I have a 1990 F150 with a 5.0L 302ci, and I know this board is primarily for newer F150's, but I am a proud owner and am experiencing some problems with no help from anyother websites. Anyway, the engine makes a fairly loud clacking type noise when at idle and upon deacceleration, I have taken to many mechanics and by listening to it with my mechanical stethoscope, we have decided that it is the main bearings. My question is whether or not I can safely replace only the mains without further problems and without rebuilding the whole engine because the top half is still in beatiful shape with the truck only having 61k miles. I have also pondered the idea of replacing the engine with something a little bigger and more powerfull, is this possible and what applications could I use. Any info on this subject is sincerly appreciated.

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 90’ F150
 K&N Generation II
 PowerAid throttle body spacer
 Flowmaster Dual cat back exhaust
 Rhino Bed Lining
To Come:
 Thorley Tri-Y Headers
 4 inch Rancho Suspension Lift
 35 inch TSL Thornbirds

 

Before you tear into the lower end, take off the valve covers and start it and satisfy yourself that the clacking is not from an overly-loose lifter/rocker adjustment.

The easiest way to tell is to take a shop rag and push on rockers as it runs (and sprays oil all over the garage) -- trying to see if you can change the sound of the clacking as you move from rocker to rocker.



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Y2K™ Jim - N8JG@Hotmail.com

Toreador Red, Keyless XLT SC SB 5.4L E4x4 4wDisc/ABS, 3.73LS, Skid, HD 7700# Towing, LT-245's on Chrome, Tube-Steps, Captain's, 6CD, Tonneau, named: "Nick"

 

I don’t believe it is up on the top end, and anyways I have already replaced all of the hydraulic lifters, push rods, and the rockers. I am taking it to get the emissions and inspection done today and am hoping it will pass with the noise it is making, I plan on asking the mechanic down at the shop what he thinks as well. Well all help is appreciated. Thanx

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 90’ F150
 K&N Generation II
 PowerAid throttle body spacer
 Flowmaster Dual cat back exhaust
 Rhino Bed Lining
To Come:
 Thorley Tri-Y Headers
 4 inch Rancho Suspension Lift
 35 inch TSL Thornbirds

 

Check out www.karkraft.com under performance
got everything from your 5.0 to the big 10's

 

Take the serpentine belt off and see if the noise stops. Make sure it isn't something simple first. Main Bearings are usually a low pitched thump, rod bearings usually chatter under load or when revving the engine in neutral. A lot of things can make noise, can u be more specific? good luck.
Dave