(SUSPENSION) FC front end into FB WRITEUP
09-11-05, 01:40 AM
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(SUSPENSION) FC front end into FB WRITEUP
Second Gen Suspension Swap Into A First Gen
By: Nik
nikstet@hotmail.com
My history
I have pondered over this swap for quite some time. The 2nd gen front end allows for a lot of different aftermarket upgrades. I also noted the improved steering ratio on the 2nd gen power steering. Other reasons such as beautiful polishable aluminum A-Arms, 4 piston caliper brakes, and only paying $100 Canadian for the entire front end made this sound like a pretty good swap
Omid’s background
By Omid M. (aka bcrx7 aka abeomid)
omid@bcrx7.com
www.bcrx7.com
History: for years I was looking for an easy way to put the bigger front brakes from a Second GenerationRX-7 on a 1st Gen. There were different ways that people thought it would work such as re-drilling the bigger rotors and custom fitting it to first gen hubs or using hubs from a FC since the outer bearing is the same. All of these were good ideas for street use, but since there is racing involved in my case, I wanted something that can be more straight forward so I don’t need to re-drill rotors everytime I get new rotors and also I wanted something that has a better upgradeability in the future. After months of working on the body and figuring out different things I got to the front suspension and brakes. I was lucky that I was working on my car at a RX-7 Shop and there was a couple of 2nd gen’s around for me to look at. Some initial measurements and comparison of the both suspension looked promising. It was at this point that I thought I might as well try it and wish that it would be a straightforward fabrication. The frame distance in the front is almost exactly the same. This helps quite a bit as it means the first gen frame can sit on the FC sub-frame comfortably. So the only problem with connecting the sub-frame to the first gen chassis is finding or creating 4 holes through the frame to bolt it on.
WARNING: Just to save my own a$$ here I do not take any responsibilities if you attempt to do this conversion and anything happens to you, your car, your dog, and/or your house before, during, or after this conversion. I am an Electrical Engineer w/ extensive background in fabrication and design and I always tend to design and test everything before attempting it.
Steps: Well first off you have to remove basically everything from the front of the car. This includes the front suspension, engine, sub-frame, tension bars and anything that is connected to these. You can get away by keeping the engine in there, but it makes your life easier if you do take the engine out. I am not going to cover anything about taking these components out as if you are going to attempt this swap, you should already be familiar with the removal of these items. Now you need to locate a 1986-1991 front suspension, sub-frame, steering column and rack. All different models have the same sub-frame and steering column. There are powered and non-powered steering racks available and from my understanding the powered one has a better steering ratio. As for the suspension you can use you 1st gen. springs, but you have to find the shocks, rotors, hubs, control arms, and calipers from a 2nd gen. Again there are many choices available here for the shocks, rotors, and calipers with the Turbo II or GXL being the best ones. As for the hubs, if you have a GSL-SE, you can just try using the 4bolt hub from the 2nd gen. and keep all your wheels the same bolt pattern. But if you want to go ahead and use the 5bolt hub, then you will have different front and rear bolt pattern unless you go ahead and change the rear to 5bolt as well.
1. Locating the sub-frame:
It’s time to locate where you want to put the sub-frame. It seems like that the front bolts in the first gen frame left from the stock sub-frame are a good start. The location of the front mount bolts for the FC sub-frame should be located 1 1/8” in from the inner frame and 1½” further back towards the firewall on both sides. This will center the wheels into the wheel well. Locate where the hole is to be placed in the rear using a center punch. Now for the size and material of the bolt: For material you don’t want anything less than Grade 8 bolts and nuts. Grade 8 allows for strong enough bolts with a lower sheer rate. The length of the bolt I used is 5”, which is the same length as the studs from the original. Start with a small pilot bit, and work your way up. I recommend putting a shaft. 1/2'” inner diameter, with a 1/8” wall will do a good job. Drill the punched holes in the frame the same size as the shaft. Make sure it’s straight and goes through to the top of the frame. Again you need a 5” + drill bit to be able to go all the way through. Grind off the heads of the studs for the original FB cross member mounts and plate the holes if you’re after the clean look. Now try lining up the sub-frame. As you have noticed if you have followed this so far, the sub-frame is not exactly flush with the frame. The reason is some obstacles that have to be overcome. There are two small ear brackets located on either side of the FC sub-frame that have to be grinded off. You have the choice of drilling the 2 nubs for alignment pins, or as I did, grind them off. Depending on the location of your new holes, you may need to use a die grinder to oval the circular hole on the passenger side of the sub-frame into an oval that matches the driver’s side
Unfortunately the frame on the first gen has these lips extending down the side on the outer edge. There are 2 options at this point: Make four notches and bend them out using an angle grinder and a good hammer. Beat them out towards the wheel well At this point if you have choose this, stitch weld the seam shut to bring back some of the structural integrity and a cleaner look. The second and preferable option is to not cut them and beat them outwards without cutting.
