RMVette

After several years on a complete rebuild, my engine still uses about a quart per 400 miles and you can tell it smokes when it’s running, but not all the time. I don't drive the car very much, maybe 5000 miles total since the rebuild and it was bored .040 over with a roller rocker, lifters and cam installed to loosen up the top end. The engine builder was a Corvette mechanic who is out of business now but was considered a knowledgeable and reputable mechanic at the time. I don’t want to pull the engine out because I don’t want to chance damage to the paint or better yet, take the time to do it AGAIN so I’m living with it. The mechanic used chrome molly rings…so my question is, what’s the possibility that the rings never seated? I didn’t drive it too hard when I got the car back from the rebuild so was there a “proper” way to break an engine in? Growing up I heard different stories on how to break one in, one you drive it at different speeds for the first 500 miles and the second school of thought was to run it like you’d stole it. It does puff some on start up, would valve seals suck that much oil in? I’m thinking the rings didn’t seat but after that many miles I doubt they ever will. Thoughts? Thanks all!

Skip Burney

I have built several engines for both my cars and antique aircraft and I have always found that as soon as is safely possible take it out and run it like you stole it, get the oil hot and run it, don`t baby it but don`t abuse it either. I have found that with chrome rings they may take a little longer to work in but once they seal they are good to go. Did you run a compression check to be sure that it`s rings and not valve guides and seals.

RobRace10

If it's a puff on startup that means guides. I would do a compression and a leakdown test. Rings should be seated by now if there every going to seat.

GTR1999

I have the EXACT same deal with my 020 over 350. About the same mileage and use. Same mild break in, Speed-Pro moly top rings, machinist provided with the piston and rings prior to bore and hone. Honed with a plate, proper cam break in for 20-30 minutes. Smokes a little, burns when hammering the gas, tried to seat the rings with engine load braking,nothing worked.
Speed Pro techs told me the rings would have been seated during cam break in.
Plugs foul in about 1000 miles.

I haven't had time to do a comp or leak test. Sure don't feel like pulling the engine again either, so I just change the plugs, check the oil and drive it the 1000 miles a year until I can get back to it.

Let me know what you find out.Either my walls are glazed,intake leaking in, guide leaking, or I have broken rings. Both banks are fouling, just about all but not all plugs fouled.

Skip Burney

You can do a leakdown test like we do on aircraft engines at annual, a sparkplug adapter in screwed into the plug hole and the piston is at TDC, then you plug an air hose into the cylinder at 80 lbs and see how much air the cylinder is holding. You can listen to the carb for a hissing noise for a leaking intake or the exhaust for a leaking exhaust valve and listen to the oil pan for noise to check for leaking rings

noonie

Last engine I did with chrome rings took around 7000mi to stop using oil. Then, towing a car and trailer over 4000 hard miles last summer, it only used less than 1/4 qt.

The term chromoly has been used over the years very loosely and depending what brand they are, dictates what they are, but if they have an actual chrome facing, then they can be difficult to break in.

Even possible that the scraper rings were put in upside down, for that much oil usage. Even seasoned mechanics can make mistakes.
Numerous other possibilities.

Run a hotter tstat and put a bunch of enjoyable miles on it and see what happens.

RMVette

I have not done a compression or leakdown check and that's my next course of action, however the plugs don't foul, idles great with a steady vacuum. Late last year I started using 100 octane low lead fuel (from a small airport that remains nameless) and I have run it hard for a few weekends in a row. The car really, REALLY likes the 100LL! I also tried blocking the radiator with cardboard and ran the RPM's up and down to get the temp up and watched the gauge so it wouldn't overheat and neither of those options helped. I was told that chrome molly rings take a lot of heat to make them seat and now I'm afraid that the cylinder walls are glazed or too much time has gone by without the engine getting very hot. After the summer I may change the valve seals when I have time but I can't imagine that it would pull that much oil from the top end. Interestingly when I bought the car 10 years ago the engine had been rebuilt and bored .030 over and it was doing the same thing. I don't know what rings were used then. It's painful to have spent all the money on the rebuild and it still does the same thing after. If the valve seals don't work, I'll live with the usage.

Footnote 1: I did have someone tell me that if the heads and intake aren't planed correctly, there would be a misalignment at the bottom of where the intake and head meets and the engine would draw vapor from the valley. Has anyone heard of that or is it ?

