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I'm in the same boat using a lot of oil on a rebuilt 454 with a coupe of plugs showing wet. The other plugs that are dry have a lot of carbon build up. Rebuilder keeps saying that it could take a long time to break in but cylinders 3 and 7 have wet plugs so that does not make sense to me. When I did compression test all cylinders were identical at 145 psi and this is an LS5 motor which should be 8.5:1 compression ratio.
I'm in the same boat using a lot of oil on a rebuilt 454 with a coupe of plugs showing wet. The other plugs that are dry have a lot of carbon build up. Rebuilder keeps saying that it could take a long time to break in but cylinders 3 and 7 have wet plugs so that does not make sense to me. When I did compression test all cylinders were identical at 145 psi and this is an LS5 motor which should be 8.5:1 compression ratio.
They did it with a cold engine and all of the cylinders were around 120 so you still think it is low?
Yes even if they are all the same. If the rings were improperly installed they probably would have been improperly installed on all the pistons hence the same readings on all cylinders. I've seen this happen on piston aircraft engines before. How much do you trust your rebuilder?
I'm thinking 150 to 170 on a fresh rebuild that has had time to seat the rings good and from how many miles you've put on it you should be broken in enough to have seated the rings by now. I'm no expert but just going on experience working on cars and aircraft since I was a teenager many moons ago.
?
Take a teaspoon of oil and dump it in the spark plug hole then do the compression test. If compression increases then the rings are not seated/seating properly.
PennGrade 20W50 Semi-synthetic with zinc. The shop who restored the car is asking the engine rebuilder about maybe trying something else so I will let you know what they say.
PennGrade 20W50 Semi-synthetic with zinc. The shop who restored the car is asking the engine rebuilder about maybe trying something else so I will let you know what they say.
I am using 10W-40 Castrol High Mileage w/Lucus ZDDP additive.
How many miles do the plugs have on them? Mine were that way after about 750 miles. The ones I checked yesterday have about 125 miles on them.
I pulled #1 plug at about 600 miles and just saw the black build-up. Then I pulled all but the 2 under the AC compressor at 1100 miles and that's when I noticed the wet plugs but they could have been that way for a while. It uses about a quart of oil every 300 miles. I don't see smoke starting cold but I do see some when the car is started warm after sitting 10 or 20 minutes.
I pulled #1 plug at about 600 miles and just saw the black build-up. Then I pulled all but the 2 under the AC compressor at 1100 miles and that's when I noticed the wet plugs but they could have been that way for a while. It uses about a quart of oil every 300 miles. I don't see smoke starting cold but I do see some when the car is started warm after sitting 10 or 20 minutes.
What do you think starting it warm and getting smoke means? The valve guides or the rings?
Blue smoke when starting and then mostly going away after is a good indication of oil seeping by the valve stem seals. Blue smoke when running is an indication of rings but could be both.
That cam needs 11.5:1, not 9.5:1. It's bleeding off all the compression at the intake valve before it closes. Motor needs less cam or more static compression ratio. Assuming that it's carbed, I'd opt for less cam and keep it streetable, something like a Crane Energizer 272H10, although I would never use a flat tappet cam again. Those days are gone. I'd call Howards and order a cam and roller lifter retro kit.
Last edited by techinspector1; 08-29-2017 at 04:40 PM.
Compression ring seating and oil control rings are completely differently things....
Your oil rings, if installed correctly, will control the oil from the first start up...There is no seating of oil rings.
As for compression rings, yes they require "some" seating... This requires some engine load, some deceleration/vacuum and some miles. Just putt putting around for 125 miles will not "break in" the rings....That being said though, at 125 miles, the rings are as seated as they are going to get.
I would definitely be suspect of the intake gaskets first, then I'd likely look at the valve seals... A boroscope down the intake manifold into the ports may be able to show you something before you pull the intake.
If neither are those are the culprit, then its probably a piston to bore clearance problem, aka. sloppy machine work for the .040 forged pistons.
I agree 120psi cranking pressure is very low... Unless that thing has a crazy cam in it bleeding off pressure, you have the compression of a 8.5-1 350. However, this is not the cause of your oil consumption, it will be the cause of low power.
Typically, engines with forged pistons WILL use SOME oil, especially on engines that have low gear ratios and run 3k rpms down the freeway. My rule of thumb is if its using more then a 1/2 qt in 500 miles of normal driving, its using too much.
For an extreme case, I recently did a 3500 mile road trip with my 496 running 3000-3200 rpms and I used 5 qts of oil on the whole trip. SO that's 1 qt for 700 miles. That's a bit higher then I like, but running high rpms for hours on end will consume more. At lower rpms, around town driving, that consumption is cut in half.
That cam needs 11.5:1, not 9.5:1. It's bleeding off all the compression at the intake valve before it closes. Motor needs less cam or more static compression ratio. Assuming that it's carbed, I'd opt for less cam and keep it streetable, something like a Crane Energizer 272H10, although I would never use a flat tappet cam again. Those days are gone. I'd call Howards and order a cam and roller lifter retro kit.
