67 C10 Pinging Sound

[IndifferentJester]

Need help resolving some recent problems that poped up. While I was deployed my truck sat and wasn't started at all. New problem arise is that I have a tranny oil leak somewhere and a new pinging sound. At first I couldn't figure out why it wouldn't shift into gear (automatic) and she sounded fine. After finding out that she needed some tranny fluid I topped her off and then all of a sudden the pinging started. It seems to only ping while in park or reverse, not in drive. I'm generally savvy when it comes to fixing my cars but I'm at a loss for this one. I notice a flare in the exhaust manifold (at the end of the video) and know that's not normal at all. Hopefully these are two separate issues and that it's not a tranny problem.

The pinging sound doesn't sound like an engine knock that I'm familiar with and dealt with in the past on a different car. Thank for the advice/help.

https://youtu.be/tQ2JPRMi8kQ

[Steeveedee]

That's just an exhaust leak; doesn't sound like any metal to metal. There isn't any pinging noise at crankshaft or valve train speed that I can hear. It may be that the "ping" is just exhaust gases reigniting at the leak. You will be getting a low and high pressure condition from exhaust pulses that can cause that. I could be wrong, but replace the collector gasket first to find out. Does it go away once the engine is warmed up all the way?

['68OrangeSunshine]

Try Copper collector gaskets. They're malleable and when torqued down will seal up.
Also they don't burn out like the composition gaskets, and can be re-used.

[IndifferentJester]

Thanks for the quick feedback. I'll order some copper gaskets and let you know how it does. Probably will take a days to get and install. I've looked high and low for torque specs but what is the torque rating for those three bolts? Also, do you recommend using a high temp copper gasket maker with the rings or is it overkill?

[IndifferentJester]

Finished replaced the two gaskets and the sound still persists but now you just hear it towards the muffler. It does seem to not happen as often after warming up, if at all. Then when I apply the gas in either park or neutral it pings again. Would a high idle be the cause also? I noticed when I'm in park or neutral my idle is about 1750 but in drive or reverse it drops to 1000. Which seems a bit weird to me.





The metal brackets don't seem to look like a good seal but its solid all the way around, they were bent before I had replaced them for the copper gaskets.

[57rookie]

With engine warmed up and choke off you should be idling at about 800ish or a little less.
If your engine does not run well when you turn your carb idle screw down to that rpm try opening the left and right idle mixture screws on your carb (assuming you have a Rochester).

[Grumpy old man]

Those flanges are so warped the only way to try to keep using them would be to use 2 thick collector gaskets on each side , I'm sure you realize it's time to replace them .

[Steeveedee]

OK, if it still does it warmed up, it isn't a rich mixture and reversion at the exhaust leak. The next thing that comes to mind is carbon tracks in the distributor cap or wires arcing over, since it isn't rhythmic. As has been mentioned, that's way too high an idle speed. See if you can get the idle down. That won't cause this problem, though. You can know that because if you used to gas pedal to get to the same RPM, it wouldn't be doing it. In other words, I'll bet it still does it at idle.

Do you have an AIR system on your truck? I see it's a '67, and that common equipment for California-bound vehicles, and C10 trucks.

[Metaldoc]

On the vid you can see a flame between the collector and it's running rich. New collector gaskets for sure.

[IndifferentJester]

First time I noticed the flanges were that bad is when this pinging sound started, but I agree with you completely. They will get replaced, just a matter of time and money (like anything else).

I don't have an air system in this truck and even went to go double check that out. I'll try to get the idle speed down tomorrow. As for the carbon tracks, would it be as simple as taking the cap off and cleaning and junk off or is it more involved than that?

For the carburetor, after everything is warmed up, should the choke plate be completely vertical? Thanks again for the help.

[Metaldoc]

Yes the choke plate should be vertical. The pop you hear is air being sucked in the bad gasket, mixing with unburnt gas, add a hot spark from the headers and pop pop pop. A mini explosion.

[Steeveedee]

Originally Posted by Metaldoc

Yes the choke plate should be vertical. The pop you hear is air being sucked in the bad gasket, mixing with unburnt gas, add a hot spark from the headers and pop pop pop. A mini explosion.

