I know for a fact other heads are cast in the states.Dart heads are cast in ross,ohio then add pro-filer in carlisle,ohio,afr in california etc..
For the op pro-filer sells a 290cc oval port which will work very well on a 427 but I'm not sure if the exhaust is in the stock location.I believe afr sells a smaller oval port as well.

 

Edelbrock is also cast & machined in USA.

 

I had a plant tour of the Edelbrock factory. The new GM BB aluminum heads are made by Edelbrock and have been made by Edelbrock for many years. They are cast at an Edelbrock forge in Fontana California and then shipped to Torrance California for CCN machining, valve installation, etc. I could see that pallets of the heads had GM logos. Just many pallets of aluminum BB heads!!

 

Long tubes. I had to ding the #3 tube to get past the steering box. Any chances to upgrading to borgenson box are not hopeful.

 

This raised port comes up on the forum every few years for both sbc and bbc.

I have worked on all kinds of c-1, 2 and 3 vettes. So lets do some logical thinking. The exhaust ports are on an angle. So if the casting raises the ports .250 inches because of the angle it might have raised it .200 and out board another .080 or something.

The head manufactures want to make a head with the best flow. Raising the exhaust port helped. But they also had to consider all the owners with all the types of pipes available. So they limited the raise in most cases to a measly .250 inches when they really found it needed more because they didn't want to deal with fitment bitching later.



so to this day you still have the stupids out there that think a raised port is unmanageable.

Hold your finger and thumb 1/4 inch apart and ask your self if this is going to make a difference.

 

Pro Top line was bought by Comp Cams those heads are now sold under the RHS label.

 

That guy is either an idiot or a liar either way I wouldn't ever give my business to someone who is either poorly informed or deceitful. If he's that stupid and lacking in knowledge how smart and up to date could he be on cylinder head preparation...probably still grinds his valve seats as that's the tried and true way for proper concentricity..........

 

The heads sit at a 45 degree angle. So a 0.250" raised port is 0.250" x 0.707 = 0.177" higher and 0.177" further outboard. There's 3 points of possible interference, the steering box, passing under the frame and the top inboard tube hitting/burning the body. With my standard exhaust ports, the tube burned a furrow into the body/paint on my '69. So I doubled up on the copper exhaust gaskets on the driver's side. 1968-72 C3s have solid body mounts and are about an 1" closer to the frame and pipes. '73 and up models were fitted with rubber spacers to cushion the ride some and therefore they have less of a problem with an interference between the pipes and the body.

 

I did not do the math and head ports appear to be less than the 45 degree angle of the block. If you lay a head on a table are the e-ports 90 deg. to the table top?

I'm just stating what I was told by a design person at DART heads when I ask about my factory porting and the raised ports.

How the tranny tail shaft is mounted can change the angle of the motor. Old rotted crushed rubber

 

George,

You may be right. I was working off the perpendicular to the head gasket surface. Since you posted your reply, I've spent an hour searching on the reference point for raised ports. The only thing I found was on Chevelles.com and they were looking at it the same way I was, but that just means there could be another uninformed group over there.

The more important point I thought was between the solid mounts and the rubber mounts, like on your Vette. That's an inch difference with respect to the body, which is where mine had the interference.

I spent a lot of time looking for heads that would work with my original closed chamber heads. And there weren't many choices without raised ports or large combustion chambers (118cc+) that would drop the compression.

If the OP knows his engine is stock, he needs to check the combustion chamber volume of his heads, which can be found from the part number. If there's some doubt as to the pistons being the original ones, I'd pull the head and get a handle on the deck height, bore and dome volume. The heads are coming off anyway. Then look at new heads based on the piston and cylinder information.

 

I just went out and looked at a set of Dart aluminum heads and the exhaust is maybe 30 degrees from vertical So if mounted on a 45 degree V-8 you would end up near 15 degrees.

Getting back to my guestamate of .200 some higher and .080 outboard.

Header manufacturers are the blame for most all fitment problems