addballer696

So I have a dilemma. Car is 1977 corvette l-82 with vortex heads and sidepipes. I wanted to re curve my Accell super coil distributor so i bought a mr gasket spring set. Tried out both gold springs (the heaviest) and was all in at 36 degrees at 1700 rpms. With 16 degrees initial timing. Throughout 1700-2400 rpm's is a very high pitched humming noise that I am assuming is pinging from such advanced timing. With the stock springs installed I'm all in at 1800 (not any better). I bent the springs to make them as stiff as possible and now im all in at 2100, still with pinging. I've never done this before but figured I'd read up from Lar's articles and try my best. As of now, I lowered the initial timing to 10 degrees and my mechanical advance is 30 degree's, as a temporary fix. Are there heavier springs out there? do i need lighter weights? The ones in there now are original to my knowledge. Any guidance would be greatly appreciated! Thanks

MelWff

the humming sound is in neutral or when you are driving?
you are using a dial back timing light?
you are sure your balancer has not slipped?
did you leave the stock weight in and just use the springs?
have you seen this?
http://www.arkansaspontiacs.org/tech...s/recurve.html

addballer696

I'm using the stock weights. The high pitched humming is in neutral. Can't really hear it when driving but the side pipes and cold air intake make it next to impossible to hear anything. Haven't checked Top Dead center but no reason to believe it's changed. I guess I'm not sure I can absolutely diagnose it as pinging since I've never been shown what that sounds like. I've driven for two years with the mechanical advance coming
In so early. Also it runs pretty horrible in anything below 40 but I'm guessing that has to do with the cold air intake.

MelWff

if you are hearing it in neutral it is not pinging. Use an automotive stethescope or even a piece of rubber hose to determine where the humming is coming from.
use your stiffest springs and using a dial back timing light with the vacuum advance disconnected set the total for 36 at 2100 if that is the highest you can do with the springs. Make sure you are using 93 octane gas.
pinging is a rattling sound not a hum.
concerning cold weather, any other changes to the car from stock other than the cold air? Original carburetor and intake?

REELAV8R

So you can observe that the initial is at 16* at idle and then observe it is at 36* by 1700 and this is with the vacuum advance hose disconnected and plugged?
Start with confirming the balancer is correct. If it's slipped then everything is off to start with.
If you are using an Accell super coil distributor then the weights are not stock GM perhaps?
Maybe the Accell unit came with heavier weights, but start by confirming your current numbers are correct.
You could also try doubling up a spring to see what effect that has.

Detonation sounds like a ball peen hammer hitting a chunk of steel repeatedly or bearings in a tin can at higher RPM's, not a humming noise.
Could be the humming is your balancer rubbing on the timing chain cover.

addballer696

Nothing in the car has changed. Its got an eldelbrock performer intake and a edelbrock 1405 carb.
Car is definitely not rattling so thats good. A 40 degree difference outside really makes it feel like a new car regardless if the engine is warm or not. Good thing i won't have to worry about that for a longgg time though. MelWFF Thanks so much for the insight.

addballer696

That is correct REELAV8ER exept I was able to modify the gold springs so now im all in around 2100, with the vacuum hose disconnected and plugged. Definitely haven't heard what you describe as detonation, but would it be possible to hear that driving with sidepipes and a cold air intake at the cowl area? Pretty sure the weights had 308 stamped on the them or some sort of number, but ill double check tomorrow and take a picture. Tried doubling up on springs, isn't possible. I'll also make sure the balancer is correct.

addballer696

balancer is correct. Its about 55 degrees today and the engine seemed a little boggy under acceleration (like it does when cold out) so I bumped up the initial timing to 21 degrees with all in at 41 degrees at 2100 rpm. Throttle response and power wayyy noticeably improved with no detonation. I'm also running 93 octane and compression should be around 10.5-11 to 1. Guess my baby just likes to run with high timing.

REELAV8R

That's a lot of timing. I guess if it was mine I'd be trying to figure out why I was reading so much timing.
What kind of cam (specs) are you running?
Mine likes lots of initial also but I limit the vacuum advance and the mechanical to prevent too much all in and too much at cruise.
All in should be in the 32* to 38* range and maybe 50* to 54* or so with vacuum at cruise.

As you said though give the engine what it wants if it runs better.