V8 RX7 Fantasy

One of my most interesting and most likely to happen fantasies is an RX7 with an SBF. Recently read where an Explorer makes a great donor for this. Engine, tranny, 8.8 posi rear end. If I do this insanity, it will be a bucks down project, so the automatic will be a part of the deal. My question is that the Ford automatic is seemingly not very stout. Can they be set up to handle 350-400hp? What Pagan Majic is necessary? Thanks, all.

You're planning to keep the auto for cost only? Surely you can sell off an Explorer auto (especially if they're not that stout and people are killing them in their Explorers towing and such) for enough to pick up a 5-speed out of a Mustang, or at least be within a six-pack or so...

And I apologize, I'm stepping on one of my own pet peeves wherein a peson asks the Internet "How can I achieve A?" and some shiny happy person (in this case me) says "A? Are you out of your mind, why aren't you doing B?"

I just can't help myself in this case. I'd love to do a V8-powered FC RX7, but an auto would just kill it for me...

Our Lemons car is a 83 RX-7 with a 302, T-5 and 8.8 Rear end. We bought it in almost running condition for $500 plus a cage and race seat for another $700. A fuel pump I pulled off another RX-7 got it running. The rear we got off craigslist for $200 and welded from the RX-7 rear onto the 8.8.

T-5's can be had pretty cheap. I just bought one last week for $150 sans bellhousing. Manuals make everything more fun.

Not done cheaply, 5.0, T5, RX7 rear end. Weighs within 20lb of stock weight for 84 GSL.

long tubes fit

slave cylinder

teaser

http://s869.photobucket.com/albums/ab256/aussiesmg/RX50/?action=view&current=007-1.mp4

The explorers use a 4R70W trans. They can handle 400hp easily. However, unless you find a 2wd V8 exploder you will have to rip the trans bare to swap the output shaft to a 2wd shaft and housing.

I used a 6 cyl (less clutches) 4r70w as a donor for my wide ratio AOD, and that trans has stood up to a few seasons of autocross and a lot of hard miles and it still is like brand new. This is on a 4500lb 245rwhp wagon.

Even the old AOD could be stout, just toss in a good VB.

I thought the Explorer's 8.8 was offset to one side and had different axle lengths. Maybe we're thinking of different model years since they were made for a long time.

Toyman and I did some measuring; the rear axle in the ThunderTerd (1986 Thunderbird LeMons car) is almost exactly the same width (~57") as a 1st gen RX7 piece and the Fox body Mustang axle is the same width as well.

Here's the cool part: there is a 29" long Ranger/Explorer rear axle shaft which, if you grab 2 of them, converts the 4x108 Fox body T Bird or Mustang rear axle to a 5x114.3 and there are all kinds of bolt on rear disc parts available from Crown Vics, Exploders and the like. (The Ranger/Explorer rear axle assembly is 54", too short.) There's lots of rear axle ratios and limited slips available either boneyard or new for that same axle.

Then you grab the front struts and front brake stuff off of a 5 bolt 2nd gen RX7, stick that on the front of a 1st gen and voila! 5x114.3 bolt circle all around with 4 pot front calipers.

Then stuff in the V8 of your choice and roast the tires.

Yes, I am an enabler.

We have the T2 RX-7 brakes on the front of our car. You can get the RE-Speed kit (awesome experience with ours) for $300 ish with SS brake lines. You could fabricate your own adapters or swap in the entire second gen subframe but you then need to figure out engine mounting again.

Since no-one else has mentioned it grannys speed shop is the place for the engine mounting kit. Its pretty simple but worth the money saving the headaches of figuring out mounting points.

ReSpeed's kit is nice but only works with the late 1st gen strut housings. About swapping the front brakes and struts: my thought was (and I need to do some measuring): use the 2nd gen/T2 front strut housings but cut them off, remove the guts and use the 1st gen replaceable inserts in those housings. The 2nd gen ball joints can easily be adapted to the stock 1st gen lower control arms, meaning using the 2nd gen knuckles too.

'86-'98 Mustang/T-bird 8.8 solid axle housings are all the same tubeflange/tubeflange width of 54.10". '99-'04 housings are a little wider at 55.51"

Overall wheelflange/wheelflange widths for the FOX 8.8 varied... ...86-'93 Mustang 59-1/2" ...'94-'98 Mustang 60-7/8" (same housing as '86-'93, but uses .705" longer axles to make room for ABS tone rings)

Left side Ranger axles are the ones used for the cheap 5 lug upgrade, and are 28 spline. Explorer axles are not compatible with the FOX housings (different bearing size).

