Pinging/detonation question

withamc · 01-25-2001, 12:47 PM

I need some help determining whether the sound I'm hearing is exhaust leaks or detonation. I haven't been able to cure the header leaks yet, and I've advanced/retarded the timing from 8 BTDC to 18 BTDC and the noise seems to remain constant. Add to that the Flowmasters are pretty loud - how do tell the difference between pinging and header leaks? Can you hear it over a loud exhaust? What sort of long term damage can I expect if it has been pinging for an extended period of time? Thanks for the help.

------------------
86 GT, GT40P heads, Cobra cam, 1.7 RR's, Cobra intake, 65mm TB, 73mm Vortech, 24# injectors, 2-1/2" BBK H-pipe (w/cats), Flowmasters, 3.55s.

Tom351 · 01-25-2001, 12:58 PM

Pinging sounds like a mettalic rattling, while an exhaust leak has a popping sound

------------------
67 Fastback - Arctic White Pearl paint
351W ,Trick Flow Aluminum Heads, Edelbrock TorkerII, Comp. Cam, Performance Automatic C-4 Trans, 3.55 gears, Front Disc Brakes, 1-1/8" Fr. 3/4" rear sway bars.

My 351W Fastback

withamc · 01-25-2001, 08:25 PM

Thanks for the reply - 2nd part of the question - is it noticeable over a loud exhaust?

01-25-2001, 09:13 PM

I can hear it on mine. Man I need a chip!!

------------------
Rick
My 89lx(updated 11/5/2000)
My 97 Cobra

90LSC · 01-25-2001, 10:28 PM

If you have a detonation problem, you will not hear it at idle. Pinging or detonation comes on when the engine is under a load. So...if you hear it when the car is just sitting there running, it is NOT detonation.

Get someone to plug the tailpipes with rags while you have your head under the hood. If the sound is louder, you have found an exaust leak.

Get it up on a rack and hunt around under it while it is running. Or put it up on jackstands(NOT JUST JACKS!!!!!)(make sure you chock front and back of a tire on the ground) and crawl around under it. If you hear the noise it is not pinging.
Lots of other ways but I would bet these suggestions get results.....Later

90dpscoupe · 01-25-2001, 11:10 PM

He also asked what kind of damage to expect from detonation? well im pretty sure your valves, and head gaskets could suffer.

01-26-2001, 12:59 AM

Huh! I've got o-ringed gaskets, I'm worried about the pistons.. although they are forged. Mine doesn't have it too bad unless I'm really getting on it then I back off it.
Funny thing though, it does it more in 3rd(detonates) gear than 2nd. The car will act kinda funny in 3rd, but I put it in second and its a jet and smooth. Man it sounds good in 2nd too!!

withamc · 01-26-2001, 01:32 AM

Thanks 90LSC - I can hear some ticking while it's idling, but I can't seem to narrow it down to a particular point. I'm almost positive I've got some sort of exhaust leak, and it gets louder when it's under load. I'm going to clean everything up and put new gaskets on when I put the new H-pipe in, but in the meantime I'm trying to see if it's pinging as well.
When I first put the engine in, I kept the original 19 LB injectors with the SD set up, and I had to advance the timing to 16+ BTDC to get it to run decent. When I put the mass air in I changed to 24 LB injectors and I was able to pull the timing back to 14. That makes me wonder if I did some damage to the engine while I was runnig the 19 LB injectors.
Thanks for your help.

------------------
86 GT, GT40P heads, Cobra cam, 1.7 RR's, Cobra intake, 65mm TB, 73mm Vortech, 24# injectors, 2-1/2" BBK H-pipe (w/cats), Flowmasters, 3.55s.

01-26-2001, 01:49 AM

Are your head gaskets leaking?

withamc · 01-26-2001, 02:27 AM

rbatson - last time I did a compression test they were all about 160 - I'm going to try and check it again this weekend.

01-26-2001, 03:26 AM

It sounds like your ok. An exhaust leak sounds like a tick. Detonation sounds like the motor is chewing tacks.

90LSC · 01-26-2001, 07:00 AM

It could also be a noisy lifter or a rocker arm maladjusted. I bet it is a bad header gasket though.

01-26-2001, 08:50 PM

Know what else ticks? A loose, cracked, leaking sparkplug wire. Maybe a loose sparkplug. Go out and start the car at night or somewhere real dark and see if you see some tiny blue sparks. Oh yeah and rrockers have been known to tick

withamc · 01-28-2001, 01:10 AM

I did put 1.7 roller rockers on about two months ago, and they are noisier, but this sounds like something else. I'm going to have the headers checked and shaved straight if necessary when I put the new H-pipe on. We'll see what happens after that. Thanks for your input.

Chris

01-25-2001, 12:47 PM	#1
withamc Registered Member Join Date: Aug 2000 Location: Thousand Oaks, CA Posts: 396	Pinging/detonation question I need some help determining whether the sound I'm hearing is exhaust leaks or detonation. I haven't been able to cure the header leaks yet, and I've advanced/retarded the timing from 8 BTDC to 18 BTDC and the noise seems to remain constant. Add to that the Flowmasters are pretty loud - how do tell the difference between pinging and header leaks? Can you hear it over a loud exhaust? What sort of long term damage can I expect if it has been pinging for an extended period of time? Thanks for the help. ------------------ 86 GT, GT40P heads, Cobra cam, 1.7 RR's, Cobra intake, 65mm TB, 73mm Vortech, 24# injectors, 2-1/2" BBK H-pipe (w/cats), Flowmasters, 3.55s.

