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for those who grind their own head...
https://ausmini.com/forums/viewtopic.php?f=5&t=31396		 Page 1 of 2
Author:  schmoogene [ Fri May 04, 2007 2:28 pm ]
Post subject:  for those who grind their own head...
sorry...i couldn't resist...the title that is. :lol:

it's actually a legit question here about the grinding and porting of chambers and intakes.

i've decided to attack my 12G202 with a grinding ball but i've a few questions about the procedure and equipment involved. Vizard doesn't really give the specifics of how to tackle this work and yet says all the volumes after porting shall be the same. how do you do this accurately...nay, precisely? ok, i will be using a template drawn up in CAD (can't get more accurate than that) so that covers the x and y axis. What about the z- axis, i.e. depth and the curvature of the ground out section?

can backyard bob really do this???

eugene
Author:  drmini in aust [ Fri May 04, 2007 2:35 pm ]
Post subject: 
To get the chamber depths the same I put a 50mm? mounted stone in the bench grinder, run it flat out and just level the roof of each chamber.
Do the chambers by eye, as close as you can, then cc the chambers. I use a 25cc horse syringe.
Smear the valves with grease to seal them.
Put head in a vice and level it, fit the plugs in.
I put a piece of perspex on the head face (smeared lightly with grease) then fill thru the 10mm hole in it. I use a mix of water and metho 33%.
Author:  schmoogene [ Fri May 04, 2007 2:55 pm ]
Post subject: 
How do you get a bench grinder to do that? i thought they had two big grinding wheels on the end?
Author:  drmini in aust [ Fri May 04, 2007 3:02 pm ]
Post subject: 
schmoogene wrote:
How do you get a bench grinder to do that? i thought they had two big grinding wheels on the end?

Sorry, bench drill, my bad...-
Image
Image

Head before final cc'ing & polishing- note the Rover unleaded inserts.
Image
Author:  schmoogene [ Fri May 04, 2007 3:13 pm ]
Post subject: 
right, so you level the head dead flat so that you can 'drill' down.

next is, how do you align the head so that when you 'drill' down over eight different valves that each chamber will be equal?
Author:  cush [ Fri May 04, 2007 3:19 pm ]
Post subject: 
so how do you do the curve for the ports etc?
Author:  schmoogene [ Fri May 04, 2007 3:29 pm ]
Post subject: 
i've been looking on ebay and you can get tungsten carbide bits that are really teethy, with various curves and tapers on it. i assume you just use a hand drill and one of these bits and carve away carefully and use a grinding stone to smooth it out a bit at the end.
Author:  drmini in aust [ Fri May 04, 2007 4:45 pm ]
Post subject: 
Yes a Black and Decker etc works but a 20,000 rpm die grinder is way faster.. :lol:
Here's my burrs I use, all tungsten carbide. Forget the $5 cheapo Chinese knurled steel lookalikes... :lol:
Image
Author:  drmini in aust [ Fri May 04, 2007 4:48 pm ]
Post subject: 
schmoogene wrote:
right, so you level the head dead flat so that you can 'drill' down.

next is, how do you align the head so that when you 'drill' down over eight different valves that each chamber will be equal?

I measured from the top of drill chuck up to the drill frame, with a vernier caliper- for each chamber.
But these days I have a milling machine, with digital readout on the Z axis. 8)

Cush, you do the ports by hand- with the rotary burr in a die grinder, flexible shaft or drill, it's an acquired skill.
It's only 43 years since I ported my 1st Mini head... :lol:
Author:  cush [ Fri May 04, 2007 5:07 pm ]
Post subject: 
drmini in aust wrote:
Cush, you do the ports by hand- with the rotary burr in a die grinder, flexible shaft or drill, it's an acquired skill.
It's only 43 years since I ported my 1st Mini head... :lol:


sorry... i meant the valve end.. if you are sticking bigger valves, how do you get the circle?
Author:  schmoogene [ Fri May 04, 2007 5:15 pm ]
Post subject: 
43 years...........hooooooooooly

well more questions then!!!

ok got the depth sussed.

what about positioning the head? do you line up the centre of the bit and the centre of the the valve stem to find your x and y axis?
Author:  TheMiniMan [ Sat May 05, 2007 12:05 am ]
Post subject: 
hee hee,,, can of worms :-)
Author:  gafmo [ Sat May 05, 2007 12:17 am ]
Post subject: 
schmoogene...I realy know where you are comming from.
I live between the two Masters DrMini and GR and I myself would love to learn how to do this exactly.
I'd Love for one of these two to teach me to do this and pass on thier tallent..but at this stage I will pass it on to them.

Unless one would like to teach me :lol:
Author:  drmini in aust [ Sat May 05, 2007 5:48 am ]
Post subject: 
I have a piloted boring tool which locates in the valve guide. One for each valve oversize. I use this to bore the port out for the bigger valves, to a depth of about 4mm. Then I blend the port into it by hand.
As for fitting the unleaded inserts- I send the head away.
To get the valve seats recut for the bigger valves, I take the head and the new valves to GR, after fitting new guides. :wink:
Author:  schmoogene [ Fri May 11, 2007 9:54 am ]
Post subject: 
late post...thanks kev

i think i'll have to get myself a few heads to play with and slowy grind away at each one. i think this is the only way you can do it coz it will take lots of time.

i'll probably only end up buying a die grinder and some carbide bits.

is this the basic grinding kit?? is there anything else that's a basic tool that will help me?
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