Can't get my engine to quit "pinging".

[csgt428]

Great info. I have an R code Mach that I had to build an engine for. It's a roller stroker 408 now with 10 to 1 compression. I found a D2ZX- dampener for it but didn't realize it had it's own timing pointer. I can't seem to get a "ping" to go away while tuning it. Is it possible my stock pointer is causing me to advance the timing to far?? I posted this in the 429 forum here first by mistake.

 

[Cleveland Crush]

Great info. I have an R code Mach that I had to build an engine for. It's a roller stroker 408 now with 10 to 1 compression. I found a D2ZX- dampener for it but didn't realize it had it's own timing pointer. I can't seem to get a "ping" to go away while tuning it. Is it possible my stock pointer is causing me to advance the timing to far?? I posted this in the 429 forum here first by mistake.

Pull #1 spark plug. Hand rotate engine to verify exact TDC on #1 cylinder. Then see where your pointer is.
Note: It will be much easier to hand rotate your engine with all spark plugs removed.

 

[boilermaster]

csgt428,
My pointer was off almost 5 degrees when I checked true tdc with a dial indicator.
Fortunately I had 2 spare pointers and one of them lined up better than the others.
If you look at how the pointer is attached to the front cover and block, one can easily see that the pointer can be manipulated by quite a bit by clocking it at the bolt holes.
once you find true tdc, lock it down and its orientation relative to the bolt holes.
Boilermaster

 

[Zach]

A reliable dial back timing light can also solve a lot of headaches of timing markers. Digital ones aren’t needed and analog ones can be found cheap just get a good one.

 

[Mac]

Last year I had a similar problem with a 289 that was rebuilt for my old convertible. After multiple attempts to retime my engine with minimal change, I did additional research. One surprising find was that as a counter balance ages, the rubber in it hardens so that the factory timing marks are no longer accurate. It was recommended to disregard the recommended settings from when the car was new and use a vacuum gauge to find the optimum setting instead. With that said, I attached a vacuum gauge to the one vacuum port on my intake manifold and turned my distributer until I got the highest vacuum reading. Then I locked my distributor in place and ran my car around to see how it ran. It ran strong with no pinging.

 

[Sheriff41]

Last year I had a similar problem with a 289 that was rebuilt for my old convertible. After multiple attempts to retime my engine with minimal change, I did additional research. One surprising find was that as a counter balance ages, the rubber in it hardens so that the factory timing marks are no longer accurate. It was recommended to disregard the recommended settings from when the car was new and use a vacuum gauge to find the optimum setting instead. With that said, I attached a vacuum gauge to the one vacuum port on my intake manifold and turned my distributer until I got the highest vacuum reading. Then I locked my distributor in place and ran my car around to see how it ran. It ran strong with no pinging.

Old balancers can slip and become inaccurate. Once the rubber dries out the balancer can also come apart and do some serious damage under the hood. Time to replace it or have it rebuilt.

 

[Stanglover]

My unqualified thoughts;
First, get the timing pointer sorted as others have said. Once that is done, check the distributor's initial timing degrees.
You do not say what distributor you're running, so as I'm only familiar with stock Motorcraft or Autolite dist. it's hard to say, but typically 14 deg. initial and 34 all in mechanical with 10:1 comp ratio ought to give you a strong motor and no pinging.
Lots has been posted on timing, so take a look at other posts for ideas.
Don't forget to check the carb settings as well as it all works together.
Good luck.

 

[boilermaster]

csgt428,
wait a minute here 408 stroker with what crankshaft ?
shouldnt you be using a neutral balance crankshaft damper and flywheel ?
please explain.
Boilermaster

 

[Fabrice]

Prolly useless info, but may you run too hot sparkplugs, you can also get ping under load even with what should be the right timing. Got that in the past with fancy double anodes plugs.

 

[Bentworker]

Are you positive the fuel you are running is 91+ octane? With a 10:1 static compression ratio you are likely pushing the limits of pump gas with iron heads and a mild camshaft.

 

[giantpune]

Are you positive the fuel you are running is 91+ octane? With a 10:1 static compression ratio you are likely pushing the limits of pump gas with iron heads and a mild camshaft.

I run 87 octane in my 10:1 engines without pinging issues.

 

[Bentworker]

I run 87 octane in my 10:1 engines without pinging issues.

Gasoline is blended differently by region. What you get away with locally might be beyond the limit of fuel sold elsewhere.

What can specs are you running? The more extreme the cam, the lower dynamic compression ratio.

 

[giantpune]

Gasoline is blended differently by region. What you get away with locally might be beyond the limit of fuel sold elsewhere.

What can specs are you running? The more extreme the cam, the lower dynamic compression ratio.

They're essentially RV cams. Smooth idling with more torque down low.

 

[Don C]

A couple of thoughts, in response to Boilermaster, the SCAT stroker kit that I have has a 28 oz. external balance. I got the balanced assembly which includes the damper and flex plate balanced for and designed for the crankshaft. This eliminates both any worries about matching and balancing components, as well as making sure the balancer is keyed to the TDC on the crankshaft. I would be hesitant to use a NOS/OEM harmonic balancer because of potential balancing, TDC location and dried out rubber and the outer ring slipping issues.

Fabrice also brought up a valid point, pinging (pre-detonation) can be cause by more than compression and timing. Hot spots in the combustion chamber can be a big issue. Engine builders will make sure the head gasket does not extend past the cylinder walls and there are not ragged edges on it. Spark plugs can be a huge source of hot spots. The ground electrode should not extend past the edge of the center electrode, when it is adjusted. In fact, I like to have the ground electrode extend to only about the center of the center electrode, to reduce both spark shielding and a hot spot.

 

[boilermaster]

Thanks for clearing that up Don, looks like it is down to the usual culprits.
Dont forget oil intrusion into the combustion chambers via a leaky underside of the intake gasket, faulty pcv system and possibly piston rings that have not seated yet.
engine oil is a huge octane killer.
Boilermaster