Complete front and rear subframe swap

[ThreeDeadZs]

I've been reading this forum for a long time, but this is my first post. How reasonable would it be to install the complete front and rear subframes from a late model sports car into a 240Z?

 

This would accomplish swapping the complete suspension, steering, and brakes; and the engine and transmission if desired. Maichor's 200SX rear suspension swap shows me the rear could be done, and it seems like the front would only require modifying the frame rails and shock towers to match the donor car's geometry. I read somewhere on this forum that some Japanese tuners may be swapping whole floorpans, but cannot confirm it.

 

Because of personal preference, I'm inclined to use the subframes from a Toyota Supra MkIII and an engine from a Supra MkIV. What models would make the best donors in the opinions of forum members? Is this a worthwhile approach?

 

ThreeDeadZs

73 240Z partially restored, still has wiring and intake problems

74.5 260Z #12 doesn't run due to intake problems

73 240Z parts car, barely runs due to intake problems

88 Toyota Camry - always runs

88 GMC Van

too many previous cars to list

[blueovalz]

Sometimes just cutting out the whole section is better than piecemeal work. Maybe cutting the entire bottom (floor included) out of an SX and welding it in place of the Z entire bottom may be less trouble than swapping this and that, and adapting this and that.

[260DET]

For the front maybe a fully subframe mounted double A arm suspensing and steering setup? If there is such a late model setup with a good reputation. Maybe a Mazda RX7 or MX5/Miata? Late model Supra?

 

Other than that its use another strut setup or mix and match parts to make a hybrid. There has been a bit of discussion at times about that option, also about custom made double A arm setups.

[ThreeDeadZs]

Yes, I agree that doing complete subsystems would be easier than piecemeal work, which is exactly my point. I'd transfer the whole floor section that contains connection points to the rear subframe, like Maichor posted doing with a 240SX rear subframe. Then I'd mount the whole front subframe, hopefully with no more than modifications/additions to the frame rails and modified strut towers. With this, there would be no Z running gear left at all.

 

The Toyota Supra MkIII (86.5-92) stock suspension is very stiff (I had two of this model) and I have read it only differs from the Supra MkIV (93-98) supercar in revised rear subfame mounting points. Another nice point about the MkIII model is that due to how expensive it is to repair and the failure rate on stock 7M engines, a donor with good suspension should be able to be found cheaply here in California. I'd use the 2JZ series engines which replaced the 7M series in 1993.

[260DET]

Using the Supra stuff will give you a nice wide track, five stud wheels, power steering, modern geometry, big brakes........ If you do it I'm sure there would be lots of interest here.

[ThreeDeadZs]

Yes Richard, using a Supra's subframes would have those benefits, plus the subframe mounted Double A Arms you mentioned earlier and power rack and pinion steering mounted on the frontside of the front crossmember which supposedly eliminates bumpsteer. Now that you mention newer Mazdas, I'll check compatibility of those and other potential donors before settling on the Supra. What other subframes (than 240SX derived ones) have been successfully installed in a Z?

 

When originally planning this project in 1998, I took my camera in to a tire shop and when they had my 87 Supra secured overhead on a lift, they let me snap over a dozen pictures of the stock suspension. I have these pictures in front of me and confirmed my previous statements. If there's enough interest, I'll scan and post relevent pictures. [bTW: Laying the camera on the ground allows distant shots from eight feet away, exactly vertical for comparison.]

 

Matthew

ThreeDeadZs

73 240Z partially restored, still has wiring and intake problems

74.5 260Z #12 doesn't run due to intake problems

73 240Z parts car, barely runs due to intake problems

88 Toyota Camry - always runs

88 GMC Van

Previous Toyotas: 90 Supra Turbo Targa, 87 Supra NA Targa, 75 Celica GT, 85 Celica GTS, stock 77 Corona, 80 p/u, 86 p/u, 90 p/u

Too many other previous cars to list, since I generally kept at least two at a time.

[260DET]

You could look at a GTR or Z32 rear subframe Matthew, they have a similar suspension setup to the S13, S14 is a bit different but not much. Nice big rear brakes on the GTR and Z32.

 

Don't know the various dimensions of the subs mounting points to the body, it may be that one would fit the S30 better than another, I'm assuming that they are not all the same.

[blueovalz]

My assumption is that most if not all options for swaps will require adapting a wider set-up onto the S30's narrow(er) unibody.

[Pop N Wood]

Why not just drive a Supra?

 

What advantage is there to grafting a Z shell onto a Supra?

[ThreeDeadZs]

"Why not just drive a Supra?" That's like asking why build a hybrid at all!

