Charlesvolare
Well-Known Member
I have a small block that's smoking at idle, but only after it's warmed up. Nothing I can tell on initial startup or while driving around. It's an la 360 with magnum heads, 10.8:1ish compression. Kb107 pistons, moly rings, fresh heads (new +.100" valves, spring pockets cut, deck surface cut). Rebuilt it last December, fresh hone and top compression rings gapped to kb's nitrous spec of .032" (I rebuilt because a ring butted and popped a ringland off, wasn't taking any chances). First start was January 3rd. Roller cam, easy break-in just to seat rings. It drove great, 500 miles the first month no problems.
Did the first oil change and did an autocross event on February 1st, the first time really driving hard on the fresh engine. One of my buddies noticed it was smoking a little and said something. Spent the next month trying to figure it out. It didn't do it before that day and has done it ever since.
I've pulled a few springs and checked valve seals, good. No noticable oil smoke on initial startup either so I'm crossed valve seals/guides off the list.
Only seems to burn oil at idle, so I pulled the intake to check the gasket. Heads are milled a little so thought maybe the intake gaskets could be leaking. Replaced the intake (chinese crosswind) with new gaskets and no change. Got a deal on an Edelbrock 7577 (Edelbrock rpm air-gap for magnum heads). Put that on, no change.
Unplugging and blocking the pcv seems to make it smoke more. No excessive blow-by. Capping off the breather and pcv with vacuum gauge on dipstick, it slowly builds pressure. Not very quickly, but enough to for sure determine no vacuum leak at the intake. I can see oil on top of the pistons looking into the sparkplug holes, as well as through a small boroscope camera thing.
Did a dry/wet compression test, after it was warmed up: (first number was dry, second wet)
1-190 210
3-205 *
5-170 210
7-200 210
2-200 210
4-210 *
6-200 210
8-180 210
From all of this, I'm guessing I have a ring problem. 1, 5, and 7 are hurt somehow. I had 500 miles on it without any problem, no smoking or anything. Definitely thought the rings would be well seated by then, especially moly rings. Drove it hard for the first time, started smoking.
Any ideas to what would cause sudden ring problems like this? Or any other suggestions as to what it could be?
Autocross event:
Smoking at idle:
Cylinder hone
Did the first oil change and did an autocross event on February 1st, the first time really driving hard on the fresh engine. One of my buddies noticed it was smoking a little and said something. Spent the next month trying to figure it out. It didn't do it before that day and has done it ever since.
I've pulled a few springs and checked valve seals, good. No noticable oil smoke on initial startup either so I'm crossed valve seals/guides off the list.
Only seems to burn oil at idle, so I pulled the intake to check the gasket. Heads are milled a little so thought maybe the intake gaskets could be leaking. Replaced the intake (chinese crosswind) with new gaskets and no change. Got a deal on an Edelbrock 7577 (Edelbrock rpm air-gap for magnum heads). Put that on, no change.
Unplugging and blocking the pcv seems to make it smoke more. No excessive blow-by. Capping off the breather and pcv with vacuum gauge on dipstick, it slowly builds pressure. Not very quickly, but enough to for sure determine no vacuum leak at the intake. I can see oil on top of the pistons looking into the sparkplug holes, as well as through a small boroscope camera thing.
Did a dry/wet compression test, after it was warmed up: (first number was dry, second wet)
1-190 210
3-205 *
5-170 210
7-200 210
2-200 210
4-210 *
6-200 210
8-180 210
From all of this, I'm guessing I have a ring problem. 1, 5, and 7 are hurt somehow. I had 500 miles on it without any problem, no smoking or anything. Definitely thought the rings would be well seated by then, especially moly rings. Drove it hard for the first time, started smoking.
Any ideas to what would cause sudden ring problems like this? Or any other suggestions as to what it could be?
Autocross event:
Smoking at idle:
Cylinder hone