My 72 gs 350 1500 mi since rebuild. It still uses a quart every 200 miles! I did my first oil filter change at 500mi. I don't notice any symptoms so I'm guessing/hoping rings still haven't seated? No motor oil ever on garage floor. I'm not ready to pour borax down the carb yet. I've done a variety of driving and engine breaking but its not getting better yet. Compression test showed #2 a bit lower. 155 compared to 165-175 on others. Silvolite pistons with Hastings Premium Ductile Rings. #2 pictured. The one thing I did wrong was the first 500 miles timing was probably too far advanced due to the wrong timing indicator. I didn't notice any detonation because I took it pretty easy on the throttle the first 500 mi.
Get it warm, 20 minutes driving, then do full WOT pulls to 75-80 (freeway on ramps are great for this). This will pretty much get up around 5,000 RPM in first and second, and that is what you want. (and avoid a ticket...) Do 2 pulls, cruise for a 2 miles, then 2 more pulls, 2 more miles. About 6 pulls ought to make a difference. Bad thing about idling a car for long time and not getting it out and doing WOT pulls right after a "cam break in" (2000-3000 varied RPM for 20-30 minutes) is the cylinders "shellacking" (glazing and burnishing) from all the oil and that makes it hard to get the rings to wear the peaks in the cross hatch (flattening) as they should. Your plug indicates long idle times, too cold a plug and/or too rich. You want a cleaner looking plug that is light tan in color. That is not all oil. Typically oil fouling is wet, carbon is black, sooty, dry. You need metal to metal wear and friction/heat and that only occurs under good load. Idling, "run in" stands, or too few miles/time on a new engine can contribute to the cause. Cast iron rings are less likely be a problem but the chrome moly rings being harder, need a little "persuasion". Dynos are great for doing this, so you need to drive it like it was being run on dyno pulls.
I have been doing more wot on and off the hyway and engine breaking at operating temperature. I have not been easy on the throttle very much the last 1000mi. Just frustrating it's not getting better. Seems like a LOT of oil consumption. I'll keep trying. I used vr1 10-30 with break-in additive and now just vr1 10-30. I guess I could add more break-in oil next time I have to add? Idk
My engine has been eating oil all year. Dad says it could be gas cylinder wash. To me that is gas cleaning the oil off the cylinders meaning more oil used to recoat the cylinders.
Break in oil is typically no detergent oil and has higher levels of ZDDP to aid on metal surface (change to surface molecular structure) to provide a passive friction protection. It will do nothing for an oil use issue or rings not seating. You may well be to a point where they are not going to seal. A borescope may help you determine if there is an obvious problem since you have been driving it with some loading. It will not get better. Are all the plugs reading the same, or just one hole? If only one is seeing a quart:200 miles, you have a problem that will not fix itself, but you need to try and pin it down, in case it is a bad valve guide, oil getting sucked in somewhere (PCV Valve) or something else and you don't pull a good short block apart for nothing.
If you had the timing too far advanced for a while I bet you now have some cracked rings and maybe some busted piston ring lands. It time for a compression test, or better yet a leak down test. If the motor was just freshened up then rings could have been put on facing the wrong way.
Compression test results 8-22-22: Number 1 is 160 Number 3 is 170 number 5 is 165 Number 7 is 160 Number 2 155 Number 4 is 180 Number 6 is 175 Number 8 is 179
Warm engine, dry (no oil added to cylinders) throttle blades all open, all plugs out and crank 5-6 revolutions per measure?
I apparently did it wrong. I did one plug at a time then replaced. Otherwise yes. Added a little oil to #2 after and compression jumped right up to 175
Not wrong. Only the engine turns over easier and if you have any holes that are "down" the engine does not always turn over evenly and that can affect the readings. So, plugs out, just makes testing a bit more consistent. Adding oil land getting a 20PSI bump is defiantly a ring seal. If it or a piston land were cracked/broken, adding oil is not likely to effect a change. A good scope should show glazing, or any excess wear on the walls on the #2, but that will require a re-hone and re-ring. Any "Buick Bros" you know in the South Chicago area?
Sure does run well though. I'm really hoping it doesn't need a rehone. The carb cold start trouble should be gone with a good rebuild I believe. Otherwise the only other thing I am disappointed with is the unnoticeable hp increase expected with the high compression pistons, stage one valves and 284-88h cam. I'm pretty sure compression is high because I still have to add racing fuel to be able advance spark where it should be.... I have correct timing indicator now I'll keep driving it till weather changes. Eventually try a top end cleaner like seafoam maybe? Idk
Babying it on the first drive didn’t help. Another thing that doesn’t help, and it’s not mentioned much at all, is DO NOT submerse the pistons with the rings in oil before install, I know it’s shown in every rebuild video, but the piston rings do not operate bathed in oil like the bearings do. WD 40 is all that’s needed, as a matter of fact Total Seal recommends WD 40 NOT motor oil for ring install. With motor oil flooding the rings and cylinder wall the rings don’t actually get decent contact for wear in, they just glide up and down on the oil.
If the part number of the Hastings rings you are running starts with a 2C, then that top ring has a chrome face and will need a much courser cylinder wall finish to break in properly then a moly face ring will. in fact if this the case then with todays oils the top ring my never break in the way it should! what was done to the heads in terms of valves, valve guides and valve seals? Also what is the valve lift of the cam you are running?
I had the same problem, burning a bunch of oil after a brand new rebuild. Turned out the machine shop put the wrong seals in the heads. Something about a Buick uses an umbrella and Chevys use a different kind? I found out about my problem when my brother was following me. He said, every time you let off the gas I see oil smoke come out of your exhaust. Just a thought.
Reputable Machine shop used Enginetech S2886-20 Seal Valve UMBRELLA 3/8" SILICONE Rings I provided 2m696030 Ta 284-88h cam IN: .460” EXH: .460” Thanks to everyone for the brainstorming. I'm still open to options.
With the motor fully warmed up, ( 10 minutes of steady driving at 45 mph) if you then pull off the road and with the engine still idling open up the oil fill cap do you get blow by gasses exiting with every cylinder that fires? another thing that I have seen in terms of oil usage and since you have had carb issues, I have seen carbs idle just fine, as in not lean and not rich, but then have seen them go very rich above idle . It does not take much richness to wash the oil off the walls and up into the chamber where its burned . In instances like this the cylinders can get washed out within 500 miles and then your burning oil even if the carb issue has been resolved. let me also ask this , if with the motor fully warmed up as detailed above, if you just idle the motor in park do you see light blue puffs of smoke out the tail pipe(s) ? If so that’s a 100% sign of bad valve seals. I know you say there new, but I am just putting it out there. also in my opinion umbrella seals since they are not held onto the valve guide have no place in a motor with any kind of performance cam. The lifters your using might be moving more oil to the top of the motor and overwhelming the guides. Along these same lines I also don’t like a higher then stock pressure oil pump when umbrella seals are used. One sure fire way to confirm this is to pull the intake manifold and look to see how oiled up the intake runners are in the head, in fact many times with this type of issue the valves that are closed when you shut the motor down will be found to have a small pool of oil sitting on there backside.
Ps. That cam your running is pretty big for 350 low compression motor! If your running a stock 2bb or Q-jet you probably not making enough vacuum to have the carbs power enrichment system working right, which once again means that if nothing else at off idle conditions the carb will always be too rich . you can’t just take a factory carb that was set up to run with 21 inches Hg of vacuum and then expect it to run right with a new cam that only makes 15 inches at idle! for the Q-jet there are 3 different power piston springs available to deal with smaller amounts of vacuum.