 

Here are my reasons... feel free to correct or comment on anything:

1. Avoidance of California SMOG laws. The cutoff is currently 1975. Now I could use a 75 Celica GT for nostalgic reasons, but the Z is a better body for a straight six.

2. Roughly 25% reduction of weight over Supra MkIII, whose curb weight is 3500lbs.

3. Supra MkIII's are notorious for being expensive to repair, especially under the hood, and especially if you don't do your own work.

4. Supra MkIV's are completely out of my financial reach. This project would be cheaper to build than buying the lowest priced MkIV, but should outrun and outmanouver the base model... especially below 60mph which is about as fast as one can drive in the mountain twisties. (Roads here are BARELY two lanes wide) Plus I would like to autocross and I don't mind being in the "open" category, as I once did in a heavily modified Supra.

5. My project had little to do with Z cars at first: I was planning a project since age 18... 21 years ago.

6. The price of this project should be less than installing a Chevy 350, big brakes, 5 lugs, support for 10" tires, bump steer mod, and so forth, but probably outperform that approach. (I'd love some feedback on this thought)

7. The original Z body is a beautiful classic car that is too old to look 'old' if you know what I mean. It's the only classic body I can buy (and I have collected three complete, worn out Z's already)

8. A Supra MkIII in stock form would need reconditioning by now, a reconditioned/upgraded one is expensive to buy, and a distressed Supra MkIII can be bought for practically nothing as a donor car (in California at least). Parts/Modifications for this model will continue to be available for a very long time. But, due to reduced weight, suspension and brake upgrades from stock Supra components should be unnecessary.

9. A reason I'm sure many on the forum can relate to: it would be unique... yet even better if it inspires copies. I'll document my project in case anyone wants to copy it.

 

I like the idea of checking on a lighter system, like from a late model RX7. But unless there are significant adantages, I'll pursue the Supra.

 

Matthew

ThreeDeadZs

73 240Z partially restored, still has wiring and intake problems

74.5 260Z #12 doesn't run due to intake problems

73 240Z parts car, barely runs due to intake problems

88 Toyota Camry - always runs

88 GMC Van

Previous Toyotas: 90 Supra Turbo Targa, 87 Supra NA Targa, 75 Celica GT, 85 Celica GTS, stock 77 Corona, 80 p/u, 86 p/u, 90 p/u

Too many other previous cars to list, since I generally kept at least two at a time.

[ThreeDeadZs]

My assumption is that most if not all options for swaps will require adapting a wider set-up onto the S30's narrow(er) unibody.

Absolutely, and that's one of the benefits. As long as the subframe connection points are within the unibody, it should work like it did for Maichor's 200SX rear suspension swap. If the connection points are in inconvenient locations, I'll add a rollbar/rollcage as a partial frame and connect it to the the floorpan at the subframe connection points, or directly to the subframe. Fender flares can hide the tires.

 

BTW: BlueOvalZ, I just went through some of your photo album. Your car is AWESOME! How many years and dare I ask, how much money have you put into your car? I'll bet you are an engineer.

[blueovalz]

Lots and lots of years, but NOT SO lots of money. It all was originally OEM salvage from other species of car. Every now and then I get extravagant, and purchase some used stuff on EBay.

[BRAAP]

Now with your detailed list, (good list by the way), this begs the question of why do you want to use an alternative suspension under the early Z?

 

The point about beating the Cali smog check is definitely a big reason to use the early Z car’s “firewall” with its stamped VIN matching that on the vehicular title of a sports car that was produced pre ‘75, (Ah-hem.. wink…) But why would you want to swap in a totally different suspension under the Z car?

 

Ok, here are the pros and cons as I see them. Feel free to view my opinions any way you want and also to add to this list of pros and cons…

 

 

1) Granted, the Z car suspension isn’t the best design out there. In fact, it has many weaknesses and issues that from a performance perspective, need a bit of attention for the car to perform well on the track and back roads.

 

2) BUT. (and this is big BUTT), the stock Z car suspension has proven to be VERY capable at autocross and many road courses around the country and world. At the national level, the fast guys are applying small, yet detailed adjustments and quality parts to the stock set up and still keeping up with, and in some instances, beating cars that are designed with FAR superior suspensions under them. For example, take a close hard look at the national level competition in SOLO-II, SOLO-I and the various road racing classes where the early Z cars compete. Compare the lap times of these Z cars to those of known superior sports cars. You would be amazed at well the lowly Datsun Z cars suspension will allow its driver to turn in FAST lap times, even by today’s standards.

