goodtyms

Like most of us, I cut my teeth on gas engines, so I've been asking lots of questions lately. I had an external headgasket (coolant only) leak right under #1 exhaust port. I figured, while I was in there, I'd do a little porting work.

The big day:



Here's an intake port in it's virgin state:


Here's what it looks like after blending, but there's still a little detailing to do:


The untouched exhaust port could really stand improving :



Blending done, polishing to go:



Exhaust runner:

goodtyms

I also, even before pulling the head, bought a spare exhaust manifold (an aftermarket wasn't in the budget) and started porting it, too.

The right side is opened as far as I'll take it, I just started on the left side. You can see how much I opened it up, especially at the top & right of the pic.



and here's a view of one port that's been opened up next to one that hasn't:

apwatson50

What type of bits are you using to port with? Could you take a picture?

Looks really nice!! Should flow a bunch more!

flashgordon

I'm just talking,or typing out loud I now that changing the shape of the intake is vary bad, and will actualy lower yor HP, on a diesol but why would you have to keep the swerlling ex port?

Under stand,this is a non turbo gas mind, thinking here, but i now that on a small block chry if you open up the ex to much you loose all the bottom end,
mind u, i hoged the port from the, installed harded seat,straight down!!

with every thing the same but my head porting (and i hoged the intake side to)in my car it ran a full sec.slower and the rpm rang changed from make of 6000 rpm to 7500,It just a go thing that i was using over kill springs and the short stroke 340

Needles to say these head didn't stay on vary long!

ok story time is over change that bit and start grinding sa more

goodtyms

I'll take a picture of the bits this weekend, but I'm rough-cutting with double-cut carbide bits in various shapes, followed by blending with 80 grit cartidge rolls in both cylindrical and tapered shapes and sizes. I've bought some of each from both Eastwood and Enco.

alborada

Most small blocks Chevy's like some backpressure to help in the bottom end also. I would think that if the ports match(head and ex manifold) and the gaskets are modified to match it should be fine, I don't know if the velocity of the exhaust going to the turbo makes a big diff or not seems like it might help egt's.

goodtyms

There's a big difference between gas and diesel engines. Diesels don't like back pressure. The main reason for porting, in my opinion, is to keep the EGTs down when I start adding fuel. The stock head is chock full of flow disturbing (power robbing) casting lines and sharp edges, especially in the exhaust area - I was pretty surprised.

apwatson50

I just did a google search and found this article. If you search for swirl it explains what it does for you. Its definately a good thing as it helps the fuel mix with air to speed the combustion process and fully burn the fuel injected. Among other things. I didn't read the whole article but it looks like it explains a lot.

http://www.diesel-central.com/News/cackle.htm

flashgordon

sounds...and look like you have dun the resurch on diesol head porting1


Is the head and ex manifold, the only nod you are doing with it?

goodtyms

Nope, I'm but trying to do it in the right order:

1) BHAF - Done, but thinking about the stock pot housing
3) 4" exhaust - done, straight piped, but thinking about a muffler and adding a 4" down pipe when I add the 12cm w/g housing
4) Gauges: Just installed EGT, Boost, Trans Temp and 4K Tach
5) Porting - while it's apart, I'm also killing the KDP and installing a piston lift pump
6) Pump timing, star wheel, AFC - as I punt it back together
7) Gov. spring - 3200 RPM
8) Injectors - possibly 190s

And sometime in the very near future, A much better torque convertor. The OEM one sucks I already have the Transgo shift kit, but that make have to wait until I get the T/C..., probably a Hughes.

flashgordon

Vary cool I was just hoping that the porting was all that you were doing........just curious what a mild head porting would do with out changing any thing els.
sound like it's going to make a vary good inprovment with all the casting flaws that you found!!!!

goodtyms

I, too, am curious about what porting alone would do, but not curious enough to not take advantage of everything (head, injector lines, etc.)being out of the way to make other mods easier. Also, I've read that porting alone doesn't help a whole lot unitil you add fuel.

I'm one of those "while I'm in there..." kind of guys

crossy

personally , i dont call that 'MILD' head porting. He's got some time invested there. JMHO. DAVE

frostie

The head porting is very mild. The picture of the exhaust manifold has been ported nicely.
I would take an exhaust gasket and hold it up to the manifold. then hold it up to the port in the head. You will see the head port is much smaller than the stock exhaust manifold port.
I would put the exhaust gasket over each port and scripe a line all the way around. then I would port the head close to the line. Do not make the head port bigger than the manifold port. You dont want the air flow to catch a lip, it will cause turbulence.
I still see the rough casting after porting. I would take off enough to make the ports smooth. The intake is almost imposible except for the bowl area. I concentrated mainly on the exhaust.
I used a burr bit, some call it a rotery file, to shape the port and to take some metal off. then I used rotery sanding discs to polish and do final shaping.
with head porting, bigger air to air, and piton lift pump and ATS manifold.
before-- 332 HP and 794 torque, at 2100 RPM
after, -- clutch started to slip at 1700 RPM, at 329 HP and 948 torque
If I could reach 2100 I think I would be near 400 HP and 1050 torque.
I will find out after I invest in a serious clutch
Keep up the good work

JDGnut

On you turbo mount on the Ex manifold... you might want to put the gasket up to the turbo... it will need LOTS of porting to match... (if you are using a stock exhaust housing..)
Also check out the Northwest Bombers website.. they have some instructions.. (or used to..) about head porting..