Like the title says first time doing this so take it easy on me here. I have to hand it any who port for a living or do it on a regular basis this is not any easy task. Lot's of hand cramps and contorting myself around trying to get to various areas in the intake tract. flipping the head around about a hundred times, trying to make everything from one port to another the same as I can and trying to keep the carbide under control, this stuff is not for the weak of resolve.
I went back and forth many times trying to decide if I should just leave it as is or try to make it better given the dangerously little information I have on how to port and my zero experience. In the end I took some of the valves off and after looking decided I could just clean stuff up a little and if I'm lucky at least would not make it any worse. These are new Dart SHP assembled heads so I certainly run the risk of messing up a valve seat or punching into a water jacket on a pair of perfectly functional heads.
Looking at the exhaust port on the stock heads it's easy to see why the exhaust would be called restrictive.
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I don't know how the exhaust could even get out of that port it's so small and narrow. The SHP ports are much better.
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My thinking is that they could stand a little improvement though. So I started by just opening up the pinched outside turn and skinning down the boss and eliminating that flat spot directly below the valve opening.
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Then removed any casting flaws with sanding rolls and leave the finish at an 80 grit.
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While removing the exhaust valves I discovered that one of the valve guides was very tight. It would not be good to start up the car only to have this exhaust valve seize soon after. I wasn't sure how to get this guide opened up so as to allow the valve slide easily and still maintain good clearances. The stems are 11/32 stems. 11/32 is .343" but the stems measured at .341". I imagine there is a reemer sized just for these valve guides. running a drill through the guide would most likely get me a very sloppy guide to stem clearance. What I ended up doing was using one of the old valves and some valve grinding compound on the stem then running it in and out and twisting it in the valve guide. This worked better that I imagined. After cleaning it up the new valve and guide felt just like the rest of them. Sweet!

On the intake ports the old heads looked quite small and restrictive compared to the as cast form of the Dart heads.
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Dart as cast
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The Dart intake ports looked pretty good as near as I could figure. I'll just clean up casting flaws and leave an 80 grit finish.
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One view from port side.
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Only real issue was how the seats were blended or matched to the port. Some were a bit off leaving a step or depression where the seat met the port so I blended these areas. Some of the seats were off enough to leave rolled up aluminum where it had been pressed in. this aluminum would flake off when I touched it with my finger.
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Finished product looks fine to my untrained eye. Had some fun doing it even though I wouldn't call it easy work. It's tedious work trying to work through the port and trying not to ding the valve seats. I ended up taping the seats with many little pieces of duct tape to protect them from damage should I nick the seat with the carbide or sanding roll. I used a carbide for cast iron. Even though it will load up since I was a first timer the cast iron carbide took off material slower preventing me from making big mistakes with an aluminum carbide that takes off material much quicker.
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That really looks nice!

 

Thanks gkull. Hope it does something too.

 

looks good. I will be doing the same when I pull mine apart. The idea is smooth to allow better flow. I may polish mine but then again I am OCD and over do everything. Did you use a dremel and sanding barrels or a stone? I have been involved in a couple drag car motors and those were polished smooth with a dremel and compound maybe valve grinding compound? been years ago, I remember when finished the ports looked very glossy smooth. Like I said OCD but The way those small blocks ran...... I can't help to think that was big part of the recipe. Just an idea yours look good and your driving on the street right. Good luck let us know how it turns out.

 

Speaking of valve compound lightly relapp your valves before reassembly to make sure they are seated. I would hate to see you do all that work and have a valve not seat and burn or give a miss fire. A cheap valve lapping tool and compound should be available at a parts store.

 

The general though these days seems to be that a 60 or 80 grit fininsh is good for fuel atomization in the intake ports. Also have been reading that rough finish is good for power in the exhaust ports as well. I was of the mind of polishing the ex ports until I read that then decided to leave it at a 80 grit finish.
Used a carbide bit on a die grinder for shaping and then sanding rolls for finish work. Dremel doesn't have enough grunt for the job.

These are brand new seats and valves so no lapping needed. I did blue them to see that all were seating evenly and looked good. Did use the lapping compound to loosen up a valve guide though.

 

For someone with zero experience it looks like you did your home work

A reemer will loosen up that exhaust valve and like posters before said, a nice polish in the exhaust port and combustion chamber will help.