 

3) WOW factor. Ok, the stock Datsun suspension really doesn’t generate much if any WOW factor at any car show or car guy gathering. The more exotic and different the important/visible parts are, the more attention it will gather, whether it truly made the car perform any better or not. That is WOW factor and it does have an influence on the choices we make, even with our suspension. (I’m currently struggling with that in regards to my Z-32).

 

4) After spending the time and money on the OE suspension of the Z car for maximum effort cornering performance, you will end up with a car that is not real pleasant for those long cruises through the back roads. The C-5 Vette is one of those cars that in stock trim, offers little compromise in ride quality vs maximum effort handling. For a world class sports car, overall it does a lot of things quite well, ride quality is plush, road noise isn’t obnoxious, handling is incredible off the show room floor and power is smooth and broad.

 

5) Adapting an existing OE suspension under the Z car, a suspension that would make the least compromises in handling and comfort, is going to be VERY difficult as the Z car has a very narrow track width and those cars that perform well with little compromise such as the C-5 Vette, have a very wide track, so altering its suspension to “fit” under the Z car will alter the geometry of that suspension to the point of.. well.. uhmm.. is it going to benefit the car other than adding WOW factor? I’d put money on that fact that it wouldn’t. At that point you’d be better off designing your own lightweight double A-arm suspension to fit within the Z cars dimensions from scratch. Not only would that allow the designer/builder to make only the compromises he/she deems worth making, but also it will have lots of that WOW factor.

 

 

Any other pro’s and con’s?

[Careless]

I'm going to go full s14 setup, just because I want to make it a fun project, really.

 

I'm ready to try my hand at fabricating all things for my car, so I'll go all the way =)

 

DO it DO it!

[RTz]

Great discussion guy's.

 

One thing that comes to my mind is, no matter how 'ideal' the suspension, an S30 is a very flimsy car.

 

You could have Porsche, Ferrari, or McLaren design the suspension, with an unlimited budget, and you'd still have a problem. Granted, it'd surley be an improvement over the original... but there is still much work to be done.

 

One of the reasons modern cars work so well AND keep noise to an acceptable level is because they are RIGID. This single attribute does wonders for a car... dissmiss it, and be dissapointed.

 

Further, keeping a Z streetable while you reinforce it, is not for the faint of heart.

[heavy85]

2) BUT. (and this is big BUTT), the stock Z car suspension has proven to be VERY capable at autocross and many road courses around the country and world. At the national level, the fast guys are applying small, yet detailed adjustments and quality parts to the stock set up and still keeping up with, and in some instances, beating cars that are designed with FAR superior suspensions under them. For example, take a close hard look at the national level competition in SOLO-II, SOLO-I and the various road racing classes where the early Z cars compete. Compare the lap times of these Z cars to those of known superior sports cars. You would be amazed at well the lowly Datsun Z cars suspension will allow its driver to turn in FAST lap times, even by today’s standards.

 

....

 

4) After spending the time and money on the OE suspension of the Z car for maximum effort cornering performance, you will end up with a car that is not real pleasant for those long cruises through the back roads. "

 

I would have to agree. You really need to set a goal for what you want to accomplish and go for it. Sounds like you really have your heart set on this so I say do it. My mildly modified 240 has taken FTD (fastest time of the day) at the Autox beating out about 60 cars including a particular C5 Z06 who ALWAYS (read ALWAYS) gets fastest indexed time (including when I beat him in raw times) but at the same time I would not exactly call it a boulevard cruiser. In fact it's not really something I would want to drive everyday but could if I had to ... then again I'm getting spoiled with A/C, cruise, radio, etc in my late model daily driver.

 

Cameron

[Pop N Wood]

How well do Supra's do in this type of racing?

 

Why do you feel the Supra suspension is superior to what can be done with a Z suspension?

[ThreeDeadZs]

Re: Brapp

I would say the Supra MkIII is like your description of the Corvette C5 in point 4, except the vette likely outmanouvers the best stock Supra. I believe point 5 in incorrect. I wouldn't change the donor's geometry at all, no matter which donor I choose. If necessary, the wheelbase may be shortened by a couple inches. This will cause one problem I read about called bucking, but a change of only a couple inches should not cause it. I'll make the body match the suspension, not the other way around. The suspension will expect a lot more weight, so the shock and spring rates will have to be reduced.

 

Re: RonTyler

You are absolutely correct, and this did not escape my attention. I have two books on race car chassis engineering that I periodically reread. From these books, I know what problems to watch for. The new subframes will probably have to be mounted to a rollcage that will act as a tube frame. I only decided this after starting this thread - thanks to the group's input.

