Home Porting...Watcha Think???

[FLA5.0]

This is a C8OE-J head and my first ever attempt at porting them, I haven't polished anything nor have I finished the head...I was looking for opinions as to whether I'm on the right track. I removed the thermactor hump and blended everything in as well as I dare. Not sure how far I can go w/o getting into the water jacket?

 

[65ShelbyClone]

You're on the right track, but you need to get a gasket and match the port exit to the gasket hole. Be sure to get the alignment right.

 

[FLA5.0]

I thought I had one...figured I'd match it up later. For right now I just wanted to have a go inside the ports. What purpose did that "hump" that I ground out serve anyway. While I was working on it, I was afraid that I was going to break through and find a pocket or cavity inside, but there was none. Also...does each port need to have the exact same amount of material removed, if so how is this possible. I mean how could you possibly know if they are all the same?

Incidentally...I'm not planning on using these heads on my car...I'm practicing for a set of D0OE-C heads that I plan to run...

 

[shttygtstang]

use a micrometer thell tell alot

 

[mike93lx]

how could you possibly know if they are all the same?

this is why professional porting and cnc porting is so expensive. the only ways to tell are with a ton of experience or a flow bench.
try as hard as you can to get them similar, but they won't be "perfect" with out flow testing them. that's one of the things you have to compromise on when you port at home.

 

[65ShelbyClone]

Micrometers will only help with an area of externally measurable thickness like the pushrod hole squeeze on the intake side. For water jackets you need sonic testing and even then I'm not sure of it works on a complexly cast item like a cylinder head. Also, CNC porting is really only expensive because most machine shops charge $75+ per hour. Since Power Heads deals with the public, they tack on even more just because they can. It doesnt take 6 hours for them to port a set of heads.

The best reason I can come up with for the exhaust port bumps is to provide a flat spot for drilling the hole down the middle. It makes manufacturing easier. As far as breaking through into a water jacket, you have to be conservative or just not worry. It helps if all the ports have the exact same amount removed, but short of trial and error and alot of flowbench time only CNC porting can do that. Most all the heads are close in dimension and tolerances, but being sand-cast none are identical.

 

[mob]

looks good, nice job

 

[saniutza]

just finished mine last weekend... looks good man

 

[FLA5.0]

Quote: "The best reason I can come up with for the exhaust port bumps is to provide a flat spot for drilling the hole down the middle."

That's sort of what I was thinking because these heads don't have the drilled and tapped hole over the exhaust port like the 66-68 289/302 thermactor head, just the hump inside.
So if I don't get all the ports and bowls exactly the same, (which is very probable), will it be noticeable? I mean will it idle/run or sound f****d up? Also, one more stupid question...say I wanted to have bigger valves installed...should I have the shop grind/install the new seats before I try to work the bowls? Or get everything the way I want it and then take them in?
Thanks for the input fellas...this is all new territory for me.

 

[Ourobos]

I believe the thermactor bumps you removed help to measure exhaust gas? I removed them on my GT40s, I had heard you can gain a few horsepower just from removing them. Like they said, you really need to port match your intake gasket, and even the upper gasket. From my understanding, you really gain power from porting in the bowl/combustion chamber. Smoothness and shape determine how much. You want a 'tear drop' shape, which help the fuel combuster more efficiently. Unless you have alot of experience in porting, or have some trash heads, you might want to leave this part to the pros, if you hit your valve seat or don't shape it properly, they're trashed anyways. Good luck!