89 le v6 slight thumping noise under light load

[jbhome]

My 89 makes a slight thumping noise under light acceleration.
It is relatively low in frequency, leading me to think it's a con rod bearing.
How hard is it to replace the big end bearings?
What would the difference in sound be if it was a main?
Engine revs freeely. Perhaps too much so.
When I kick down to pass, the tack has gone well into the 8K region. (no rev limiter?)
The rpm seems really high. My Hyundai IL4 2.5L turns 3K at 70MPH.
The camary is running 4k+

Thanks for any help.
Jim

[TBayToyotaBoy]

I can't speak to the problem you're having, but I know that my V6 cruises at approximately 3000rpm at 100kmh, so 4000 at 70mph (112kmh) sounds reasonable. I'll take the highway to my evening class tonight and I'll double-check though.

[marc780]

jim, i think maybe its time for a new engine, or a used japan one. In-car overhauls are for engines still in relatively good condition with low wear, if the engine has rod or main noise already, patches are usually futile and a waste of time and money- unfortunately.