Aluminum medium rise?
or
Cast iron low rise?

Mcollinstn, The manifold I asked about at the start of this thread is a cast iron low rise.

I am interested in the Holley dual plane PN 300-42. Apparently it is a copy of the Chevy dual plane high rise and works well with the large rectangular port heads I have. I wish it was available with brass inserts. Is such an animal available?

What happens when you don't have brass inserts on a marine motor?

The aluminum medium rise dual plane found on all 502's and 454 magnums is a pretty respectable piece. Can be found discarded in people's garages everywhere. A real bargain piece.

If you have rectangle port heads, I am SHOCKED that you have the iron low rise...

The brass inserts are wonderful if you boat in salt.
If you boat in freshwater, they aren't necessary. Helpful yes. Necessary no.

For performance dual planes with brass or bronze water passages on a BC, you are choosing between about three intakes. And the GM/Merc one is fine up to 450hp.

hostile ,i have the aluminum.



btw , mcollinstn is the man of much knowlage on here.

The only reason I think it is iron is due to the rust stains on the inside of the thermostat mount. I guess I a magnet would answer the question definitively.

Anyone have a 454mag intake for the holley 4bbl with the brass inserts that they want to get rid of?

I guess not that many people have them lying around the garage!

Someone throw me a bone or manifold.

the aluminum will have the water passage like this.

If you use the alu intake with no brass inserts in saltwater, it won't last for more than about 3-4 years.

I'm also looking for the same intake, Just found one today Edelbrock Performer RPM is also a copy of the org high riser...

I have a Chevy high rise, dual plan, rectangular port, aluminum intake taking up space if someone would like it.
Part Number 3933163.
It came of a 425HP/454HO crate motor and has never been used.
The GM Performance parts catalog says that it is also used on the LS-6 and 502HO engine assemblies...
$50 plus shipping...

Open72, I have those on my 454mags. I just refinished like you did. 1 of mine had that same casting flaw as yours. The other was fine. I filled in that flaw with JB weld and smoothed it down to look like it was suposed to. That white looks good. I did mine in Aluminum high temp engine paint and them a few coats of clear.

You can get a spacer 3/4" to 2" to adapt a Holley to that manifold. I was told my engine would really like a 1.5" spacer.