ZL1, 427 Anniversary Edition
Does anyone know of a web site dedicated to the General Motors Performance Parts, Anniversary Edition ZL1, 427 crate engines. This is the all aluminum engine of which GMPP only made 427 engines. I'm hoping that there is a discussion, question and answer, type site that other buyers of these engines can discuss issues they may have occurring with their engines. I am experiencing an unusual oil consumption issue with my engine, and I am wondering if others are experiencing the same issues. GMPP (now Chevrolet Performance), seems quite hesitant to divulge any information about it. I installed one of these engines in my 1967 'Vett, it runs extremely strong and is very street drivable. No oil leaks on floor, and absolutely no smoke coming out of the side pipes. No smoke on start up either.
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Re: ZL1, 427 Anniversary Eddition
Corvette Forum, C6 Discussions might be one.
Corvette Action Center , Tech Center might be another. -
Re: ZL1, 427 Anniversary Eddition
Thanks Don for this information, I'll try and look up these sites. I need to mention that these 427s are not the newer versions that came out in the past few years. This 427 is like the ones produced back in 1969. They were made from the original tooling as their predecessors. They were reproduced in 2008.Comment
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Re: ZL1, 427 Anniversary Eddition
Herb------
What is the oil consumption?
Keep in mind that there are at least a few factors that bode for higher oil consumption on these engines. The first is the fact that they use forged pistons. Forged pistons necessarily use a greater piston-to-cylinder wall clearance than cast pistons. In my opinion, forged pistons are to be avoided in street engines and I think they were a bad choice for the GMPP "ZL1" engines. Back in the old days (e.g. when the L-88 and ZL-1 were first manufactured), the only way you could get a piston strong enough for really high performance applications was to use a forged piston. Nowadays, hypereutectic cast are nearly as strong as forged and MUCH better for street applications.
In PRODUCTION, GM has used forged pistons VERY sparingly and, I believe, primarily because of the downside attributes for street applications.
The other problem with the "ZL1" engines involves the crankcase ventilation system. My opinion is that the "breather cap" system is inadequate for this engine.In Appreciation of John HinckleyComment
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Re: ZL1, 427 Anniversary Eddition
Joe, thanks for your input on this matter. The oil consumption works out to be approximately 1-qt every 375 miles. There is 15w50 Joe Gibbs HR-1 oil in the engine at this time. The car is driven nearly everyday to car shows and cruises, etc. It is driven normally and not beat. There is now 2780 miles on the engine. There was a huge oil breather on the valve cover when we took it out of the crate. I substituted it for the smaller more cosmetic one seen in the attached picture. There is a PCV valve on the passenger side valve cover. The inside of the tube leading from it is dry, not oil soaked, so I have to believe it's breathing correctly. GM says some of the earlier engines have a heat shield on the bottom of the intake manifold, which seems to be contributing to excessive oil consumption. This winter we will be removing the intake to see if ours has it. I can't imagine what this has to do with it, but we'll take it apart to see. Plus we will be doing an engine leak down test to see if there is an issue with the rings. There is absolutely no smoke coming out of the exhaust as you start the engine, or when driving it down the road. So I don't know where this oil is going. HerbComment
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Re: ZL1, 427 Anniversary Eddition
Herb------
A quart in 375 miles is pretty high. Based upon your description, I think you are probably correct that crankcase ventilation is OK. However, when you remove the intake manifold, check the manifold runners and the intake ports in the heads for oil. If you find any, that will tell you the oil is coming from the top and not the cylinders. If the ports and manifold are essentially dry, then you know the oil is coming from the cylinders.
The kind of situation which you describe in which the engine does not smoke or leak but has high oil consumption usually indicates a condition in which a very small amount of oil enters the combustion chambers but does so almost continuously.In Appreciation of John HinckleyComment
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Re: ZL1, 427 Anniversary Eddition
Joe, I'm following your logic concerning a small capillary type of continuous flow of oil being sucked into the intake ports of the intake manifold. Maybe this has something to do with GM's input abut a baffle plate being mounted underneath the intake manifold. lt's Just enough to slowly consume the oil reservoir but not enough to cause noticeable smoke. Here is another tidbit of information for you to ponder. Several times I needed to travel 50 miles to and 50 miles back to Manheim, Pa. to have work done to the Expel Ultima paint chip protective coating we had installed on our car. I traveled at 78 MPH in 5th gear (Tremec Trans.), engine RPM 2100. Even though this was a steady trip out and back, I noticed that it consumed oil at a faster rate then all the local driving when the RPM is constantly varying. I would think just the opposite would happen, but perhaps this is telling us something...your thoughts....HerbComment
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