 

Take a look at this article. I find his work interesting.

http://hotrodenginetech.com/pipemax-...-head-porting/

Also lots of interesting reading here on port finish.

http://speedtalk.com/forum/viewtopic.php?f=15&t=34837

If anyone is considering porting for the first time the bulk of what I learned came from this book.



As usual I found his book easy to read and understand. Lots of info and good illustrations in a relatively short book.

 

Dart is a grteat start. On the intake a little rough is good. If it's too smooth. The fuel won't atomize like it should. Nice looking job!

 

Looks like your chambers could use some additional deshrouding. It will provide more flow than anything else you've done untill now.

 

I'm not sure I know enough to go about that succesfully. Are you talking about the chamber size itself and gasket matching so to say? Or inside the camber and some of the metal around the valve edges where the valves are sunk below the level of the chamber. They seem to be sunk pretty deep in the holes. There is also a lump in the area of the spark plug that rises well above the rest of the chamber. I don't know what effect removing these areas would have since it looked to be integral to the design of the chamber itself.
Now that you mention it the intake does look kinda shrouded between the 2 o'clock to 4 o'clock position and then again between 5 o'clock and 7'oclock positions.

 

id leave the chambers be until you can practice on old heads/flow..that one gets tricky.

 

It looks like a beautiful job. Now you see why people suggest to dump the old stock heads. Just a couple of suggestions, lightly round or chamfer the combustion chamber edges so that they don't become a sharp, hot edge and cause detonation. Then cc the chambers so that they are all equal volume.

 

You can't tell in the photos but the combustion chambers have been lightly rounded as you suggested. I cc'd the cambers and they are all at 61cc's give or take 1/10th of a cc. The plug threads into the combustion chambers were also a nice source for a hot spot and they too were rounded off. Nothing sharp in there anymore. Appreciate the compliment.
One thing that is not consistent is the port volumes. The exhausts are within a cc or less of each other. but the intakes range from 195 to 198.6 ccs before my porting work. Now range from 196.2 to 199 cc's. These are supposed to 180 cc heads

 

You need to scribe the bore size from underneath the engine to the head. Then you need to size the sides of the chamber where the valves are closest to the wall to the scribed line. Deshrouding to the gasket line is the wrong way to do this.

What you need to realize is that the more the valve lifts of its seat the more the shrouding plays a role. So the deshrouding needs to be tapered/concave towards the seat as to speak. Normally you grind away the chamber on the gasket surface to the scribed line and make a gradual approach to the seat. You normally don't touch the area just above the seat as this is seldomly an obstruction to flow at that amount of lift.

If the chamber is not enough relieved on the plug side (depending on lift, it might be necessary to deshroud it there as well.

Look up some pictures of AFR's on internet.

If this is a Darthead as mine, you will also see that the area just in front of the valve towards the quench area needs to be reworked also.


Don't go hacking in there. Go slow and work with a steady hand. You'll find out that moving your hand around makes the bite of the bit less or more depending on the way you approach the surface.

When all is said and done, you measure the cc's and try to equilize them as much as possible.

Edit : I noticed that on the side of your intake boss (where the valve guide sits in) is till to large. This is the area with the most obstruction to flow. Thin the sides more as to have a thinned bos in that area. Leave the front of the boss alone. Do not overdo this as you don't want to make the boss to thin.

 

Thank you very much this is good info.

 

unshrouding the valve is where you will find power!!!

 

I have re-built everything [frame off-almost] all by my lonesome on my real baby [T/TYPE] and many one off custom parts, however I don't touch transmissions other than the simple valve body mods and I don't mess w/the heads, my hats off-to you for even trying! good luck! yep you rock!

 

Welcome to Dart.
My Conquest heads were supposed to be 200cc new
Closer to 220.

Their 200cc heads pour closer to 200 these days.


I dont know why they do that!

Id say for your first time leave things be at this point. when you get into playing withthe chamber or even the short turn things change quickly and mistakes are hard to fix at that point. Put em on

 

The short turn is the area where you can hurt flow the most. Leave it alone, unless you know exactly what you're doing. Usually, you only smooth out things, but don't change the angle of the short turn.

Also, the throat needs to be around 90% of the diameter of the valve seat width. So keep that in mind. Usually you just smooth things right below the seat and work more on the roof/boss area.