L89 Heads & Overheat (cont)

**Joe L.** · May 28, 1999, 10:53 AM

Re: L89 Heads &amp; Overheat (cont)

Tom----

I can't speak for Wayne, and certainly he's the best person to explain what he meant, but I'll offer this:

Cylinder head gaskets often have "tabs" or configurations which "overhang" cylinder block or cylinder head perimeters. In addition, they often have "tabs" or configurations which slightly "overhang" or can be seen protruding into oil return passages or are otherwise visible in the "valley" area of the engine. These types of conditions do not necessarily indicate that the gasket is incorrect do not infer that "overhang" or "protrusion" into coolant passages is suspect.

As Wayne mentioned, aluminum head engines generally use a composition type gasket. Most original GM head gaskets for cast iron block/heads are of the shim steel type. However, the coolant passages and other important configurations of the gaskets are generally the same. The primary reason for the gasket type difference is to protect the aluminum head from "brinelling" which could be caused by a steel shim type gasket and to help guard against dissimilar metal(galvanic) corrosion.

**Joe L.** · May 28, 1999, 10:53 AM

Re: L89 Heads &amp; Overheat (cont)

Tom----

I can't speak for Wayne, and certainly he's the best person to explain what he meant, but I'll offer this:

Cylinder head gaskets often have "tabs" or configurations which "overhang" cylinder block or cylinder head perimeters. In addition, they often have "tabs" or configurations which slightly "overhang" or can be seen protruding into oil return passages or are otherwise visible in the "valley" area of the engine. These types of conditions do not necessarily indicate that the gasket is incorrect do not infer that "overhang" or "protrusion" into coolant passages is suspect.

As Wayne mentioned, aluminum head engines generally use a composition type gasket. Most original GM head gaskets for cast iron block/heads are of the shim steel type. However, the coolant passages and other important configurations of the gaskets are generally the same. The primary reason for the gasket type difference is to protect the aluminum head from "brinelling" which could be caused by a steel shim type gasket and to help guard against dissimilar metal(galvanic) corrosion.

**Tom B.** · May 28, 1999, 01:05 PM

Re: L89 Heads &amp; Overheat (cont)

Joe,

I don't want Wayne or anyone to think I was being critical, in fact I would be more relieved if that's exactly what this diagonal strip is, a "gasket corner reinforcement strip", and it's "appropriate-ness" to being there. In a way that would be "more" of an indication to me that the gasket was not "mis-matched", and please, I'm not concluding that it is or it isn't.

I may have left this out of one of my descriptions so in order to keep a clear picture: this "strip" is a diagonal, going from (what I remember) the top left corner to the lower right corner of the oil drain-back galley. Again, it's about 5/16" wide and doesn't appear to be large enough or wide enough to be obstructing anything.

I'm understanding your information Joe, I just want anyone to know that in this oil drain-back galley, this "diagonal" is more than just an overhang or "protrudence" around the edges. Also, around the circumference of the galley, the gasket edges are flush, (which I also realize is no indication here of how the gasket affects the "unseen" coolant passages, etc). Thanks again, Joe.

**Tom B.** · May 28, 1999, 01:05 PM

Re: L89 Heads &amp; Overheat (cont)

Joe,

I don't want Wayne or anyone to think I was being critical, in fact I would be more relieved if that's exactly what this diagonal strip is, a "gasket corner reinforcement strip", and it's "appropriate-ness" to being there. In a way that would be "more" of an indication to me that the gasket was not "mis-matched", and please, I'm not concluding that it is or it isn't.

I may have left this out of one of my descriptions so in order to keep a clear picture: this "strip" is a diagonal, going from (what I remember) the top left corner to the lower right corner of the oil drain-back galley. Again, it's about 5/16" wide and doesn't appear to be large enough or wide enough to be obstructing anything.

I'm understanding your information Joe, I just want anyone to know that in this oil drain-back galley, this "diagonal" is more than just an overhang or "protrudence" around the edges. Also, around the circumference of the galley, the gasket edges are flush, (which I also realize is no indication here of how the gasket affects the "unseen" coolant passages, etc). Thanks again, Joe.

**Jerry Clark** · May 28, 1999, 02:23 PM

Re: L89 Heads &amp; Overheat (cont)

HI Tom :

I have only owned one aluminum head engine, an L-89 and several big blocks I have never noticed the "diagonal" offset condition you describe. It is, of course, always possible that at some time an aftermarket company produced such a design however from an engineering standpoint it would be highly unlikely and serve no purpose that I can imagine. If I were in your shoes I would be concerned about the situation also.

