Are there any repetitive noises that could be confused for rod knock? Something's athumping and I'm praying my 305 is not ready to go. Its a '92 TPI...less than 200k miles on it, well maintained. Does anyone have good news for me?

 

the only thing else it could be is a loose torque converter(if auto) or a cracked flex plate

 

a bad connecting rod sounds very distinctive. Very 'ting'-y, as if someone was rapping on your engine block with a ball peen hammer at the same rate as your engine RPM's. Loud too....good luck.

 

my 305 tpi let go with only 36k on the clock, same issue, it was cylinder #6. started off sounding like a valve tap but progressivly got louder. it is difficult to tell the sound difference between a rod knock, piston slap (cracked or burned piston), or a broken or loose flexplate. you can have a group of 30 experience mechanics diagnose it and theyre all going to come up with something different. the only true way of knowing is to investigate. i can tell you though, you can buy a crank and bearings for $150 from advance auto.

 

The car only thumps once it warms up. Does that change anything? On the plus side, this may be a chance to throw in that 350/383 I've always wanted

 

only when its warm doesnt really help that much, but it can rule out some possibilites. a loose convertor or cracked flex plate would sound the same all the time. piston slap would possibly quiet down when warmed. if you want to, pick up a bottle or two of "no smoke" oil additive. if it makes it a bit queiter, it is probably a rod bearing. my mom's windstar runs on the no smoke oil because the oil pressure is so low.

 

when the motor warms up the oil get thinner. a bearing going would do just what is happening to u. what wt of oil r u useing? might be a good time to get the 350 ready. if u want it to last a little longer and arent going to salvage anything from the 305 stick some thicker oil and or additive in there and u may get a little xtra time.