How to port my own head?

[the88bird]

Me, my brother and dad all work at the same small machine shop. My dad want to attempt to modify his own head. What needs to be done? He has his mind set on making his own. Just needs some help on what to actually do to it.

[the88bird]

Looking to put a Crane 190071 cam in it. Need to know what to do to the head to put this cam in.

Like this:

[Spoolin-SVT]

Part1
Here are the results of the big valve flow vs a small valve in D port iron heads. I'd imagine they would be comparable to the oval port as well. I've always wondered how much of a gain would be picked up due to the reduction of a short side radius and added cylinder wall shrouding. I tried to get as much flow as I could utilizing the stock valve, just to be a hero, but gave in and bought a couple test valves from ferrea. The #'s will do the talking.

The head used is one of my flow bench test mules. It is a iron D port head with a closed combustion chamber. The head has been completely ported and combustion chambers have been reworked. The only changes made between the tests were the cutting of the seat and a larger 1.89 valve was used. Obviously the bowls were blended and combustion chambers unshrouded after the larger seat was cut. No changes to port throat and runner.


The head was tested on a costom built fully computer controlled bench utilizing Audie metering equiptment. Bore was used to simulate cylinder wall shrouding, 1/2 in. clay port raidius, tested at 28" depression. Flow numbers have been rounded to nearest whole number, and have not been inflated.

Valve lift STOCK VALVE 1.89 BIG VALVE
.050 26 19
.100 66 67
.150 92 98
.200 126 145
.250 150 181
.300 169 202
.350 183 214
.400 197 217
.450 209 222
.500 212 220
.550 210 221

As you can see, there is obviously a big gain in flow that can be made by using the larger valve. However, I don't think you would see these gains by having your machinist fit the larger valves in without doing some bowl work, short side work, and combustion chamber unshrouding.

Also keep in mind that the intake runner of this head is stock size, just cleaned up a bit. I think the port itself is becoming the restriction in the head now, so it looks like I'll be back at the grinder. Seems like the flow picks up real well in the midrange, then tapers off a bit and settles down. Oh well, more R&D


Part 2
The test below is of an iron D port closed chamber head with 1.89 intake valve size. This is a continuation of my last post, big valve vs small valve. The last #'s I had seemed to taper off at about .350 lift and my feeling was that the port cross-sectional area was becoming a limiting factor in achieving the upper range flow.

I spent about 6 hours last night recontouring the port throat area just before the bowl area. The flow improvements were substantial.There was no modification made to the port opening location or size. The vlave guide boss has not been removed. I also had a very poor .050" lift flow reading and the new port shape more than doubled the previous reading.

I am finished with intake port R&D. I have spent over 100 hrs in the development of the intake port shape, and have decided to move onto the exhaust ports, as I am going to have a hell of a time achieving a minimum 80% intake/exhuast flow ratio now. There numbers have NOT been inflated in any way, and are accurate.

Testing details: custom 1200 cfm computer controlled flowbench using Audie metering equiptment. Test depression was 28" H20. Cylinder bore used to simulate shrouding, 1/2" clay radius on port inlet, 1.89" 45 deg. valve. cfm readings rounded to nearest whole number.

.050 49
.100 88
.150 118
.200 162
.250 191
.300 215
.350 230
.400 241
.450 242
.500 242
.550 242


No aluminum required.

Part 3
Enlarging the intake runner cross-section will not net any flow improvements. They are also very thin in some areas. Spendmost of your time in the bowl area, dressing up the valve guide boss and put a nice short-side radius in there. Unshroud the combustion chambers, as there is quite a bit of flow to be had if you do it correctly.

As for the exhaust ports, be carefull in the bowl area. Don't remove the step on the left side of the valve guide boss if you are looking in the bowl as this area is thin. Just do a mild cleanup in the exhaust bowl and a nice short-side. As for the exhaust port enlargment, go for it. Just leave the floor alone, raising and widening the port is where you can increase some volume. J.D Laramee reccomends a 1.45" round port I believe and I have tested this design and it works well. Basically, start at the port floor and mark a 1.45" circle beginning at the floor, effectively raising the port and widening it.

These are some general guidlines, and the best way to know just how far you can go is get another head and have it cut in half to see water jacket placement. Good Luck!

Bo



This is something I found a while ago online and saved it. Hope it helps