Just for over- precaution, I also put a plate on the frame rail for weight distribution. For this I used a 1/8”x 2”x 3”steel plate under the bolt to distribute any force over bigger area. I went ahead and welded the bolt to the steel plate as well as the plate to frame for a permanent worry free installation.
2. Securing the rear sub-frame:
The rear two holes have to be drilled in the frame. Some people have the FC sub-frame holes line up centered on the frame of the FB, but I was not so lucky. I moved the hole over 1 inch and filled the old mount hole.
The rear of the sub-frame does not sit even to the frame. Make a 1”x2”x2” spacer block to fill this gap and distribute the weight. Drill a ½” hole thru the sub-frame 1” over should it not line up with the center of the FB frame, as well as centering it in the 1” spacer block. I welded the spacer on the FC sub-frame for added strength
Once again weight distribution could be an issue. For this I used a 1/8” x 2” x 3”steel plate under the bolt to distribute any force over bigger area. I went ahead and welded the bolt to the steel plate as well as the plate to frame for a permanent worry free installation. However since these bolts basically pass through around where the stock steering arms where located, there shouldn’t be any worries about any stresses but safety is always first; hence the plate.
Now the sub-frame can be fully bolted on and you can sit back and take a look. Now the steering rack can be bolted back on the sub-frame if you took it off before.
3. Fabricating the steering column:
The steering column isn’t too bad of a swap. The one obstacle you’ll discover is that the second gen column doesn’t contain the headlights, wipers, or turn signals on it. There is a fairly easy work around to this though. You’ll need both a first gen column and a second gen column to make one that will work for this application. Remove both columns and set them side-by-side. You’ll notice a separation point for the columns. They are different style for the upper and lower outer column. Use propane or MAP gas torch to heat up and melt the plastic sleeve for the collapsible steering column. Use a big pair of pliers and wiggle the lower shaft off of the upper shaft. This unveils the inner columns. On the inner columns, there are 4 plastic plugs. These plugs are the locations of the plastic sleeve for the collapsible column. Heat them up with a torch and use a pair of pliers and remove the inner lower column from the inner upper column. If your car has steering lock, you’ll need to insert the key to remove the column. You’ll need to use the upper outer portion from the first gen column, as well as the upper inner column from the first gen. For the lower you’ll use both the inner lower second gen and the outer lower second gen. Reassemble the column and measure to fit Should you choose to, an aluminum cotter pin will replace the plastic inner sleeves in the steering column. .The columns fit tight, so you will need to cut the second gen lower column down. In order to keep this collapsible, the reducing section should be removed. This will allow the inner and outer to gap. I then put the inner column into the upper outer, attached the lower outer, then mocked the bottom of the outer lower column in. I tack welded it with 3 tack welds and filled the gap with plastic to keep the column collapsible.
.
4a. Putting the suspension in (stock shocks and springs):
It’s time to put the shocks and springs in. You should use your first gen springs and top mount and the FC shocks. This will allow the car to ride at stock height. All you need to do is remove the top mount and spring from the FC shock using a spring compressor and put on the first gen spring and top mount.
4b. Putting the suspension in (aftermarket coilovers):
If you can first gen coilovers, it might be possible to fit the spring perch over top of the FC shock but I have not tried it personally. But a good thing now is that you can use any coilover setup from FC’s, even expensive setups such as Teil or Mazdaspeed. In case you are using a camber/caster plate, the original boltholes on top of the shock towers have to be enlarged slightly as the bolt pattern on the FC is slightly bigger and most of the camber/caster plates are designed for FC’s.
