13B into 12A- Crossmember Question
 

Real easy question, the cross member that needs to be slotted to put a 13B into a 12A car, is everyone talking about the suspension part that the motor mounts are on or the mount on the front of the engine? If it is the part on the enginge will a part from a SE work without putting slots in the part?

Is that all RB sells for $80 is the SE mounting bracket?

The part under the engine that the engine mount, bolts too.
we used a GSL-SE engine mount bent a bit on a 12A crossmember.

crossmember - the part that bolts to the body, that the suspension and engine mounts bolt to.

engine mount - the crosspiece that bolts to the front cover

What I would do would be to use all the 12A stuff and space back the transmission mount and possibly make the driveshaft 20mm shorter. Moving weight rearward = GOOD. :) Costs more, though.

What?
 

Please say you're kidding...That is WAY too much work to slap a 13B in.
With my old '81, all we had to do was drill new holes in the crossmember
to make it fit, and didn't have to suffer all that.

I could understand if the car was a race car or an autocross racer, but I think moving everything
back a litle bit will have neglible benefits at best.
The stock RX-7 has a great balance to begin with.

The old "Ford" mentality, - "If it ain't broke, don't fix it."

a 13b doesn't weigh much more then a 12a? Why would you spend lots of $ move it back.. Might as well do that to a 12a using that thinking? Doesn't Racing beat sell some special front engine mount to make that easy? I'm sure you could make it work with what you have anyway for free?

I don't want to spend the money. This is a quick fix. This summer I will have the SE front end in the car and the engine will bolt right up to that crossmember.

The RX-7 has far from ideal weight distribution... the GTU racers were moving the engines back 6 inches and down 2 to get as much weight rearward as possible! (A stock GSL-SE is around 54/46. Race chassis designers feel ideal is around 35/65)

Really, though, look at it this way... either way you do it (slot front engine mount or slot rear X-member) you're going to be doing modifications. And 20mm MIGHT be a small enough change that the driveshaft won't need modified. And if it is, well, drive it hard enough and you'll be wishing for a T2 transmission which will require transmission crossmember and driveshaft modification ANYWAY... so if you're already resigned to having to modify the trans crossmember and driveshaft, why go the extra trouble of moving everything forward to the stock GSL-SE engine location too?

Heck I was even thinking about shifting the engine even further rearward, like 4 or more inches :) Just until it gets to be too difficult to access the oil filter or the slave cylinder bolts, mind you...