Oil consumption & smoke on a 327/350 hp

[Gerald C.]

Here's the story:

My freshly rebuilt engine has about 500 miles on it. When installed, it ran pretty well. It was a bit rough. but I attributed that to the new engine and a timing issue. I took it on about a 200 mile ride and went through 22 gallons of fuel and 2 quarts of oil. The car was also smoking. The engine shop said that the fuel was "washing" down the cylinders and the smoking would stop once the fuel and excess oil burned off.

We readjusted the floats as you can imagine, the carb was running very rich and re-tuned the car. We changed the oil and the plugs. The compression test was about 155 to 160 lbs. per cylinder.

I went out again yesterday and it was still smoking and the plugs got fouled again. The gas consumption wasn't TOOOO bad, but I did go through another 1.5 quarts of oil. I'll connect with the engine shop tomorrow, but I wanted to reach out to see if anyone had any ideas on this issue.

Thoughts and questions????

Thanks,

Jerry

[Dennis O.]

Re: Oil consumption & smoke on a 327/350 hp

I had almost the same problem. Lots of smoke on start-up, excessive oil consumption, and fouled plugs on a fresh rebuild. It turned out the engine was built with a Hi-Voluime, Hi-pressure oil pump. It is my conjecture that the pump supplies more oil to the rocker arms than the drain system can handle, and it overwhelms the oil seals on the guides. Another symptom was a pegged oil pressure guage except at hot idle, when it showed 55 lbs. I ended up replacing the Hi-Volume pump with a Melling standard volume pump. That pump comes with a hi-pressure spring installed and a medium pressure in an envelope in the box. I ordered a standard pressure spring from Melling, and replaced the pump in the car with it. I now have 35 lbs a hot idle, it runs at 50 lbs, I have no smoke at start-up, the plugs have cleaned up, and oil consumption is back to normal. It seems that just about every engine builder out there cannot resist putting a "racing" pump in these engines.

Replacing oil the pump solved all of my problems. This may not be your problem, but it sure sounds like it. If it looks like this is your problem, let me know and I will get you the Melling numbers for the pump and spring. Can your engine builder (or your receipts) tell you which pump was installed? Seems to make a huge difference. If you use the Fel-Pro one piece pan gasket, changing the pump is not as daunting a job as it may seem at first.

[Duke W.]

Re: Oil consumption & smoke on a 327/350 hp

All anyone here can do is guess. It's up to you to determine from the shop what was done to the engine.

What pistons and rings were installed? Manufacturer and part number? Were the cylinder walls properly finish honed for the installed ring technology?

What about the heads? Were the valve guides rebuilt? Is the valve stem finish compatible with the new valve guide material? What type of valve seals were used?

You should have received a detailed invoice with manufacturer and part number of all installed parts, but it's amazing how many people don't get such.

The archives are full of rebuild horror stories. My advise to all is to thoroughly research any engine rebuild project. Select all parts that may require replacement - manufacturer and part number, and MANAGE the "engine builder". If you just turn over your project to some guy and let him make all the decisions you may end up with a disaster even if the guy had been in business for decades and has a "good" reputation.

Once you can post answers to the above questions, some here may be able to offer advice on how to proceed, however if the carburetor is OE or a correct OE replacement and hasn't been screwed with by bubba it should not be excessively rich and fuel economy should be no worse than low to mid teens for city to highway driving.

Here's a recent story from a local chapter member. He sent his '66 300 HP heads out for rebuild to correct high oil consumption. He didn't get a parts invoice, but found out what parts were installed after talking to me. The parts supplier was an outfit named QualCast, which I had never heard of, but they may only supply parts to the trade, and it appears that they may manufacture some parts, but may also just repackage F-M and Dana parts.

From the napaonline.com cross reference it appears that the installed valve springs are equivalent to the GM 3927142, which was the spring designed for the Trans Am racing cams. It's nominally 110 pounds seat force with a rate of 358 lbs/in. versus the second design OE small block springs (3911068, Sealed Power VS677) which are 80 pounds and 267 lbs/in, which with careful seat height setup will contain lifter pump up until 6500+ that is far beyond the point where a 300 HP engine without massaged heads and the McCagh Special cam will make useable power.

Now what would possess the guy to install these springs. I have no idea, but it's the same mentality that gets you high volume, high pressure oil pumps, high flow water pumps and all sorts or other aftermarket hot rod parts that just screw up the engine.

I suggested to the owner that he get those gorilla valve springs out of there before they started pulling rocker studs. The engine is now out for a complete rebuild including the heads again.

Duke

[Gerald C.]

Re: Oil consumption & smoke on a 327/350 hp

Dennis,

My oil gauge is pegged until the car gets really hot. This may be my problem. Let me check with the engine builder to see what he put in. As mentioned, he builds a lot of racing engines!

