502 BBC burning a bit of oil.

Grumpy · Apr 28, 2017

Gm says my new 502HO is useing oil at the rate of 1 qt every 500 to 600 miles is because on a few of these motors the rocker arm studs didn't get sealed. Is that even possible? I have about 7000 mi on the motor,no signs of an oil leak anywhere, all plugs look good with no signs of oil and it runs Great.

A phone call to the GM Regional Maintenance Representative might be in order. the service order writer at many dealerships will hope they can brush this off as it will cost them time and money to fix and not make them a profit. and even if the oil is leaking through the threads on those rocker arm studs, a dealership mechanic could simply, cure that problem by temporarily removing the rocker studs, carefully cleaning and degreasing the studs and threads in the heads and coating them with a decent thread sealant then re-installing them and re-adjusting the valves would clear that issue up.
obviously doing a leak-down test to asses the piston rings seal too the bore walls would be a logical test you might think about doing to get more data you can use, as would pulling the valve spring retainers and replacing the valve seals on all 16 valves and checking the valve stem to valve guide clearances.
Id suspect the valve seals might be defective or need to be replaced or they were never installed on a couple valves , or the rings never properly sealed to the bore walls, or a pvc valves defective or improperly hooked up, Id also put the car up on a lift and look at the valve cover and oil pan gaskets.
many 502 BBC engines used low tension rings to reduce rotating drag, and low tension oil rings do allow a bit more oil to flow past the rings so oil usage does tend to be a bit higher
Id also suggest an oil change and your use of a good 10w30 weight oil to help the rings seal to the bore walls,
this may be a good place too point out WHY you may want to use a DART AFTERMARKET BLOCK, a 502 O.E.M. block has significantly thinner bore walls as the casting is noticeably thinner than the DART block, and I'd point out that, G.M. uses low tension rings to reduce drag, in the engine too improve mileage, but low tension rings also allow slightly higher oil consumption, so its not at all un-usual for a G.M. 454-502 to use about a quart of oil every 500-700 miles , so youll generally want to check your oil level every time you fill the gas tank! you can do a LEAK-DOWN test and generally see the difference in the leakage or loss of ring seal due to the thinner bore walls in the O.E.M. bore walls.
but ID also point out that your issue is hardly rare and adding a quart of oil every second or third gas fill-up is hardly un-usual with a high performance BBC.
I've used either one of these two products, applied on clean dry threads by dipping the stud threads just prior to assembly on those threads, waiting a minute for the stuff to start to get tacky,then screwing them in for decades

the rotating assembly bearings ,wrist pins and complete valve train,valve springs, lifters, valves and valve guides and the pistons and rings are where a great deal of the engine heat is generated, and those components are initially cooled with oil flow that absorbs and transfers the heat collected , and transported from those components to the block and coolant, so having a constant flow of pressurized oil flow over those parts are mandatory for maximum durability.thus adding a larger capacity baffled oil pan and an oil cooler will generally enhance and extend an engines life span.

http://garage.grumpysperformance.com/index.php?threads/oil-system-mods-that-help.2187/

http://garage.grumpysperformance.co...sion-and-oil-cooler-increases-durability.176/

'

From a recent TSB from GM on oil consumption.
excerpt
A higher rate of oil consumption is normal for vehicles equipped with manual transmissions that are driven aggressively. By "aggressive," we mean operation at high RPM (3,000 RPM to redline), with frequent use of engine braking (using the engine to slow the vehicle). Vehicles that are driven aggressively may consume engine oil at a rate of up to 0.946 L (1 quart) every 805 km (500 mi). This is normal for a vehicle that is driven aggressively. No repair is necessary. This characteristic does, however, require the owner to check the engine oil level at sufficiently frequent intervals, especially when driving aggressively, to assure the oil level remains within the recommended operating range.

