[sdbob]

Probably not this problem. On SD455s the rocker studs break into the intake ports and the valve cover bolts also which can leak oil into port if not sealed properly. If the heads hadn't any port work probably not this problem. Hopefully its valve seals.

[TCSGTO]

I wouldn’t worry about the actual compression test numbers. Yours are consistent across the board and look good.
I still vote for oil coming from up top not the rings. Many more times than not oil smoke at idle is getting sucked into the chamber through a seal/guide or PCV, not pushed in from the piston. If it was smoking under heavy throttle then I’d suspect a ring/cylinder issues.
Will your camera reach down the intake runner and see the valve head? If so check for oil deposits on the stem and head. You may see raw oil in the cylinder head port too if it’s running down the valve.

[DavesGTO]

I have a small DEPSTECH endoscopy scope, I’ll get some pictures! Thanks all for the support!


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[DavesGTO]

Broken foot hobbling me but I took a few pics. Can’t the intake off right now but took off the carb and took a few pics of #1 and 7 intake valves. Got a new set of e3 plugs and did the leak down test. This pic of the plug is after 15 minutes run time. I can hear air coming from the PCV tube coming out of the valve cover. Snapped pic of the leak down gauge after 2 minutes. Not good? Thanks for your help!







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[geeteeohguy]

Originally Posted by DavesGTO

Broken foot hobbling me but I took a few pics. Can’t the intake off right now but took off the carb and took a few pics of #1 and 7 intake valves. Got a new set of e3 plugs and did the leak down test. This pic of the plug is after 15 minutes run time. I can hear air coming from the PCV tube coming out of the valve cover. Snapped pic of the leak down gauge after 2 minutes. Not good? Thanks for your help!







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That's a very forgiving leakdown tester. Most have 30% at the end of the moderate range and anything above that is considered high. You want less than 20%, less than 10% preferred. The 383 in my '61 Chev had 30% leakdown in every cylinder and 195 compression in every cylinder and had tons of blow by. On teardown, the rings were worn out totally. A rebuild with new rings and a line-hone job on the cylinders totally fixed it. Another clue you have a lot of excessive blow by is that the engine oil turns pitch black very quickly.

[steve25]

Air heard getting into the crankcase like you have going on is at minimum a reason to pull both heads and look at the cylinders at this point!

[DavesGTO]

Thanks guys! First ride in 16 years on Friday to my buddy’s shop to do the front end. Then home for the teardown.


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["QUICK-SILVER"]

How much run time this engine got on it?

First picture I'm seeing a mirror like finish on that cylinder wall.

New rings without hone?

Food for thought
Clay

[DavesGTO]

Originally Posted by "QUICK-SILVER"

How much run time this engine got on it?

First picture I'm seeing a mirror like finish on that cylinder wall.

New rings without hone?

Food for thought
Clay

I would say it has idled for maybe a total of 4 hours, never been under load. Didn’t want to drive it until the front end was done but my buddy said to drive it the 3 miles to his shop on Friday, first time it will be on the road. Reputable local shop did the rebuild but not a Pontiac specialist. Was told by my dad new pistons and rings?


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[lust4speed]

Originally Posted by DavesGTO

...it has idled for maybe a total of 4 hours, never been under load...

My suggestion is to drive it moderate for a half mile, and next half mile start getting on it. Last two miles to the shop drive it like you stole it. Rings are not going to seat at idle and other surfaces are not getting enough oil splash to properly seat in.

I tell my friends that if they let the new engine idle for over a few moments in the first five hundred miles after taking it home they own whatever damage is done.

[steve25]

Come on!
Lets get real here!

Plugs getting that darn black after only some idling time is 95 % not in anyway shape or form from rings not seating, and if by chance it is from the 5 % that's left, then that motor will never perform right!!

[lust4speed]

Plugs show a massively rich idle. My contention is that the raw gas from all that idling is going to wreck ring seal - or in other words if rings don't seal up it will be the result of improper break-in and not how engine was assembled. My suggestion was to get it out on the road and cease and desist letting engine lope along at idle washing down the cylinder walls.

