I have a pretty stock 72 LS5. I did the motor 20 years ago. The car has sat around for most of those 20 years. I put a few hundred miles a year on it. It uses probable a quart every 300 miles. That sucks but at the rate I have been driving it I have just lived with it. I used Keith Black Hypereutectic pistons (flat top low compression)and had it bored .030 over. I did open the top ring gap as they advise with the KB hypereutectic pistons to .026 when I assembled the engine. I understand that the top ring runs hotter causing the top ring to expand more. The large ring gap is to avoid top ring binding. I have also read some horror stories about the KB pistons and I don’t think I would use them again. I did throw some new umbrella seals on the intake valves in a vain attempt to stop the oil use. Like I said I have just lived with it and throw a set of plugs in it every once in a while. I took it out a few weeks ago and got on it and as I got up to 4-5 K and felt a bad miss. Different than a plug miss. I pulled the plugs and there was some fouling so I finaly decided to look further into it. I just did a compression test and had a low of 137 to a high of 150 psi. I bought a cheap leak down tester. It showed a high of 35% to a low of 25% leak down. As I said it was one of the cheap ones So I don’t really know if those numbers mean anything. It was impossible to calibrate and was all over the place. I would advise anyone looking to get a leak down tester to not waste their money on cheap garbage. The compression test and the leak down test was done on a cold engine. While I was rotating the engine by hand looking for top dead center I was rocking the rockers and feeling the hydraulic spring or bounce in the lifters. I found number one cylinder was hard as a rock with no spring. I backed off the rocker and let it sit over night And it’s still hard as a rock. Looks like I will have to pull off the manifold and check out that lifter. One other good thing is the cylinder with the highest compression and the lowest leak down was the one with the bad lifter. So I don’t think I broke a valve or piston. I would love to pull the manifold off and find a leak between the intake runners and the lifter galley. That would explain the oil consumption. I have to see if the lifter is stuck in the pumped up position. I think that was the source of my miss the last time I had it out. I shall see.
Oil use
Boc
1 - 9 of 9 Posts
Joined
·
77 Posts
I have a pretty stock 72 LS5. I did the motor 20 years ago. The car has sat around for most of those 20 years. I put a few hundred miles a year on it. It uses probable a quart every 300 miles. That sucks but at the rate I have been driving it I have just lived with it. I used Keith Black Hypereutectic pistons (flat top low compression)and had it bored .030 over. I did open the top ring gap as they advise with the KB hypereutectic pistons to .026 when I assembled the engine. I understand that the top ring runs hotter causing the top ring to expand more. The large ring gap is to avoid top ring binding. I have also read some horror stories about the KB pistons and I don’t think I would use them again. I did throw some new umbrella seals on the intake valves in a vain attempt to stop the oil use. Like I said I have just lived with it and throw a set of plugs in it every once in a while. I took it out a few weeks ago and got on it and as I got up to 4-5 K and felt a bad miss. Different than a plug miss. I pulled the plugs and there was some fouling so I finaly decided to look further into it. I just did a compression test and had a low of 137 to a high of 150 psi. I bought a cheap leak down tester. It showed a high of 35% to a low of 25% leak down. As I said it was one of the cheap ones So I don’t really know if those numbers mean anything. It was impossible to calibrate and was all over the place. I would advise anyone looking to get a leak down tester to not waste their money on cheap garbage. The compression test and the leak down test was done on a cold engine. While I was rotating the engine by hand looking for top dead center I was rocking the rockers and feeling the hydraulic spring or bounce in the lifters. I found number one cylinder was hard as a rock with no spring. I backed off the rocker and let it sit over night And it’s still hard as a rock. Looks like I will have to pull off the manifold and check out that lifter. One other good thing is the cylinder with the highest compression and the lowest leak down was the one with the bad lifter. So I don’t think I broke a valve or piston. I would love to pull the manifold off and find a leak between the intake runners and the lifter galley. That would explain the oil consumption. I have to see if the lifter is stuck in the pumped up position. I think that was the source of my miss the last time I had it out. I shall see.
Hopefully it’s nothing major.
1968 Malibu Sport Coupe, 489c.i. 590hp 600tq, TCI 200r4 Freakshow 3,600 stall, 3.73 12 bolt posi
Joined
·
15,653 Posts
Does your engine puff smoke when you start it then clear up after it warms up? or puffs whenever you give it gas? could be valve seals worn or dried out letting oil get by
Joined
·
77 Posts
Maybe a very little but not like a quart evry 300 miles. It’s weird the plugs look like they get darker on one side like they are getting sprayed. First I need to pull the manifold and check out the lifter and make sure the manifold is not leaking.
Well Boc from what I have read it looks like you have a few problems and that motor has to come apart to analyze and repair. Many years ago when those KB pistons came out I looked at them at a trade show and just did not like the design or the fitment of them . The salesmen were touting all the innovations of them and benefits. I did not like the space between the ring lands etc etc . I would never use them in a build . My favorites depending on build and overall price wre TRW FORGED AND CAST SEALED Power Silvolite and Badger. Later I found out the KB,s proved to be problematic so I was right in not liking them . Mind you I am no engineer just a well seasoned machinist. At this point before you start spending good money after bad I suggest go through the whole thing get rid of those pistons. When you rebuild use Hastings Moly rings rebuilder pistons Durabond H series cam bearings Michigan federal mogul or King engine bearings and a Melling oil pump. For your cam and lifters Isky Howards Crower Clay Smith and stay away from that fast ramp crap Fel Pro gaskets . believe me you will be ahead of the game rather than to try and cure the ailments you have. Find a good local shop that does the garages and trucking companies to do your machine wok then do as much as you can yourself . patients attention to detail cleanliness in assembly has its rewards . this is the best honest advise I can give you at this stage of he game. you know what they say " you cant make chicken salad out of chicken - - - - . Hope this helps you . Alex
Joined
·
77 Posts
So I figure I will start to take the intake off to see what is going on with the lifter and see if there is any oil getting sucked in under the manifold. I take the carb off and I think let me do another compression test without the carb before I pop the manifold off. The numbers jumped to 170 psi to 185. I had only one cyl at 160. The previous numbers were 135-150. It is a Quadrajet and I had the primaries propped fully open and I thought I had the secondaries open also but maybe I screwed that up. I believe the second test and go with those numbers Meaning the rings and pistons aren’t as bad as I thought. I pop the manifold off and I really don’t see anywhere where the gasket or manifold was leaking oil. I can look in the intake ports of the head and see the intake valves and I can see they are coated with a black coat of oil. I already did put new umbrella seals on. I’m thinking loose valve guides? The heads were supposedly done when I had the motor done. At least they charged me for knurling and sizing the valve guides. The lifter that was pumped up solid now has the .030-.060 spring in it now. Go figure. I’m going to take a valve spring off of an intake valve that’s fouling a plug and see how much play or rock is in the guide. I know not very scientific but what do I have to loose if I’m probably going to pull the engine to take the heads off anyway.
Joined
·
77 Posts
Pulled the heads off and popped a few valve springs off. The valve guides are looser than a French whore. I’m kind of happy that at least I finally got to the bottom of what’s been my oil burning and plug fouling problem. I just dropped the heads off at the machine shop for an evaluation. Obviously not the same place I took them to 30 years ago. I got a real good reference on the new shop. I will see what they come up with after they tear them down and go over them.
1 - 9 of 9 Posts
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
