67 L79 Oil Consumption

[Gary R.]

Re: 67 L79 Oil Consumption

I have the same deal. I haven't been able to get much time into it but have pretty much narrowed it down to the rings. The compression test was very good at 185-205,the leak down on the RH bank was bad at 50-60%. The exhaust ports and intake ports didn't have any oil in them, the PVC was free and clean. I even swapped intake gaskets( mostly to test out Hylomar) but it didn't matter.

I have 4,500 miles on them so I don't think it's seating issue. The rings are Speed-pro moly top rings, reg iron 2nd ring. The federal Mogul guys pretty much said the rings will be seated by the time the cam was broken in during the first break in. I did beat on it some but that didn't work either.

I'll just have to pull the engine and go over it to see. In the meantime it runs pretty good so I'm just going to drive it until Fall!

[John C.]

Re: 67 L79 Oil Consumption

WOW, thanks to everyone for all of the response, I believe I can rule out the PCV system as it appears to be operating properly. Duke, the heads were completely rebuilt as well, including new valves, seats, guides, seals etc. I did have to install screw in studs and guide plates due to some push rod wobble in one head. It was my intention to keep the exterior as NCRS correct as possible but to install the roller valve train/cam components. The cylinders were bored .30 over and the block was lined bored. Used forged pistons and balanced the rods etc. The oil pump is listed as M-55 high pressure but not high volume. You guys have given me a lot of good information. I'll send this to the machine shop and proceed accordingly with the test I can run myself. If I cannot find anything as you suggest, then I'll pull the engine for the third time and check the cylinder bore etc. I honestly appreciate everyone's response and help. Thanks jc

[Duke W.]

Re: 67 L79 Oil Consumption

There are several different valve guide rebuilding technologies and even more seal technology choices.

I suggest you find out exactly what was done vis-a-vis the valve guides/valves.

...manufacturer/part numbers of all parts used including the valves. Some valve guide technologies need specific surface plating on the valve stems for best compatibility and often have specific seal technology recommendations.

Duke

[John C.]

Re: 67 L79 Oil Consumption

Thanks Duke, I can easliy check that and with it being so consistant to all cylinders and the rings being replaced recently the valve system would be very logical area to inspect. I'll keep you posted and thanks again. jc

[William G.]

Re: 67 L79 Oil Consumption

Greetings,

I find I am always (very) interested in oil consumption issues.

Two questions.....please:

Ken Anderson states to squirt WD-40 into cylinder and pressurize same at 180 psi. Then look for "stuff" coming up the intake guide. With a new valve job how is the pressure/WD-40 going to get past the valve face? Once it does (if it does) then certainly it will travel up the valve stem.....but can it exit the cylinder (combustion chamber) via the valve face?

What is considered acceptable, average, or normal oil consumption on a small block of, say, 300.....350........365/375 hp? Back "in the day" oil consumption was maybe, what, 800 to 1200 miles to a quart? And while on the subject, is the volume of oil between the add and full marks on the dipstick of a small block truly a quart? Or something less? I'm in the process of checking mine....but until I'm down a quart and in the meantime; is it a quart or more like 2/3 of a quart?

Bill

[Domenic T.]

Re: 67 L79 Oil Consumption

william,
I saw that too, once past the valve seat it would take the least path of resistance and exit the port to the carb.

I have a differential compression tester and it uses 80 PSI thru an orifice and measures leak down.

The hard part about using it on a car is that you need to lock the flywheel at TDC compression stroke. You can lock it in gear if it is a stick shift.

Then you listen at the exhaust, carb or breather for leakage.

Leak down under 60 PSI is not to good, but it can happen if all the ring gaps line up which can happen as the rings rotate in the cylinder.

It will point out a bad set of rings or leaky valve.

The pump up compression test can lie if there is oil in the cylinders ( especially cold ) but the differential tester will eventually blow all the oil out and give a true leak down test.

Greetings,

I find I am always (very) interested in oil consumption issues.

Two questions.....please:

Ken Anderson states to squirt WD-40 into cylinder and pressurize same at 180 psi. Then look for "stuff" coming up the intake guide. With a new valve job how is the pressure/WD-40 going to get past the valve face? Once it does (if it does) then certainly it will travel up the valve stem.....but can it exit the cylinder (combustion chamber) via the valve face?

