Knocking and Pinging ??? Any ideas?

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Mar 3, 2004 | 07:28 PM

C32B

Thread Starter

Instructor

Joined: Apr 2003

Posts: 174

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From: Fairfax VA

Knocking and Pinging ??? Any ideas?

My 69 350/350 has recently started knocking and pinging. To my knowledge nothing has been done by the previous owners to accomodate unleaded fuel. The previous owner advised me to run Amoco High Octane (93) and I would be fine. It ran fine through the summer and on my weekend outings until just recently.

Any ideas such as adding fuel additiive, octane boost, etc. or could it be something more terminal :confused:

Any advice is much appreciated!!

Mar 3, 2004 | 07:57 PM

Steve's74

Burning Brakes

Joined: Feb 2004

Posts: 958

Likes: 1

From: In the Beautiful Shenandoah Valley of VA

Re: Knocking and Pinging ??? Any ideas? (C32B)

It's possibly just the time of the year. The warm temperatures you are experiencing (me too) are out of line for this time of year, as the fuel companies are still utilizing "winter blend" fuels. A winter blend has a more volatile combination of hydrocarbons to make for smoother starts and running in the winter, and will ping on early motors without knock sensors when temperatures spike. It takes time for the gas companies to switch their stocks over. In another month, the pinging may go away just because of fuel blend changes.

Of course, you may have a mechanical condition causing the ping too.

Mar 3, 2004 | 09:57 PM

72ls5fla

Drifting

Joined: Aug 2003

Posts: 1,327

Likes: 16

From: Fl

Re: Knocking and Pinging ??? Any ideas? (Steve's74)

I agree with the fuel blend ..

My car can run dierent from state to state, all relavent to the gas I have in the car. I do add Lead Supreme 130 (real TEL addititve). I get about 95-96 octane leaded fuel for about an extra 25 cents per gallon.
The TEL additive seemed to negate the blend problem for me.

The company that sels the additive is called Kemco and located in Utah.
They sell the stuf by the case 12 x 32oz quart bottles.
I add 1oz per gallon.

Hope this helps some.

Bill

Mar 3, 2004 | 10:21 PM

Melting Slicks

Joined: Oct 2000

Posts: 3,023

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From: TEXASTEXASTEXASTEXAS TEXASTEXASTEXASTEXAS

St. Jude Contributor

Re: Knocking and Pinging ??? Any ideas? (C32B)

Could be carbon buildup in the cylinders causing pre-ignition. Try running a couple bottles of Techron additive through it, and if that don't do the trick, some folks swear by dribbling water or ATF fluid through your carb while it's running, just enough to almost but not quite stall it out.

JB

Mar 3, 2004 | 10:21 PM

C32B

Thread Starter

Instructor

Joined: Apr 2003

Posts: 174

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From: Fairfax VA

Re: Knocking and Pinging ??? Any ideas? (72ls5fla)

Thanks guys for the input. I'm hoping you both are right but I'm going to monitor closely and get in the shop if it persists. It's the original engine with a prior rebuild (may be a different cam) and I'd like to keep it original. :yesnod:

Mar 4, 2004 | 07:27 AM

isosceles

Melting Slicks

Joined: Jul 2002

Posts: 3,128

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From: Deltona (son of Deland and DAYTONA) FL

Re: Knocking and Pinging ??? Any ideas? (JB)

Quote:

Could be carbon buildup ....
JB

If you suspect carbon, use GM Top Engine Cleaner. You pour 2/3 of the can in with the motor running, then pour the last 3rd in real fast and the motor stalls. Let it sit for 15-20 min, restart (instructions on can). Do it on a breezy day because it causes lots of smoke. Other car manufacturers use it on some of their scheduled maintenences.

Mar 4, 2004 | 08:56 AM

SpyderD

Pro

Joined: Sep 2002

Posts: 690

Likes: 1

From: near Memphis TN

Re: Knocking and Pinging ??? Any ideas? (isosceles)

Hmmm, I never heard of the "winter blend" but it makes sense. I just had the same problem. 10.7 compression with the new engine installed in October so I always on the lookout for detonation and check the plugs for signs religously. Never had pinging until Saturday when the temps went up to the 60's and I heard some rattling going up a hill. I thought I got some bad gas.

I reduced the vacuum advance a bit and I may retard the timing a degree or two, so I am listening carefully for the pinging to return. One thing to note - just reducing the timing one or two degrees may make that pinging go away.