I just ran seafoam through my '00, 53k mile Z28 per the instructions. In through brake booster line, half can, bout 5 minutes sitting.

I got barely anything. There was some barely noticeable light white smoke, and pretty weak fumes. Nothing compared to some of these people talking about it looking like a insect fogger.

No way I'd leave it in overnight, and dropping the oil pan to check for sludge afterwards imho would be f-ing insane. If you're that worried about sludge wouldn't it be easier to cut your oil filter open?

I don't think the stuff is snake oil, but I don't think it just totally wipes carbon like people think. Doesn't seem like it can hurt, but then again I don't think any additive is going to be strong enough to dissolve such things without being a risk to seals, hoses, and gaskets at the same time.

Maybe you get more smoke using a whole can, or dumping it in at the end?

 

When me and my buddy did mine a few years ago (gm top engine clean- not seafoam) we let it sit for about 4-5 hours...... then we started it up: BILLOWS OF SMOKE - the neighbors actually called the fire dept. because they thought the BLOCK was on fire! LMAO...... I had just did a cam swap so I was trying to "do all the little stuff too"


also: we did it a SECOND time shortly thereafter (same day) and let it sit for about an hour.... and know where near the smoke as the first time... hope this helps.

BTW: wanna know how I clean the top end of my car now? A lil nitrous once a month!!!!

 

You're supposed to keep the engine running while you're pouring in Seafoam or GM Top Engine Cleaner. I used the GM stuff and sprayed it down the throttle body and kept it running. If the motor stalls, you're supposed to start it back up and keep pouring until the can is empty, then turn the motor off. I let mine sit while I changed the plugs and wires which was a few hours. When I started it up, it blew LOTS of smoke out.

Jason