I'm thinking of "porting" my heads myself. Basic gasket match the intake and exhaust. If that goes well I was thinking of changing the bowl shape. Anyone have any info on this ? Can I do it relatively easy ? Or is this something best left to a machine shop ? Thanks, Darrel
You don't want to "change" things much. Just blend everything together. If you do any enlarging beyond the gasket match, the tops of the ports are where you get benefits. The intake can be matched, blended, and raised some... all with a "brushed" finish. The exhaust goes the same, but with a "polished" finish to it. The intake port should not be smooth, in other words. The exhaust port can benefit from anything all the way up to a mirror finish. If you get brave, you can cut back the guide bosses, however there are differing views on this... The bosses help valve stability and heat transfer from the valves, so some folks don't recommend cutting them back. If you get new valves, a port job can be complimented with back cut, tuliped, and necked down valves. All of these options save weight and aid flow. Weight savings in the valvetrain is good for stability, longevity, and RPM capabilities. Good luck Dave
haven't pulled the heads yet but everything is stock. The block is a E3TE. Guess it would help to mention this is a 351w.
Ouch, porting cast iron = no fun! I worked for a professional head porter for a number of years. Ratio411 is correct that you do NOT want a smooth finish on the intake. Most of the increased flow will come from the short turn (area on the bottom of the port where the floor curves down to the valve)...however, you can do more damage than good if you don't know what you're doing. I would concentrate on the exhaust port...get rid of the thermactor bump (you'll know it when you see it), and open it up a bit. Do NOT "port match". Ideally you will have ~1mm difference between the intake and head, and head and header. If you do not leave this, you'll get reversion and cancel out any positive effects you could have gotten from porting. There's too much information to post here. See if you can find any books on it, or search the internet (google) to see what else you can dig up, and good luck!
This makes good sense. What you are saying is that you want the head larger (minimally) than the intake, and the header larger than the head? So that the air flow direction does not encounter any sort of 'step'? Dave
I've seen the reversion dam argument go both ways. A mis-match on the trailing edge will cause a turbulance too that will hurt flow too. Your gasket is probably bigger than your head and intake. The worst thing that will happen is that you'll have a slow spot right where your flange is. Not the worst thing, but it's not great either. Better to have a nice even transition though. Find out which one is the big port (manifold or head). Make a template out paper including the bolt holes. Then, blue (or magic marker) the small port flange (probably the head), "bolt" on your template and scribe the flange with an awl. You'll have a little scratch in your bluing or magic marker. Then just color in the lines. Or port both of them to match the gasket. Either was is an improvement. Open up stock parts as much as you can. Especially right under the seats. Not too much though, because the valve still needs a place to land. I've rarely seen someone overflow an engine with stock heads, aside from cleveland and boss stuff. Be very careful not to get over excited and grind through into a water passages. Basically getting rid of the casting flash and smoothing out the valve guide is the most you want to do for the first time. I'd stay away from the combustion chamber. Maybe just touch up the area around the intake valve so it's not so shrouded. The bath tub CCs aren't as sensitive as the heart shaped ones. Get some good double cut burrs or you'll be there all day. R&J Tool and supply will treat you right. The short shank cylinder rounded tip burr is what I use most of the time. The long shanks are good for some stuff, but you can't let it get away from you, because it's really easy to nick a seat. The tapered burrs are good for getting into and blending tight corners. Cast iron is hard enough that you won't accidentally grind out too much. They're good heads to practice on. That aluminum will come off quick though!
You got it, ratio411! I've also heard the the argument go both ways, but my (old) boss had taken all the Reher-Morrison classes and had all the books, which i got to steal for a couple of days. They had researched it quite a bit, which is the point where i give up trying to dispute it [shrug] I do see your point though, where if the gasket is significantly larger than the transition, you'll develop a pocket.
Gasket matching is just like learning to color in elementary school. "Stay inside the lines....the lines are your friend." Simple. As long as there is some small amount of material left inside the scribed line you'll be fine on the reversion issue. Several areas to be careful of though. On a stock ford iron head you do not touch the floor of the port other than reworking the short side radius. The floor of the port past the short turn is a "wasteland" in iron Ford heads. The valve pocket diameter should be held to 75-80% of the valve seat size. Work on raising the roof of each runner and try to remove as little material from the outer walls as necessary. This will help flow and velocity. Scribe the cylinder bore size onto the head and relieve the combustion chambers around the intake and exhaust valves to unshroud them. Let me know if I can help.
One other thing. When you port the head, set it up on a 2x4 and put your shop light under the head so if you're working on the intake port flange it's shining up through the valve or if you're working under the valve it's shining through the intake port. When you do the CCs and you have an old junk valve, put it in there so you don't have to worry about nicking the seats. I try to port my heads before the valve job, so if I do screw up a seat I only have to have one valve job done.
Should the corners of the ports be rounded or squared ? Also, on the CC's, should it be shaped like a bowl with a taper to the valves or should it be the same depth all around ? Thanks guys, Darrel
You won't be able to get the corners really "squared", and it doesn't really matter a whole lot, so long as it's the same on both the head and the intake. Taper the bowl to the valves. I wouldn't do too much bowl work, just remove as much material as you can on the outsides of the chamber near the valves (using the head gasket as a reference).
One of the internet articles I read on the subject said to basically unshroud the valves using 3/16 around the valves as a guide. Any thoughts ? Also, if I use the head gasket as a guide won't this decrease compression ? Does anyone happen to know the compression or any other info on a stock 351w engine with an E3TE cast number ?
