Anyone have experience with head porting?

[1972RedNeck]

Does anyone have experience with porting a set of V6 heads? How much airflow is there to be gained? How about larger valves? Anyone had a set of heads worked over?

[bigblockv6]

I had the heads ported and polished on my 478m during the build, of course the Magnum engines already have larger intake & exhaust ports as well as valves over the non Magnum engines namely all 305 and 351C engines. Don't know which engine you have but if it's a 305 using Magnum heads will actually lower the compression on the 305. You may just want to have the 305 heads ported and polished and have larger valves from Cat Diesels installed because larger Magnum exhaust valves have hollow stems filled with sodium that are notorious for snapping from over revving the engine.

[James]

I've done some preliminary testing (305 head only) using putty in the intake port. Here is the charts I came up with:

First one is before intake port mod. Second one is after intake port mod.

It show a significant improvements.

My goals is to do every cylinders with the intake manifold and carburetor attached to achieve the best possible and equal flow rate between the cylinders. This will be my winter project.

[1972RedNeck]

I've done some preliminary testing (305 head only) using putty in the intake port. Here is the charts I came up with:

First one is before intake port mod. Second one is after intake port mod.

It show a significant improvements.

My goals is to do every cylinders with the intake manifold and carburetor attached to achieve the best possible and equal flow rate between the cylinders. This will be my winter project.

Big improvement for sure. Did you just add a "lump" in the intake floor to smooth out the corners a bit?

Good to see some actual flow numbers. Are those at 28" of water? Compared to something like a BBC head, these heads flow terrible in stock form.

I recently made a deal on a 478 that I am going to build this winter (hopefully). Plan is to offset grind the crank to get it over 500 cubic inches. It is a Magnum engine.

Can any larger valves be installed in the Magnum head? Does anyone have flow numbers on a Magnum head?

[1972RedNeck]

I had the heads ported and polished on my 478m during the build, of course the Magnum engines already have larger intake & exhaust ports as well as valves over the non Magnum engines namely all 305 and 351C engines.

Any flow numbers by chance?

What are the stock valve sizes for the Magnums?

[bigblockv6]

Presently I'm no where near any of my V6 engines and parts but the exhaust valves on The Magnum's are oversized and considerably larger than those on the 305 engines. Intake valves on the Magnum's are slightly larger over the 305's intake valves.

[bigblockv6]

Can any larger valves be installed in the Magnum head? Does anyone have flow numbers on a Magnum head?[/QUOTE]

There is really no reason to install larger valves on Magnum heads, they're large enough as it is, the next step is to get rid of the hollow stemmed sodium filled exhaust valves and replace them with Cat Diesel 3304 #016305 exhaust valves.

[1972RedNeck]

There is really no reason to install larger valves on Magnum heads, they're large enough as it is, the next step is to get rid of the hollow stemmed sodium filled exhaust valves and replace them with Cat Diesel 3304 #016305 exhaust valves.

What is the valve stem diameter? I presume it is rather large? Any advantage to sizing it down a little if I am going to have new guides put in?

If we could fit a larger valve and open up the port above it, don't you think it would flow better? At almost 90 cubic inches per cylinder, we are going to be trying to force a lot more of air out of each cylinder compared to something like a similar size big block Chevy that has 25% less volume (6 vs 8) to feed through better flowing heads to start with...

[bigblockv6]

the Cat exhaust valves will have smaller diameter stems so guides will. Z have to be pressed in, again I will bring up that Magnum valve diameter are plenty big enough and that's something you need to se for yourself.

[1972RedNeck]

the Cat exhaust valves will have smaller diameter stems so guides will. Z have to be pressed in, again I will bring up that Magnum valve diameter are plenty big enough and that's something you need to se for yourself.

Ok, I will believe you for the time being as I have never had the head off of a magnum yet.

Also, Cat doesn't show 016305 as being a good part number and neither does Google...

[James]

Can any larger valves be installed in the Magnum head? Does anyone have flow numbers on a Magnum head?

I have a set of magnum heads, but I don't have the casting number handy. I am planning on flow testing them at a later date. When I do I will post the results here.

[James]

I created a new thread for the Magnum head flow testing.
https://6066gmcclub.com/showthread.php?t=50774

[1972RedNeck]

I created a new thread for the Magnum head flow testing.
https://6066gmcclub.com/showthread.php?t=50774

Fantastic!