1987 ford f-150, 302 c.i., auto, 127k. within the past 500 miles the engine has developed a knock until it warms up, usually lasts 3-5 minutes and is generally heard at idle. sounds like a rod or main bearing knock to me but local 5 star dealer says it is crankshaft end play and is normal for the 87 302. I disagree with that suggestion because i'm pretty sure i know what sound bad bearings make. however, the knock does go away when engine is warm, and i have hammered it and still can't hear a sound after engine warms up. question, do main/rod bearings knock the same or worse when engine is warm/hot. also, the knock has become a little longer lasting and louder over the past two weeks yet still goes away when engine is warm. the engine carries great oil pressure (between the r and m of normal and never moves-is that normal?) and idles smoothly and is very quiet.

 

Hi charo15 and welcome to FTE

Does the knock change when you put it in gear? The ones I've seen with too much crank end play did.
Quite often a rattle/knock that goes away after a couple minutes of running is a piston noise....usually a collapsed skirt.
It's not a common thing on 302s but anything is possible.
Most of the time if you have worn bearing they will be louder when the engine is hot due to clearances opening up and oil thinning out.
Your oil pressure gauge will never move as long as you have any pressure. It is really an idiot light that looks like a gauge. It uses an idiot light sender and everything.

 

thanks for the reply, the knock stays the same whether in gear or not, it will increase in frequency when throttling up but only to a point, say 1200-1600 rpm's, beyond that it disappears...as far as i can tell anyway. If your opinion is correct about the piston skirt what would be the appropriate action...fix (motor rebuild, will it eventually shell out?) or leave alone.

 

could be a piston knock, my 5.0 did the same only at idle

 

87's should have a real pressure guage, although I don't trust the accuracy if it either. I am experiencing a knocking in my '87 as well, and I only notice it very faintly at idle when the truck is warmed up. 123000 on the clock, and still runs relatively well. The sound I hear is like that of a diesel, but really faint, and not constant. I want it to last until i have enough saved up for a 351 swap, so I'll drive it gentle until then.

 

my 87 5.0 lost the right bank of pistons due to malfunctioning speed density fuel injection. it stated with a low piston slap at idle and within 3000 miles it was toast. and with 118000 miles on it it was no shame. good luck on nursing it untill you can do the swap