low throttle pinging
 

I've got a 73 f250 with stock 390 engine that I just got back on the road. Before I did head gasket replacement I had a low throttle ping, that is still there now. When I tap the gas pedal I pings, but it goes away with just a slightly harder push to the pedal. Still really, really light touch and its gone. I did hear a slight ping going up a steep hill today as well, but thats unusual. My timing is set to 10. Also I've got a different carburetor now then I did before when it was still pinging.

Any thoughts?

This could be over-advanced timing curve, lean mix, or a combination of both. Did this engine have an EGR valve at one time?

No, never had an EGR.

But now I'm wondering if its a ping at all.I just drove it again and its really just a high pitched noise that I guess I think is a ping. Does anybody have a video of what a ping sounds like? Is a high pitched noise normal at lower rpm or low throttle? Same when going up hill, its just an unexpected high-pitched sound. Count it be just how the engine sounds.

I'll try retarding it a little and see how it goes. But I've never checked my curve before. Isn't there a simple procedure of it I can do with just a timing light?

No, never had an EGR.

But now I'm wondering if its a ping at all.I just drove it again and its really just a high pitched noise that I guess I think is a ping. Does anybody have a video of what a ping sounds like? Is a high pitched noise normal at lower rpm or low throttle? Same when going up hill, its just an unexpected high-pitched sound. Count it be just how the engine sounds.

I'll try retarding it a little and see how it goes. But I've never checked my curve before. Isn't there a simple procedure of it I can do with just a timing light?

Pinging is not a high pitched noise. It would be hard to pick up on video. Pinging sounds like marbles rolling around in a coffee can. Pinging is also more prevalent when you're loading the engine, not at low RPMs when you just get on the throttle.

Are you sure you're not just hearing a belt squeal? Maybe it makes sense for you to post a video demonstrating the sound, instead of the other way around.

Yea fmc, you're right, I need to have a buddy ride with me so we can make a video. That will be easier. It doesn't happen in idle.

Thanks for chiming in. I don't think what I'm hearing sounds anything like marbles in a coffee can. I'll try to do a video today and check back

Ok, here is a video. Sorry its a little shaky, I just took it on my way home from work while driving. Took some side roads to home so no cars would be around :)


I was doing it the whole time off and on but at about 20 seconds you can hear it sustained it for a few seconds, even pushed past it for a split second and the let off the gas. So you'll hear it go away for a split second and back again when it slows down. Maybe it is an rpm thing?

Any ideas??

Oh and forgot to mention, the load knocking/rattling is my driver side window :) need some rubber for it.

Damn... I didn't hear anything with my laptop speakers.

Josh

I turned it up pretty loud and couldn't hear anything wrong. Sounded pretty good to me.

Certainly no pinging, right? Must be my imagination then. It doesn't feel wrong or bad or anything, but it just not what I expect to hear when I hit the gas. I guess thats just engine doin' its thing.

Thanks guys.

I thought I heard an exhaust leak... But definitely no pinging..

x2 on the exhaust leak. Check where the down pipe connects to the manifold to see if it's tight.

I am running headers, but I'll check all the bolts on those tonight. Thanks for the tips guys!

Went to go tighten up my header bolts on your guys' account of hearing exhaust leak. Found a massive crack where the primaries meet the collector :( Such a bummer, I don't have money to put nice headers on right now. Trying to decide if its worth holding off to get nicer new ones and drive it as is for a little bit or get $200ish ones now.

ALSO, I had somebody drive in the truck with me and he heard the high pitch sound! He said it didn't sound like anything coming from the engine at all but that it sound like a whistle. Like air was zooming by a whole and made a whistle sound. Has anybody heard of this before? I double checked all my vacuum plugs made sure they didn't have any small cracks in them... not sure where else air could 'woosh' by like that except the air horn on the carb. Can carbs whistle? :-X04