Crossmember mod question

For starters, I'm finally starting to install parts rather than remove them.

Now, on to the dilemma A month or so ago I picked up the install kit that Rob (xschop) was offering, which included a crossmember that had the control arm pickup point on the crossmember moved 3/4" up to compensate for spacing the entire crossmember down by the same amount. The issue I seem to be having is that the motor mount bolts (TPC motor mounts) interfere with the control arm when in that position. I haven't bolted it all together yet (and actually have the control arms completely off now), but I started putting it back together and the motor mount will not sit flush on the crossmember. Am I missing something here? It looks like when you tighten down the motor mount, I could conceivably cut off the last thread or so, which might buy me enough to miss the control arm, but man, that would be tight.

I sent Rob a PM about this already, but thought I'd put it here in case anyone might be able to enlighten me. Knowing how much Rob has done w/ these conversions and for this community, I'm guessing I'm doing something wrong!

Any thoughts appreciated!

Are you bolting this down with the bellhousing attached to the motor?

Nope, no engine yet (just got it off the pallet and onto an engine stand before I closed up the garage for dinner). Just at the test fitting stages. How would the engine impact this? In case I wasn't clear, by motor mount bolts, I mean the ones that bolt to the crossmember, not the ones up on/by the block.

I modified my crossmember and relocated the A arm holes upwards 3/4"

I also had to reprofile the rear flanges so the A arms could pivot upwards, I'm not sure if Rob modified your crossmember.

This picture shows the modified rear flange on the crossmember (passenger side looking aft)



This picture shows the crossmember (before redrilling) in a trial fit with the engine mounts. Be aware that the crossmember has to be relieved to clear the oil pan.



Crossmember relieved to clear oil pan.

I did misunderstand what you were referring to. So, the bolt attaching to the up right is now too long since the control arm is move up .75in. Is there enough thread on the bolt for the nut to attach to?

Sorry for the late reply. I just got back from the Holidays week up in the Ozarks.
After seeing your post, I just realized I forgot to cut off the extra thread from the bottom TPC's uprights. You simply need to bolt them down and trim all the extra threading that extends past the nut. I forgot what the thread pitch he used, but when I did a 1" X-member/control arm relocate, I got a shorter profile nut and thinner washer then chopped the spare threading for maximum clearance. There are no safety issues if you have a thread locker nut or Loc-tite. Happy Holidays to everyone....

Okay, cool, thanks for the help guys. I was thinking a thinner nut and washer and then cutting the threads would do the trick. Any tricks to shortening that bolt and not hosing up the threads? Usually just leave a nut on, make the cut, then wind the nut off and *hope* it cuts the last thread or so good enough. Will a hacksaw cut that bolt?

Use thinnest (1/16") washer, bolt-down, Magic-Mark the extra threading, remove, hack-saw (I used 4.5" cut-off wheel)....then clean thread endings with a fine file or Dremel.

Maybe Mike has a pic of that bolt/nut inside the control arm pocket so others can see what we're talking about.

I also clearanced your X-member just like the pics Mike posted for the aft portion of the control arms and the steering rack bosses near the oil pan as well as engine upright set-back at the X-member

Here are two more pics.

The first indicates how close the A arm is to the engine mount nut Note the modified rear flange..



This pic shows Xschops bump steer block, you have to use the earlier rod ends as the later ends have a female thread.



Simple way to shorten bolts, screw nut on bolt, decide where to cut, use a hacksaw and cut off excess bolt. File the cut face of the bolt exactly flat and perpendicular to the threads, this will allow the nut to be removed and re-fitted easily

Thanks Mike. It's hard to get a good picture, but even the taller nut that comes with the TPC uprights should clear the control arm curvature when using a 1/16" thick washer.

One last question on this - what's the best way to get the control arm aligned in the crossmember slot? I've got it pretty much there, but it's slightly off, enough that I can't get the bolt in. I was considering getting a tapered pin to use to align it, but I'm concerned I'll end up expanding the hole in the crossmember, rather than pulling the control arm straight w/ the hole.

Should it be this tight? I did notice on the "inside" of the crossmember there are some slightly raised areas a little above where the new mounting hole is - maybe I should just file those down a bit? How tight of a fit should it be in there?

Otherwise, things are finally starting to move along, albeit at a painfully slow rate. New engine is off its pallet, on the engine stand now getting some cleanup. Motor mount bolts are shortened, which worked perfectly. BTW, one useful trick - I put 2 nuts on the bolt, and lined them up so the slot between them was exactly where I wanted to cut, so they acted as a sort of mitre box for the hacksaw.

Did you already install the 3/4" X-member spacers?

Kind of Lost me as the inner control arm interface on the X-member is the same diameter in the upper area as well. Nice trick on that upright bolt too.






https://944hybrids.forumotion.com/t55p210-nailed-itxschop-s-53-lm7-build?highlight=nailed+it

Yeah, spacer's are installed.

On the first pic you just posted, on the bottom part of the crossmember, see what looks like a "line" right about where the new hole will ultimately go? So that line is actually a slightly raised area there (ie, more material), relative to where the original holes are. There's a similar raised area on the underside of the upper part in your pic as well. Since the control arm bushing goes in between those holes, I'm thinking the slightly reduced space in between the crossmember sides is making it harder than it should be.

I've got another one at the shop and see what you're talking about. I'll hit it with a 60 grit sanding block. I sprayed lithium grease on my RX7 arms (same X-member interface dims) and they slid right in
When I first did this mod, I thought the X-member would hold the control arm more rigid.

I think I'm going to pull the crossmember off and do a little filing/sanding and fitting with it on the bench, rather than laying under the car and having metal filings falling on my face No biggie.

Is the RX-7 control arm the same bushing diameter as the 944 one?

Yes, but it is Polyurethane

I wonder if Mike had to sand his down any or if your C/A bushings are thicker?

Did not have any problems getting the arms and bushings into the crossmember. Had to use a few judicious taps with a hide face to get the bolts through.