The oil consumption issue
The following wandering thoughs were put down in answer to the ongoing oil consumption discussion and I thought that it might be good to get additional mileage out of it here, too. If interested, read on....
The comment was made about the variance in oil consumption on Northstar engines being more of a concern than the actual consumption of any given engine...thus the following comments.
Good point about the difference in consumption....
The real issue is the limitations of the production tolerances on the honing process for the cylinder bores. Size is no problem..they are all dead nuts. Surface finish is the issue. It is imperative that the "smoothest" possible surface finish from the process retain enough oil to not starve the top rings under continuous heavy load and high RPM. Unfortunately, to make the smoothest possible surface finish "rough" enough to retain oil...the resulting "roughest" or most aggressive surface finish the process is then capable of will contribute to a 1000 miles per quart or worse.
There is really no magic here. All the automakers have access to the same honing process and honing equipment manufacturers. Thus, they are all "stuck" with the same variation in production. As engine specific outputs have risen and the operating RPM of the engines have risen over the years all the engine makers have gone to a more agressive surface finish for proper oil retention. And all run into the same situation with variation in oil economy. If you do some reading and research you will find that all engine makers will state that roughly 1000 miles per quart is "acceptable" or "normal" in some fashion.
Not to say that the 'average" engine gets that oil economy...but...and engine that gets 1000 miles per quart will have absolutely nothing wrong with it at disassembly and inspection.
Fact is that the engines that tend toward the high end for oil consumption seem to look the best at high mileage...whether it is the higher oil supply to the top of the piston or the frequent spiking of the oil in the sump with fresh additives due to more frequent adds (or both) is up for debate.
Back in the "old days" of 350 cu in engines that made 180 HP it was entirely possible to make the cylinder walls mirror smooth and the engine would live and use virtually no oil. Won't work today with the HP over 1 HP/cubic inch and RPM up to 6000 continuos and 6500 RPM shift points. The top rings will not take it without microwelding to the ring lands of the pistons.
The honing operations have received many improvements over the years as technology in the honing arena improved. Today, diamond stones with a water based honing coolant is the norm for long life stones that do not change over time. The older processes with vitrous stones and honing oil change significantly as the stones break in and wear and the stones had to be changed frequently as they wore out...so each hone was going thru a continual cycle of break-in and wear out of the stones. Generally on a V8 two cylinders on each bank are honed at a time and then the other two are done in the next station by two other stones....so any given engine has 4 different honing stone sets in the differenct bores. Depending on what the life of the stones is and when they were being replaced there can be some variation in the surface finish (in regards to oil consumption) from cylinder to cylinder and bank to bank. Usually when the stones are new they make the most aggressive cut and leave the most aggressive pattern. The stones get smoother as they wear and the pattern gets less agressive. All the stones are "broken in" in initially on scrap blocks but there is obviously some change in the next several hundred blocks.
To put things in perspective, an average engine builder might hone one or two engines a week. A major NASCAR engine builder might do 400 or 500 engines a year..... EVERY DAY the engine plant that makes Northstar engines hones 1000 blocks...that's 8000 bores. And even more are done on a lot of days...the 1000 number is very loose. There is a great deal of process control placed on the cylinder wall surface finish but the inherent variences in the process will certainly lead to a considerable difference in oil economy in some engines...and absolutely nothing will be wrong with them.
Personally, if I could pick my engine from the line, I would go for one that uses about 1500 per quart. Seriously.
One thing that was done on the original Northstar engines was a process called plateau honing. In this process the cylinder walls are "marked" with a very agressive hone that leaves fairly deep scratches. The high points of the hone pattern are then smoothed with a second hone plateauing off the tops or tips of the "peaks". Under a micorscope this looks like a flat platueau with relatively deep, narrow crevices for oil retention. This process worked very well for oil retention and durability but was inconsistent for oil consumption to some extent. The current process has been improved with a more conventional hone that is not deliberately plateaued and is more consistent. Plus it uses the diamond stones that last far longer and are much more consistent over time.
The other thing that the modern engines sacrifice oil consumption for is friction. The thinner rings and lighter spring load rings are desireable for power, sealing of compression, less friction and lighter mass for less ring flutter at high speeds. Unfortunately, there is no free lunch here, and the lighter rings let a little more oil by.
The 2000 and later Northstar engines get hard anodized top ring lands to resist pound out and wear since the ring lands were moved closer to the top of the piston. One unfortunate side effect of the hard anodizing is the microscopic "pebbly" finish of the anodizing that tends to cause lack of seating of the SIDE of the ring to the SIDE of the ring land. This pebbly area will retain oil and cause oil consumption until the anodizing is polished smooth as the rings "break in" to the ring lands. The anodizing is hard, however, so that is why the "drive it like you stole it" advice works , particularily on later Northstars, to ensure good break in and sealing for less oil consumption. Many of the oil consumption complaint engines that have been analyzed at the factory had the anodizing on the piston ring lands virtually unscathed...as in never broken in due to gently driving and babying. The engine likes heavy loads, high RPM to break in completely.
The heavy load/high RPM also promotes ring rotation on the piston to keep the rings freed up and mobile. The oil comsumption complaints from the older Northstars typically come about due to ring sticking in the ring lands due to carbon buildup and the rings gradually getting stuck in place. they have to move to work. Keep them exercised.
Hopefully this rambling will shed additional light on the subject....
