My 12A blew an apex seal, and I'm going to be rebuilding it in a couple of months, but I'm trying to get as many of the parts together as possible now. I thought it would be a good idea to replace the engine studs after 27 years in the car.

two questions:

1) would replacing the studs be a good idea or a complete waste of money?

2) does anyone sell new stock-spec or strengthened stud kits for the 12A?

 

EDIT: For those who care not to read, it is all in the tuning.

Not studs, the stock 12a comes with bolts. Big difference. I haven't checked for studs in a long time for 12a's, but it is one of those arguments that end up like the electric fan vs clutch fan debate.

Main points are:
STUD KIT POSITIVES:

Rotor housing deflection reduced - increases apex seal life
Less material machined from housings and plates than with doweling, reducing the possibility of cracking
High boost engine expansion reduced.
Less prone to stretching under high boost applications.
More accurate tensioning of engine.
Less chance of bolt breakage.

STUD KIT NEGATIVES:
Engine must be accurately drilled, reamed and tapped to give 0.2mm clearance (depending on stud kit used). This means irons and rotor housings.
Oversized studs or larger diameter studs?

Most companies sell larger diameter studs, which won't do much but have a higher clamping force. If you go the route of oversized studs, and get your parts machined to match, it will act like dowels, so to speak.


I for one would not get them. A 13b can make over 1000hp and not break the dowel area's. It is all in tuning. 1000hp will not brake the plate, but a detonation will.

 

Also, Mazda had the 4 rotor that is 3 feet long (actually 34 inches, but whatever) and not run any extra dowels. 4 extra structural parts, 8 more original dowels, 16 inches longer, 2 extra pieces of Ecentric shaft, 2 more rotors and the seals. Never twisted the housings.

Another edit so I don't post *****: If you really want to do something with the tension bolts, put a ring of silicone around the center section and allow to dry before putting them in the engine. This will help dampen the harmonic vibrations the engine puts out at higher RPMs.

 

wow, I wasn't aware that the rotary was so resilient. I really appreciate the feedback.

 

Xtremerotaries in Australia make and sell them. Whether they are required I do not know. My 12AT only runs 7psi boost.

 

All this is great, but methinks Portland didn't know the actual "studs" are in fact BOLTS, so maybe his Q is "should you replace the OEM Bolts", putting aside the "switch-to-studs" issue...??
Stu Aull
80GS

 

Since this is a rotary and not a piston engien, it doesn't need the main bolts replaced like head bolts do. The torque specs are lower and they don't stretch/weaken with reuse.