im getting a weird noise at low idle. it sounds like a knock but as soon as i give it some throttle it comes to life and the knock goes away. it also seems to be loading up at low idle. any idea what it could be? its a carbed 305. also it seems to be hard turning over when its hot.

 

had that happen to me in a 89 Chevy truck. Luckily it was a few bolts that missed tightening by the power steering pump that holds the accessory bracket on. Try to pin point where the noise is coming from. If not a bearing might be going

 

i was thinking if it was a bearing it wouldnt it do it all the time? i was always under the impression that the more you rev a bearing it would get louder not quieter. could it be out of time and the carb loading up? it sat for a while when i sold it. also im noticing it loosing a few rpm and then gaining it right back as im driving down the highway.

 

after doing some looking today i notice the line from the pcv valve to the front of carb was sucking shut. after fixing the problem it needed the throttle adjusted and it started to idle better. could this have been the problem?

 

It could do it if it where worn bearings. At low idle speeds, theres less oil flow, so if the clearances are larger than they should be, it can knock. Used to have an old S-10 with a remote oil filter that did it when I first started the engine. Once it got oil, it quieted down.

How fast is the knock? That can tell you more about what it is. If its a slow knock, then it could be something in the valvetrain like a lifter thats gone south.

 

it seems to be a slow knock. im wondering if the pcv valve being totally blocked it wasnt letting the engine breath properly . it seems to be fine now that i fixed that line and used the choke when starting it. i have about 55 pounds oil pressure after warm up and around 60 or more when its cold.

 

oil psi sounds good. maybe it was bad gas or something from sitting. They say the worst thing you can do to a car is let it sit??? Sea foam would be a good idea if it sat a while just for the hell of it. its not going to hurt anything

EDIT: I work at a refinery and can tell you they don't make gas like they used to. It evaporates faster and doesn't keep its octane rating for over two years like the old stuff we used to burn.