1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

[Chris G.]

I have had this 1970 Big Block Corvette fully restored And running since 1997. Second and Top Flight judged in 2008 and 2011. Engine was rebuilt by Custom Speed Enterprises to stock, just had to get it running and finish putting back together. Since day one and 10,000 miles later it has always used a quart of oil every 300 mile which I think is very excessive. The spark plugs are always black and oil wet. Why? What's going on here? Using Shell Rotella 15W40. Have tried many different sparks plugs, my best ones are Champion. Can't run new AC DELCO plugs, they always fail. I have saved the last two sets of plugs to examine. Can post pics. I know when the engine starts not all cylinders are firing until oil clears out. Very short blue puff of smoke at cold start, otherwise exhaust is clear. Runs great. I've heard this is a very common problem. Valve stem guides/seals? Intake manifold leaking oil into pushrods valley. 4Speed Convertable. Why can't this be fixed? Iam sure this is a common problem!

[Terry M.]

Re: 1970 Corvette LS5 454 4 speed Consumer allot of oil from day one

I have had this 1970 Big Block Corvette fully restored And running since 1997. Second and Top Flight judged in 2008 and 2011. Engine was rebuilt by Custom Speed Enterprises to stock, just had to get it running and finish putting back together. Since day one and 10,000 miles later it has always used a quart of oil every 300 mile which I think is very excessive. The spark plugs are always black and oil wet. Why? What's going on here? Using Shell Rotella 15W40. Have tried many different sparks plugs, my best ones are Champion. Can't run new AC DELCO plugs, they always fail. I have saved the last two sets of plugs to examine. Can post pics. I know when the engine starts not all cylinders are firing until oil clears out. Very short blue puff of smoke at cold start, otherwise exhaust is clear. Runs great. I've heard this is a very common problem. Valve stem guides/seals? Intake manifold leaking oil into pushrods valley. 4Speed Convertable. Why can't this be fixed? Iam sure this is a common problem!

There are a lot of reasons why your engine may be using excessive quantities of oil. A cylinder leak-down test may help isolate, or at least eliminate, some sources. A compression test, with and without oil added to the cylinders, would be a second best choice.

Without some diagnosis on your part, those of us using the internet crystal ball will have to stick to conjuring up the spirits to help you.

BTW: Run from anyone who tells you this is "normal."

[Tom L.]

Re: 1970 Corvette LS5 454 4 speed Consumer allot of oil from day one

Had nearly identical symptoms on my '72 LS5 about 5 years ago but it wan't a fresh rebuild, still had OEM pistons. Leak down test didn't provide any clues that were conclusive so I borrowed a scope and went down the runners to take pics of the valves. I was able to see PUDDLES of oil sitting on the closed valves. I removed the valve covers to remove springs and check the valve guides, they were shot. Had the heads properly rebuilt, haven't added a drop of oil between oil changes since. And I do drive the car 1500-2000 miles a year. Good luck!!

[Jim M.]

Re: 1970 Corvette LS5 454 4 speed Consumer allot of oil from day one

Make sure your engine has the umbrella type valve stem seals. The positive type seals don't work well on a big block. Regards, Jim

[Chris G.]

Re: 1970 Corvette LS5 454 4 speed Consumer allot of oil from day one

Jim, I don't know how to check if engine has umbrella type valve stems? I thought I was told several years ago that in order to use umbrella stems, some machining would have to be done on the heads , because of dual compression springs? Hence complete head removal.

[Jim M.]

Re: 1970 Corvette LS5 454 4 speed Consumer allot of oil from day one

Chris:
It might be worthwhile to check with your engine builder to see if they recall what seals they used. However you may be able to see what you have by removing a rocker cover, even with dual springs, especially with the valve closed. The umbrella type seals do not actually attach to the head in any way and just ride up and down with the valve as it opens and closes. They fit inside the stock valve springs with no problem. GM used a white plastic one originally at that time; current ones can be had in pliable Viton elastomer and work really well. Good luck with the search.

[Joe L.]

Re: 1970 Corvette LS5 454 4 speed Consumer allot of oil from day one

Jim, I don't know how to check if engine has umbrella type valve stems? I thought I was told several years ago that in order to use umbrella stems, some machining would have to be done on the heads , because of dual compression springs? Hence complete head removal.

Chris------

1970-72 Corvette big blocks originally used a special type umbrella valve seal. It was an integral unit with the valve cap ("retainer"). A standard umbrella seal as was used for all 1965-E69 and 73-74 Corvette big blocks will not work with the dual valve springs used for all L1969-72 big blocks. As long as you have the original valve caps, new seals are available from Fel-Pro. The only other way to seal the valves on L1969-72 Corvette big blocks with original dual valve springs is to machine the valve guides and install certain positive valve seals that will fit within the inner valve spring. As has been mentioned, positive seals are not always the best way to go with a big block.

