Missing and Pinging

-
S

ssennett

Member
Joined
Oct 10, 2013
Messages
5
Reaction score
0
Location
Vancouver Wa USA
Hello All!!
I have had my Valiant 2 door with a 225 Slant six for about four months been doing body work and rust abatement on it and need some engine advice. I have had a miss since I got the car. New plugs, wires, cap, rotor, valve adjustment, checked timing. Everything I can think of. in first gear no pinging, second and third, pinging real bad and you can tell that there is a miss at idle. I am thinking I may need to change the intake/ exhaust gaskets and rebuild the carb. Has anyone else experienced this? Any suggestions are greatly appreciated. Thanks!:banghead:
 
Compression test it first, and you might save yourself a lot of time diagnosing.
 
What year car?

Agreed; start with the compression test; that will most likely pinpoint the missing cylinder. Did you look at the plugs to see if any particular one was different looking from the others? Is the miss a steady miss like it is from one cylinder only, or is it an erratic, irregular miss?

The other thing you can do to isolate a weak cylinder is remove each plug wire one at a time from the distributor end!) and see if the engine vibrations that result from that cylinder being 'dead' is the same on each cylinder, or if there is one cylinder where the engine 'miss' does not change much when you 'kill' the spark to it; that would be your weak cylinder. Be careful, the sparks may bite you as you remove or insert each distributor wire!

Pinging is mostly associated with incorrect, advanced timing, or a lean carburation condition; are you sure you set the timing right? Did you do it with a timing light? Did you properly disconnect and plug the vacuum line to the distributor's vacuum advance when you set timing? (Just tyring to make sure that the proper procedures were followed.)

BTW, it is not uncommon for the pinging to get worse in higher gears; the easiest way to get an engine to ping is to be in higher gears and low RPM's and open the throttle. So the no pinging in 1st gear is not by itself an issue.

When you hear the pinging, is is just right after you push down the throttle in higher gears and then does it go away quickly, or does it persist even as the engine RPM's increase? Is there any bogging or stumbling of the engine when you first try to accelerate?

Changing the exhaust gasket would only be necessary if you saw/hear an exhaust leak. You can check for intake leaks at idle with an atomizer spraying small whiffs of gas or other suggested liquids around all the intake flanges.

Check for leaks in the vaccum hoses and distributor advance and that the vacuum hoses are connected correctly.
 
Other things that can cause pinging is overheating and OIL USE
 
Tell us the year of your engine and the carburetor model. It really matters. Early ones are simple. 1976 ones not so simple.
 
ssennett said:
Sorry for 6the late response... this is a 66 Valiant and the carb is a Holley Model 1920
Click to expand...

A 2 pronged approach,all low buck. 1: Blowing out the idle circuit on the carburetor. A compressor & rubber tipped blow gun,works best.If not,sometimes a can of carburetor cleaner(with the red nozzle tube),sometimes works. Find the air fuel mixture screw. Turn it clockwise, mark the turns until seated. Back the screw ,all the way out. Take the tip,stuff it in the open hole. Hit it with the air tip/carb cleaner, multiple times.
Install the mixture screw,seat it bottomed out slightly, don't crank hard on it. Turn it out,to the marked turns from bottom you started with. Not guarantee, it works sometimes.Most stock /6's ,spend most of their life on/near the iidle- off idle circuit. Mine did this,same symptoms. After that, I would do a leak down/ compression test.
 
I agree that the idle circuit is a problem in Holley 1920's. I went thru ~4 carbs over decades before finding one that made the engine idle smooth. However, that doesn't sound like the OP's issue. In my case, the engine ran great once the rpm's increased so it ran more off the main jet and economizer.

Pre-ignition or "pinging" is usually from too much spark advance. Modern engines have a "knock sensor" which senses pinging and retards the spark until it goes away, always hunting for that boundary (gives best economy and power). I think it can be exacerbated by a lean mixture, and also by hotter incoming air.
 
You must log in or register to reply here.
-

Back
Top