should i be changing head or intake gaskets?
i have a 2000 F150 4.2L V6 that gets, on a good day, 13 mpg in town. at about 2700-2800 rpm, 65+mph in 4th, just before the 5th gear upshift, i can hear valve clatter.
is this a sign?

other info: 70,000 miles, 3.55 open axle, 245/75R16 goodyear kevlar mudders, leer camper on a shortbed regular cab. only mod is the gotts mod, which made no difference i can see. i do carry a good set of offroad recovery tools, but i'd be surprised if it was as much as 500 pounds. this truck has the heavy duty payload and towing packages.
it threw a code a while back, which was some vacuum valve on the intake or something like that. i wiggled a connector and the code went away. I recently replaced the fuel pump and its relay.

what do you guys think?

 

hi, what you may be hearing is (what us brit calls) pinging. valve knock. if you do a search i think you will find it is not uncommon and better still nothing to worry about.
for piece of mind get the oil pressure checked using a machanical gauge.
hope this helps bokker.

 

i hope not! we must be talking about two different things. what we (me, anyway) call pinging, or knocking, is properly called preignition, and is bad; it can result in a hole in the piston. not good.
valve clatter, on the other hand, as i understand it, comes from the valve train itself, that mechanism on top of the head. it can be a problem, but unless a valve drops, the damage is limited to the valve train and a poor running engine.

i think.

 

hi, search ping this may help. the only way i could stop ping was to back off the throttle.
i am not saying it is ping but it may not be a gasket issue. but could also be carbon build up etc. bokker.

 

I thought searching would be a waste of time, since i thought i knew was i was talking about, but i try to keep an open mind, so i searched. had to search "engine ping" and got a great tip - which i should have known if I'd thought about it. if what i am hearing is preignition, then running a tank or more of high - octane fuel should result in some improvement. so i will - thanks for the tip! your advice was spot-on.

however, depending on how you meant it, i'm not sure i agree on "backing off the throttle" - as i see it, this stops pinging like "not driving" stops accidents. the problem is still there, you're just staying away from the situation. as i understand it, pinging, or preignition, is an incorrect operating condition, even if it's just bad gas, it needs to be corrected. it can be avoided, as you suggested, but that's not a fix. anyway, I'm going to try the high octane fuel, so if it is preignition rather than in the valve train, i should see a difference. I'll let you know, and thanks for the help!

 

PS
bokker, are you in the UK with a 4.2L V6? what's that in?

 

hi, i did have a f150 1997 but sadly , no more. bokker.