What is considered acceptable, average, or normal oil consumption on a small block of, say, 300.....350........365/375 hp? Back "in the day" oil consumption was maybe, what, 800 to 1200 miles to a quart? And while on the subject, is the volume of oil between the add and full marks on the dipstick of a small block truly a quart? Or something less? I'm in the process of checking mine....but until I'm down a quart and in the meantime; is it a quart or more like 2/3 of a quart?

Bill

[John C.]

Re: 67 L79 Oil Consumption

Thanks again gentlemen for all of your help. I'm going to top off the oil tomorrow and hit the road for another 160 mile trip hitting the RPM's a little harder and see what develops. I'll pull the plugs and check the oil level when things cool down and follow up with the compression and leak down test as well as an inspection of the valve guides and seals. At least checking this out provides some great time behind the wheel. Once again, I appreciate ALL of your help and i'll let you know what we find.

Thanks jc

[Clem Z.]

Re: 67 L79 Oil Consumption

with screw in studs some studs go into the intake ports,did you use sealer on those studs ???

[Timothy B.]

Re: 67 L79 Oil Consumption

John,

If you end up with the motor apart, check the oil pump gear height as a high volume pump has 1.5" tall gears and the standard volume has 1.3" tall gears.

If the stock L 79 is supposed to use a standard pressure/standard volume pump you may want to consider changing back but be careful with the Melling pressures even on a stock pump. I am not saying that's your problem, it's just my opinion. Check the archives or post a picture of what's in there now as the standard relief spring on the Melling has high pressure.

I never figured out why my 350 used oil except to say I took the motor apart and re-ringed it with moly rings and had the heads checked again. I never found anything wrong and when assembled it used oil the same way.

[Bruce B.]

Re: 67 L79 Oil Consumption

Just out of curiousity, what kind of oil did you use when the engine was broken in?
A good synthetic can prevent the rings from properly seating.

[John C.]

Re: 67 L79 Oil Consumption

I'll check the studs for sealer when ispecting the seals and guides. The machine shop is big on using Valvoline 15-40 for the oil, non synthetic so I followed their suggestion. This particular shop has rebult a lot of NCRS correct engines and used various combinations of components. They are working with me and they as concerned about finding the issue as I am so we're trying to eliminate one item at a time. I have printed all of the feedback from these discussions and will forward them to the shop next week to see if triggers other thoughts. Thanks again for all of the input.

jc

[Duke W.]

Re: 67 L79 Oil Consumption

10W-40 is a SM or SN oil - not the best for vintage engines.

Go to this thread from a couple of days ago:

https://www.forums.ncrs.org/showthre...88090&uid=1464

Download the engine oil article from the link. Print it. Read it how ever many times it takes to understand it, then educate your "engine builder".

Duke

[John C.]

Re: 67 L79 Oil Consumption

Thanks Duke, I'll forward this to them as well. I have seen and read your post in the past which have appeared to be nuts on. There seems to be a lot of opinions but you have the education and experience to back it up. They'll have this Monday. Thanks again, jc

[Joe C.]

Re: 67 L79 Oil Consumption

with screw in studs some studs go into the intake ports,did you use sealer on those studs ???

I can't say that they go into the intake ports, at least on the double humps, but I do know that they all go into the water passages. No sealer on those threads will cause sizable coolant leaks into the rocker boxes.

I am firmly convinced that some of these "phantom" oil consumption issues are likely due to porous or otherwise defective castings which create issues when heated. There are too many of these unsolved mysteries extant with original castings, and the slipshod manufacturing processes and lack of adequate quality control involving machining operations surely must have carried over into the casting operation. After chasing this same problem with no resolution involving a previous 327 I built, I can tell you that I had tried all available options at the time before I scrapped the block.

[Clem Z.]

Re: 67 L79 Oil Consumption

I can't say that they go into the intake ports, at least on the double humps, but I do know that they all go into the water passages. No sealer on those threads will cause sizable coolant leaks into the rocker boxes.

I am firmly convinced that some of these "phantom" oil consumption issues are likely due to porous or otherwise defective castings which create issues when heated. There are too many of these unsolved mysteries extant with original castings, and the slipshod manufacturing processes and lack of adequate quality control involving machining operations surely must have carried over into the casting operation. After chasing this same problem with no resolution involving a previous 327 I built, I can tell you that I had tried all available options at the time before I scrapped the block.

correct as i was thinking of BBC engines