1st gen RX-7's used 2 different width rears... ...'79-'85 12A cars w/ 4 on 110mm lug pattern is 56-3/4" AF/AF (add 1/4" for drum brakes, add 1/2" for disc) ...'84-'85 GSL-SE w/ 4 on 4-1/2" lug pattern was 58-3/8" w/ rotors

A 58" WF/WF rear is almost perfect for fitting big wheels/tires for the drag strip, as it enables you to use common offset wheels (15 x 8" w/ 5-1/2" backspace wheels and 275/60-15 radials can fit)

I don't recall the exact measurements but I knew it was real close. I had a 1st gen axle standing in the shop when we were measuring, scratching our chins and talking over eVil plans...

Mine is still running the 1st gen RX7 rear, its a lottery but some RX7 rears are running 8's.

So this followed me home. $500, and it has one of the nicest cages I've ever seen.

I have piles of 302s, a few mustang 8.8s, some broken T5s I need to learn to fix, and 25 or so 17" Mustang wheels. I also have two 5 lug FC parts cars.

I need to have a 325hp, 2000lb car with 5 on 4.5 disks on all four corners. I don't know how to make it happen up front.

"Chapter 5: Tremec/Borg Warner T-5"

cwh wrote: One of my most interesting and most likely to happen fantasies is an RX7 with an SBF. Recently read where an Explorer makes a great donor for this. Engine, tranny, 8.8 posi rear end. If I do this insanity, it will be a bucks down project, so the automatic will be a part of the deal. My question is that the Ford automatic is seemingly not very stout. Can they be set up to handle 350-400hp? What Pagan Majic is necessary? Thanks, all.

that way would be easier with a 1st gen.

In reply to btp76:

Wow, that is an awesome score. When you swap to the 5x4.5 Ford suspension let me know and I will take all those 4x110 1st gen Mazda wheels off your hands, especially the mesh ones in the car.

The mesh ones are 15 x 7s, but I'm not certain of the bolt pattern. PM me an offer.

Consider using a 4 cylinder. LNF Ecotec, stick a larger turbo on it, use either auto or manual trans out of a Kappa series and you'll have 400 BHP/400 TQ., considerably better than the Ford V8. More bucks I'd think.

I have fords. If I were to do something else it would be LS based.

hobiercr wrote: In reply to btp76: Wow, that is an awesome score. When you swap to the 5x4.5 Ford suspension let me know and I will take all those 4x110 1st gen Mazda wheels off your hands, especially the mesh ones in the car.

Yeah those are sexy, and finding 4x110 is pretty hard.

Common combination for rx7 v8 'optimimumness' ( its a word, shut it!!)

FB with FB front subframe (suspension, stronger k-member, rack and pinion steering, 5x114.3 brakes, 4 pot calipers) and the swap is mostly bolt in from what I hear.

v8 with rear end swap, from an explorer would give you rear disc, lsd and 5x114.3 pattern and is a little more stout.

but I would still drive one with a rotary and not have to do any of that, well maybe do all of that in a 1st gen and just put an FC 13b in it.

I saw that for sale but its was too far away. Awesome deal.

To get the 5 lug bolt pattern and larger brakes an FC front subframe swap is your best bet. Re-Speed which I mentioned earlier in the thread (a couple years ago) is now basically out of business with a lot of unhappy RX-7 ppl in their wake.

If you are going with the FC subframe swap the LS is pretty easy to mount and ChrisV on this forum has posted his templates to mount a 5.0. With the stock SA/FB subframe the LS doesnt fit without oilpan or steering linkage modification but the 5.0 fits in easy with a fox body pan and granny mounts.

The Explorer rear is offset so wont work without shortening. A 94+ 8.8 like we were running in our Chump RX-7 was a bit wide. I would run a stock LSD RX-7 disc rear with 4x100 to 5x114.3 adapters personally if it is a road race car.

Let me know if you have any questions.

• Greg

I'd still love to do this with a 1UZFE Lexus V8 and a R154 5 speed. Keeps the weight down, capable of 9k RPM... sproingggg.

having just bought an sc400, i second that idea