I have a 1990 RS with a TBI 305 stock. I've been trying to locate where it is coming from. It is not noticeable when the engine is cold, but when its hot and the oil pressure drops a bit it is noticeable. It is constant, as well it is most noticeable after I give it some gas and the engine idles back down. I was able to get a stethescope and found the sound is loudest about six inches behind the harmonic balancer on the oil pan. Any ideas what this could be? Any help would be appreciated.

 

oil pressure gets low and the engine makes a knock? sounds like you have some loose rod bearings. do you hear a ratatat-tat when you rev the engine?

 

sounds like a rod knock could be a bearing thats on its way out.. has it been doing this for a while? a lot of miles on the engine? sounds like a tiny person is in there with a tiny hammer tapping 'dink dink dink'.. it doesnt do it when cold huh.. might be oil flow Im sure you already checked your oil level and filter any metal on the dipstick? try changing to a heavier oil if it gets quieter then its probably bearings, but thicker oil is only a band-aid

hopefully its something simple.. I have a work van that gets noisy when its past due for an oil change, fresh oil and she quiets down

 

Thanks for the quick replies. I hear a rat tat tat right after I give it some gas and the engine starts to idle down. It just started a couple of days ago and I only put a couple of miles on it. There is no metal on the dipstick, the oil level is fine. If it is loose rod bearings what would the fix be??

 

Well you'd have to change them. But basically its time for an engine rebuild. just changing a rod bearing can maybe buy you some time. But without resizing the rod, and depending on damagae to the crankshaft journal. its really best to rebuild. Maybe an upgrade?

 

here are your choices

pour liquid sludge into the oil to quiet it down and run it till it breaks

or

short block rebuild

there are no mickey mouse fixes if you want to correctly fix a knock

 

Thanks for the replies, looks like it's rebuild time, but if I'm doing a rebuild I'll need to upgrade to get more ponies out of her.