73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: enaberif on April 25, 2009, 05:10:56 pm
-
Ok I'm not sure whats going on with my truck I'm going to give some run down on it. Its a 1980 that was purchased and has a 305 motor in it. I've changed the plugs, cap, and rotor already.
When I drive around everything is fine but once I put some load on the motor I can hear a knock/tick/ping I'm not sure which.
I've checked the valve lash and its fine, I've swapped out the exhaust manifolds to the block for new ones and there isn't any donuts needed connecting muffler pipe to manifolds.
So now today I went outside popped the cap off the distributor to check where the rotor was pointing and its pointing in the right direction but one thing I've found is that when I plugged the #1 spark plug so I could hear air bypassing when the air stopped I looked at my harmonic balancer and notice that the timing mark was at around 12-14 degrees TDC.
So does this mean I'm perhaps going to have to get a piston stop now and figure out where TDC is on my harmonic balancer? Or do I perhaps have a problem elsewhere internally?
Remember it only makes this knock/tick/ping noise when its under load.
-
Set the ignition timing first
-
Set the ignition timing first
Ignition Timing? I'm unfamiliar with this?
Only timing I've ever done is while the truck is running with a timing light. Is this the same thing?
Because whether I'm at 8 degrees or 12 degrees the noise is still there.
-
The ignition timing is what you are observing with a timing light. So, yes, it is the same thing.
-
The ignition timing is what you are observing with a timing light. So, yes, it is the same thing.
Yup then it don't matter what I do.. advance.. retard I still hear the noise.
I'm going to get the oil changed tomorrow and put some 10w40 in and see if that may help.
Otherwise I think I may have either a) very odd exhaust leak b) valve train noise
-
Can you hear it when you rev up the engine without a load on the engine?
-
Can you hear it when you rev up the engine without a load on the engine?
Negative.
If I put my foot on the brake and rev it then I can. Otherwise no.
Trust me I'm just as baffled as this as probably other people!
The other thought I had was the exhaust manifolds aren't the proper ones for my truck... but then I don't know what ones ARE proper.
-
Are you timing it off of the balancer? Verify TDC with #1 piston all the way up. Remove the #1 plug and watch it hit tdc with a flash light or long piece of mechaincs wire etc. Verify the mark is TDC.
Tell us how you are setting your timing.
-
Are you timing it off of the balancer? Verify TDC with #1 piston all the way up. Remove the #1 plug and watch it hit tdc with a flash light or long piece of mechaincs wire etc. Verify the mark is TDC.
Tell us how you are setting your timing.
Yes off the balancer.
I let the truck warm up unhook the vac advance (plug it up) then hook the timing light up and check where the mark is in accordance with the timing tab. I've tried it between 8-12 and its made no difference.
With using the wire or something that will fit in the plug hole I just spin the engine and when it stops by the object the mark on the balancer should align with the 0 mark on the tab?
-
No, you want to see it actually come all the way up before it goes back down. Don't confuse it with a positive stop.
-
I know this is a shot in the dark but could it be your u-joints? Just last week I was trying to track down a "tick/ping" only under pressure that had me pulling my hair out. I checked all loose trim on the body panels, parking brake cables rattling against the frame and through brackets, and checked all the fluids. I put the truck up on stands to tried to replicate the sound. I still couldn't find it. I found a leaking pinion seal and replaced it along with all the gear oil. The sound was still there. With the window down, it sounded like the sound was coming from behind my seat. With the window up, it sounded like it was coming from right outside the window. I know that sound travels wierd so I wanted to check everything. It was getting late and Auto Zone was going to close soon(Sunday) so I ran to pick up a pair of u-joints. They weren't loose or anything but I wanted to rule them out as they were the original u-joints that came with the truck(still had the melted plastic used to lock in the caps). That did it! My "tick/ping" was gone! Hope this helps or are able to rule out something.
-
No, you want to see it actually come all the way up before it goes back down. Don't confuse it with a positive stop.
I'll try. That side of the engine bay is a bit harder to navigate then the other hehe.
I assume at the point where it reaches the top and just before it goes down is TDC for #1?
-
spark knock is from timing being to far advanced just turn it down a bit and try her
-
spark knock is from timing being to far advanced just turn it down a bit and try her
Like I've said I've tried between 8-12 and it does the same thing.
-
try more lol just trying to eliminate anything it can be i know something was wrong with my distributor shaft replaced it and problem fixed
-
I posted about a similar problem a few weeks ago. My noise only starts after it under a load but after it starts it keeps going. If I let the engine idle for 10 minutes it starts to go away. Past week Ive gone over my engine with a stethescope trying to locate where its coming from. I have yet to find a mechanical cause to the noise. I did notice however that there may be a crack in my header gasket, could this be what is making my noise? I dont no if this would apply to you since you said you pulled the manifold already. Does anybody no of a simple test to rule out if its the gasket leaking?
-
Finding an exhaust leak should be easy to detect with a stethoscope. Make sure you are using it with just the hose on the end and not the probe.
Yes verify TDC and your mark. Many things can cause pinging which I'll get into more later if you verify the accuracy of your timing mark. For now I'm taking my bike out, it's beautiful outside. Good luck
-
Alright I didn't have a chance to verify TDC today but I did notice something very weird when I was checking the timing.
When I had my timing light on my harmonic balancer I got it to sit at 8 BTDC but when I watch the mark it would disappear for a brief second then come back. This was without vac advance just mechanical.
I was under the assumption this mark should ALWAYS be there regardless.
So I'll be pulling the wires and checking them now...
-
How old is your timing chain? If it was sloppy though, you'd probably see the timing mark moving around.