hi everyone.


i was told from a reliable source that a spark knock occurs when the engine is cold..
and a ping occurs when the engine is a operating temps.

basically my camaro... with a 305 carbureted.

in the mornings around 2500 rpms. light accel. id say about 20% throttle.
i get a pinging noise.
exeptionally noticable at WOT

after it warms up.. the noise is gone.
sounds exactly as a ping.
so what i have done is until the car warms up. i keep it under 2500. until she warms up.

anytime after it reaches 200 degrees coolant temp. you can WOT all day long without a noise.
but it only happens in the mornings.

would you all suggest to back down the timing.?

i chose a hot hot day. advanced the timing until it pinged at WOT driving.
and back off a few degrees until i didnt hear the ping anymore.

suggestions are welcome

 

not sure too much how all that works myself. but what you can do is start by changing the knock sensor located above the oil pan on the passenger side. it has a wire going to it. that MIGHT cure your problem. it helped mine. its like 30 bucks or so at auto zone. also might change your type of gas that you are using. maybe try a tank of premium. that could help as well. even though its much more expensive it might cure the problem as well. then i would start my retarding your timing too.

 

actually im running 93 octane.
and the motor is carbureted.
i performed a wire "tuck" for the lack of a better way to put it.
i got rid of allllll the wires i didnt except the generator wires and obviously the fan,12v wire for distributor and tach signal wire.

so im not running a knock sensor

 

Since you are running a carb and no knock sensor my best guess is you are hearing piston slap. When the engine is cold and the pistons are cold they will rattle around in the bore and it sounds like knock.

 

hmm
well either way. it doesnt sound like it should be there lol
but i backed down the timing and it went away..
but i guess my question is . if i were to keep it under the rpm that it makes tne noise at.
and it only happens COLD not when its hot
could i still take advantage of the timing being advanced and have a little more performance.
or should i just back it down completely to prevent anything.

the only reason it confuses me is because i dont hear it when its hot, and under a load.

 

Is your car still computer controlled? IF it is the computer may be adding in too much timing when it is cold causing the knock. I burn my own chips and the stock timing is aggressive when the engine is cold. Once it reaches around 120 degrees the timing backs off some.

 

no its no longer computer controlled.
swapped in a stand alone hei distributor

 

one thing to consider is when you can actually hear the pinging or knocking it means you have a bad problem. an engine can and will ping or knock without you being able to hear it. Ask anyone who dataloggs. I have seen my knock count go over 100 in just a few minutes of running( when i had my TBI still on) while data logging but i could not hear anything.
What is ur base timing set at? what kind of advance are you using mechanical? or vacumm? and have you tried changing the weights or springs in the dissy?

 

"Spark knock" and "ping" are the same thing. The ignition is lighting the mixture too soon. Detonation is arguably a different situation, where the mixture is being lit by something other than the spark.

Advancing the timing until you get pinging and then backing it off a couple of degrees is a poor way to set timing. SBC's are pretty consistent about liking 34-36 degrees total mechanical timing at WOT. From there, you tailor the mechanical advance curve for proper starting and to bring it all in at an RPM appropriate for your cam.

The other factor is the vacuum advance - you can get adjustable vacuum cans that allow you to turn back the advance so you don't get that light-load pinging.

 

ok thanks five7kid.

i have vacum advance

the only problem is that the bottom end was already built when i bought it

according to the original owner it has a performance cam in it.
you can hear it, sounds lopey

and the timing is god knows where.

my next project is going to be to take the timing cover off and make sure myself where tdc is and get a correct timing tab.

after that i can find out where my timing is..

what should my base timing be??

and i did not touch the springs in the dizzy.

it sucks because i would love to take full advantage of how i can control the advance at wot.

but i dont know the specs of the cam...

if it matters the car as ALOT of top end power. alot

 

If you have the time and money a depth gauge and degree wheel can be used to determine the most of the cam spec like lift and duration that may help you but it willbe kinda of costly and time consuming and you have to know how to use the equipment but I'm sure if you did a search of the forums you could find out how to do it. I'd recommend it if ur gonna go as far as to take of the timing cover. You can then degree the cam which is the only real way to be get ur timing truely accurate.
Base timing stock is 8 deg but depending on the setup people will run anywere from 4 to 10

 

Check your timing first or run a higher grade of octane. Also there is on some HEI, if I remember correctly, an internal adjustment accessed from the outside of the distributor with an Allen wrench. The directions may tell you the initial setting and what to do if there is pinging.

 

dont i need an adjustable cam sprocket if i want to mess with the cam timing??

i know it has a double roller timing chain.
and i dont think its adjustable.

checking the cam sounds a bit time consuming. but ill search on it.

a friend of mine told me to actually time the cam at 4 degrees to get "*** loads" of torque.