1969 ZL1 (Joe's)

[Geoff C.]

[Joe L.]

Re: 1969 ZL1 (Joe's)

Geoffrey-----

Now, this is getting into a complicated area. In fact, I've been in a "quandry" about this for quite some time. I may even be able to use this as an additional excuse for why I haven't finished the project yet.

First, a little background and review: my project involves building and installing a "ZL-1" engine and not a complete replica ZL-1. I will be using mostly all original GM pieces and reproductions thereof that were used on 1968-72 Corvettes. However, the overall combination of components will not be one that GM ever used. It will be one of the "unbuilt" combinations of components. In other words, one that GM could have built, but never did. You see, most of the high performance configurations that GM used during the 66-72 period for all Chevrolet models were combinations of a relatively small number of basic components that they had in their "parts bin". Even with a relatively small number of basic components, there are a large number of possible combinations-----some of which they used and some of which they never did. I will, however, be using some INTERNAL engine components of modern design, but mostly of GM manufacture/sourcing.

As far as the hood goes, I won't be using the L-88/ZL-1 style hood. I HATE that hood. I feel about it like I do about side pipes and "3 deuces". It's garish and "hot-roddy". It doesn't fit, at all, with the lines of the car, either, and, as such, looks like an "afterthought". The only reason for it, ever, was functionality----they needed a high rise hood to allow the use of a high rise manifold with the big block. So, they came up with this horrible looking thing. Racers don't care too much about looks, though, so it served its purpose well. I'd NEVER have one on my car, though. Ever. If it came to that, they'd be no "ZL-1" for me.

So, what to do? Well, I solved that problem by using the 1971 LS-6 intake manifold. This is one of the components from the 66-72 GM "parts bin". With it, I can use the 68-72 style big block hood. Alas, I do have to change the hood, but that's an easily reversible change when I get to the day that I re-install the original small block in the car. In any event, the hood-to-radiator support seal that I'll be using will be your 1274410 reproduction of the 1972 big block and LT-1 air dam. That's the most efficient one in the 66-72 Corvette "GM parts bin" that will also mate perfectly with the hood I'll be using.

Now we get to the "complicated" part and the reason for my "quandry". What to do about a radiator? There are several ways to go and stay within the 66-72 GM Corvette "parts bin" parameters and a few choices that fall just a bit "outside" of that.

All original L-88 and ZL-1s (except 1969 with THM-400 transmissions) used the aluminum GM #3007436 radiator. This is the radiator that I'd love to use. I have 3 NOS examples of it [none for sale], although I wouldn't use any of them. I'd purchase one of Tom DeWitt's reproductions of it. A far better piece in terms of functionality/performance and exactly original in terms of configuration. The best of all possible worlds. I have 3 NOS examples of the GM #3966597 support [none for sale] for the 3007436 radiator, so I'm all set there. This radiator also uses the aluminum external supply tank, just like my original small block. So, I don't even need to change that. But, if I wanted to or ever need to, I have 8 NOS spares of the GM #3016340 tank [none for sale]. Also, the radiator-support-to-radiator seals would be the same as 69-72 with 350 and aluminum radiator EXCEPT the upper and lower horizontal seals would need to be 2" longer. I think that your 1274311 seal kit could be modified (cut) to work perfectly.

So, where's the problem? Well, GM NEVER used a radiator shroud in conjunction with a 68-72 big block application and the 3007436 radiator (i.e. L-88/ZL-1/ZR-2). So, no shroud to fit this application exists or ever existed. That's also why there's no reliable source of information on the shroud seals---there NEVER were any because there never was a shroud. 1965 L-78 was the only big block application that ever used a shround in conjunction with the 3007436 radiator. However, the 65 fan shroud will not work with the 69+ style support.