5. Putting the brakes on and your options:
As I mentioned before you have several options of your brake setup and wheel bolt pattern. As for brakes all the GXL, TurboII’s, GTUs, and GTU come with 4-piston front calipers and 11” brake rotors. Anything has single caliper pistons and same size brake rotors as GSL-SE. If you have a GSL-SE model, then you might want to stick with your stock 4x114.3 bolt pattern, which is also available on the early GX models on FC’s. Using the hubs and rotors from the 1986-88 GX models you can keep your original bolt pattern, however the brake size stays the same. You can upgrade the brakes by using the GXL or TurboII brakes and the 4 bolt pattern hub and get a machine shop to re-drill the brake rotors which are 5 bolt pattern to the 4 bolt pattern you want. Now if you don’t have a GSL-SE or you don’t want to have the 4-bolt pattern, then you are stuck with the 5-bolt pattern brakes that come with the FC’s. This is somewhat inconvenient b/c you will have front 5-bolt and rear 4-bolt wheels. You can change the rear bolt pattern to 5 as well; but this involves more machining and it is not going to be covered in this write-up.
6.Engine Modification:
You’ll need to use 2nd gen engine mounts The engine mounts needed are the ones from a second gen from the side, not the one that bolts thru the oil pan. You will need 2 of them. Custom engine mounts may be necessary. The first gen drive shaft will line up on the new engine and trans location
More detail coming soon
7. Installing and wiring the adjustable struts from a GXL or TurboII
Coming soon!
8. Installing and wiring the speed sensitive power steering
Coming soon!
Conclusion:
Well this is all I want to say for now. As you can see this write-up does go into much more detail on how to do this swap. I tried to cover as much as I could about how to do this swap. Again remember I do not take any responsibility for any danger you put yourself in by attempting this swap.
For any questions or concerns you can contact nikstet@hotmail.com
Credits:
Thanks to Omid at bcrx7.com for the general swap idea and the general requirements for the install. Also thanks to Grant (grantmac on bcrx7) for the visual and the advise on how to improve on it.
By: Nik
nikstet@hotmail.com
My history
I have pondered over this swap for quite some time. The 2nd gen front end allows for a lot of different aftermarket upgrades. I also noted the improved steering ratio on the 2nd gen power steering. Other reasons such as beautiful polishable aluminum A-Arms, 4 piston caliper brakes, and only paying $100 Canadian for the entire front end made this sound like a pretty good swap
Omid’s background
By Omid M. (aka bcrx7 aka abeomid)
omid@bcrx7.com
www.bcrx7.com
History: for years I was looking for an easy way to put the bigger front brakes from a Second GenerationRX-7 on a 1st Gen. There were different ways that people thought it would work such as re-drilling the bigger rotors and custom fitting it to first gen hubs or using hubs from a FC since the outer bearing is the same. All of these were good ideas for street use, but since there is racing involved in my case, I wanted something that can be more straight forward so I don’t need to re-drill rotors everytime I get new rotors and also I wanted something that has a better upgradeability in the future. After months of working on the body and figuring out different things I got to the front suspension and brakes. I was lucky that I was working on my car at a RX-7 Shop and there was a couple of 2nd gen’s around for me to look at. Some initial measurements and comparison of the both suspension looked promising. It was at this point that I thought I might as well try it and wish that it would be a straightforward fabrication. The frame distance in the front is almost exactly the same. This helps quite a bit as it means the first gen frame can sit on the FC sub-frame comfortably. So the only problem with connecting the sub-frame to the first gen chassis is finding or creating 4 holes through the frame to bolt it on.
WARNING: Just to save my own a$$ here I do not take any responsibilities if you attempt to do this conversion and anything happens to you, your car, your dog, and/or your house before, during, or after this conversion. I am an Electrical Engineer w/ extensive background in fabrication and design and I always tend to design and test everything before attempting it.
Steps: Well first off you have to remove basically everything from the front of the car. This includes the front suspension, engine, sub-frame, tension bars and anything that is connected to these. You can get away by keeping the engine in there, but it makes your life easier if you do take the engine out. I am not going to cover anything about taking these components out as if you are going to attempt this swap, you should already be familiar with the removal of these items. Now you need to locate a 1986-1991 front suspension, sub-frame, steering column and rack. All different models have the same sub-frame and steering column. There are powered and non-powered steering racks available and from my understanding the powered one has a better steering ratio. As for the suspension you can use you 1st gen. springs, but you have to find the shocks, rotors, hubs, control arms, and calipers from a 2nd gen. Again there are many choices available here for the shocks, rotors, and calipers with the Turbo II or GXL being the best ones. As for the hubs, if you have a GSL-SE, you can just try using the 4bolt hub from the 2nd gen. and keep all your wheels the same bolt pattern. But if you want to go ahead and use the 5bolt hub, then you will have different front and rear bolt pattern unless you go ahead and change the rear to 5bolt as well.
