Strange 3946074 ( ZL-1 & L-88 ) heads

[nuch_ss396]

Guys!

I saw a pair of '074 heads on eBay that have "D" shaped
exhaust ports instead of the standard round exhaust ports.
The seller claims that they are rare, but I think they may
have been welded up to mimic the '077 ZL-1 service heads.

Have any of you ever seen, or owned a pair of '074 heads
with non-round exhaust ports?

Here's the auction: Strange '074 Heads

Steve

[TXSS]

I had a set of 074 heads that had a D shaped exhaust port. After close inspection you could see where the bottom of the exhaust port had been filled with aluminum, blinded in and then machined. It was nicely done and hard to tell. The shape was exactly the same as an 077 aluminum head.

[nuch_ss396]

Rick,

I reviewed some of my BBC SHP books and found that back in
the late 1970's and beyond, the engine builders knew that
modifying the exhaust ports to match the '077 heads would
be better for performance than the stock round exhaust port
design. Only question I have is did the modified '074
heads you had run any better than the stock '074 heads with
round exhaust ports.

Steve

[jerry j]

Hi, When GM cast the first batch of D port ex port heads they had the 074 casting #, the part # was different than the 074 round port casting part # a few months after they changed the casting # to 077. I had some of these D port 074s when new, I think around 1980.
Jerry

[nuch_ss396]

[ QUOTE ]
Hi, When GM cast the first batch of D port ex port heads they had the 074 casting #, the part # was different than the 074 round port casting part # a few months after they changed the casting # to 077. I had some of these D port 074s when new, I think around 1980.
Jerry

[/ QUOTE ]

Jerry,

Are you certain about this? I would have thought that the
change to the exhaust ports would have mandated a different
casting number. Think of the early 3933198 ( ZL-1 & L-88 )
intakes. GM used the standard 3933163 intake, milled down
the divider, then removed the "163" portion of the casting
number and stamped in a "198" in their place.

I would expect GM to do the same with the '074 heads with a
drastic change cast into the exhaust ports.

I'd like to hear more about this.

Steve