Ive never had a rocker stud leak oil into the intake ports, but in theory its possible so coat the threads with sealant thread locker before they get installed. and leak or you find a loose stud, never had any issues removing them if required ,with the proper socket and breaker bar later either,
I'd also point out that the clearance in the piston ring grooves and back-spacing has a huge effect on the way the rings seal.
if the oil is not frequently changed, sludge build-up behind the rings greatly reduces the ring seal efficiency.
once varnish or burnt oil residue builds up behind piston rings they will fail to seal to the bore walls effectively increasing oil burning and oil fouling spark plugs
https://www.bgprod.com/catalog/engine/bg-quick-clean-for-engines/

viewtopic.php?f=53&t=1797&p=4586#p4586

viewtopic.php?f=53&t=3897&p=26602&hilit=tool+groove+piston#p26602

step ONE
if the bores not concentric, and bore walls parallel and the bore surface consistent in its surface Finish or if you had the bore honed without the use of torque plates simulating a cylinder heads bolted in place, the rings WILL NOT SEAL as effectively , as they would if you had prepped the bores correctly or won,t seal effectively at all.
BEFORE you select any piston rings for any application, you obviously must know your bore diameter, and piston ring groove sizes, so check with the manufacturer to verify they will work in YOUR application,some of the 1/16" top compression rings are designed for limited mileage and race use , where they are replaced fairly regularly, thats certainly not true of all 1/16" rings but its potentially an issue on a street driven car.
be aware that rings have a top and bottom side , and must be installed with the proper side facing the top of the piston, and rings require a certain back and end gap clearance.

http://www.tooltopia.com/fowler-72-646-300.aspx

viewtopic.php?f=53&t=247

viewtopic.php?f=53&t=3897

viewtopic.php?f=53&t=5454

viewtopic.php?f=50&t=11026&p=48766#p48766

READ THE LINKS BELOW

viewtopic.php?f=51&t=588&p=4946&hilit=honing+plate#p4946

http://www.totalseal.com/pdf/ts_rings_article.pdf

http://www.kb-silvolite.com/news.php?ac ... ad&N_id=27

http://www.connectingrods.net/connectin ... tretch.php

viewtopic.php?f=53&t=1797&p=7233&hilit=cleaning+piston+groove#p7233

viewtopic.php?f=53&t=3759

http://www.dartheadstv.com/video_detail.php?mId=13335

http://www.enginebuildermag.com/Article ... _know.aspx

http://www.aa1car.com/library/honing98.htm

http://www.circletrack.com/techarticles ... ation.html

viewtopic.php?f=53&t=1797&p=4586#p4586

http://www.rosspistons.com/information/index.php

http://www.enginebuildermag.com/Article ... ishes.aspx

http://www.enginebuildermag.com/Article ... inish.aspx

http://www.aa1car.com/library/ar293.htm

http://www.enginebuildermag.com/Article ... ishes.aspx

http://www.enginebuildermag.com/Article ... rings.aspx

http://www.hastingsmfg.com/ServiceTips/ ... mendat.htm

http://www.stockcarracing.com/techartic ... index.html

http://www.circletrack.com/howto/4639_m ... index.html

http://www.carcraft.com/techarticles/pi ... index.html

http://www.enginebuildermag.com/Article ... oning.aspx

http://www.enginebuildermag.com/Article ... shing.aspx

http://www.stockcarracing.com/techartic ... index.html

piston rings move both in and out of the piston grooves and rotate as the piston moves thru its 360 degree rotation, keep in mind its the ring groove SPACING, and gap indexing and relationship to the rings, that is designed to minimize the loss of cylinder pressure thru the ring gaps, thats key, here, not where the gaps are exactly located , because the fact is that piston rings do tend to rotate in the piston groves in most engines, and its rare to find the ring gaps in the same location once the engines been run for several hours. Id also point out that failure to have the bore honed with the correct deck plates tends to reduce the ring seal. in fact having the rings rotate in the piston grooves tends to reduce bore wear, and keep the grooves clearance free from carbon build up

if you have oil ring expanders with the plastic bits,they are there to prevent you from over lapping the ends of the oil ring expander, theres some oil ring expander s that are vertical ,some horizontal, but all have the ends butt , none over-lap
BTW GAPLESS PISTON RINGS HAVE TWO PIECES THAT EACH MUST BE GAPPED< THE IDEA IS THAT THE TWO GAPS IN THE SET ARE ON OPPOSITE SIDES OF THE PISTON GROOVE

BTW, remember to visually verify the stud length and cut them a bit shorter if required you don,t want the lower end protruding into the intake port and any threads doing that do NOTHING to increase the stud rigidity but they sure can reduce port flow rates if left sticking down into the air flow path

502 BBC burning a bit of oil.

Grumpy

The Grumpy Grease Monkey mechanical engineer.