1993 sho engine knock/rattle

[zanthony74]

I just had a 60k performed on my 93(it has 150,000) when I bought it a couple of months ago and around 1400-1700 rpm I hear a rattle/knocking noise coming from somewhere when the engine is under load. It doesn't seem to match the engine speed so I don't think it is a rod. It's intermitant when you hold the rpm steady. It only makes the noise when you rev it to a higher rpm. It fades away as the rpm's climb over 3000-4000rpm. It sounds like a rat a tat tat but deeper. I tore it all part hoping it was something like a cam chain tensioner, but they were both pumped up just fine. The pads have pretty good grooves wore in them. I don't know if they are suppose to have that like some kind of chain guide. Everything else looks fine, the shims and everything. I have a couple of LT1 camaros that I know inside and out. Have built motors for both...but this damn thing....Ugh!
Any ideas?
Thx
Z

http://www.omahafbody.com/Zsothercars.htm

 

[sdpatt]

Is it a tinny rattle like a loose catalytic converter heat shield or a deeper knock like a large clearance connecting rod bearing? Do you have any location information as to where the sound is originating?

 

[sideSHO]

Is it a tinny rattle like a loose catalytic converter heat shield or a deeper knock like a large clearance connecting rod bearing? Do you have any location information as to where the sound is originating?

The heat shields came to mind for me too.
Seeing as how it is not rev matched.
My heat shiels would rattle like crazy,till they fell off.
Ohh yeah,listen to Scott.
He's forgot more than most will know about the SHO.
And welcome to the forum!

 

[zanthony74]

Not the cat, it has a new performance y-pipe with new cats from Ford Performance Specialists. I think it is the rods. I bought some bearings and I think I going to change them.

 

[SHO--ripper]

Hopefully it's not too late.

 

[zanthony74]

Tore it apart, found a smoked rod bearing. They were all wore, but one was really grooved and brassy. Crank look good. Put it all back together after hand porting and polishing the runners/plenum and the intake ports on the heads and some big bore butterflies, and no more knock. In fact the car runs like it has never before. Amazing what cleaning out and porting the intake will do.

yo