinking there should be a magazine article somewhere giving you a better clue on it.
Otherwise back it off from pinging as described above and live with it. (been there, done that)

[gadget73]

He's using a Chevy HEI distributor. On those, the center plate limits the advance, the weight of the actual weights and the springs used messes with where it comes in. On a Duraspark distributor, it has plates, probably like a Mopar distributor. Usually you flip them over to get a different advance limit. There are 2 or 3 different plates, each with 2 notches for different advance limits. Springs are changed to alter where the timing comes in.