Can you send me the info on the pump you used?

Thanks,
Jerry

[Michael H.]

Re: Oil consumption & smoke on a 327/350 hp

I had almost the same problem. Lots of smoke on start-up, excessive oil consumption, and fouled plugs on a fresh rebuild. It turned out the engine was built with a Hi-Voluime, Hi-pressure oil pump. It is my conjecture that the pump supplies more oil to the rocker arms than the drain system can handle, and it overwhelms the oil seals on the guides. Another symptom was a pegged oil pressure guage except at hot idle, when it showed 55 lbs. I ended up replacing the Hi-Volume pump with a Melling standard volume pump. That pump comes with a hi-pressure spring installed and a medium pressure in an envelope in the box. I ordered a standard pressure spring from Melling, and replaced the pump in the car with it. I now have 35 lbs a hot idle, it runs at 50 lbs, I have no smoke at start-up, the plugs have cleaned up, and oil consumption is back to normal. It seems that just about every engine builder out there cannot resist putting a "racing" pump in these engines.

Replacing oil the pump solved all of my problems. This may not be your problem, but it sure sounds like it. If it looks like this is your problem, let me know and I will get you the Melling numbers for the pump and spring. Can your engine builder (or your receipts) tell you which pump was installed? Seems to make a huge difference. If you use the Fel-Pro one piece pan gasket, changing the pump is not as daunting a job as it may seem at first.

Jerry,

I had a simular problem with oil gauge being pegged, I changed over and put a standard Melling oil pump in and now my pressure is like Dennis's. This may not be your problem but a good place to start, if not I would look at valve guides and seals next before going on to the rings.

Mike

[Gene M.]

Re: Oil consumption & smoke on a 327/350 hp

I don't buy the engine builder's story one bit. A high pressure pump should not create high oil burning. The guides are bad fit, oil seals are junk, rings orientated wrong, or something screwed up with piston ring cylinder wall fit and finish are all possible issues. Ring gaps could be excessive and some aligned up. New engine is no excuse to run rough. They ran smooth when new. Less than 10 mpg is pretty bad for an L79.

I would be taking that engine apart to see for myself what is wrong. Starting with cylinder head guides and seals.

[Dennis O.]

Re: Oil consumption & smoke on a 327/350 hp

Oil pump Melling 10553; spring 55049. Make sure you get that pump, as Mellinhg makes another pump that is functionaly the same. The other standard pump (ironically built to GM's specs) has a lighter body casting and is more prone to breakage. Also, consider getting a new Melling pickup assemblt, as these are press fit, "one time only" installations. If you need one, I have the Melling tool used to install the pickup in the oil pump body. I think if you properly tack weld the old pickup to the pump body, you should bee all right, because the pickup is probably brand new. Good Luck.

[Dennis O.]

Re: Oil consumption & smoke on a 327/350 hp

Gene,

Trust me, a hi-volume. high pressure pump WILL cause excessive oil consumption. When I changed mine out, my problems went away just like flipping a switch. An oil pump change is a lot easier and cheaper than gettting into the heads of a new rebuilt engine. In light of what the OP says about his high oil pressure readings, I will guarentee you this is the place to start, especially if he finds out he has the HV/HP pump.

Denny

[Gene M.]

Re: Oil consumption & smoke on a 327/350 hp

Denny,
It would be sufficient to have a stock pressure and volume output oil pump. No need for racing stuff here. But the oil consumption has to be making it's way into the cylinders in order to burn. The oil pump pressure is not going to put it into the cylinders unless the drain holes are all closed off by casting flash or foreign material. That would allow the valve guides to be over burden with oil if the guides are loose and/or the O ring seals are NG or MISSING.

As Duke states above there is something not kosher with cylinders or guides allowing oil into the combustion chamber.

[Gary R.]

