Well up in Tahoe this weekend I think the engine developed a noise to what sounds to me like piston slap. Not good either way.

Question is, what is my best option? I have a 98 Navigator 4x4 with the 2v 5.4. I have no issue with rebuilding the motor, or possibly just slapping in a replacement. But what about upgrading to DOHC? What all is involved? Will I need to change out the computer and engine harness if I go that route? And I'm not positive, but doesn't the newer 2v motors have more hp? like 99 and up?

Any guidance is greatly appreciated.
Thanks!

 

Y

Don't worry about it. Mine (97 5.4L) got the Slap at about 30K. It now has 218K on the engine. Still has the Slap, but once it warms up, the engine runs absolutely beautiful. A friend of mine had a 97 Expedition with the 5.4L in it. He had the Slap as well. His had 323K on it when he traded it in. Still ran fine. I'm really inclined to believe these motors last longer WITH the Slap.....

 

haha, mine has always done it in the morning too, never really thought much of it since it went away. But now it does it all the time, especially under a light load it slaps around like crazy. Doesn't sound too good, kinda makes me nervous. lol.

 

Y

If it does it all the time, it is not piston slap....Might be a bad rod. Piston Slap only happens when the engine (usually only with aluminum skirted pistons) is cold. There is extra room for the piston skirt to rock back and forth until the piston begins to heat up. When it heats, the skirt expands to fill the cylinder, and the piston no longer rocks back and forth, and you get no more rattling. If the piston is too tight when cold, it expands, and if tight enough, internal parts break.

 

Let me clarify a little. The slapping, or knocking I hear is only under a light load.... like going down a flat road with the throttle on real light. Under heavy acceleration or idle it isn't apparent. It's not a deep knock so I don't think it's a bearing issue, plus oil pressure is still good. Almost sounds like it could be valve train noise. It's similar to the noise you hear on a cold start, which is apparently piston slap on these things. It does burn a little oil so maybe the rings are just shot.

Does anybody have any info on the DOHC swap? I've considered doing this before but I don't know what it would consist of. At least for future reference if anything.

 

have you checked for exhaust leaks around the header? dont know wut the piston slap sounds like but an leak makes a ticking noise. volume depends on the size of the leak.

 

I'm positive it's not an exhaust leak.
It may just be more apparent because it's been 20 degrees outside, I dunno. Guess I'll find out, I don't plan on doing much until the motor just gives up.

So nobody has any info on changing to a DOHC motor? Or if the 99 and up SOHC motors have more hp than the 98's? I searched around and didn't find much......

 

Get Back to work!! I say let it ride and rebuild it when it blows, then slap on a whipple!!

 

Maybe I should have named the title "DOHC engine swap." lol.

I don't plan on doing anything until it either turns into puff the magic dragon or locks up. But I'm curious what my options are beyond a stock rebuild.

 

My truck has piston slap when it is cold...goes away totally after it warms up. No oil loss and no smoke at all. !59,xxx miles on it right now. Runs awesome..

 

From what I have looked into, It may be more of a valve sound. Could be the retainers on the valves get a little loose when underload.