mellow65

iTrader: (2)

i'm curious how many people bothered to put the spacer for the rear section of the subframe.

most swaps i read people pretty much just bolted them up and put them as flat on the frame. and that's how i did mine, but the more i look at it, the more i can see where this would mess with some front suspension measurements as the suspension cycles up and down.

mainly the caster is most effected by the A arm having a slight tilt forward. so as the wheel goes up the wheel moves forward and adds more caster.

so i guess my question is for those that have done this and wonder how it drives. do you notice anything funky? anyone done some rally crosses or auto crosses with it? anything weird about it?

thanks

82transam

iTrader: (18)

I recently completed an FC subframe swap on my T2 FB, been too busy to post about it, but I am planning on doing a post sometime soon with a few things I learned while doing it that don't seem to come up in other posts.

The spacer you are asking about is one of those things, most guys just seem to bolt it in, but if you look at the frame rail on the FC you'll see it is not straight like the FB, it curves down in the back. I'm not sure exactly how critical this is, but I chose to make a 1/2" spacer for my swap

I didn't try to to the install without it, nor have I driven a swapped FB that didn't use the spacer so i can't really say how nessesary it is or not but it sits in there nice and level and everything else seems to fit nicely as well.

bshusted

iTrader: (1)

I did not use a spacer and have not noticed anything unusual. I am very happy with how it handles. When I get further into fine tuning the suspension, I may decide to add one and see if I notice a difference. For now, I'm running without.

peejay

I made a one inch spacer. I feel it is mandatory, and thinking that it is not is absurd.

The subframe needs to bolt to the body, and to do that the mating surfaces must be flat and parallel, and to do that the rear of the subframe needs to be spaced because the FB body rail is a straight line and the FC body rail has an inch deep jog in it.

I simply cannot fathom not using a spacer. That's like adapting your car to five lug wheels by only putting one lug bolt in.

You'll need welding ability to tackle the job anyway. A spacer is not hard at all to make, mine is a three sided box made out of 1x1 angle iron, and one of the old tension rod bolts is welded in to it for use as a mounting stud. Same thread as the original subframe studs, IIRC, so when I pull the subframe off to get the engine out I don't have to remember which one was what. (Oh yes, it's EASY dropping the engine out the bottom! Putting it back in is hard tho)




I also braced the ends of the crossmember to each other, similar to how convertibles did.

(Note the shock mounts I put in the strut towers )

82transam

iTrader: (18)

I agree its mandatory, but you came up with 1" peejay? I used 1/2" (two pieces of 1/4 flat stock stacked and welded to the subframe itself) and its pretty close to parallel (if I were to do it again I'd add another 1/8"...)
I used a vert subframe and definatly plan on getting the brace for the rear of it, definatly not a bad idea to strengthen it up a bit.
Also, to the OP be sure you drop some tubes through the FB frame rails and put some 1/8" plate on teh top to keep it from collapsing when you tighten the bolts down. I used 1/2" grade 8 bolts for mine, probably overkill but better safe than sorry...

peejay

I came up with 1" by bolting the front of the crossmember in place, then whipped out the tape measure.

I was originally overthinking it and was going to make some morphodited bracketry that came down from the steering gearbox and idler arm mounting points, but then I found that the angle iron I had lying around from a failed radiator mounting scheme was a perfect fit, so that's what I made it from.

The guy I first heard about the swap from (abeomid on the old Mazspeed forum) also found that he needed to make a 1" box, so my measurement jibed with his.

I was originally worried that the boxes would distort the body, since they end up in the middle of a span on the inside edges. I painted it with crappy rattlecan so any cracks or flexing would show immediately. I've taken side hits hard enough to bounce the inside wheels a foot up, and run under hard braking across deep ruts (would tend to bend the aft ends of the subframe inwards) and so far, nothing is moving.

So, I guess it's strong enough. Now, if only I could get the rearend to handle the same things...

My goal is to have a car that I don't have to worry about "saving". If the course is rough and torn up, let everyone else slow down for the rough bits. I had a lot of problems with the FB front suspension dealing with that, the FC is way stronger - better bushings, better steering arms, bigger spindles. It's one of the few pieces that I don't have to think about.

82transam

iTrader: (18)

Weird, 1/2" seemed fine on my setup. Oh well, at least we both agree the spacer is nessesary lol

mellow65

iTrader: (2)

well i guess you have all kind of talked me into putting it in there. i was just feeling lazy.

mattp

iTrader: (3)

There's a 20mm difference between the front and rear of the frame rail. See attached.

peejay

Weird indeed. I've heard that the nose of the FB is prone to permanent twisting, I wonder if this is related.

But IMO, as long as the subframe surfaces fit flat against something and the nut fits flat against the subframe, you're good to go.

If I was going to do it again, I'd look into sectioning the body or the subframe, bring the control arm pivots higher. The FC suspension needs a lot more spring than the FB did.

82transam

iTrader: (18)

Definatly put the spacer there.

If the difference is 20mm then technically we're both wrong lol, I didnt go big enough and peejay went a tad too big...
Whatever, I agree peejay, as long as it sits in there level then its good to go, as I said if I were to do it again I'd probably add another 1/8"

peejay

That's the difference between bolting on stuff, and modifying your car. You can't go by definitive instructions, you have to look at the car you have and the parts you have and do what you have to do to make it work.

Kinda why i get a kick out of "what jets do I use in my carb?" Umm... I don't know, that's the sort of thing that people pay me a good amount of money to figure out for them.

mellow65

iTrader: (2)

lol, i'm far from a bolt on guy.

just take a look at my build thread.

https://www.rx7club.com/build-threads-293/finally-my-build-thread-some-weird-crap-here-938042/

i knew i should had done it, not sure why i talked myself out of doing it. i'll go back and fix it. as soon as i get a garage back.

82transam

iTrader: (18)

^clearly not a bolt in guy lol, guess I missed your build thread before, but damn thats looking good!
Given all the metal work you've done so far, putting a small spacer on that subframe won't be much work for you.
Guess its time to sort through the pics I took during my subframe swap and post a thread about it. I did a few things differently than the other ones I've seen so far (not saying its better, just different )