Re: Oil consumption & smoke on a 327/350 hp

I too had a similar issue with my 72 only I built the engine and didn't use a HV pump. I checked the pictures of the pump Dennis had installed to see if it looked like the one in my 350 but it wasn't. Right now I'm running 15w40 oil and that might be part of the cold psi on the gauge, when it's hot it's about 40 psi @800 rpm. I was sucking down a qt of oil every 5-600 miles and just didn't have much time to address it. I have some old threads here, I think with pictures. I checked the PVC, replaced the intake gaskets, did compression and suspect leak down tests, and just couldn't believe I fit the rings wrong during rebuild. I also didn't buy into to beating the heck out of a fresh rebuilt engine as some suggest but I tried using the engine to load the rings, nothing worked and I was ready to pull the engine again. The one thing I always suspected were the SR Torquer heads I used. I pulled the plugs and they were always a fouled mess after about 700 miles. So before I pulled the engine I had the original 72 heads rebuilt and had positive seals installed. I swapped the heads on the 4th of July this year, recurved the distributor, and still have to rejet the carb but after I fired it up and burnt off the oil in the cylinders I didn't see anymore smoke. I drove it home and parked it until yesterday when I took a break rebuilding diff's and fired the car up. I took it for a 12 mile run and back home. I would normally see smoke about 10 minutes into driving but it was clear. I still have to tune the carb then I'll see how the car runs on a longer ride. When I put the Torquer heads on the work bench and went back later there was oil free flowing out the intake runners. These heads came with umbrella seals and just didn't work. I could clearly see the chambers were divided between oil fouled side on the intake and the white lean side of the exhaust. I am also switching over to Penn 10w40 oil and getting away from the Rotella I have in it now.

[Gary R.]

Re: Oil consumption & smoke on a 327/350 hp

Here is the link with the pictures of the heads I pulled off. https://www.forums.ncrs.org/showthre...999#post671999 The car seems to run better with the 194 heads too then the 202's but it's not a 5500+RPM engine either

[Gerald C.]

Re: Oil consumption & smoke on a 327/350 hp

I spoke to the engine builder and he said the oil pump is not a hi volume-hi pressure pump and he knows it is not a pump issue. There may be an issue with the intake manifold seals. More to follow.....If need be, he'll redo the motor for me, but I hope it doesn't come to that!!! I really don't want to take the motor out at all.

Jerry

[Dennis O.]

Re: Oil consumption & smoke on a 327/350 hp

All I can say is that if your oil pressure gauge is pegged at hot idle, the oil pump is NOT performing to Chevrolet specs. Over the years, I have found that Chevrolet engineers did a very good job designing these engines so everything worked together well. I will stick my neck out and say that your engine builder is lying to you if he says that kind of oil pressure is normal and can't (or won't) document the specific pump/spring combination he installed. I think he is banking on your last statement. I would change out the oil pump. It is not that expensive nor that much work (much less than pulling the heads or engine); you you don't even have to drain the coolant (but you already know that). All I can say is that you have the EXACT same symptoms I had with my L79 and changing the pump solved my problems completely.

[Jack H.]

Re: Oil consumption & smoke on a 327/350 hp

All I can say is that if your oil pressure gauge is pegged at hot idle, the oil pump is NOT performing to Chevrolet specs. Over the years, I have found that Chevrolet engineers did a very good job designing these engines so everything worked together well. I will stick my neck out and say that your engine builder is lying to you if he says that kind of oil pressure is normal and can't (or won't) document the specific pump/spring combination he installed. I think he is banking on your last statement. I would change out the oil pump. It is not that expensive nor that much work (much less than pulling the heads or engine); you you don't even have to drain the coolant (but you already know that). All I can say is that you have the EXACT same symptoms I had with my L79 and changing the pump solved my problems completely.

I agree and think it's definitely worth a shot considering it's the path of least effort to begin with and some indicators are suggesting this as at least a potential issue.

Unless things have changed, part of the problem is that the oil pump vendors ship the pumps with 2 springs, and unfortunately, the one you want is not the one they chose to install by default. So unless things have changed, or you engine builder too the extra step to notice and also actually make the spring change, this may be a problem...may or may not be "THE" problem, but "A" problem none the less.

[Duke W.]

Re: Oil consumption & smoke on a 327/350 hp

The normal hot oil pressure for for all L-79s according to AMA specs is 40-45 psi at 2000 engine revs and it should not materially increase above this engine speed. This spec applies to ALL small blocks except late '63-up with mechanical lifter camshafts, which are 55-60 psi. Standard oil pressure engines should have a 60 psi dash gage and 80 psi on the late-'63 up mechanical lifter versions.

GM does not specify idle oil pressure, but at typical L-79 idle speed of 750 revs it should typically be close to 30 psi.

If your engine does not conform to the above you probably have some aftermarket hot rod oil pump.

Although high oil pressure should not theoretically increase oil consumption by a large amount, it could contribute due to oil flooding in the rocker boxes and more oil slung up on the cylinder walls from the rotating assembly.

If a freshly rebuilt engine consumes a quart of oil in 100 miles then there is very likely a major problem with the valve guides/seals or piston rings/cylinder walls. If the engine idles properly at 750 with the mixture screws out 1-1.5 turns then I doubt if manifold sealing is a problem as it will also cause a vacuum leak, which will result in very poor idle quality at nominal carburetor settings.

No one has a magic wand that can determine your problem. You need to do some research and start by finding out EXACTLY what was done during the rebuilt including ALL processes and parts.

Duke