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Head porting tips
https://ausmini.com/forums/viewtopic.php?f=5&t=38557		 Page 1 of 1
Author:  Volodkovich [ Sat Dec 08, 2007 8:28 pm ]
Post subject:  Head porting tips
Ok,

So i just started porting my spare 12g940 head today. Its going on fast road 1293. Following Vizards bible for port sizes / shapes etc.

Can anyone give me some tips for porting? i.e what carbide burs you use for what parts of the ports / chambers, how to get a good finish etc

I have got two old valves and put them in the lathe and centre drilled them a tiny bit so i can scribe the shapes of the chamber. Should i leave these valves in the head while i do the chambers so i dont knick the seats?

Any useful info would be appreciated

Cheers
Author:  drmini in aust [ Sun Dec 09, 2007 8:33 pm ]
Post subject: 
Here's the burrs I use in the ports- I run them in a 1/4" die grinder (24,000 rpm but I can slow it).
I also use a few different stones for finishing in the valve throats, round ones are handy there.
For polishing I use a bit of 8mm steel rod 130mm long, with a hacksawed slot in one end. I wind strips of 120 grit aluminium oxide abrasive cloth in there. For this job I slow down to about 7000 rpm or it'll go into orbit.
Image

<edit> yes leave the valves in the head, thin their heads down a fair bit too.
Author:  mason [ Sat Dec 15, 2007 6:15 pm ]
Post subject: 
when grinding the inlet ports watch you dont cut into the push rod holes. Ive done that before :oops:
Author:  drmini in aust [ Sat Dec 15, 2007 6:18 pm ]
Post subject: 
mason wrote:
when grinding the inlet ports watch you dont cut into the push rod holes. Ive done that before :oops:

You don't get good performance allround by making it too big there. Most HP is won or lost around the valve throats and seats. :wink:
Author:  TheMiniMan [ Sat Dec 15, 2007 6:29 pm ]
Post subject: 
It`s the "Angle of the Dangle" that is the important thing
Author:  Volodkovich [ Sat Dec 15, 2007 6:59 pm ]
Post subject: 
Yeah, im not making the straight section before the split larger at all, im just smoothing it out and taking out casting imperfections.
I went through into the water jacket where you did doc. I have another head here i can use, or i can try weld it up (or get the old man to give it a shot). Didnt think i would go through there with only 1.4" inlets.
Other than that its all going well. I turned up some little sleeves that push into the port and cover the seats to stop me nicking them when porting the throats, seems to work well.
Author:  drmini in aust [ Sat Dec 15, 2007 7:10 pm ]
Post subject: 
These heads bronze weld in the inlet ports (with oxy acetylene or oxy LPG) pretty good, don't try to arc weld in there though or the hole will just get bigger. :lol:
I used nickel bronze rod instead of manganese bronze, it's stronger and less runny.
You need to preheat it to 700C or so before and during welding- I used a 2 burner camp stove and afterwards slowed the cooling by building a teepee of blankets over it (but not close... :lol: )
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