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Discussion Starter · #1 ·
I'm planning on doing some porting on a 2L head and need some advice on how to set up a flexable shaft grinder.

What I'd like to do is connect a flex shaft to a bench grinder and use that to port the head. This seems like a much more cost-effective way of setting up a head porting project than buying an expensive, purpose built, flex shaft grinder.

I can buy flexable shafts with the 1/4 in collets but I'm not sure how to make the connection to the bench grinder. Has anybody actually done this and can you make some suggestions about how I can put something like this together?
 

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Not sure if thats a good idea?

Hi there Jim,

this doesn't answer your question in any way, but I think the connection to a bench grinder is going to get you rpm that are way too high. I am just finishing up the (mostly) cutting, (very little) grinding and sanding/polishing on a porting job and did it all with a hand drill turning quite slowly at about a third of its maximum rpm, which was time consuming but went well otherwise. When turning faster, I found it hard/impossible to control (other than when polishing/sanding). To give myself a little more room, I put an extended smaller chuck in the drill chuck. Grinding doesn't work well with aluminum - just clogs up the grinding bit.

Just a thought...

Regards
Bob
 

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Discussion Starter · #3 ·
Hi, Bob. I used to use just that combination. Although time consuming (professionals sure wouldn't do it) the slower turning drill allowed a little more controol. But, I also combined that with a air-powered die-grinder which was so LOUD you really need a closed shop some distance from other people (you also have to do when nobody else is in the shop).

I have an electric die-grinder from Harbor Freight (i.e., cheap) and a speed controller which would be a bit quieter but the flex-shaft grinders I've seen on U-tube are even quieter and you could use one of them just about anywhere. I think the trick with them is the ability to control the speed of the burr.

In any event, they're just a motor with a flex shaft/collet attached. But they're also pretty expensive. They're not that complex so it seems like you ought to be able to just make one.

Regardless of what you use I think the key is being able to control the speed.

BTW I owe you an email . . . . :)
 

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71 Berlina 74 GTV 17 Giulia Q4
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I'm actually as we speak taking a break from porting a head out in the shop. I used a couple of cutting tools with an air grinder and the HF die grinder and have not seen the need for a flexible shaft, imho. If you are using JimK's specs from his book you will see there are parts where you need to take off several mm's. This being the third one I've done this time I got a carbide round end cutting tool to take off a lot of metal quickly and it does take it off fast, so much so care is required and stopping frequently to measure is a super must. The when you get to within a mm of where you want to go I used these from fastenall: you can get them in 80 grit if you want but either way as the wear down they get a nice rounded end that is great for just past the guide hole and the curve in the throat under the valve seat. that's my 02 and good luck and happy grinding

1-1/2" x 1" x 1/4" 60 Grit A/O Flap Wheel
Manufacturer: Sia Abrasives
Category: Flap Wheels
Type: Flap Wheel
SKU: 0800740
they come in a bag of 10 and you'll need every one of them maybe more
 

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71 Berlina 74 GTV 17 Giulia Q4
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Just to give you an idea of how much metal we are talking about I'm finishing up and have cleaned up at least 6 or 7 messes like the one below. lots of aluminum! It will be worth it though. I used what I could afford cam wise and on sale too boot but with the IAP 11mm lift cams, the porting, motronics, a set of very old but very special Shankle headers (much larger diameter than the IAP headers that are on the Spider motor, 1st porting job) and other assorted mods (how's that for sentence structure 180out? which btw is a great handle) I did a run around East Texas the other day with a full tank and on the FM roads from the Lake to Tatum, Henderson, Longview, and back to the gas station to fill back up after 83 miles between 70, 75, and 80 mph and got 27 mpg (spica Wes HP pump) and a compression check at home read 180, 180, 179, 181.
have fun!! Jim you probably know all that but maybe it'll let others know it can be done. I would also add that wearing an apron is a great idea. I should have.
 
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