[boardog]

Looking at a 455yc block and a set of #18 heads. I know lots of different blocks got the yc stamp. Heads are #18 with a 71 date code. I think they are off a big car. No other info on the block. Supposed to get more info tonight. Anyone familiar with the heads?

[PunchT37]

That ain’t the casting number. It’s on the center ports.

18’s are a rare ‘68 350HO head.

[b-man]

There were no casting #18 heads produced for the 1971 engines. The #18 heads are rare and were used on 1968 350 HO engines.

Look on the 2 center exhaust ports for the casting number, it’s probably #66.

[25stevem]

Yup, if it’s got pressed in rocker studs then it’s the 66 casting.
These where big valve small intake port volume heads, to the tune of like 9 to 10 CCs less in runner volume!

My uncle had a wagon with this motor in it and even with its Q-jet carb it was game over at 4200 rpm.

The motor felt like it was almost not going to make it to the 1-2 shift point that the governor of the TB400 was set for!

[b-man]

I had a set of those #66 heads on a daily driver 455 with Tri-Power and the 068 cam, untouched and not milled down for compression.

It easily saw 5000 rpm when I needed it, ran a respectable 13.899 at 101.85 shifting into high right at the finish line, TH400 with a 2.56 open rear.

The engine and car: https://forums.maxperformanceinc.com...22&postcount=4

[Baron Von Zeppelin]

Going by the stamped EUN & VIN the block is 1971 production year.
#66 heads came on those YC 455 in 1971

Plant code D is Doraville iirc - full size cars