I sold my irons and I'm starting with brand new oem factory irons with 0 miles. I have two housings from my last motor that also have 0 miles and have had holes drilled for hollow dowel pins like in the picture below. If I decide to stick with a dowell pin setup then I will just use the two housings I have and buy another to replace the one the last shopped ruined. however if i go with studs I will sell the other two and go with 3 brand new housings. but i cant decide which to go with. I've heard several different things from different builders and I'm a little lost.

What i have been told is that I cannot run 3 straight hollow dowel rods like this all the way from the front iron to the rear iron without some special bore alignment or something like that. I was told that because the front rotor ahead of the fat center iron needs to "float". So i would need 3 hollow dowell pins for the rear iron to the fat center iron then 3 more smaller hollow dowel pins from the front iron to the fat center iron. This doesn't make any sense to me as letting the motor float is letting it flex to me which seems like what I was trying not to do by dowel pinning it in the first place.. This seems very confusing to me so I considered using a stud kit but apparently the stud kits have issues with sealing collant. So I'm currently at a stand still until I can figure out what to do.
Thanks in advance for any input.

 

I wanna know the same thing.
And is this even necessary for a 550hp 20b NON c or d code block to be studded or doweled.

 

I think it would be pretty hard to assemble a 3 rotor with full length dowels. That said I see no good reason why they would be an issue in terms of stress.

What makes you think studs cause coolant leaks? I have run studs in some of my engines without any leakage issues. Coolant seals should be unaffected by studding, and as long as the machining is done properly to accomodate tension bolt seals or o-rings, the ends should not leak either.

 

I would just consult Chips

 

I have consulted Chip and we have gone over the pros and cons of each method. I just want to get some info from everyone before I decide on one method.

 

I'm considering using some oversized tension bolts that fit as tightly as the factory alignment dowels. Align the motor and ream all of the irons and housings to smoothly and tightly fit the smoother and larger diameter tension bolts that would now fill the areas they occupied before when they didnt touch the walls when they just slipped in and sandwiched the motor together and only relied on the alignment dowels to keep it rigid. any thoughts?

 

has anyone had any issues with stud kits like the guru 12.7 or other kits leaking coolant or have they sealed easily?

 

Can't help you but maybe you can help me. Looking on Mazdatrix website, they have dowel pins for 20b.
Does the 20b only have two stock dowels located in the front housing or is there two 20b specific dowels and then the rest are standard 13b?

 

There are a whole lot of opinions about this.... Ive had an fd engine doweled, would never do it again. I would NEVER do it on a 3 rotor. It was the machinists first time. Turned out perfect. I recommend someone with experience and a fixture for it. There is very little material left after you do it. I personally think it compromises the structure of the engine.

I really like studs that act as dowels. You leave more material AND get better clamping. Its no problem if you find the right machinist.

Im not in the "engine twisting camp" Im in the housing expanding outward camp. Ive seen evidence so that is how I base my opinion.

As ecu's get better and better along with the right equipment/tuner this becomes less of a problem. Spend as much time on ignition and charge cooling as you do on studs/dowels

There was a local guy here that bought out all my RE stuff. He was over 1000hp on his 3 rotor. He had the GURU stud kit that he fitted using an old drill press. Don't laugh, it turned out straight and true. If a machinist gives you flak about how hard it is, move on to one that understands what needs to be done. Of the few years he messed with it his main concern was breaking drive-trains, not leaking coolant.

In the end things will break, as Im sure you have been told, pinned or doweled, dented rotor, ob-longed stat gears, cracked side plate, take your pick.

 

the factory dowels in the front housing allow the housing to float(tapered on one end), i also do not believe it is even necessary.

studding is better than dowelling IMO. oversize tension bolts will be more reliable for high HP engines than the pencil size factory tension bolts and hollow dowels which still will bend under stress.

 

so do you feel that using studs to tightly torqued down would make the front housing not able to move (float) and cause the bearing to wear prematurely or even break the e shaft? should I just use over sized tension bolts on the back half of the motor and run the the factory through bolts and use the factory tension bolts on the rear? I realize stuff will inevitably break or need to be replaced from normal wear I'm just mainly concerned with breaking the hard to replaces stuff like the e shaft, center bearing and fat center iron.

 

Run 7 studs thru the whole block and the rest run the stock bolts then run the two solid dowels, Balance the rotating assembly and line bore the block and you will be golden

 

goopy do a full length 20b solid dowel that is machined for side oil feed

 

if the front rotor really floated like mazda intended there would be more frictional wear(etching) on the iron, rotor housing and the dowels. i have no idea what their real thoughts were there, but it wasn't necessary.

if anything the center rotor is the one that needs the attention in balance and additional clearance(excessive step wear, rotor tip to housing tapping and rotor corner tips to side housing tapping where the other 2 generally do not give those symptoms).