What exactly is meant when everyone says, "Slot the motor mounts" to fit a 13b into a first gen? Everyone talks about it but no one explains it

Bottom line is the 13b is 20mm longer than the first gen, so that 20mm has to come from somewhere.

Motor mount - where is this supposed to be slotted?
Or is it on the crossmember below that I'm supposed to slot, and move the mount forward 20mm? There's not much room on the crossmember for that.



Or is it on the mounting bracket? Here's a pic of each side. Again, if I slot 20mm back I'm running out of space. The slot will be open to the back, and I don't want to trust just the tranny mount to keep my torque-y 6-port in place.

 

Personally I went with the Racing beat engine bracket when I was still using the front cover mounting method, but if there isn't enough room for the full 20mm on the engine bracket you could try doing 10mm on that and 10mm on the crossmember itself. There should be enough room for that. Again though I haven't personally done this, but I don't see why it wouldn't work.

 

im pretty sure people just slot the engine mount thing.. Your second pic. i saw a pic of one that was slotted and they didnt have it open in the back at all.

 

Either that or just flatten the front mount bracket.

 

^Thats actually a better idea!

 

Not really, working the metal like that will actually weaken it and I wouldn't want to
weaken a critical part like this. I've seen the slotted mounts and they weren't open
at all and there was still plenty of meat around the mount point to be safe.

 

I'm leaning towards the RB bracket. TGFarrell, you're right, I don't want to bend it to shape. 82 and Cshaw, the reason I'm asking is because I measured the damn thing and 20mm is right to the edge. Like this:



So the slot would have to be open to get 20mm:



Still waiting for anyone who has actually done this!!

 

Here is the link

https://www.rx7club.com/showthread.p...hlight=notched

 

Another way is to cut near the bends, add 20mm of similar thickness steel to move the OEM slot rearward, then weld. But that's two long welds on a critical part.

I think the way I'll mod mine is to slot it like the red slot pictured above, and add a steel section on the outer edge. It's less critical and is only two short welds; one above and one below the slot on each side.

 

the old school way is to slot the mount bracket, and the trans crossmember.

or you could flatten the bracket a little, bending it a little isn't going to affect its strength in any meaningful way

or just buy the RB part....

 

Yes also slot the trans crossmenber. There is room for the driveshaft yoke to slide more into the trans tailhousing.

You can also weld a gusset onto the motor bracket to strengthen it. When slotting stuff be sure to use large washers and Nylox nuts.

 

I've got a full RB exhaust system so I can't move anything rearward.

 

I have a full RB exhauast and I slotted the front a little and the trans mount a little ( one half of what I needed on each). There is enough play in the exhausts mount to move it back some.

 

Didn't realize there would be so much discussion on this

While I agree that bending metal does weaken it, the amount that this would need to be bent is negligable, it's not like you're bending it in half or something extreme like that. But to each their own, like I said when I was using the front cover mount I just got the RB part, made it nice and easy

 

I've used RB mount bars in the past, and they are excellent. I fully recommend them. But this time I need to spend money on other stuff, and I'm curious if I can do a mod to the stock bar to mimic the RB part. That is: only going forward because the exhaust also has to be backwards compatible with a 12A, and my powerpulse muffler needs an over the axle section fabbed since I had to cut it to make it fit the REPU. The REPU has its own muffler now so all that's needed in the FB is a short u-bend piece. I need the engine placement to be accurate is what I'm saying, so moving forward like any GSL-SE crossmember or RB bar is the only option for me.

 

Gsl-se front lower crossmember wins Everytime. No slotting required. I don't know if the mounting plate is any different.from 12a-13b. I'll find out soon though.

 

Budget wise---------------notch the stock mounting plate--freebie!

Access to cheap used parts or a GSLSE at the wrecker-----change crossmember--reasonable$$ but dirty work

RB plate----definitely ideal, clean and easy, but more $$$$

 

Just for information's sake, I have been running a slotted mount bracket (not notched, but slotted all the way) on a very large SP 13b for about 30k miles of hard driving with no ill effects.


Isaac

 

That's really helpful flightofpain, to know it's not a danger. Here's my slotting job, it didn't turn out very perfect but I have the room to set it where I want it:



Slotted crossmember 7mm on one side, turned into 10mm on the other



Slotted bracket, got about 13mm on one side and 15 on the other

Now I put the motor mounts back on about 7mm ahead of where they were, both sides, and the bracket should fit fine when I drop the engine, with the trans still in the same place = no slotting trans mount.

 

Good job! Now paint that mount so it looks pretty

 

Yeah looking good!

 

Too cold to paint! And I don't have a heated garage, I just want to get her running for now. It's been like 8 months.

 

Hmmmmm, what about the kitchen???

 

don't get caught in that train of thought now! i've done that and i always end up hating myself for it. go ahead take the extra 2 hours (if that) use high temp paint (it's so close to the engine i don't know if regular paint will hold).

i work at a carwash beside a car dealership, they're outside doing body work and painting in 40 degree weather. just keep the paint inside heat it up to room T (the mount also). shake it go outside spray it bring it back in, several coats .

otherwise, that looks like it may get bad pretty fast, spread to your car's chassis or the engine, or itself and just break while going down the road.... but it's up to you.

 

^Agree, I've painted stuff in the middle of the winter and it lasts just fine. I wouldn't paint a whole car unless it was in the 70's, but small stuff with spray paint will be fine, just takes a while to dry.