That's what I was thinking, up until he said he had the same noise after the collector gaskets were replaced. It may well be, as mentioned, that the collector seal is still compromised. OP- you might try wrapping several layers of aluminum foil around that joint, as a temporary check that the leak is the problem. Easy to put on, easy to take off, so an easy test for a cure.

To answer the question about carbon traces in the cap for the OP, you should be able see light carbon marks in the distributor cap, if that is the problem. The center carbon electrode may be ground up by a misaligned rotor electrode. Not saying this is the problem; it's just something to check for, since this noise is pretty random.

[IndifferentJester]

Will try the foil trick tomorrow and give an update, along with checking distributor. Is there an easy way to put new flanges on? I feel like it'll involve taking it somewhere or pulling the exhaust system out to replace them. Ive never had to replace flanges before.

[Metaldoc]

I have cut the new flanges in half and welded them back together over the pipes. It is an option if your flanges are welded in.

[IndifferentJester]

Hmmm as I don't have a welder nor do I feel confident in doing so would a split flange work?

Something like this? Two on each pipe?
https://www.ebay.com/itm/FX38-3-3-7-...tZNykW&vxp=mtr

[Metaldoc]

Those have only two bolts were there should be three. not sure if they make a three bolt one. You could straighten the old flanges on the pipes with a big adjustable and just replace the gasket. Just don't tighten it too much and use an exhaust sealer.

[Grumpy old man]

Those are 3 bolt flanges (I've never seen 2 bolt header flanges) that have seen more than their time , They are bent / warped . No copper gasket or tinfoil is going to fix your issue , they need to be replaced but until you can get someone to fix it for you you can use 2 thick collector gaskets on each side and drive it like you stole it . You don't have dist problems you don't have carb problems you have a worn out exhaust problem , dump those worn out headers buy some rams horn manifolds and have a new exhaust installed . stop wasting your time chasing demons you don't have .

P.S. get a pressure washer and start cleaning up the underside of that truck .

[IndifferentJester]

Appreciate the feedback from everyone. I'll order two sets of gasket as Grumpy mentioned for a temporary fix. I'll still check the distributor regardless (since everything else is so dirty). Any recommendations on what brand of rams horn headers?

[Grumpy old man]

I just bought a set of 2 1/2 inch straight dump chrome rams horns from Jegs for $127.99 shipped .The have standard cast in the same price range . they just showed up I'll post a pic shortly .

You can buy header collector gaskets from your local parts store .

[Grumpy old man]

here are a couple pics

[Steeveedee]

Originally Posted by Grumpy old man

Those are 3 bolt flanges (I've never seen 2 bolt header flanges) that have seen more than their time , They are bent / warped . No copper gasket or tinfoil is going to fix your issue , they need to be replaced but until you can get someone to fix it for you you can use 2 thick collector gaskets on each side and drive it like you stole it . You don't have dist problems you don't have carb problems you have a worn out exhaust problem , dump those worn out headers buy some rams horn manifolds and have a new exhaust installed . stop wasting your time chasing demons you don't have .

P.S. get a pressure washer and start cleaning up the underside of that truck .

I was suggesting the aluminum foil as a temporary measure to verify that the leak at the collector was or wasn't the issue. It was not recommended as a repair.

[IndifferentJester]

Thanks for the pictures Grumpy, always nice to see rather than read what people are mentioning. What part number is that set? Will there be issues with clearance since their straight down?

Due to weather and work replacing the gaskets took me awhile. I switched out the collector gaskets again and doubled them up as previously suggested. I'm still getting pings, which i can only assume the connection at the collector gaskets needs to be completely replaced or there's a leak somewhere else. Instead of beating a dead horse, I'll more than likely switch to rams horns.

The PO installed 40 series flowmasters; with that being said how much does exhaust system piping generally for in regards to getting it installed? Bending pipes and making a full exhaust system is beyond my skills and equipment (mainly bending and welding). Thanks for waiting and the help.