JohnG

Can anyone tell me what the difference is between a 390 and one marked 390 HD ?? an extra main bearing??

thanks!
John

FFR428

Where is it marked 390 HD? Is it stamped or cast in? All FE and FT blocks had 5 mains. But some blocks had the HD crank webbing and crank saddle. And some thicker cyl walls.

kdtrucker

Never heard of a 390 HD!! Do you mean HP?? There were some of the old 390's that bared the HP in the cast just like the old 406's.

terryrb

I have a 66' Fairlane GTA with a 1974 390 V8 truck block. It has a mirror image 501 on the front of the engine block. It is supposed to have more casting support in the bottom end, higher nickel content, and supposedly thicker cylinder walls. Can you see a casting number on your block? If it starts with a 'D' it is a 1970 series. The second digit is usually the year. Example: D4 would be 1974.

Hope this helps!

Terry B.