The following wandering thoughs were put down in answer to the ongoing oil consumption discussion and I thought that it might be good to get additional mileage out of it here, too. If interested, read on....
The comment was made about the variance in oil consumption on Northstar engines being more of a concern than the actual consumption of any given engine...thus the following comments.
Good point about the difference in consumption....
The real issue is the limitations of the production tolerances on the honing process for the cylinder bores. Size is no problem..they are all dead nuts. Surface finish is the issue. It is imperative that the "smoothest" possible surface finish from the process retain enough oil to not starve the top rings under continuous heavy load and high RPM. Unfortunately, to make the smoothest possible surface finish "rough" enough to retain oil...the resulting "roughest" or most aggressive surface finish the process is then capable of will contribute to a 1000 miles per quart or worse.
There is really no magic here. All the automakers have access to the same honing process and honing equipment manufacturers. Thus, they are all "stuck" with the same variation in production. As engine specific outputs have risen and the operating RPM of the engines have risen over the years all the engine makers have gone to a more agressive surface finish for proper oil retention. And all run into the same situation with variation in oil economy. If you do some reading and research you will find that all engine makers will state that roughly 1000 miles per quart is "acceptable" or "normal" in some fashion.
Not to say that the 'average" engine gets that oil economy...but...and engine that gets 1000 miles per quart will have absolutely nothing wrong with it at disassembly and inspection.
Fact is that the engines that tend toward the high end for oil consumption seem to look the best at high mileage...whether it is the higher oil supply to the top of the piston or the frequent spiking of the oil in the sump with fresh additives due to more frequent adds (or both) is up for debate.
Back in the "old days" of 350 cu in engines that made 180 HP it was entirely possible to make the cylinder walls mirror smooth and the engine would live and use virtually no oil. Won't work today with the HP over 1 HP/cubic inch and RPM up to 6000 continuos and 6500 RPM shift points. The top rings will not take it without microwelding to the ring lands of the pistons.
The honing operations have received many improvements over the years as technology in the honing arena improved. Today, diamond stones with a water based honing coolant is the norm for long life stones that do not change over time. The older processes with vitrous stones and honing oil change significantly as the stones break in and wear and the stones had to be changed frequently as they wore out...so each hone was going thru a continual cycle of break-in and wear out of the stones. Generally on a V8 two cylinders on each bank are honed at a time and then the other two are done in the next station by two other stones....so any given engine has 4 different honing stone sets in the differenct bores. Depending on what the life of the stones is and when they were being replaced there can be some variation in the surface finish (in regards to oil consumption) from cylinder to cylinder and bank to bank. Usually when the stones are new they make the most aggressive cut and leave the most aggressive pattern. The stones get smoother as they wear and the pattern gets less agressive. All the stones are "broken in" in initially on scrap blocks but there is obviously some change in the next several hundred blocks.
To put things in perspective, an average engine builder might hone one or two engines a week. A major NASCAR engine builder might do 400 or 500 engines a year..... EVERY DAY the engine plant that makes Northstar engines hones 1000 blocks...that's 8000 bores. And even more are done on a lot of days...the 1000 number is very loose. There is a great deal of process control placed on the cylinder wall surface finish but the inherent variences in the process will certainly lead to a considerable difference in oil economy in some engines...and absolutely nothing will be wrong with them.
Personally, if I could pick my engine from the line, I would go for one that uses about 1500 per quart. Seriously.
One thing that was done on the original Northstar engines was a process called plateau honing. In this process the cylinder walls are "marked" with a very agressive hone that leaves fairly deep scratches. The high points of the hone pattern are then smoothed with a second hone plateauing off the tops or tips of the "peaks". Under a micorscope this looks like a flat platueau with relatively deep, narrow crevices for oil retention. This process worked very well for oil retention and durability but was inconsistent for oil consumption to some extent. The current process has been improved with a more conventional hone that is not deliberately plateaued and is more consistent. Plus it uses the diamond stones that last far longer and are much more consistent over time.
The other thing that the modern engines sacrifice oil consumption for is friction. The thinner rings and lighter spring load rings are desireable for power, sealing of compression, less friction and lighter mass for less ring flutter at high speeds. Unfortunately, there is no free lunch here, and the lighter rings let a little more oil by.
The 2000 and later Northstar engines get hard anodized top ring lands to resist pound out and wear since the ring lands were moved closer to the top of the piston. One unfortunate side effect of the hard anodizing is the microscopic "pebbly" finish of the anodizing that tends to cause lack of seating of the SIDE of the ring to the SIDE of the ring land. This pebbly area will retain oil and cause oil consumption until the anodizing is polished smooth as the rings "break in" to the ring lands. The anodizing is hard, however, so that is why the "drive it like you stole it" advice works , particularily on later Northstars, to ensure good break in and sealing for less oil consumption. Many of the oil consumption complaint engines that have been analyzed at the factory had the anodizing on the piston ring lands virtually unscathed...as in never broken in due to gently driving and babying. The engine likes heavy loads, high RPM to break in completely.
The heavy load/high RPM also promotes ring rotation on the piston to keep the rings freed up and mobile. The oil comsumption complaints from the older Northstars typically come about due to ring sticking in the ring lands due to carbon buildup and the rings gradually getting stuck in place. they have to move to work. Keep them exercised.
Hopefully this rambling will shed additional light on the subject....
