Overporting Smog Heads

Well, I guess this is a case of getting too greedy, or too stupid. These were pretty much my first attempt at porting, and I started pretty conservatively. I basically just cleaned up the factory castings and tried to straighten out the flow paths and gasket match the ports.

After learning a little more about porting, I decided to do some more bowl work and re-do the exhaust ports which never really satisfied me, as I was never sure how to deal with the thermactor holes.

I saw a piece somewhere on the net where the guy completely ground out the exhaust bumps and valve stem supports and decided that even if I lost a little valve stem stability, this would be worthwhile for the flow gains.I figured these smog heads could use all the help they could get.

Can you say water jacket? Now I know what it means to cook toast by toasting it until it burns and then 15 seconds less.

Maybe this will help someone down the line and be a good opportunity for anyone else that has messed up to post their disasters.Here are some before and after pics:

Ouch man. That always sucks. It looks like you were doing a great job before you hit water though! Nice entry at the intake bowl, great finish in the chambers. Do you know anywhere local to you that can weld cast iron?

As hard as it is for me to admit it, I may not use these heads anyway. It all depends on whether I can get the other machine work I want done cheap enough. When it starts getting close to $500, I start thinking bare aluminum castings.

On the other side of it, I have 4 similar castings that have been completely machined by a machine shop that I picked up for $20 a pair at a swap meet. This includes surfacing, valve seat grinding and new plugs. So I could spend some time this winter grinding on them.

One of the things I strive for most, is to keep everything as close to the same as possible as I'm grinding away. To keep them close, I try to grind each port in steps, doing a little to each of them at once. So if I broke through in one exhaust port, chances are that I'm paper thin on the others. The upside is that I'm a trotline fisherman, so this head is not a total loss! I'm also considering grinding through the ports completely in one chamber, to get an idea where the trouble spots are.

It does suck though, because I have over 40 hrs. in each head because of all the polishing I did. Not only were the combustion chambers mirror polished, but the entire exhaust ports.

Oh well, it kept me off the streets last winter, I guess it can again this one. I can only do better this time around, although it will be harder to keep motivated as I now know how cheap you can pick up some good used aftermarket aluminums, although there is not as much satisfaction in getting there that way, and my budget is crazy small.

Oh, one last thing, I haven't started reworking the other head, so it is still like the before photos. I also should mention that I already own a set of 1.90/1.60 swirl polished stainless steel valves, springs, and shims for these heads, so that is one thing to keep me interested in playing with them.

Wow. I am totally in awe of your work! That's some impressive polishing you've done there, and if you're not going to use them, I'd section through the head along the exhaust port and clearcoat it for study and display as a conversation piece. You obviously have not only a lot of time in them - but a great deal of control. Kudos.

David

Originally Posted by PSIG

I'd section through the head along the exhaust port and clearcoat it for study and display as a conversation piece.

David

That's not a bad idea. I could section the intake and exhaust ports and see where the "meat" is and where it isn't. I'm definitely not using the head I busted through, and that would be easier and more useful than grinding away on each port.

If I wind up doing it, I'll post some pics here.

Just Braze'em up !! No need to toss them.

They should not be a total loss if you can braze them.

What heads are those? I ported the exhaust ports on a set of DOOE 351 heads very similar to that without any problems.

One thing about the exhaust ports and lowering of the valve guide. You may not have enough support for the valve unless you have some valve guide sticking out. I had the valve guide flush with the roof. When I had to rebuild the engine a few years ago, I had several guides that were worn out after only about 4000 miles. When I rebuilt the heads, I had the guide trimmed down with about 1/4 inch protruding out to provide more valve support.

BTW -blkfrd, that 65 is awesome. I can't help but look at it and wonder though, what would that look like with a honeycomb grill with lights in it? And maybe a little Cobra in the middle? It would definitely be a different animal, but it might be pretty cool.

I've got a couple of more pics to show a different angle on the problem, and have decided to document this a little more, as when I tried to research porting heads, I always felt a little shorted on pics.

Originally Posted by eshoess

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What a scumbag.

If you have any questions on porting I suggest talking to Darin Morgan at Profiler Performance in Ohio. You can also go to his website Darin Morgan | Home and email him through there. He is a real good guy and always up for helping the fellow gearhead buddy. I wouldn't count these heads as a total loss even if you can not have them welded up. If the heads are slim pickins out in the world, I might have a second thought on possible repairs or other heads floating around. I am getting misc heads from a buddy just so I can practice as much as possible.Your method for porting I think is a very good one. Doing a little each pass through. Scotty at Re-incarnation told me the least amount removed is best while working a head to improve its efficiency. Since I am a novice to porting, I actually just got done playing with a go-kart head I was doing bowl work on. Now I just have to install it on a go-kart and see how I did. The pictures are helping me out btw.