1. Locating the sub-frame:
It’s time to locate where you want to put the sub-frame. It seems like that the front bolts in the first gen frame left from the stock sub-frame are a good start. The location of the front mount bolts for the FC sub-frame should be located 1 1/8” in from the inner frame and 1½” further back towards the firewall on both sides. This will center the wheels into the wheel well. Locate where the hole is to be placed in the rear using a center punch. Now for the size and material of the bolt: For material you don’t want anything less than Grade 8 bolts and nuts. Grade 8 allows for strong enough bolts with a lower sheer rate. The length of the bolt I used is 5”, which is the same length as the studs from the original. Start with a small pilot bit, and work your way up. I recommend putting a shaft. 1/2'” inner diameter, with a 1/8” wall will do a good job. Drill the punched holes in the frame the same size as the shaft. Make sure it’s straight and goes through to the top of the frame. Again you need a 5” + drill bit to be able to go all the way through. Grind off the heads of the studs for the original FB cross member mounts and plate the holes if you’re after the clean look. Now try lining up the sub-frame. As you have noticed if you have followed this so far, the sub-frame is not exactly flush with the frame. The reason is some obstacles that have to be overcome. There are two small ear brackets located on either side of the FC sub-frame that have to be grinded off. You have the choice of drilling the 2 nubs for alignment pins, or as I did, grind them off. Depending on the location of your new holes, you may need to use a die grinder to oval the circular hole on the passenger side of the sub-frame into an oval that matches the driver’s side
Unfortunately the frame on the first gen has these lips extending down the side on the outer edge. There are 2 options at this point: Make four notches and bend them out using an angle grinder and a good hammer. Beat them out towards the wheel well At this point if you have choose this, stitch weld the seam shut to bring back some of the structural integrity and a cleaner look. The second and preferable option is to not cut them and beat them outwards without cutting.
Just for over- precaution, I also put a plate on the frame rail for weight distribution. For this I used a 1/8”x 2”x 3”steel plate under the bolt to distribute any force over bigger area. I went ahead and welded the bolt to the steel plate as well as the plate to frame for a permanent worry free installation.
2. Securing the rear sub-frame:
The rear two holes have to be drilled in the frame. Some people have the FC sub-frame holes line up centered on the frame of the FB, but I was not so lucky. I moved the hole over 1 inch and filled the old mount hole.
The rear of the sub-frame does not sit even to the frame. Make a 1”x2”x2” spacer block to fill this gap and distribute the weight. Drill a ½” hole thru the sub-frame 1” over should it not line up with the center of the FB frame, as well as centering it in the 1” spacer block. I welded the spacer on the FC sub-frame for added strength
Once again weight distribution could be an issue. For this I used a 1/8” x 2” x 3”steel plate under the bolt to distribute any force over bigger area. I went ahead and welded the bolt to the steel plate as well as the plate to frame for a permanent worry free installation. However since these bolts basically pass through around where the stock steering arms where located, there shouldn’t be any worries about any stresses but safety is always first; hence the plate.
Now the sub-frame can be fully bolted on and you can sit back and take a look. Now the steering rack can be bolted back on the sub-frame if you took it off before.
3. Fabricating the steering column:
The steering column isn’t too bad of a swap. The one obstacle you’ll discover is that the second gen column doesn’t contain the headlights, wipers, or turn signals on it. There is a fairly easy work around to this though. You’ll need both a first gen column and a second gen column to make one that will work for this application. Remove both columns and set them side-by-side. You’ll notice a separation point for the columns. They are different style for the upper and lower outer column. Use propane or MAP gas torch to heat up and melt the plastic sleeve for the collapsible steering column. Use a big pair of pliers and wiggle the lower shaft off of the upper shaft. This unveils the inner columns. On the inner columns, there are 4 plastic plugs. These plugs are the locations of the plastic sleeve for the collapsible column. Heat them up with a torch and use a pair of pliers and remove the inner lower column from the inner upper column. If your car has steering lock, you’ll need to insert the key to remove the column. You’ll need to use the upper outer portion from the first gen column, as well as the upper inner column from the first gen. For the lower you’ll use both the inner lower second gen and the outer lower second gen. Reassemble the column and measure to fit Should you choose to, an aluminum cotter pin will replace the plastic inner sleeves in the steering column. .The columns fit tight, so you will need to cut the second gen lower column down. In order to keep this collapsible, the reducing section should be removed. This will allow the inner and outer to gap. I then put the inner column into the upper outer, attached the lower outer, then mocked the bottom of the outer lower column in. I tack welded it with 3 tack welds and filled the gap with plastic to keep the column collapsible.