[grivera]

If not already done, make sure you check condition of oil and/or change it before running that engine further as it is likely diluted with fuel.

[DavesGTO]

Thanks for all the input! Have 6 quarts of Lucas break in oil and a new Wix filter to put in before I head over to the shop. Guess the silver lining at this point is the smoke should keep the mosquitoes away.


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[geeteeohguy]

Originally Posted by lust4speed

Plugs show a massively rich idle. My contention is that the raw gas from all that idling is going to wreck ring seal - or in other words if rings don't seal up it will be the result of improper break-in and not how engine was assembled. My suggestion was to get it out on the road and cease and desist letting engine lope along at idle washing down the cylinder walls.

THIS^^^. 4 hours at idle without driving a new engine is a death sentence. My bet is the rings have never seated and now, likely won't due to washed out cylinder walls/no lube to the rings. Likely a re-hone and new rings will be needed. Never, ever idle a new engine for extended periods. Break in the cam for 20 minutes, dump and fill with fresh oil, and go DRIVE it at varied speeds under load. Accel and Decel to seat rings.

[Dragncar]

Best thing you could ever do to seat in fresh rings is drive it up a mountain on a windy 2 lane road. Or a drag strip ! Break the cam in, dump the oil, fresh oil and drive it.
4 hours at idle is crazy. Not good for anything, cam, rings, nothing.

[John Milner]

Before I tore it down, I would certainly put some miles on it and see if the problem goes away. I have had several that smoked some right after a rebuild but after putting some miles on it and getting it tuned right, they don't smoke at all and still run fine to this day.

[DavesGTO]

I’ll update after the trip to shop, maybe a pic or two. Idle time is cumulative, about once every 4 to 6 weeks, 15 minutes a pop. I’m a 70 guy so wasn’t in on the restoration when my dad started it. Once I saw what was happening I had to finish it up as he wasn’t going to get it done. Got involved about 20% into it. He was skipping stuff he shouldn’t have and doing stuff way out of order. Why I am doing the front end now. At least he got to see all back together. Thanks for all the replies, really appreciated!


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[geeteeohguy]

Originally Posted by DavesGTO

I’ll update after the trip to shop, maybe a pic or two. Idle time is cumulative, about once every 4 to 6 weeks, 15 minutes a pop. I’m a 70 guy so wasn’t in on the restoration when my dad started it. Once I saw what was happening I had to finish it up as he wasn’t going to get it done. Got involved about 20% into it. He was skipping stuff he shouldn’t have and doing stuff way out of order. Why I am doing the front end now. At least he got to see all back together. Thanks for all the replies, really appreciated!


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Unfortunately, running an engine for 15 minutes at idle every few weeks without driving the car is about the worse thing you can do. It never gets warm enough for long enough to burn all the condensation out of the crankcase and exhaust. So you end up with contaminated oil that can be corrosive to bearings, etc. Better off to let the car sit for even a couple of years at a time than to fire it up and run it a few minutes. Much less wear and tear.

[DavesGTO]

Yea, unfortunate how it has turned out. I did what I could to make things right once I got involved but wouldn’t drive it with the front suspension the way it was. Expecting the worst case as that seems to be the norm for me.
Drove it to the shop on a back road, car has 4 miles on it now. Didn’t puff any major white clouds but never got out of 2nd gear (last car had a 3:90, prefer that over the 3:23). Wife had to put recirculate on in her car, I could see the haze when I gave it some gas and when stopped. Embarrassing, I’ll have to drive at night to put some miles on it. I have a 70 WS short block out of my old judge. Would like to put that in but concerned about bolt patterns for ancillary equipment. Car has a/c, ps and 80 amp alt.
One positive note, changed from auto to 4 speed. Peter Serio did a great job on the gauges and speedometer. Got lucky and put the right gear in the trans, speedometer was accurate and worked like new. Can check that off my list.


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