Footnote 2: An old shade tree mechanic told me to go buy a bottle of Bon Ami (a cleaning power like Comet but it has very fine particles) and shake a tablespoon in the carb while I ran the RPM's up. I was stunned and asked what that would do other than locking up the engine! He said it would take the glaze off the cylinder walls just like honing the engine and allow the rings to reseat. I don't think I'll try that one!

fauxrs2

I think it far more likely that the mechanic made an error in assembly than the rings having not seated by now. The speed pro rings I used on my recent build were seated before I had driven a mile.

Ring tension could be too low, end gaps could have been filed too large, the rings could have been installed upside down...much easier to make a mistake here.

mds3013

First of all, I am no expert on engine rebuilding like some of the guys on the forum. What I would do is install new plugs and go about 20 miles. Pull all plugs and see if any have black or oily insulators. At least this will show if problem is with one cylinder or perhaps more than one or the entire engine. My 74 Z28 had a scratch on one cylinder wall and caused similar problem. Only #2 plug showed oil on insulator and sure enough when I pulled engine there was the defect in the cylinder wall. Good luck, mds...

63mako

I had this happen with valve covers with inadequate baffles under the PCV hole. Have also seen the baffles removed for bead blasting and cleaning during rebuild and not reinstalled. Sucked oil spray from the rockers into the intake through the PCV and used about the same amount of oil you are using. All the plugs looked the same when removed and didn't look oil fouled. Might check that. Puff on start up is usually valve seals or guides.

midyearvette

if you are indeed using that much oil with no apparent major leaks, then this much oil loss could not be attributed just to the valve seals alone. ......your rings would definately be seated by now.....if you are running "low tension" oil rings, this can sometimes be a problem on a street engine especially when equipped with forged pistons.....the fact that the engine was honed for the rings is puzzling ....if the bores were sized correctly, you might get 1000 miles a quart loss with forged pistons especially if on short trips......good luck...

birdsmith

Footnote 1: I did have someone tell me that if the heads and intake aren't planed correctly, there would be a misalignment at the bottom of where the intake and head meets and the engine would draw vapor from the valley. Has anyone heard of that or is it ?

RMVette, this is where you've finally gotten onto something. Unlike some V8's that have valley pans (Pontiac, Cadillac, etc.) and some others that have bolts that pull the intake manifold all in the same direction (down) like Fords, the smallblock Chevy was designed to be CHEAP to manufacture which means an absolute minimum of parts. While its inherent simplicity can be the shadetree mechanic's best friend, it is also its Achille's Heel. Even the slightest error in assembly or [re-]machining can cause leaks between the intake manifold and heads that will literally suck copious quantities of oil into the chambers. The fact that the bolts that attach the intake are facing away from each other on opposite heads and therefore pulling in opposite directions doesn't help matters much either. I have personally built TWO smallblock Chevys (out of a total of seven or so) that sucked down a quart of oil at the rate of one every 125 to 200 miles, and they were both fresh rebuilds. One of those is in my Vette now and I had to take it back apart twice after the initial build (the first time I couldn't believe that it could possibly be sucking that much oil up through the intake ports so I had it bored +.030" over and put new pistons in it, which didn't fix the problem) before I FINALLY managed to correct the problem by having the heads resurfaced to correct the error that my original machinist made. I put it back together and it now uses ZERO oil after over 30,000 miles of blissful running. If the machining error or mismatch at the intake joints isn't too great you may very well be able to correct the problem by removing the intake, cleaning all the surfaces THOROUGHLY, and reinstalling it with some extra-thick gaskets and very carefully lining both sides of the gasket with thin beads of Permatex Grey Hi-Temp RTV, torquing the intake back down very carefully and then letting it sit for a minimum two full days before you start it. If that fixes it, consider yourself very lucky. If it doesn't, the only way you're gonna be able to fix it is pull the heads back off and find out where the machining error was made. I've got moly rings in mine too, and I tried to entertain all those pipe dreams about rings not seating, but eventually I had to get to the root of the real problem which is as I've described it above. I have replied to at least a couple of other posts on this subject and been basically ignored- the thread continued as though I never said a word on the matter because most people in all their collective infinite wisdom seem to think it just plain absurd that this could happen at all ("a QUART of oil every hundred miles through the intake ports?? COME ON!!!??!) but TRUST ME- this IS your problem. It's not an urban legend, wive's tale, or some old shadetree mechanic's fable- it's as real as your New President. If it turns out to be something else I will personally FedEx you a six-pack of whatever you like- I like Fat Weasel Ale myself. All The Best...

