maximum head porting

[Plechtan]

Does anybody have a old cylinder head( maybe a cracked 331?) they would be willing to take a band saw to? I would like to see a cut down the center of the exhaust and intake ports , as well as a cut between the ports, centered on the head bolt and between the intake and exhaust. this would give some idea how much material exists and where the water jacket is. The cut through the valve guide would show material around the bowl. The only head i have here is from a 90 comanche. I don't think is is worthwhile to put allot of work into a non HO head.

[Alex22]

I've got a 0721 or 0630 laying around that I took a saw to. Hopefully I'll remember to take pictures at work tomorrow.

[SilverXJ]

Someone already has done this. I have the images on my computer at work. I'll try to remember to put them up tomorrow.

[5-90]

Someone already has done this. I have the images on my computer at work. I'll try to remember to put them up tomorrow.

Please do! I've not yet done so myself, but I have a #0630 (cracked,) a #2685 (late 258ci,) and a #2686 (not for anything else) so far, and I'd eventually like to get the #7120 and #0331 as well - and section a cylinder on each (and section the rest of the head /by/ cylinder for porting experiments...

[SilverXJ]

[1bolt]

Very nice pics. The area's to worry about busting through aren't the roof or floor, but the push rod pinch point. Although if you're getting really aggressive the short side radius could become a problem.

[Plechtan]

This is a intake port i assume, but what model head? The scaryiest thing i see is the holes for the rocker bolts! no wonder they crack when you put 7/16 studs in.
The exhaust port it the thing that has the most restriction, i would really like to see a section of that. This picture shows how much material we have top and bottom, but it would be interesting to see how much room there is side to side.

[SilverXJ]

Its a 7120 or 0630 head going off the location and shape of the exhaust ports.

[Alex22]

I snapped these with my phone today. Its a 0721 head, for some reason i cut the rocker studs off with a sawzall before loading it in the band saw. But if I ever start working on this again and use stud mount rocker arms I would consider using an end mill and offset plunge into the existing hole to try to get it centered better.
Intake




Exhaust





Hope this helps.

[5-90]

Nice - although I'd like to section a bit more when I finally collect and chop up my heads.

SilverXJ - can you confirm the number of that head you've pictured?

[Plechtan]

I assume the top 2 pictures are the intake, and the others exhaust.

Has anybody tried to build up material on the intake port floor? The chevy 6 had great success with a "lump port design" I will see if i ca get some picts of this. They actually raised the floor and instead of having a smooth curve into the valve area, the floor of the port had a hump or lump on it, it tended to increase velocity. Epoxy was commonly used on the intakes, and some people even tried to build up the exhaust port with weld.

[Plechtan]

I found som pictures of the Chevy lump port.

ShortTurnWithLumpVeiw1.jpg

[Alex22]

I assume the top 2 pictures are the intake, and the others exhaust.

Has anybody tried to build up material on the intake port floor? The chevy 6 had great success with a "lump port design" I will see if i ca get some picts of this. They actually raised the floor and instead of having a smooth curve into the valve area, the floor of the port had a hump or lump on it, it tended to increase velocity. Epoxy was commonly used on the intakes, and some people even tried to build up the exhaust port with weld.

Yep, top 2 are intakes and the bottom 2 are the exhaust.


The same thing is also done on the Ford BOSS 302 heads. The reason the ports respond so well to the port stuffers is that they were a poor design to begin with.

If you look at picture the pictures you posted of the lump port chevy you can see how the stock port had a flat floor that led up to the ~80* angle leading up to the seat. Picture #1 shows how the port now has a swooping lump that starts to turn the air before it gets to the sharp turn. I don't think that the jeep head will see the large gains that both the lump port and BOSS heads had.
When a port has a nicely shaped short side with a properly sized runner leading up to it the stuffers will have little to no effect on the ports. The worse a port is to begin with the easier it is to make gains on, but, the ports on the 4.0 heads are already pretty nice.

[1bolt]

I agree with Alex and was going to point out the exact same things. The idea behind those radical mods is to make a very poorly designed port work more like a well designed port...

The 4.0 HO head flows better than many BIG BLOCK muscle car heads of the 60's.