I have been reading up on head porting and cleaning up passages for smoother flow, as well as reading other's take on the subject, and viewing several videos showing methods & tools used. What Doc and others suggest is "less is more". Just gasket match, remove the gross (medical term) casting imperfections, and blend abrupt changes in surface elevation in runners, bowl, and combustion chamber.

I am having oversized Engbld 1.70", 1.44" valves installed on a .030 over bore engine. The slant six combustion chamber dose not lend its self to reliving much vertical material along the cylinder perimeter adjecent to the valves due to being rather tight. What should one do in this area, smooth & blend as allowable with out encroaching on the metal ring of the head gasket?

I have read that ideal relief is 0.20 D of the valve. There is no way that kind of clearance can be achieved in a slant head with over sized valves. So the improvement in breathing must come from the increase in valve size, but is not optimal due to the valves being located too out board in the combustion chamber. So in other words we take what we can get, and call it good?

After removing or smoothing any sharp surface changes in the combustion chamber should that chamber be polished, left with factory ruff casting stippling, or smoothed up some?

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

smoothing all surfaces is always a good idea, makes the combustion camber larger so you have to check volume of the chamber. what compression are you aiming for?

http://victorylibrary.com/mopar/chamber-tech-c.htm

Here is a link to a tech paper i used when revamping my chambers. The result is similar to what one sees in dark rooms in rural Illinois or Virginia.

Dude who wrote the article is banned from the site for being overly passionate bout auto engineering......thats a real endorsement.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

This is a dark science, with swirls and flows it's hard to really know what to do without a flow bench to verify that you've actually made improvements.
I polish the chambers of my heads which some claim to be ill advised. They say they want the turblence that a casting will give you, I don't quite understand this. When I say polish I simply mean with the stone and a little bit of paper. It shouldn't make your chamber volume to large, but be mind ful off it.
One thing that you really need to keep in mind when porting or doing bowl work is too keep it consistent between chambers. I don't always have the biggest runners, but have even flow between cylinders with simple eye balling.

Are those porting templates in the MP 6 cylinder book?

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'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

I noticed when I put on the Aussie gasket,besides being very much largerthat stock,that the intake/exhaust ports are different sizes. I read somewhere that this is desirable. Should I leave them like this when I go to open them or make them all equal.

Sandy in BC
Very nerdy indeed... Thanks. I'm more of a science guy, so this was good to read.

Based on this guy's dimensions, there ain't much one can do to improve relief on an oversized valve slant six head other than a bit of blending & smoothing that I can see.

Do you have any photos showing the material you removed that you could share?

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

runvs_826:
I think it has something to do with laminar flow. Fluid dynamics is above my pay grade, not to mention thermal dynamics... While I'm a science guy, my level of understanding this "head stuff" is barely above that of black magic. However I willing to learn.

Doc, I still have your "X'ed up" head photos book marked. I learned a long time age that the best experience is to use someone else's.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

No pix.......we used an old vertical mill to rough it out....then hand blend.

Not a lot of material is removed. Big valves with no relieving may be a waste of time.......

I recommend getting your fingers into a Jeffries modified chamber. No photo works quite the same for me.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

This article worked for me. http://www.sa-motorsports.com/diyport.aspx
It stresses short side radius improvement. It also says to use a die grinder rather than a dremel tool, advice which I ignored. I figured if I screwed up I would rather do it slowly than suddenly. Also I was wintering at a construction site in Vermont with no TV, so I had plenty of time on my hands. All work and no play makes Jack a dull boy, etc.

Rug_Trucker:

This one on sale at Mancini Racing for 5 bucks marked down from $29.99?

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Hey!....thats me!....cept the Vermont part.

I just spent 3 months working on our house like it was a contract....no TV is worth 2 hours a day. A ton of music on vinyl and CBC radio is worth another 15 mins.

The Blonde costs me an hour. Im OK with that.

"Wintering" .....a very descriptive verb

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Yeah....Im the one who destroyed this rare, vintage automobile.....

slantfin:
That is an under statement...

Nice photos, and info on that page. The more of this stuff I see & read the clearer the task becomes. This project would be cake if one were able to shadow an experienced porter looking over his shoulder, and asking questions very step of the way. But, gaining insight, and "virtual" experience through the ether is harder. Thanks.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

sandy in BC:
Ah, I'm familiar with my fingers, but what is a "Jeffries modified chamber"?

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Thanks, I've been wanting one of those manuals. Just ordered one. Had to call it in though. Apparently there is a $10 minimum on web orders.

C

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-76 Cordoba, 360 4bbl
-68 Valiant, 273 2bbl
-67 Dart /6 4bbl, Leaning Tower of Power!!!