Can't Stop the Ping

[double_T]

I can't stop the ping! I've been retarding the timing with the Unichip, to the point there's noticeable power loss. I'm in Denver (5200 ft) on 91 octane. When its good and warm you have to pull the timing back to the point of misfiring....

Poor Man Recipe
'01 Cherokee: 4.2 crank and rods, stock cam, 26lb injectors, 677 pistons, 62mm throttle body, 0331 head, gibson cat-back. The block was not decked or bored. AFR is just a tad rich. My ideas are:
-deck the block and different pistons?
-maybe degree the cam back a tooth
-thicker head gasket
-different cam
-maybe all four?

I'm headed off to get some Amoco 100 octane to see what that does....

I have so much else going on right now I've only been able to search forums so much... my head is starting to hurt. Thanks for any help!

[IH 392]

What head gasket did you use?, if it's thick and without the block decked and shorter pistons the quench is probably way to much, that'll cause excessive pinging, the 258's were notorious for that!

[Cheromaniac]

I'm running the same recipe (0.088" quench) and I don't have any pinging problems in the denser air of sea level and 110+*F outside temps (also using 91 octane). I'm even running the hottest Champion RC12LYC plugs. Something else must be amiss.
Is the cam position sensor indexed correctly?
How hot does the engine run?

[double_T]

I'm running the same recipe (0.088" quench) and I don't have any pinging problems in the denser air of sea level and 110+*F outside temps (also using 91 octane). I'm even running the hottest Champion RC12LYC plugs. Something else must be amiss.
Is the cam position sensor indexed correctly?
How hot does the engine run?

The engine does seems to run a little hot, but it's been pretty hot out here. I had a buddy hook it to the computer at the dealership and he said it was on. I will check that though, thanks

[double_T]

A good number of folks have listened to that engine and figured detonation/pre-ignition. But we all had a good laugh when we found a crack in the flywheel...

[SilverXJ]

Did that fix it?

[double_T]

Did that fix it?

We'll find out next week...
I'll be sure to update.

I'm running 3.55's with 31's. Did you ever get those 4.11's in? If so, what kind of difference did it make? It's not too far down my list. I can't remember if you had an auto? Man, I spent 2 months hunting for a 5 speed in good condition, to no avail. It's easy on the old knees though!

[Cheromaniac]

A good number of folks have listened to that engine and figured detonation/pre-ignition. But we all had a good laugh when we found a crack in the flywheel...

Well that's a big relief!
I was shocked when you told me that the engine pinged on 91 octane living a mile high. At that elevation you should be able to run the engine on 85 octane catpiss.