Thermostat housing, 300HP base engine

[Jeff S.]

I understand that a new judging guide for '66 is in revision & not yet available. My previous edition is loaned out, but apparently it indicates that both of the 327 engines used the xxxx369 cast iron housing. I believe this is in error, and that 300HP (as well as big blocks) employed xxxx660 die cast aluminum, with only L79 using '369' cast iron part in '66. Looking for confirmation of this ...

Thanks,

Jeff

[Brian M.]

Re: Thermostat housing, 300HP base engine

Base engine used 660 cast.

I understand that a new judging guide for '66 is in revision & not yet available. My previous edition is loaned out, but apparently it indicates that both of the 327 engines used the xxxx369 cast iron housing. I believe this is in error, and that 300HP (as well as big blocks) employed xxxx660 die cast aluminum, with only L79 using '369' cast iron part in '66. Looking for confirmation of this ...

Thanks,

Jeff

[Jim C.]

Re: Thermostat housing, 300HP base engine

Jeff,

I agree with you. I've had only two Corvettes over the years, and both have been 1966 base engine (327/300) models. I was the third owner of my first one (#16401 - Coupe) and can say without question that the car was virtually untouched when I bought it in 1984. I wrote down every number I could find on it. I no longer own the car, but I just checked my records, and the last three digits of the thermostat housing, as I recorded them in 1984, were 660.

My current 1966 (#27592 - Convertible) base engine was "body on" restored in 1984 - 1985. I've spoken to the owner of the car from that time period, and he did overhaul the motor. As he was going through the restoration, he also documented "all the numbers" as he came across them. He even submitted his findings to Noland Adams for inclusion in his '63 - '67 book. This same prior owner has since sent me his original handwritten list, and the last three numbers on the thermostat housing, as he wrote them in 1984-85, are again, 660. Twenty years later, when I bought the car in 2006, the thermostat housing that was installed on the motor had a part number that ends in 660. That part is still on the motor today because I believe it's correct, and original to the car, even though my old manual says otherwise.

Jim C.

[Joe L.]

Re: Thermostat housing, 300HP base engine

Jeff,

I agree with you. I've had only two Corvettes over the years, and both have been 1966 base engine (327/300) models. I was the third owner of my first one (#16401 - Coupe) and can say without question that the car was virtually untouched when I bought it in 1984. I wrote down every number I could find on it. I no longer own the car, but I just checked my records, and the last three digits of the thermostat housing, as I recorded them in 1984, were 660.

My current 1966 (#27592 - Convertible) base engine was "body on" restored in 1986. I've spoken to the owner of the car from that time period, and he did overhaul the motor. As he was going through the restoration, he also documented "all the numbers" as he came across them. He has since sent me his original handwritten list, and the last three numbers on the thermostat housing, as he wrote them in 1986, are again, 660. Twenty years later, when I bought the car in 2006, the thermostat housing that was installed on the motor had a part number that ends in 660. That part is still on the motor today because I believe it's correct, and original to the car, even though my old manual says otherwise.

Jim C.

Jim-----


You can be sure that whatever the manual says, the correct thermostat housing for the 1966 300 hp application was the '660'. In fact, this thermostat housing was used for virtually all 1966-72 Corvette applications excepting 66-67 L-79, 67-69 L-88, and some 1970-72 applications using the GM #3972128. The latter was virtually identical to the '660'.

[Jim C.]

Re: Thermostat housing, 300HP base engine

Joe,

If you say it, then I KNOW FOR SURE, it's right!!! Thanks for confirming the 660.

Jim C.

[Jim S.]

Re: Thermostat housing, 300HP base engine

Jeff,

As Jim said "Joe.'s The man" !

Here is a picture of a correct 300 HP if it helps.

Jim

[Jim C.]

Re: Thermostat housing, 300HP base engine

That's it!!! Thanks for the picture Jim.

[Jeff S.]

Re: Thermostat housing, 300HP base engine

Thanks to all. My '660' is as shown in the thumbnail, except the part number is on the water neck instead of the flange. (mid-July '66 assembly date). I'm not sure it is original, but at least we know the Judging Guide is incorrect if it states '369'. Perhaps this will be fixed in the next rev.

[Brian M.]