.
4a. Putting the suspension in (stock shocks and springs):
It’s time to put the shocks and springs in. You should use your first gen springs and top mount and the FC shocks. This will allow the car to ride at stock height. All you need to do is remove the top mount and spring from the FC shock using a spring compressor and put on the first gen spring and top mount.
4b. Putting the suspension in (aftermarket coilovers):
If you can first gen coilovers, it might be possible to fit the spring perch over top of the FC shock but I have not tried it personally. But a good thing now is that you can use any coilover setup from FC’s, even expensive setups such as Teil or Mazdaspeed. In case you are using a camber/caster plate, the original boltholes on top of the shock towers have to be enlarged slightly as the bolt pattern on the FC is slightly bigger and most of the camber/caster plates are designed for FC’s.
5. Putting the brakes on and your options:
As I mentioned before you have several options of your brake setup and wheel bolt pattern. As for brakes all the GXL, TurboII’s, GTUs, and GTU come with 4-piston front calipers and 11” brake rotors. Anything has single caliper pistons and same size brake rotors as GSL-SE. If you have a GSL-SE model, then you might want to stick with your stock 4x114.3 bolt pattern, which is also available on the early GX models on FC’s. Using the hubs and rotors from the 1986-88 GX models you can keep your original bolt pattern, however the brake size stays the same. You can upgrade the brakes by using the GXL or TurboII brakes and the 4 bolt pattern hub and get a machine shop to re-drill the brake rotors which are 5 bolt pattern to the 4 bolt pattern you want. Now if you don’t have a GSL-SE or you don’t want to have the 4-bolt pattern, then you are stuck with the 5-bolt pattern brakes that come with the FC’s. This is somewhat inconvenient b/c you will have front 5-bolt and rear 4-bolt wheels. You can change the rear bolt pattern to 5 as well; but this involves more machining and it is not going to be covered in this write-up.
6.Engine Modification:
You’ll need to use 2nd gen engine mounts The engine mounts needed are the ones from a second gen from the side, not the one that bolts thru the oil pan. You will need 2 of them. Custom engine mounts may be necessary. The first gen drive shaft will line up on the new engine and trans location
More detail coming soon
7. Installing and wiring the adjustable struts from a GXL or TurboII
Coming soon!
8. Installing and wiring the speed sensitive power steering
Coming soon!
Conclusion:
Well this is all I want to say for now. As you can see this write-up does go into much more detail on how to do this swap. I tried to cover as much as I could about how to do this swap. Again remember I do not take any responsibility for any danger you put yourself in by attempting this swap.
For any questions or concerns you can contact nikstet@hotmail.com
Credits:
Thanks to Omid at bcrx7.com for the general swap idea and the general requirements for the install. Also thanks to Grant (grantmac on bcrx7) for the visual and the advise on how to improve on it.
09-11-05, 02:08 AM
#2
lightened fb
Join Date: Aug 2004
Location: vancouver, bc
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congrats on getting it done!!, welcome to the tight steering club, are you running the power steering hooked up or disconnected? i am personally running a disabled power steering, theres a thread in the fc forum on how to do that so it will never bind.
good thourough rightup too, now with more people thinking about this swap theres gonna be no parts left in the junkyards for the fc people,
good thourough rightup too, now with more people thinking about this swap theres gonna be no parts left in the junkyards for the fc people,
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10-24-05, 09:49 PM
#9
nother rican witha rotary
Join Date: Mar 2002
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i actually understood from somewhere that the fc strut assembly would fit in the fb's strut assembly spot with lil fab to the holes or somethin along those lines...someone please correct me on this one because there is a gtu at a local junkyard that i want 2 rip off the front struts off of if this is true
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