[Joe L.]

Re: 1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

I have had this 1970 Big Block Corvette fully restored And running since 1997. Second and Top Flight judged in 2008 and 2011. Engine was rebuilt by Custom Speed Enterprises to stock, just had to get it running and finish putting back together. Since day one and 10,000 miles later it has always used a quart of oil every 300 mile which I think is very excessive. The spark plugs are always black and oil wet. Why? What's going on here? Using Shell Rotella 15W40. Have tried many different sparks plugs, my best ones are Champion. Can't run new AC DELCO plugs, they always fail. I have saved the last two sets of plugs to examine. Can post pics. I know when the engine starts not all cylinders are firing until oil clears out. Very short blue puff of smoke at cold start, otherwise exhaust is clear. Runs great. I've heard this is a very common problem. Valve stem guides/seals? Intake manifold leaking oil into pushrods valley. 4Speed Convertable. Why can't this be fixed? Iam sure this is a common problem!

Chris------

This is a classic problem for both small and big block Chevrolet engines. I once fought it on a small block engine. I did everything under the sun to correct it AND I MEAN EVERYTHING IMAGINABLE and I never succeeded. I finally gave up. After everything I tried, I do not think it has anything to do with valve guides or valve seals-----I tried everything imaginable in this regard including new guides and, finally, brand new Chevrolet cylinder heads. I tried every type of valve seal that exists.

I believe this problem has to do with one of two things:

1) Incorrect angularity at the interface between the intake manifold and cylinder head allowing engine oil to enter the intake ports. If so, though, no intake gasket or sealer will solve the problem. A new manifold won't solve it, either, as I tried several. I tried everything imaginable (and some things you could not even imagine). Nothing worked.

2) Some problem with the PCV system that I never was able to figure out.

Of the two items listed above, I kind of think that it's a PCV problem. Why? Well, when I removed my intake manifold (MANY times), I noted there was oil throughout the manifold, not just at the ports. If oil were drawn in at the manifold-to-cylinder head interface, I could not see why any oil should even be in the lower intake manifold ports, let alone further up the ports and into the plenum area.

So, all I have to offer regarding this problem is more questions and no real answers. This was one problem that actually beat me.

[Chris G.]

Re: 1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

Thank you Joe for all your insight and ideas, WOW had no idea it could be this complicated. It does appear to effect all cylinders. I removed plugs and numbered them, can post pic if need.

[Mark E.]

Re: 1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

Joe,

As Rodney Dangerfield used to say, I suddenly feel depressed.

[Chris G.]

Re: 1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

Everyone, is there a small laser camera out there to go thru each intake runner to view the top of each valve my 1970 454 for oil deposits?o

[Joe L.]

Re: 1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

Everyone, is there a small laser camera out there to go thru each intake runner to view the top of each valve my 1970 454 for oil deposits?o

Chris------


There probably is but you don't really need to. I can virtually guarantee you that there will be coked oil on the top of the valves. The more you drive it, the more there will be. At some point, when you remove the intake manifold you're going to find the intake ports in the heads wet with oil. You'll probably also find the ports in the intake manifold wet with oil and, perhaps, even the plenum wet with oil. Wet ports in the manifold and plenum are the thing that leads me to believe that the problem is not related to leaks at the intake manifold-to-cylinder head interface. If that's where the oil is entering, engine vacuum ought to pull it only into the heads, not the intake manifold. The only way that I can imagine oil getting into the intake manifold is through the PCV system.

[Chris G.]

[Chris G.]

Re: 1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

Attached Photo of last set of Champion plugs taken out of my 1970 454 big block, and labeled per cylinder. Champion RBL15Y4 with about 2000 miles on them. Very Oily and black for only 2000 miles. Pervious set of plugs the same a few years ago. My brothers 1974 454 corvette 4-speed uses no oil at all. What was changed from 1970 to 1974 besides compression ratio (mine 10.25:1) and valve covers design? I am sure there are many other small changes.

[Richard M.]

Re: 1970 Corvette LS5 454 4 speed consumes a lot of oil from day one

Chris, Speculations as mentioned so I cannot add anything to the testing, however...

If you decide to get a digital endoscope camera they are very affordable now and work well. A friend gave me one as a present last year. Photos below. The diameter is apx 0.390" x 2" long with a 6' cord to a USB connector. it came with s/w to record videos also. It's like this one.

A sample video using it to check C1 hydraulic power top valve bodies.

Rich

https://youtu.be/bAFWMCe1EMk