FOMOCO466

Back from FL, saw some of the sights with the fam for TurkeyDay, cruised the 99 Expy EB with 5.4 3" body and 35 BFG's on stockers..... no tickets, no issues....VA- FL and FL-VA.
Do have a question for the gearheads out there. I rebuilt my 5.4 at 138K due to oil pump fail. I changed EVERYTHING but the block, and timing chains/tensioners
Crank
Rods
Pistons
Rings
PI Heads
Installed 02 Mustang GT cams
Plugs
8 COP's
Block still had the crosshatch in the cyl walls so I just honed it and went on.
The question I have is unless I ran HI test I had spark knock...while crusing...
like I said I'm runin a 5.4, 3:73's, 35's,no CAI, NO programmer, just the airfilter-fender adapter removed (pre gotts mod) loaded with 8 people (4 adult-4kids) and a cargo carrier on top.

Is there that big of a change with the stock vs. Mustang cams that would toss the timing that far off? I've towed witht he truck since the motor build....about 8k on the build so far, but this is the first time I really noticed it that bad..my wife even sitting in the pass seat could hear it and asked if we got bad gas.

Any Ideas?

MPG meter said @ 8-14 mpg avg while runnin @70-80

Kattumaram

In a clean engine only three things can cause detonation (aside from low-octane fuel and assuming the PCM is delivering the right air/fuel mixture ratio): High compression ratio, advanced timing, hot plugs, or a combination of the three.

There is the possibility that one of the temp sensors is giving a bad reading, engine coolant temp, ambient air temp, intake air temp. The PCM uses all those sensor inputs to determine the amount of spark advance for various strategies. Find those sensors and do a wiggle test of the connectors and see if the problem clears.

I'd suggest as well running a compression check of at least one cylinder adding a teaspoon full of oil through the plug bore before running the test. That'll tell you if the CR is higher than stock.

I don't see the cam as a cause of your trouble.

BTW: My 94 Lincoln Town Car, 4.6L/AODE, gives 17mpg at 95mph.....31mpg@50mph.