Good Luck

Jerry

**Jerry Clark** · May 28, 1999, 02:23 PM

Re: L89 Heads &amp; Overheat (cont)

HI Tom :

I have only owned one aluminum head engine, an L-89 and several big blocks I have never noticed the "diagonal" offset condition you describe. It is, of course, always possible that at some time an aftermarket company produced such a design however from an engineering standpoint it would be highly unlikely and serve no purpose that I can imagine. If I were in your shoes I would be concerned about the situation also.

Good Luck

Jerry

**Everett Ogilvie** · May 28, 1999, 02:39 PM

Re: L89 Heads &amp; Overheat (cont)

As we disassembled my '69 L89, we found this same diagonal. And, if memory serves, I think I have seen it on my '66 big block once when the valve covers were off for adjusting the rockers. Seems like it was visible through a head oil drain back opening and was clearly "overhanging".

The gasket we removed during the L89 disassembly was a McCord (this engine was apart in 1970 to fix a valve problem). The gaskets on the '66 should be the factory originals. Even though I may not be remembering all the specifics correctly now on the '66 vs the '69, I am pretty sure it was visible on both.

Don't know if this helps, or adds to the confusion.

**Everett Ogilvie** · May 28, 1999, 02:39 PM

Re: L89 Heads &amp; Overheat (cont)

As we disassembled my '69 L89, we found this same diagonal. And, if memory serves, I think I have seen it on my '66 big block once when the valve covers were off for adjusting the rockers. Seems like it was visible through a head oil drain back opening and was clearly "overhanging".

The gasket we removed during the L89 disassembly was a McCord (this engine was apart in 1970 to fix a valve problem). The gaskets on the '66 should be the factory originals. Even though I may not be remembering all the specifics correctly now on the '66 vs the '69, I am pretty sure it was visible on both.

Don't know if this helps, or adds to the confusion.

**Wayne M.** · May 28, 1999, 02:40 PM

**Wayne M.** · May 28, 1999, 02:40 PM

**GDaina** · May 28, 1999, 11:57 PM

Nothing unusual about the head gasket.....

composit gaskets, such as Fel Pro Blue are made like that. To satisfy your fears, go to your local Automotive Store such as Pep Boys or NAPA and ask to see a Fel Pro Blue Gasket. With all due respects, I think you are making a mountain out of a mole hill. The design of the gasket has no bearing on your overheating, unless, the head gasket is blown.

**GDaina** · May 28, 1999, 11:57 PM

Nothing unusual about the head gasket.....

composit gaskets, such as Fel Pro Blue are made like that. To satisfy your fears, go to your local Automotive Store such as Pep Boys or NAPA and ask to see a Fel Pro Blue Gasket. With all due respects, I think you are making a mountain out of a mole hill. The design of the gasket has no bearing on your overheating, unless, the head gasket is blown.

**Tom B.** · May 29, 1999, 03:24 AM

Re: Early '68 427 Overheating

Thanks all over again, Wayne. Your information has solved alot. The previous owner maintained the 68 in the same restored condition that I got it and I think there is a way for me to check, if I should need to, about any questions I might have concerning the coolant passages. For now our overall discussions with everyone have cleared up alot which included the TI distributor, center carb jets, the heads and head gaskets, etc.

I think it has been collective advice for me to focus on fine tuning the components of my cooling system and go from there. Jack is also working on a temp sending unit with me. I think I have access to a list of all the GM cooling system improvements to the early 68's you mentioned and I will be insuring that mine (December build) should have them in place.

In the next few weeks as hotter tempertures get here I hope to have in place all this good information. Thanks to everyone that contributed.

**Tom B.** · May 29, 1999, 03:24 AM

Re: Early '68 427 Overheating

Thanks all over again, Wayne. Your information has solved alot. The previous owner maintained the 68 in the same restored condition that I got it and I think there is a way for me to check, if I should need to, about any questions I might have concerning the coolant passages. For now our overall discussions with everyone have cleared up alot which included the TI distributor, center carb jets, the heads and head gaskets, etc.

I think it has been collective advice for me to focus on fine tuning the components of my cooling system and go from there. Jack is also working on a temp sending unit with me. I think I have access to a list of all the GM cooling system improvements to the early 68's you mentioned and I will be insuring that mine (December build) should have them in place.

In the next few weeks as hotter tempertures get here I hope to have in place all this good information. Thanks to everyone that contributed.

L89 Heads & Overheat (cont)