The collecting of engine parts continues....
There were two other boxes that arrived with the crank...
The heads were extremely well taken care of for transportation, thatīs good! But it was a real mess to get every little plastic chip out from all small cavitations in the heads, I promise you!
A big part of an engines character depends of the cylinder heads. As you are well aware of an original ZL-1 from 1969 had the heads with die cast number 3946074, aka the #074. These heads are quite common on eBay but often goes for high prices. Itīs strange but if you struggle for the originality they are the way to go and pricing goes in the same direction I guess...
Since our effort here is to get something close to original but not a number matching ZL-1 clone so why not go for something more spectacular like a pair of period correct "over the counter" cylinder heads from Chevrolet?
Decision made and the hunt begun...These heads, probably made for racing, has 14011077 as casting number and are often known as the #077-heads. They are not as easy as the #074 ones to find at eBay but if youīre patient you can get some for the right money....and we did!
These ones seems to be in a very good shape as being used parts and also complete with valves and springs.
Both the #074 and the #077 were Chevrolets first heads with open-chambered design. The big difference between these different heads are the design of the exhaust ports. The D-shape, or C-shape, of the #077-head is the major difference. It is said that the #077-heads will get you like 30-40 extra horsepower compare to the #074 ones.....?!
Here is a pic where you can see the D-shape clearly:
As mentioned before the #077-heads were "over the counter" and were never standard on any engine from Chevrolet. They were made for racing purpose only. The story is that the special shape of the exhaust port probably was a thing that TRACO, who cooperated with Chevrolet during this period, tested and found out that it worked out great. TRACO got more horsepower out from their engines, maybe due to the heads, than the engineers from Chevrolet and itīs possible that Smokey Yunick got hold of an TRACO Can Am-engine and copied the D-shape ports.
The first series of the #077-heads were made in the mid of the production year 1969 and they didn't come with a cast date number, I've been told. If I look closer at our heads I found some numbers that could be the casting date but I'm not sure how to decode them?
The #077-heads were produced as long as in the 1990:ies....
One of the heads could have been made the 2:ond of October 1974, 1984 or 1994?
...and the other one the 20:th of November 1974, 1984 or 1994?
When ever they were made they really seem to be in an excellent condition. No cracks or welding as I can see. No helicoil inserts and they have never been media blasted or painted either. The valves are stainless and appears to be brand new. The machine work done for the valves must be professionally made, the way it looks. I did a test with red spirit on the valves and they did not leak at all.
The exhaust ports have gotten some small grinding jobs too:
I don't think the light surface rust on the springs will be an issue when the motor is up for assembly but who knows..?
Please fell free to complete the history of these heads or correct me if I have written something wrong!