The 3007436 radiator was used with some small blocks (ZR-1). In this application, the circular steel fan shroud was used. This was the same one as used for most 68-72 Corvettes with base engine and manual transmission. I have my original, an NOS original, and several perfect used originals of this shroud [none for sale]. I might be able to shorten one of the used ones by 2", otherwise retore it to as-new condition and use it. However, this sort of falls a bit "outside" of my 66-72 Corvette "parts bin" parameters. I do have a friend that's a big-time HVAC contractor and he says that he has the equipment to shorten the shround so that it looks un-modified. But, it still won't be an original configuration. With this shroud I could use one of several NOS GM #3919772 seals [none for sale] or, more likely, one of your excellent reproductions of it. I also have some concerns, though, that even with a shortened version of this shroud there might be some big block fitment problems. This sort of installation gets into an area of "re-engineering" that I don't really want to get into. But, I might.

Another option for me would be to use the GM #3019190 copper/brass radiator. This is the radiator used with 1969 L-71/L-88/ZL-1 with automatic transmission. It's also the radiator used with all 1969-72 big blocks with THM-400 and is SERVICE for all 69-72 big blocks with manual transmission (it's the same as the original GM #3018571 which was discontinued in March, 1970 except that it has oil cooler provisions. These could also come in handy if I ever decided to add an engine oil cooler). I have 2 NOS examples of the 3019190 radiator [none for sale]. I would use these with either the GM #3966596 or GM #339176 NOS supports that I already have in the collection [none for sale].

The 3019190 can be used with the GM #3956119 plastic fan shroud, as was used for all 1969-72 big blocks (except L-88/ZL-1/ZR-2). I have about 6 of these and they're still available from GM. Of course, all 3019190 radiator installations use the external supply tank. As I mentioned above, I'm all set there.

I'd use the 3019190 radiaor in combination with your 1274311 radiator-to-support seal kit and your 1274418 shroud seal kit. Altogether, this would make for a clean and stock installation.

Another option would be to use Tom DeWitt's aluminum "reproduction" of the GM #3019190 radiator. Painted black, this unit would appear just like the 3019190, but have the advantages of an aluminum radiator. I'd be able to do a clean and stock installation just like I would with the original 3019190 copper/brass radiator as described above. Once again, though, I'd be getting a little outside of my 66-72 Corvette GM "parts bin" paramters. But, not too far outside as far as apparent configuration goes.

So, my head's in a spin. I just KNEW that there was some good reason for my procrastination with this project.

[Joe L.]

Addendum

Pardon. I see that you have a ready-made radiator-to-support seal kit for the 3007436 radiator, so there's no need to modify the 1274311 kit as I mentioned. The kit is your number 1274440 and that's, obviously, the one to use if I go the 3007436 radiator route.

Something I'm trying to figure out, though. You show a seal kit in your shroud seal section for "69-72 with HD radiator", your number 1274426. What is that? As I mentioned in my first post, I know of no shroud that was ever used with the "HD" radiator (i.e. GM #3007436) except the circular steel small block shroud used with this radiator in ZR-1 (small block) applications. That shroud uses your seal 1274404. So, what's the 1274426?

[Dick W.]

Re: 1969 ZL1 (Joe's)

Joe, after reading that you think that "your heads in a spin". I got so dizzy that I fell outta da chair :

[Patrick H.]

Re: 1969 ZL1 (Joe's)

And just think, he could have installed a support, radiator and shroud in the time it took him to type it all.

Patrick

[Geoff C.]

[Joe L.]

Re: 1969 ZL1 (Joe's)

Patrick-----

Yes, but which set-up to install? That's the whole problem here. Why, of course I'd go right out and install it if I knew which one to install. To be or not to be, that is the question.:D

[Patrick H.]

Re: 1969 ZL1 (Joe's)

Easy decision.

Use the aluminum reproduction of the GM #3019190 radiator. Material differs but you can easily create an installation in which everything fits and APPEARS 100% correct for a hybrid ZL-1/LS-6 through the use of some radiator paint. Even better, bring the new radiator down to your local radiator shop, have them hose on some of the sticky black paint they use, and it will look entirely like Day 1 at the factory.

Larger capacity, better material and a shroud that fits. What more could you ask for?

Now call DeWitts and order yourself up a nice reproduction and get to it.

Patrick