Steering, Suspension, & Brakes

Hey, new guy here. I am a Spitfire guy although it has been many years since I have driven one. For 20 years I have had a nice Toyota 4AGE Blacktop sitting in my garage and now I am going to put it to use. I recently bought two 1979 Spitfires and between them hope to get one running sporting the 4AGE and 5-speed trans. I know the rear diff and axles won't be up to the task so I have been working on a solution to provide a 4 wishbone transplant with a heavier diff. I want something that has enough strength to accept a turbo V-6 if, at a later date, I decide to go that way.

So far here are units that I have considered; Miata, Subaru, BMW, Audi, 240Z, Mustang with an 8.8 diff, and custom home built. Most of these are assembled in a factory sub-frame which can drop out as a unit, which is attractive.

The first hurdle I need to resolve is how to fit one of these units into the rear of the Spit' when the track on a larger car can be up to 10" wider. And a second hurdle is that most of these use McPherson struts by design and adapting short coil overs can be challenging.

Width or track can pretty easily be done by cutting and rewelding the shortened axles if they are tubular. The downside of that is as the axles get shorter it of necessity moves the A-arms inboard and toward one another. It seems to me that this would provide less stability as the whole subframe would need to be narrower then. Another factor is that smaller-width suspension assemblies come from smaller cars which use more fragile differentials and axles defeating two of the purposes of the swap in the first place.

So I am in a quandary as to what to do. What is the best option for grafting an existing rear sub-frame assembly to a Spitfire rear end? It looks like a Frankenstein would have to be created.

Randy

Check out my article on the 7.5 Toyota differential here:

[forum.britishv8.org]

Jim, your article on the 7.5 Toyota makes me wonder if a Cadillac CTS diff might be an option, as well. It appears to be about the same size and is available in a number of ratios, as well as in a locker version. They are quite common in junk yards--and while not the strongest casting (it's aluminum and had to be upgraded for the CTS-V), it seems that for something light like a Spitfire, it might be an interesting option.




Edited 2 time(s). Last edit at 05/04/2023 04:37PM by Airwreckc.

One option you didn't mention is the C4 Corvette rear suspension. I use that suspension at full width in my car but it can be narrowed fairly easily by shortening the half shafts and lower arms (camber rods). If you look at the video at about 3:10 in you can see how he narrowed it to work in a Bug Eye Sprite. [www.youtube.com] . The differentials come in two versions: Dana 44 (manual trans cars) and Dana 36 (automatic trans cars). The Dana 44 is very strong but also very expensive. The Dana 36 is much more affordable and has plenty of strength for your application

Have any of you had experience with modifying the C4 suspension to coil over and tossing out the leaf spring? My worry is that the leaf would really restrict narrowing and be difficult to work with to get a proper spring rate. Otherwise, it appears to be a good choice for the Spitfire.

Randy

You can't use the leaf because it is a one piece fiberglass unit that can't be shortened or have the rate reduced by taking out leafs. I have coilovers on mine and it is a simple matter. The bracket that attaches to the upright was changed when I discovered the shock was topping out on droop, I used the one on the right to correct it.

Have you looked into the Nissan R200? They use them in plenty of high hp setups across their lineup.

Infiniti R200 is the same as Nissan with better ratios.

Basically what Rob Ficalora uses behind his 302 powered MGB

'1996 Nissan Skyline viscous limited slip differential (same R200S case as Nissan 240SX). 3.54:1 gears. Uprated halfshafts from "The Driveshaft Shop" in Salisbury, North Carolina.'

Personally I like the Jag IRS but it might be a bit much for a Spit.

Jim

What do you suppose the Nissan R200 or Infinity setup could withstand in terms of HP/torque? I know the drag set uses the 8.8 inch Ford gears with brutal launches and high horsepower and they stay together. Not aluminum cased, however. I was wondering about an 8.8 Lincoln set-up myself. Light-looking and abundant 8.8 diameter gearings here in the USA to choose from.

Regarding the Lincoln axle. I saw one for sale recently and it had no springs or shock adsorbers. Just airbags with an air pressure ride control. Could this possibly work for a track car?

I recently bought a 4-link rear axle/suspension from a 2005 Passat wagon. It was the model with a 1.8T inline-four and 4motion AWD. It is very beefy but maybe too heavy. Aluminum differential but steel everywhere else. Does anyone have experience with that beast?

Randy

Does anyone have a web page(s) or more pics of the Nissan installation that Kenny Ard posted?

Randy

How much power to do plan to send to this IRS?

R200 is a little over 8" and will handle a lot of power. I had a picture of a Datsun Z drag car popping a wheelie years ago. The half shavts and cv's are the weak links.F150 axles with Dodge Intrepid hubs fix that. I have a R230, 3.67 ratio out of a TurboZ in my garage that is a little over 9" that I would trade for a R200.

I will be using a 4AGE Blacktop initially and claims for that engine range from 160-170 HP stock. Later I may replace it with a modern V-6 and that could run up to 400 HP. In a car as light as a Spitfire, and without drag race starts, I think an 8" ring gear could probably cope. I am quite sure an 8.8 Ford diff would handle it. What I don't want to do is graft in something so heavy that it defeats the advantage of using a light car.

what pictures would you like?

I know these differentials handle up too 400 hp and maybe more

I got my installation kit from GoodParts.com he's got good info on these diffs also



Edited 1 time(s). Last edit at 05/21/2023 10:12PM by Kard150.

The last few days I have been thinking more of selling my Toyota Blacktop and instead am looking into the Chevrolet 3.6 V6. It is a 60-degree V and would squeeze into a Spitfire I think. You can source one from a Chevy Impala pretty cheap and a FWD unit works fine to bolt up to a RWD trans. 302 HP normally aspirated. It weighs only 70 LBS more than a Toyota Blacktop. I think I found one locally for cheap today

What do you suppose a Blacktop in like new condition is worth now? Mine includes the air inlet system with box and filter and the wiring loom and computer control box which I sourced from a guy in Australia. Also the 4 independent throttle bodies and linkage and the swoopy tubular exhaust header stock from Toyota. Looks very racy and totally angry. :-)

Randy