I'm about to add two extra dowels per rotor to my motor. What is the best way to go about milling and reaming the holes? Do you drill through the housing and into the iron, then ream and flip the housing and do the other iron? Or just drill through the center iron/housing/into the front(or rear) and ream at the same time? How deep into the front iron are the holes usually drilled?

My plan was to drill through the center iron through the housing and about 1/4" into the front iron, then ream to 15mm. I would then clamp the rear stack together and indicate in on the reamed center iron holes and repeat. Probably going to grind stock dowels to 0.001" under and to whatever length I need.

I've never seen a write up of this, so I'm just assuming this is how it is done. Any info or corrections would be most helpful. Maybe I'll make a write up while I'm doing it.

 

https://www.rx7club.com/showthread.p...housing+dowels

 

I've read that write-up before, but I plan on running the dowel through the housing so that both ends of the dowel are embedded in the irons, much like stock.

 

I am assuming these are going in place of bolt holes. The problem with drilling is that the drill will use the original hole as a pilot and just follow its path. If the holes aren't lined up perfectly you will not have a straight hole. An end mill has much less tendency to follow the hole path especially if you plunge slow. It is meant to cut horizontally. A long end mill will however deflect more than a short one so the idea is to keep the shortest stack of parts and have a good way to re-find the hole location you want to use.
I would stack the middle and rear iron with the original dowels in place and use an end mill to establish a good base lined hole. Now stack the housing under the middle iron and re-find the new hole center of the iron with a dowel chucked up (or better yet colletted). Now you can mill a matched rotor housing hole.
Ok now you have two irons and a housing with nice matched and aligned but undersized holes. Stack all three, re-find the hole center and drill through all 3 with a drill that is properly sized for the finish reamer. The drill shouldn't wander since the known straight hole will act as its guide. Now you can ream to size and have a beer.

 

If your using stock dowel pins your going to have to use a 39/64 drill bit and then ream it with a 16mm reamer. If your good you can do it with a drill press that's the way I have done them on my motors. I have a center plate that I use for a guide I'll do the center plate first and then stack the housing with the center plate and drill all the way through. Then you move to the front and rear plate using the housing as your guide and drill those. Be careful with the front you can only go down about a 1/2 inch maybe less if you go further than that you won't have enough threads for the tension bolts to grab on to. Once you have drilled all your plates and housings. Just go through the same steps with the reamer. It would be very helpfull for you if you had two junk center plates, one for use as a guide for the drill bit and the other one as a guide for the reamer. All I can say is keep checking your measurements. If you look at the pictures you'll see where I put the extra dowels. You can probably add one more right by the spark plug area but there is not too much material there. Good luck to you.

 

BFP's!!