Chasing ping/knock for 2 weeks, time to refer to the experts...

[shynsly]

How do, all? I know there's other threads about ping/spark knock, but I've searched/trolled most of em and am not finding anything that applies I haven't tried.

I have a 79 with a pretty much stock 351m that was (supposedly) rebuilt about 15k miles ago. Had it about 6 months as my daily driver, and it's run like a champ, until last Tuesday.

Cruising into work on the highway at about 55, ironically, I had JUST been thinking how great it seemed to be running that morning, and then I stopped at a red light to make the turn up onto post. As I began to accelerate up the small hill, all the sudden it starts knocking/pinging like crazy. And it's been doing it ever since, despite trying ever suggestion I've come across.

It doesn't make a peep at idle, just purrs like a kitten. If you rev it up somewhat gently, no noise, though if you're out of gear idling and crack the throttle open, it will make one or two sharp "Tink" sounds. On the road, cruising or decellerating, no issues, sounds like normal and runs great. It's only under load, accelerating, it will just make a constant, loud, and fluctuating "tink-ta-tink" sound.

I've replaced the distributor (thinking maybe bad advance mechanism?) and played with the timing till the cows come home. Also changed out the brand new Autolite plugs for some Motorcraft coppers properly gapped, no change.

I just finished rebuilding the carb today (edelbrock 1406 with performer 400 manifold, no EGR/emissions), seems to actually be running a little better (I knew it needed the rebuild), but no change on the pinging.

I've checked for vacuum leaks and sea foamed the crap out of it, even tried the glass of water through a small vac. line, no dice.

Checked for the possibility of an exhaust leak or loose torque converter bolts, all seems well.

Pulled the valvecovers, everything looks new and clean, pushrods are all straight and tight (will rotate but no up and down movement) and ran it abit opened up, everything looked good and made a helluva mess spraying oil from every push rod just fine.

I have a friend who's been playing with old Fords all his life and tends to know what he's talking about, he suggested that possibly the timing chain has stretched or jumped a tooth... but it seems to me that wouldn't that actually retard the timing at the distributor and just make it run like crap, but not ping? Also, seems like a lose chain would cause the timing to jump around, but mine seems rock solid watching it under the timing light.

I'm not ruling out the possibility of a knock/bearing/etc., but wouldn't it also make the noise at idle and especially deceration (i.e. if it was a wrist pin)? Also seems like it would be a bit more 'rythmic' in time with the RPMS, this is very sparatic. And I've tried pulling every individual plug wire, none seem to change or effect the noise much, if at all.

Kind of at my wit's end here, especially with this ole girl being my daily driver. Any helpful insights would certainly be appreciated.

[sackman9975]

Originally Posted by shynsly

Cruising into work on the highway at about 55, ironically, I had JUST been thinking how great it seemed to be running that morning, and then I stopped at a red light to make the turn up onto post. As I began to accelerate up the small hill, all the sudden it starts knocking/pinging like crazy. And it's been doing it ever since, despite trying ever suggestion I've come across.

Ironically, I have a story too about how great I thought my engine was running, only then 8 miles down the road my crankshaft snapped.......but no pings. Just total shutdown.

I don't think my story has anything to do with yours, however with all that you've done, you've seem to hit just about every step to cure the ping. Sounds like spark knock and sometimes there no cure for it if you've broken a piston ring. I would suggest you get your hands on a compression tester and test all your cylinders next.

You said you've replaced the distributor, was it it a new one or one from a boneyard? Is it vacuum advanced? Did you hook a vacuum pump to the advance (if equipped) with the cap off to make sure it was moving like it should? Or do you have electronic ignition (MSD or Accel)?

Hopefully we can figure this out. My first car had bad spark knock. It was only cured once I pull the engine and rebuilt it (there's another story why this was done). There were 3 pistons with broken rings.

[BIG GUY]

I would check your #1 piston at top of compression stroke and see where your rotor is pointed.

[BIG GUY]

Also you might have bad gas?

[miesk5]

yo,
Noise from inside the timing chain cover is a good indication that there is too much slack in the chain. Another way to spot excessive play in the timing chain is to remove the distributor cap and turn the crankshaft in one direction (w/long breaker bar) until the rotor moves, then turn it in the opposite direction until the rotor starts to turn the other way. If the crank has to be turned more than about half an inch to move the rotor, chances are the timing gears and chain need to be replaced. Still iffy on exact measurement so;


I use a short length of garden hose; BEWARE OF FAN & SERPENTINE BELT!) to aid the listening process.

You will hear the chain if it is slapping.

I think you could also put a timing light on the engine to check for a very sloppy chain. The timing mark should "wander" all over the place under the light


Timing Chain Replacement in a 351M by by UTfball68

Also listen for alternator, water pump, power steering, etc. noise.

[shynsly]

Thanks much for the replies, fellas. Have to apologize, as I wrote my op in a bit of a hurry, and I left out a few details.

Bad gas was my very first thought, too, as I had put $40 worth of 87 from my local Shell station in the day before and hadn't driven much on it. But I've never had a problem with 87 octane or that station's gas before. I've since burned all that off and ran through two tanks of 91 from two different stations with octane boost to no avail.

I also tried pulling all the belts off and running it to eliminate any accessories (bent alternator shaft, etc.). No luck, noise still present.

