hey guys picked up a 1989 formula 350 with 700r4 trans. when i start this thing whether its hot or cold it will run and idle smooth as glass. but if i slowly brings the rpms up to 2000, it deveops what sounds like a rod knock coming from the passenger side of the motor. now heres the wierd part. if i dont gradually rev the motor, if i just bring the rpms up quick there is no knock at all, revs up smooth and sounds normal. now here is where it gets really wierd, i let the car sit for a couple hours and did some errands came back fired it up and no knock sound at all even if i brought it up slowly like i did before, i got excited shut the car off went inside to get my buddy to show him came back out fired it and there it was again. but its always quite if i do a quick rev? any ideas? ill try to get a video of it soon. any ideas guys? new to this site just lookin for suggestions
thanks Jason

 

It could be many things.
A spun bearing, cracked broken flex plate, cracked piston or a lifter sticking.

 

i thought it could be those things too, at first but then again a rod would do it all the time no matter at an idle or not, i was leaning towards a broken or cracked flexplate also and got underneath of it but didnt see anything(more or less a quick glance) a lifter i can see that but why would it make the noise sometimes and other times not? i dont think its a cracked piston cause the thing still has power, it doesnt idle rough or anything to that nature. anymore ideas as to where to start lookin would be much appreciated
thanks Jason

 

Well now you have an excuse to give it hell, all the time! Lol.

 

When my old 305 spun two of its rod bearings it didn't make the sound all the time. How many miles are on the motor?

 

The easiest way to tell is to get underneath the car and rev it up until it makes the noise. You'll be able to tell if it's coming from the oil pan. If it is, my guess is it's going to be a rod bearing.

 

the car only has 138k, really? it didnt make noise all the time? thats wierd lol. im used to the lsx world. before this i had a 01 ss with a SD tuned forged 408 with LS3 heads and intake, 9.5 compression, th400 with hughes 3500 stall, 12 bolt with 4.10s that ran 11.30s all day, with full interior, cruise and ac

ill have to do that thanks for all your help guys, ill post pics of the old car and the firebird i just picked up
Jason

 

here is the bird i just picked up for 1400 bucks

 

here is the old car that my dad and i built

 

Mine only had about 127k on it when the rod bearings went. It spun two of them actually. Mainly because my father-in-law used to drive it and it was from oil change neglects. I think he probably put about 20k on that engine with out EVER changing or adding oil to it. He's an idiot, I know. That's why my mother-in-law gave me the car. I wasn't surprised when I tore apart that 305.

Anything is possible man. Depends on how the previous owner took care of it.

 

the kid i picked it up from, drove it hard for about 8,000 miles, and i think he only changed the oil once since he had it, but before that he bought it off an old couple this car was hers and the old man had a 90 formula 350, dont know how long they'd had owned it. car is in much worse shape than it was when he bought it from them, its ok though, with the snow here im gonna tear into it here soon

 

I havent heard what this tpi sounds like when a injector is stuck, but you can get knocking sounds if you got a stuck injector.