Re: Thermostat housing, 300HP base engine

Now I feel all warm and fuzzy.

Joe,

If you say it, then I KNOW FOR SURE, it's right!!! Thanks for confirming the 660.

Jim C.

[John H.]

Re: Thermostat housing, 300HP base engine

Thanks to all. My '660' is as shown in the thumbnail, except the part number is on the water neck instead of the flange. (mid-July '66 assembly date). I'm not sure it is original, but at least we know the Judging Guide is incorrect if it states '369'. Perhaps this will be fixed in the next rev.

I'd expect to see the part number on the base flange on a '66 or '67; typically the part number on the neck wasn't seen until '68-'69.

[Jim S.]

Re: Thermostat housing, 300HP base engine

I'd expect to see the part number on the base flange on a '66 or '67; typically the part number on the neck wasn't seen until '68-'69.

John,

With these thermostat housings it get even trickier. As a collector of parts ,I'm no Joe Lucia, but in this case I have three of these . As you can see the one I posted reads from left to right The other two I have , That I didn't post, are reversed, with the GM on the right and the 660 on the left and it reads upside down from the one I shot .

I pulled all these from existing 60s cars in my junkyard diving days, but never saw the difference in the casting #s until later .So I have no idea which came first and which one goes with which years . I assume that this was a running change that eventually led to the #s appearing on the neck.

Do you have any idea which one go with which years, or which one came first?

Jim

[Peter L.]

Re: Thermostat housing, 300HP base engine

Jeff - I think I've seen someone having put the '369 on a base motor so it can be made to fit, but then the next trick is to install the "correct" upper radiator hose and not have it look like a "plumber's nightmare." Pete

[Joe L.]

Re: Thermostat housing, 300HP base engine

John,

With these thermostat housings it get even trickier. As a collector of parts ,I'm no Joe Lucia, but in this case I have three of these . As you can see the one I posted reads from left to right The other two I have , That I didn't post, are reversed, with the GM on the right and the 660 on the left and it reads upside down from the one I shot .

I pulled all these from existing 60s cars in my junkyard diving days, but never saw the difference in the casting #s until later .So I have no idea which came first and which one goes with which years . I assume that this was a running change that eventually led to the #s appearing on the neck.

Do you have any idea which one go with which years, or which one came first?

Jim

Jim-----


During the 66-72 period when these thermostat housings were used in PRODUCTION, they were used across the Chevrolet line of vehicles. They were also used for some Pontiac applications. So, these things were being manufactured by the MILLIONS. These are a permanent mold casting so there had to be a large number of molds from which they were produced.

With respect to the orientation of the number on the neck, I expect it was just a matter of it being different on different molds. One guy that made the molds did it one way, another guy did it the opposite way. It might even be an indication of different manufacturers, too.

As far as the numbers on the neck or the flange, that's another matter. I think that represents the choice of different manufacturers. Some did it one way, others did it the other way. It may very well be that certain manufacturers predominated during a certain period of time. It may also be that a certain manufacturer that did it with the number on the neck generally supplied certain engine plants and another that used the number on the flange supplied other engine plants.

I think trying to figure all this out at this point is going to be futile.

[John H.]

Re: Thermostat housing, 300HP base engine

I have the GM drawing for the 660 housing, which was released in February '65; the note says "Cast manufacturer's identification, part number & general motors trade mark 3/16 x 3/8. Location optional". (Nowhere on the drawing does it suggest where those items may be located).

A second optional construction was added in September '68 which added .008"-.015" high cast raised circular beads .060" wide around the bolt holes on the bottom surface.

As Joe noted, there were multiple suppliers, each of which no doubt had multiple-cavity molds, and according to the drawing they could put the part number anywhere they liked. We'll probably never know which supplier served which engine plant at which time, but the Bowtie 67's I've observed over the years have all had the part number on the base flange. Haven't looked at any Bowtie C3's.

[Jim S.]

Re: Thermostat housing, 300HP base engine

John and Joe

Thanks for the imput. Like I said, all three of mine were from Mid 60s cars ,so I agree with John that at least in the mid to late 60s they all have the #s on the flange.

I always wondered why the #s ran right side up or upside down. Multiple suppliers and no instructions on where to put them, pretty much answers that Question.

As Always you guys are a Font of knowledge!

Jim