pings and compression

[pastry_chef]

A fellow on another board has a Pontiac 455 that pings with premium fuel (cast iron head). The camshaft is a hydraulic flat Summit 2802.

Advertised Intake Duration: 298
Advertised Exhaust Duration: 303
Intake @ 050 - 224
Exhaust @ 050 - 234
Intake Valve Lift : 0.466 in.
Exhaust Valve Lift: 0.488 in.
Lobe Separation (degrees): 114

He has checked initial timing and the advance curve are mild. Two pressure gauges have cranking PSI at 160.
I don't hold much value in cranking PSI but I'd think it would need to be at least 10% higher to ping. Anyone here see a well tuned engine ping with 160?
My personal thought is the cam may be retarded..

[pastry_chef]

A big correction, this actually has aluminum heads.

[n2xlr8n]

I've had it happen, too.

I started with cold(er) air, then made sure my exhaust was functioning like I thought.

What do the plugs look like?

[Roundybout]

What compression ratio is it running? If reasonable I'd look into the timing curve and verify the timing is what you're seeing. Timing mark/balancer could be off. I'd want to look at the plugs and see if all of them are showing signs of detonation as a clue.

Coolant and air inlet temp are factors if the above is not out the ordinary.

[PackardV8]

X2 - something's not as it seems. An aluminum head cranking only 160 PSI shouldn't be pinging.

[pastry_chef]

Thanks for the comments.
I've located another Pontiac owner with nearly the identical combination of parts and his runs great. I thought the combo would be fine for premium pump gas.
The Qjet expert / engine builder wannabe over there was outright declaring the cam is too small and the root of the problem! As usual he gets upset and even insulting to anyone who challenges his opinion. There is far more legit knowledge here.
Mr. Vizard the Pontiac V8 community needs Torque Master, please.

[Bob Hollinshead]

What heat range plugs are in it?

[dfarr67]

lean?

[pastry_chef]

What heat range plugs are in it?

Champion 9YC at first, then Colder BKR7E installed with no change.

Here is a in car video.

[pastry_chef]

lean?

This could be a possibility and must be verified.

[Ozonkiller]

What is deck height/quench?

[mag2555]

Sometimes if the Cam has been proven to be in right all it takes is a sharp edge of the milled head deck of the chambers to be exposed out to make a local hot spot that can set off the charge , or the same with a piston valve notch edge of even a exposed edge of a thread of the spark plug itself or the hole for the plug tapped in the head, or a sharp edge on the face OT margin of a Exh valve.

I have been following this tread on that Pontiac web board and he really needs to pull the timing cover and degree or atleast check the Cam to get things to a known base line, then move on to maybe yanking one head to look for sharp edges and this all is assiming his air to fuel ratio is ok and he has no vacuum leaks and no plugs cross firing !

I have also seen cases where they guy had the firing order wrong yet the motor did not back fire!

[Kenny M]

I have a 1974 Trans Am SD 455 9.3to1 175 lbs cranking. H Roller 224 230 490 500 114 in at 110. Iron round port heads, Stock intake and Q Jet with Ram air exhaust manifolds. I run it on California 87 Junk fuel 36 degrees total. Never pings. Something must be wrong. I have used that same summit cam in pontics and they don't ping. What makes the Pontiac engines ping is the fast ramp comp XE type cams and tight lobe centers.

[pastry_chef]

Thanks everyone. This noise has been confirmed as something other than ping/detonation. Does the same with 100 octane.

[gruntguru]

Thanks everyone. This noise has been confirmed as something other than ping/detonation. Does the same with 100 octane.

Has it been identified yet?