I have a 68 El Camino with the origional 325 hp 396 bb and need to know how I determine if the heads are oval or rectangle port. Any help would be greatly appreciated.

Hi Bob - Welcome to TC! :D

If you indeed do have the original 325/396 you have the oval ports. The 325 and 350 horse engines had oval ports and the 375 horse version had rectangle ports. :thumbsup:

There is a number under the valve cover.

There is a number under the valve cover.
He means a casting number. You then can look up said number on Mortec.com and find out which heads you have.

I have a 68 El Camino with the origional 325 hp 396 bb and need to know how I determine if the heads are oval or rectangle port. Any help would be greatly appreciated.

Rectangles had an identifying mark on the exterior of the heads. The same sort of visual ID marker as was seen on the "Camel Hump" SBC heads. On the BBC the marker is located in a different place on the head. Read on.

Look at the front surface of the head viewed as you stand infront of the car looking over the rad support. There will be a parting line / casting line that runs across the front surface of the head. The line is NOT parallel to the deck of the block or the deck mating surface on the head itself. Along that line you should see a little "bump" that sorta resembles a capital "D" with the straight section of the "D" more or less parallel to the ground. Lets just say the "D" looks like it is lying down on the straight part of the letter.

Look right along that crack / parting line I mention about midway across the front surface of the head. THe marker is less than 1/2 inch across the straight part of the "D" and it sticks up from the surface of the head about .125 or possibly .250 inch.

No hump = Oval head

If the sideways D is there, yes they are rectangle port. But if it is not there that is no guarantee they aren't. I have a set. One has the sideways D clearly on both ends of the head. The other one is fine on one end, but very very faint on the other. Just a bad casting on that one end.

If the sideways D is there, yes they are rectangle port. But if it is not there that is no guarantee they aren't. I have a set. One has the sideways D clearly on both ends of the head. The other one is fine on one end, but very very faint on the other. Just a bad casting on that one end.

Huh live and learn! Could there have been some "cosmetic" surgery on one of yours to attempt to hide its ancestry from some pryiong eyes? I am the first owner of a GM crate that came with Rectangle. Both ends of both heads have the casting identifier. I owned these heads from day one so I know their history. I have to agree that after thinking about it grinding the "D" off makes little sense. You cannot run oval manifolds on rectangle heads only oval mflds work on oval heads so making a rectangle head look like an oval seems a rather pointless effrort. Ahhh well as I said "live and learn"

Get the casting number and date as you may need them later
http://www.yearone.com/updatedsinglepages/Id_info/gm_engine_id/gmidimages/enginedetail3.jpg

What Mike said, here is a pic. of a unmolested 990 head. :)

http://i707.photobucket.com/albums/ww75/blackcherrySS/BBCSquarePortHead-1.jpg

A sample of the tab on a square port head.

Huh live and learn! Could there have been some "cosmetic" surgery on one of yours to attempt to hide its ancestry from some pryiong eyes? I am the first owner of a GM crate that came with Rectangle. Both ends of both heads have the casting identifier. I owned these heads from day one so I know their history. I have to agree that after thinking about it grinding the "D" off makes little sense. You cannot run oval manifolds on rectangle heads only oval mflds work on oval heads so making a rectangle head look like an oval seems a rather pointless effrort. Ahhh well as I said "live and learn"

In this case, The one end did not appear to have been modified or molested. It was just that way.

I have seen all sorts of crazy stuff people used to try on stock cars. Like grinding the winters snowflake and numbers off aluminum intakes and painting them orange to make it look like a cast iron oval port intake.

Without getting into a long, drawn out description of the head markings on all heads, while it is true that the bump on the casting is an indicator to rectangle port, not all of them have it, as early ones do not. And early 70's oval ports have a rectangular shaped bump that looks a lot like the rounder 68-70 square ports. So it is not a sure thing on that casting indicator. Earlier poster is right, better get the casting number to be sure what you have.

Jeff Dotterer
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