 

Re: Heavy85

Your are right, thanks for the wake up call. My goal is a car that I can enjoy driving around wet roads in the mountains without fear of going off the road. Many people die here in one car accidents. I even went off the road once due to debris in the road that blew out both front tires instantly. Had I been going the other way on that road I wouldn't be around to tell you about it. Autocross is just a game to me that I would like to participate in. I have no intention of beating others, just challenging and improving my own driving. Driving where I live is much like autocrossing already, but double the speed and add blind corners, deer in the road, old ladies going 20mph, idiots who cannot stay in their own lane, occassional semis which are too big to stay on their side on a curve... Manouverability could save my life. I want a fun, fast, manouverable, comfortable car for driving under 60mph. Heck, it could even have a top speed of 80mph for my purposes. Writing this makes me think more of a quick rev 4 banger like an SR20, but the 2JZ-GE VVTi (1998 to 2003? in luxury cars after the Supra was discontinued) should give me instant response across the entire power band, and tuners don't want this engine (those that can fit a straight six want the turbo version) so I can actually buy a low mileage engine relatively cheaply. Then, if I get power hungry and get deeper pockets, I can build a 2JZ-GTE with as much as 1000hp with stock internals. Such power would be absurd for my car, but I'm just pointing out the benefits of the engine design.

 

Re: Pop N Wood's question:

Based on the San Francisco Region SCCA website, I found Supra MkII's (~82-86) and MkIV's (93-98) winning in their classes, but no MkIII's even listed. MkIII's are luxurios GT cars that are extremely heavy (3500lb curb weight) and made for high speed racing like a Corvette. How many Corvettes do well in Autocross? The ones I raced appeared to have a hard time staying on the track and never seemed to be able to use all their power. They don't have enough room to throw the weight around. What benefits are there to the Supra suspension? That was answered by Richard (260DET) "Using the Supra stuff will give you a nice wide track, five stud wheels, power steering, modern geometry, big brakes......" and I responded, "plus the subframe mounted Double A Arms you mentioned earlier and power rack and pinion steering mounted on the frontside of the front crossmember which supposedly eliminates bumpsteer." Also, and I'm just guessing here, I know the suspension was not revised much between MkIII and MkIV, so I should have several equipment options available to me. When I was active with SOGI (a Supra club) there were many members with modified engines that could wipe up the floor with supercars. But the MkIII is just too *#@^ heavy! To get similar results from a Z suspension, buy the complete brakes and suspension sets from Arizona Z car for $3800 (I just checked) but that still doesn't account for the rear end and CV shafts. Up front, you would need to do heavy modifications (if even possible) to match the front mounted steering rack and other design improvements. Then you will still have a 1969 design using McPherson type struts. The Supra MkIII (and many other new suspensions) are double A Arm and was designed in 1985 or 1986. The Supra is a high end car and built of expensive components. The original Z car was built to be economical, and was built of cheaper components. That said, I'm still not convinced I've chosen the right donor. I still have to give serious consideration to S13's, S14's, GTR's, Mazdas, and other Toyotas.

 

Another part of my idea is simply to use EVERYTHING from one car, whichever donor is best for my application, not just a Supra. I actually bought my first Z in order to swap in a 2JZ in the first place. Since I like the engine so much, it seems only natural to use absolutely everything else. Also, it would be a matched set and would require nothing aftermarket except coil over springs. Plus, I'm a Toyota guy. I know their products extremely well. Building this car with Toyota equipment would take advantage of my previous experience. Nissan is quite similar, of course.

[ThreeDeadZs]

Hey Richard (260DET)

I just noticed that your recommendations do not include how you are doing your current project car. How well is your S13 suspension working out? Effectively, you've done exactly what I'm talking about - using the complete front and rear subframes and equipment from a donor car. Now that I see you have done exactly this project, I'll put very serious consideration into the GTR and Z32 subframes as you recommend. Which engine will you use in your project? Or is the car on the road yet?

 

If I chose to copy your project, would you be forthcoming with the details? I really like your photo gallery. There's a small shadow at the center of one of your pictures that is extremely enticing!

[RTz]

How many Corvettes do well in Autocross? The ones I raced appeared to have a hard time staying on the track and never seemed to be able to use all their power. They don't have enough room to throw the weight around.

 

Tangental to the topic, but I thought I'd answer your question... C4's and C5's have collected an impressive number of National trophies in both Superstock and Street Prepared classes. In fact, the very existence of Superstock lies in the hands of the C4... pre-C4, A-Stock was "it".

 

If you're not seeing fast Vette's, you're not looking in the right places.