I have the factory L82 cam that has these specs.
Intake lift 447/ exhaust lift 447
RPM minimum 2000 to maximum 5600
Intake duration 222/ exhaust 222
Compression ring seating and oil control rings are completely differently things....
Your oil rings, if installed correctly, will control the oil from the first start up...There is no seating of oil rings.
As for compression rings, yes they require "some" seating... This requires some engine load, some deceleration/vacuum and some miles. Just putt putting around for 125 miles will not "break in" the rings....That being said though, at 125 miles, the rings are as seated as they are going to get.
I would definitely be suspect of the intake gaskets first, then I'd likely look at the valve seals... A boroscope down the intake manifold into the ports may be able to show you something before you pull the intake.
If neither are those are the culprit, then its probably a piston to bore clearance problem, aka. sloppy machine work for the .040 forged pistons.
I agree 120psi cranking pressure is very low... Unless that thing has a crazy cam in it bleeding off pressure, you have the compression of a 8.5-1 350. However, this is not the cause of your oil consumption, it will be the cause of low power.
Typically, engines with forged pistons WILL use SOME oil, especially on engines that have low gear ratios and run 3k rpms down the freeway. My rule of thumb is if its using more then a 1/2 qt in 500 miles of normal driving, its using too much.
For an extreme case, I recently did a 3500 mile road trip with my 496 running 3000-3200 rpms and I used 5 qts of oil on the whole trip. SO that's 1 qt for 700 miles. That's a bit higher then I like, but running high rpms for hours on end will consume more. At lower rpms, around town driving, that consumption is cut in half.
The engine has about 850 miles on it now. The comment on 125 miles were on a new set of plugs so we could see about the oiling of the plugs.
Currently it is using about 1 quart in 300 miles.
I do have 3:55 gears so it is about 3500 at 70 MPH.
Last edited by LenWoodruff; 08-29-2017 at 08:36 PM.
My guess is you have the wrong or improperly installed oil rings ... no way that much oil gets them by even at first start up..and if it does not smoke on cold start, its not seals
The engine has about 850 miles on it now. The comment on 125 miles were on a new set of plugs so we could see about the oiling of the plugs.
Currently it is using about 1 quart in 300 miles.
I do have 3:55 gears so it is about 3500 at 70 MPH.
Ok, got ya.
Yeah I still think you have something going on. Its either pulling oil in through the intake gasket, bad oil seals, or rocker arm stud threads...
1 qt for 300 miles is way too much, even running at 3500 rpms.
My dad had a shop rebuild his L79 with forged pistons and it also drinks a bunch of oil. It runs great, doesn't smoke, but drinks oil on the highway. He uses about 1/2 qt in 300 miles on the highway. We haven't really investigated it much because he really doesn't drive it much, and it runs well when he does, but it consumes too much for my taste. It was professionally built by a well known machine shop in Houston. Sealed Power forged pistons w/moly rings....Machined guides with PC seals etc...
I think the pistons are too loose in the bores and its getting ring flutter, thus oil consumption..
Yeah I still think you have something going on. Its either pulling oil in through the intake gasket, bad oil seals, or rocker arm stud threads...
1 qt for 300 miles is way too much, even running at 3500 rpms.
My dad had a shop rebuild his L79 with forged pistons and it also drinks a bunch of oil. It runs great, doesn't smoke, but drinks oil on the highway. He uses about 1/2 qt in 300 miles on the highway. We haven't really investigated it much because he really doesn't drive it much, and it runs well when he does, but it consumes too much for my taste. It was professionally built by a well known machine shop in Houston. Sealed Power forged pistons w/moly rings....Machined guides with PC seals etc...
I think the pistons are too loose in the bores and its getting ring flutter, thus oil consumption..
They put in forged pistons since the L82 had it originally.
I would take logical steps to determine the cause (easiest to most difficult - some of which you've already done):
1) Check PCV
2) Leakdown Test
3) Boroscope through intake and spark plugs (if you have a scope)
4) Remove intake - check gaskets, intake runners, back of valves
5) Check/Replace valve seals
6) Check/Reseal rocker studs
7) Pull passenger side head and check guide clearance
8) Pressure test heads
9) If all else fails pull the engine, re-hone the cylinders, and install new rings
OR....
1) Run it like you stole it and stock up on oil and plugs : )
Another thing you can do before re-honing the block is to swap heads from bank to bank to see if the problem cylinders follow the heads or not.
I think this would be the easiest to fix/eliminate as a possibility. I would use the sealer Permatex (Aviation) I recommended earlier. Clean threads with carb/brake cleaner on both heads and studs. You could do all in an hour. (50 ft/lb torque on the studs) As the engine warms and the oil thins and is splashed/dripped onto those studs, the vacuum condition in the intake runner, particularly at cruising speed, will suck that oil in the runner and burn it.
Last edited by jimvette999; 08-30-2017 at 09:20 AM.
08-29-2017, 07:47 AM