HOOAH

I had a very similar problem with a stroker motor that I had professionally built. The only addition to your symptoms was that I was using an enormous amount of fuel. Being a high perfromance engine I didn't think that would neccessarily be that unusual. After kicking tires at a local speed shop recently and explaining my problem, they told me about the possibility that my rings were washed out. I have never heard of this but they explained that if the fuel/air mixture is way out of wack with excessive amounts of fuel dumping into the engine, it could actually wash the oil from the cylinder walls and subsequently prevent proper ring seating during break in. I have not torn it down yet so not sure if that's what my problem is but thought I would chime in as just another possibility. Try googling "washed rings" and various explanations will surface. Good Luck with your problem!

howarsc

I have seen this a few times. Especially when an engine is rebuilt but the carb is out of adjustment. If it ever ran real rich or continually flooded before you fixed the issue then you probably washed the rings and the rings are worn out. Even in just 500 miles...

The valves seals are cheap and fairly easy to replace. I would start there.
-Scott

'75

It seems that if this were the issue, it would be very hard to tune the carb due to the massive vacuum leak. Are there issues with the idle ?

...Roger...

Interesting........I remember being told years ago by some older mechanics they used to through the spark plug hole inject crushed walnut shells to remove the carbon from tops of pistons sooooo it would not surprise me if the Bon Ami trick was not tried also.

midyearvette

actually it was tried by chevy dealers in 1955 with the intro of the 265 cu mill!!......some smoked like a crop duster because of improper factory honing and you would mix a tablespoon of bon ami with an oil can of 30 weight and squirt it into the carb with the mill running at a fast idle....i dont know if it worked..i was a wash boy back then and remember going to the grocery store for the bon ami!!......

birdsmith

Here we go again... THERE WILL BE NO EVIDENCE OF A VACUUM LEAK BECAUSE THE OIL THAT IS BEING SUCKED THROUGH THE INTAKE JOINT IS LITERALLY PLUGGING THE LEAK!!!
It's not just 'vapor' that's being pulled into the intake ports, it's raw oil that is draining down into the valley from the cylinder heads through passages drilled on either side of the ports. Look at motor oil (especially newer multi-viscosity oils) when it's heated to operating temperature-it's roughly the consistency of kerosene. It will find any little crack it can capillate into and EASILY fill it ESPECIALLY if it has crankcase pressure working on one side and even the TINIEST little vacuum leak on the other side. THAT IS ALL IT TAKES. They don't call WD40 or Liquid Wrench 'penetrating oil' for no reason!!
As for the 'gas wash' issue, if you know for a fact that your carburetor is running really rich, was it doing that beforehand? And if so, why would you put it back on the engine and run it that way without getting it corrected? My aforementioned 350 had a Holley spreadbore double pumper on it for a short while that had leaky secondary boosters dripping raw gas into it when it was parked,'washing down' the cylinder walls with gas- one night it leaked fully TWO QUARTS of gas that went down into the cylinders and eventually into the crankcase. Once the intake issue was corrected and I replaced the hokey Holley spreadbore with a correctly set up Quadrajet it ran perfectly and didn't use a drop of oil.
I've spent at least a few minutes writing this in an effort to allow you to benefit from some of my own tribulations, none of which were (like yours) any of my own doing. MY MACHINIST MADE A MISTAKE. IT DOES HAPPEN. You have a gorgeous-looking Corvette and it deserves to run properly (for that matter, all of them do). Go ahead and thumb your nose at what I KNOW TO BE TRUE or ignore it altogether, but trust me on this- throwing a new carburetor at your car or dumping Bon-Ami down the intake WON'T fix it. As they say, "There's no magic in a can!"

AzMotorhead

Bon Ami " Hasn't scratched yet"
Easy thing to check first would be PCV valve and filter

RMVette

I’m not sure who you’re referring to in your response and maybe you have me mixed up with who responded back. I’m not disputing anyone here; all I’m trying to do is gather as much info as possible to make the best decision I can before I do anything and I’ve been told by more than one person to look at the intake. My Q-Jet doesn’t run rich because I rebuilt it prior to getting the engine back but that doesn’t mean that I didn’t make a mistake and screwed that up. Lord knows I’ve messed up enough and had to repair it again. Life lessons so to speak. I will enjoy the car for the summer before making a decision on what to do, and I’ll at least change the valve seals.

By the way, thanks all for the input. Ya’ll have more experience than me and this forum is a great way to share information.