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01-25-2001, 12:58 PM	#2
Tom351 Registered Member Join Date: Oct 2000 Location: Atlanta,GA,USA Posts: 278	Pinging sounds like a mettalic rattling, while an exhaust leak has a popping sound ------------------ 67 Fastback - Arctic White Pearl paint 351W ,Trick Flow Aluminum Heads, Edelbrock TorkerII, Comp. Cam, Performance Automatic C-4 Trans, 3.55 gears, Front Disc Brakes, 1-1/8" Fr. 3/4" rear sway bars. My 351W Fastback

01-25-2001, 08:25 PM	#3
withamc Registered Member Join Date: Aug 2000 Location: Thousand Oaks, CA Posts: 396	Thanks for the reply - 2nd part of the question - is it noticeable over a loud exhaust?

01-25-2001, 09:13 PM	#4
rbatson Guest Posts: n/a	I can hear it on mine. Man I need a chip!! ------------------ Rick My 89lx(updated 11/5/2000) My 97 Cobra

01-25-2001, 10:28 PM	#5
90LSC Registered Member Join Date: Mar 1999 Location: Dallas,TX USA Posts: 28	If you have a detonation problem, you will not hear it at idle. Pinging or detonation comes on when the engine is under a load. So...if you hear it when the car is just sitting there running, it is NOT detonation. Get someone to plug the tailpipes with rags while you have your head under the hood. If the sound is louder, you have found an exaust leak. Get it up on a rack and hunt around under it while it is running. Or put it up on jackstands(NOT JUST JACKS!!!!!)(make sure you chock front and back of a tire on the ground) and crawl around under it. If you hear the noise it is not pinging. Lots of other ways but I would bet these suggestions get results.....Later

01-25-2001, 11:10 PM	#6
90dpscoupe Registered Member Join Date: Jun 2000 Location: sanantonio, Tx, usa Posts: 1,407	He also asked what kind of damage to expect from detonation? well im pretty sure your valves, and head gaskets could suffer.

01-26-2001, 12:59 AM	#7
rbatson Guest Posts: n/a	Huh! I've got o-ringed gaskets, I'm worried about the pistons.. although they are forged. Mine doesn't have it too bad unless I'm really getting on it then I back off it. Funny thing though, it does it more in 3rd(detonates) gear than 2nd. The car will act kinda funny in 3rd, but I put it in second and its a jet and smooth. Man it sounds good in 2nd too!!

01-26-2001, 01:32 AM	#8
withamc Registered Member Join Date: Aug 2000 Location: Thousand Oaks, CA Posts: 396	Thanks 90LSC - I can hear some ticking while it's idling, but I can't seem to narrow it down to a particular point. I'm almost positive I've got some sort of exhaust leak, and it gets louder when it's under load. I'm going to clean everything up and put new gaskets on when I put the new H-pipe in, but in the meantime I'm trying to see if it's pinging as well. When I first put the engine in, I kept the original 19 LB injectors with the SD set up, and I had to advance the timing to 16+ BTDC to get it to run decent. When I put the mass air in I changed to 24 LB injectors and I was able to pull the timing back to 14. That makes me wonder if I did some damage to the engine while I was runnig the 19 LB injectors. Thanks for your help. ------------------ 86 GT, GT40P heads, Cobra cam, 1.7 RR's, Cobra intake, 65mm TB, 73mm Vortech, 24# injectors, 2-1/2" BBK H-pipe (w/cats), Flowmasters, 3.55s.

01-26-2001, 01:49 AM	#9
rbatson Guest Posts: n/a	Are your head gaskets leaking?

01-26-2001, 02:27 AM	#10
withamc Registered Member Join Date: Aug 2000 Location: Thousand Oaks, CA Posts: 396	rbatson - last time I did a compression test they were all about 160 - I'm going to try and check it again this weekend.

01-26-2001, 03:26 AM	#11
rbatson Guest Posts: n/a	It sounds like your ok. An exhaust leak sounds like a tick. Detonation sounds like the motor is chewing tacks.

01-26-2001, 07:00 AM	#12
90LSC Registered Member Join Date: Mar 1999 Location: Dallas,TX USA Posts: 28	It could also be a noisy lifter or a rocker arm maladjusted. I bet it is a bad header gasket though.

01-26-2001, 08:50 PM	#13
rbatson Guest Posts: n/a	Know what else ticks? A loose, cracked, leaking sparkplug wire. Maybe a loose sparkplug. Go out and start the car at night or somewhere real dark and see if you see some tiny blue sparks. Oh yeah and rrockers have been known to tick

01-28-2001, 01:10 AM	#14
withamc Registered Member Join Date: Aug 2000 Location: Thousand Oaks, CA Posts: 396	I did put 1.7 roller rockers on about two months ago, and they are noisier, but this sounds like something else. I'm going to have the headers checked and shaved straight if necessary when I put the new H-pipe on. We'll see what happens after that. Thanks for your input. Chris