The "new" dizzy is a rebuilt motorcraft unit from Pepboys with both mechanical and vacuum advance, but even with the vacuum disconnected and capped off, I still get the pinging. I've dialed the timing all the way back as far as I can go and still have the truck be able to move under it's own power, and always, I get pinging under load. I guess there's a remote possiblity the new dizzy could be bad as well, but I'm guessing more likely the old one was fine and my problems are elsewhere.

One interesting, and possibly telling, observation... yesterday, after I rebuilt the carb and still had the issue, I put the timing back up from around 4* to around 11* BTDC base without the vaccum advance connected where I had seemed to get the best running out of it before all of this started, and it definetly not only seemed to make the pinging much worse, but also caused a very rough running condition complete with shaking anytime I accelerated up to about 45mph, at which point it would smooth out some.

Not a pro-mechanic by any means, but that would definetly seem to suggest it's something internal.

I've been wanting to try cranking the engine backwards manually to check for slack in the chain, but all of my bigger sockets and what not got stolen, so I've got to see about borrowing some until I get mine replaced, lol. Though, like I said, just from watching it, the timing light shows my timing to stay rock steady at any RPM, not dancing around like I've been told it should if the chain is shot.

So, I'm kind of at a loss... if I need a new chain, so be it, guess it's as good of a time as any to go ahead and do my first cam swap while I'm at it. I'm just trying to make sure that's actually the problem before I throw a bunch of money at it, especially right around Christmas, ya know? Thanks again, Gents.

[Alvin in AZ]

Originally Posted by shynsly

...definetly not only seemed to make the pinging much worse, but also
caused a very rough running condition complete with shaking anytime
I accelerated up to about 45mph, at which point it would smooth out
some.

Compression test! :(

I've been wanting to try cranking the engine backwards manually to
check for slack in the chain, but all of my bigger sockets and what not
got stolen, so I've got to see about borrowing some until I get mine
replaced, lol.

15/16" :)

Though, like I said, just from watching it, the timing light shows my
timing to stay rock steady at any RPM, not dancing around like I've
been told it should if the chain is shot.
...if I need a new chain, so be it, guess it's as good of a time as any
to go ahead and do my first cam swap while I'm at it.

Yeah I agree, don't sound like a timing chain.

...but I'd like to suggest just advancing the cam timing
and not the whole cam at this point? :)

Only do a cam when you overhaul it?

Alvin in AZ

[george_c]

Has the balancer moved? It the rubber gets old the balancer and timing mark can slip. Check where top dead center is compared to zero degree of timing.

[shynsly]

Originally Posted by Alvin in AZ

Compression test! :(


Yeah I agree, don't sound like a timing chain.

...but I'd like to suggest just advancing the cam timing
and not the whole cam at this point? :)

Only do a cam when you overhaul it?

Alvin in AZ

Thanks for the reply, could it possibly be a head gasket, you think? I'm not getting ANY funny smoke or smells out of the tailpipe. I had checked for bubbles in the radiator and didn't see any, but will have to check again. Also just changed the oil last weekend, didn't have any coolant in it. But, oddly enough, my thermostat housing gasket seems to have started leaking within the last week or so. Haven't messed with it, but the area under it is wet and there's a small puddle of coolant around the base of the distributor now. Could just be a "coincedence"... but I don't really believe in those, lol.

Thanks again for the help, and I'll pick up a compression tester on Thursday and give it a shot.

[shynsly]

To all who tried to help, thank you thank you, very much appreciated. But to Alvin in AZ, in particular... must give credit where credit is due. Thank you so much for the tip about the compression test. All I know about cars I've kinda figured out for myself in the last 10 years or so, so my knowledge is limited to the things I've already had to figure out, and in this case, I suspect you saved me a LOT of heart ache and hassle, not to mention probably a lot of money. Turns out, #'s 5 and 6 are building all of about 10psi, and #7 isn't far behind them at about 70. All others are running around 120 or so, which seems a bit low, but than again, 351m is not exactly a "high compression" beast, lol.

Took the next step, finally went out and bought my first real live air compressor (Yay me!)... popped the schrader valve out of my compression tester's hose and pumped some air into #5 at TDC... sure as shit, it all came right back out through the crank case. Same for #6... would seem I got some broken rings.

So... I'm in a pickle, limping my only vehicle around on 5 1/2 cylinders hoping and praying it holds together at least through the back side of the holidays until I can start (financially) looking at getting ahold of a new motor. Which, sucks... but, I'm glad I didn't drop the mad $$$ into trying to replace all the top-end parts of this boat anchor just to find out it was still... well, a gas guzzling boat anchor, lol. And I have you directly to thank for that... so my hat's off to you, kind and wise sir. Take care, and happy holidays to you and yours!



Posting the results of my trouble shooting process here, so that hopefully in the future, should anyone else experiance these same odd symptoms, a google search or the like may steer them down the right path as Alvin has me, thanks again, Brutha!

[sackman9975]

Really? Alvin gets all the credit? I guess I'm just chopped liver......

[Alvin in AZ]

Originally Posted by sackman9975

I guess I'm just chopped liver......

I'm guessing you are too. :/
...now that you've gone and whined about it. ;)

Butthead in AZ

[dansmith4478]

possibly you have bad bearings, im currently dealing with having to replace my main bearings.. not fun