OK, I'm back on my head ( engine head in case anyone is wondering ) after summer hiatus and I have some questions before I go any further. So far I've concentrated on removing sharp edges and protrusions. I've cut the valve guide bosses down pretty severely but I'm not sure how far I should go with them. Somewhere I read that one side, either exhaust or intake, should be nearly removed but I don't want to weaken anything or cut through into water. Also between the exhaust and intake ports on each cylinder the walls seem pretty thick and there isn't much relief directly under the valve; how much of that material needs to be removed. Again, I don't want to cut through into water. Finally I've heard several people talk about polishing the "bowls" but I'm not clear exactly what that means. Are we talking about the combustion chambers or the area directly under the valve seats? Any thoughts or suggestions are appreciated.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

The area right under the seat is what is the Bowl. Although it is not common to poslish this area. The combustion chamber is what is polished most of the time. Although I personally never poslish a combustion chamber.

There is so much indiffernace in peoples oppinion on this subject that you can get many anwsers that are the conflicting.


You must be carful when porting. You can hurt flow much easier than you can help it. Two rules that are a must. Exhaust polished - Intake rough finish.


Do not port any of the bottoms of the ports except for very light clean up. If bigger is wanted, remove it from the top of the port, or sides. In the bowl area is very important, also where the bowl curves up to the bottom of the port (this is called the short turn). The short turn is very important. Making the ports bigger IMHO is not needed with these heads. The guide boss could be used to direct the flow on the intake side to help get the flow out of the valve to go where you want it ( create swirl and keep the intake charge off the cylinder walls).


Do a google search on "DIY heat porting". You will find enough info to keep you reading for days & be able to learn alot more about what your trying to achive. The /6 head is a low port head, much like the early small block Chevy heads. Think about how water flows around and over things. Although we are not trying to move water some of the basics are close to what is going on. Sometimes you want the air to follow the wall/floor (slow radius) , sometimes you want to turn it, sometimes you want it to shear and let go of the wall (sharp edge, valve seat area), sometimes you might want to bias the flow to one side of the valve (swirl and directing). There is much going on in a head port and bigger does not always, or even hardly ever, give more flow. The size of the port needs to corresponed to the size of the valve.


In these mag articals there is a Part I,II and III of porting the Mopar BigBlock heads. Again there ports are very close (although bigger) to the style ports the slant has. Infact these three articals can give you very good guidlines to you needs. Read them all. They are at the bottom of th elistins.

http://www.moparmusclemagazine.com/tech ... page5.html


Jess

Thanks for the info, Jess. I have the DIY Porting article bookmarked and have referred to it often so I understand the general process. I'll also check out the other references you gave me. What I was looking for is some specific information regarding the 225/6 which I believe you also provided. Thanks again.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

Good info from Jess there.

Spend most of your time on the bowls and blending the bowls into the valve seat area. This is where most of the gains are. Removing most of the exh and intake guide bosses also gets you some substantial flow. Leave some of the int guide and blend into the valve stem (like a little tent). This is not as necessary on the exh side. You will sacrifice some guide wear longevity on the exh valves, but not too much, and will gain quite a bit of flow. Do not touch the floors except to smooth transitions.

Lou

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Home of Slant6-powered fun machines since 1988

Thank you gentlemen! Now I have a plan of action. The bowls are all pretty well roughed out but I might do some more work on the guide bosses. Other than that it's gasket matching and some final smoothing/polishing.

Next I need to relieve the areas around the valves because I'm installing oversize valves. My plan is to lay the head gasket on the head and mark the bore. Then I can open up around the valve edges without cutting into the gasket mating surface. Next I'll CC the chambers and even them up; then get the head milled to get everything to the desired chamber size.

I'm working slowly and deliberately because I don't want to ruin the head and have to start over.

_________________
David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

Also, be very careful on the port walls between int/exh ports on a given cylinder. There is a bump there on the side wall you can feel from the bowl side and you CANNOT smooth out this bump completely. You will hit water.

I thought I was leaving enough material on my 1st head, and left a thin spot in #6 exh port that let loose on the dragstrip after some pounding. Luckily it sealed itself up under low load so I could drive 500 miles home!

Lou

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Home of Slant6-powered fun machines since 1988

Thanks for the heads-up! I asked about that area specifically because it looked like it was thicker than it needed to be. I've worked on it some but fortunately not very much. I'll steer a wide path around it.

_________________
David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

David,

When you talk about opening up around the valves (in the head) using a gasket trace to avoid going to far, it makes me wonder two things: valve size and gasket.

My most recent porting and unshrouding for 1.70 valves showed me the wisdom of using the big opening Aussie head gasket if you round one up. I had sold my last one thinking I had another and had to go with a 3.55 hole. It allows JUST enough for unshrouding the 1.70 valve BUT...I would not do the unshrouding by hand as it seems you are thinking to do. Just have the machinist do it when the head is milled and use a milling machine on it too. With Menko's help I posted a pic here not long ago of how much you can cut out...it is impressive, but I don't see how it could be done with precision by hand. (Unless you are only talking about hogging out rough crap in the combustion chamber, which I did too, then polished.
rock
'64d100

Rock, I was planning to just grind out a small crescent adjacent to each valve, but there's no reason I couldn't get it done by the machinist. It would add a few bux to the machine cost but shouldn't be that much. My plan is to get the valves installed and now I guess the unshrouding done then I'll CC the chambers and decide how much to shave the head. I want to take some off the block too, probably about .100 but I want to get the head where I want it first then compute how much to take from the block to get my final CR. I'm shooting for about 9.5:1 as the final static CR. So it looks like I have about 3 more trips to the machinist before I'm ready to assemble the engine.

Here's the place for a sanity check... does anyone see any "gotcha's" here that I need to beware of?

_________________
David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.