Project 83 RX7 Stage Car

Alright, when I originally bought the Mazda RX7 GSL two years ago I planned on rebuilding the engine and porting it, just to see what it's all about and to say I've done it. Well I rallycrossed it last summer and overheated it due to a split old rubber hose. So it was time for the rebuild. I pulled the engine a few months ago and disassembled it. Then me and a few friends drove from Wisconsin to South Carolina for Sandblast Rally earlier in March, where I really got the itch to build a rally car and decided to do that with the RX7, to kind of kill two birds with one stone.

And so the journey begins.

Having the engine already out, I finished cleaning it up and am waiting on carbide bits to do the "rally port" (huge street port) before I send them in to get resurfaced.

I then pulled out the interior and found some rust by the rear wheel wells that will need to be patched. I pulled the dash out yesterday and made measurements for the roll cage. I ordered a tube bender and 1.75" die today. Meanwhile today after work I got all of the passenger side sound deadening chiseled out.

Some plans for the car include 2nd gen front subframe, j vab coilovers, fia spec roll cage. I might swap a Toyota 8" in and will probably put a more functional 4 link rear end set up. I will try to keep this updated whenever I work on it.

I have a red leather interior, if anyone needs something let me know.

Here's some pictures of the build so far.

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-Zack



Edited 1 time(s). Last edit at 03/25/2015 08:47PM by zack13277.

If it wern't for the free volvo that plopped itself into my life a couple years ago I probably would have built one of these. Very excited to see it progress!!!

In your other thread you were asking for some photos of some of the suspension tweaks spoken of. That is if you call cutting and welding "tweaking". Seeing as no one posted pics of a aftermarket 4 link here you go. Not that it matters but that is a toyota axle hanging in there. Refer to the double g motorsports website ( I put the link in your suspension thread) for measurements if your going to do this. Rx7 wheel base is basically the same as escort if I recall correctly so it should lend itself easily to using the ford measurements.

Cool, thanks. Are those John V's coilovers? They look really nice.

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-Zack

Yes they are his. And most things look nice after a trip to the anodizing bath... So put it this way; Even with an open diff I had alot of fun this winter.

If your going to go with his suspension do so in advance. It can take time for him to get the inserts from bilstein and it can just take him a fair bit of time to get them ready for you unless he has them in stock.

If you are going to go the 4 link/ towers I definetely don't discourage it especially after looking under an rx7 at pick n pull last week. Not terrible for a road car but particularly the links stood out as way short for longer travel stuff. It does have a cool watts link though! But just keep in mind that it is a reasonable amount of work. I say this cause it hurts to see projects start and never seen to the end.

Save yourself a bunch of irritation and decide on this prior to the cage going in. Not having it in the way will make the job significantly easier.

Understand that this is just a theory, but I have a theory on the RX-7 4-link. Poking under one of my shells, I wonder if the lower links are more or less fine in terms of where they go on the shell. I'm pretty sure they go up to about where the lateral brace thing on the interior is, so pretty much where you'd put a new 4-link setup anyway. So I'm wondering if you could just punch a hole in the sheetmetal and add an upper link - fundamentally tabs, welded to boxed in plate going in multiple planes attached to that lateral brace thing.

Still needs new tabs on the diff, new lateral location (the stock watts link is not so good) and I'd do new lower links... but what's wrong with where the lower links attach to the chassis? Using those ones seem like it's one less thing to have to cut off the car and replace with something you're trying to precisely locate and make strong enough.

Serious question from someone relatively familiar with 1st gen RX-7s, but only familiar with rally stuff in theory.

ill chime in.

if you look in the mazda motorsports prep manual they reworked the rear design, and that includes the watts link, for road racing cars.

the group b cars look like they maintained the lower link, then added or more likely extended an upper link in parallel with the lowers. However, the stock watts link is not good for the longer travel we want.

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First Rally: 2010 First RallyX: 2004 (a bunch)
Driver (0), Co-Driver (7)
Organizer (3), Volunteer (3)
Cars Built (2.5), Engines Blown (2) Cages Built (0) # of rotations (3.5)
Last Updated, Apr 9, 2023

Yeah the lower bar looks long enough, and like you said Dan I could probably just make the top one longer. I'll probably make a panhard bar if I don't like the watts link.

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-Zack

I'd be concerned with the Watts link being a limit on total travel. The placement next to the nose of the diff does not leave it much space. Panhard bar is easy, and it works okay. The watts link can be better if you can tuck it away out back.
I have no clue what the roll center placement would be effected, but I don't think any of us even know what that does in a rally car.

Looks good! Cant wait to see how this thing shapes up. Fasinated by those engines. But also confused.

R

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Rob
Devil Bat Racing
Grand Rapids Mi
Planet Earth

https://www.facebook.com/devilbatracing

http://www.robsackyta.com/

I can't wait to put the engine together, I practiced porting tonight and turned out pretty good. Real thing is up next. Removed almost all the sound deadening, just a little in back to go.

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-Zack

Quote
zack13277
Yeah the lower bar looks long enough, and like you said Dan I could probably just make the top one longer. I'll probably make a panhard bar if I don't like the watts link.

Yeah, was just trying to sanity check with the rest of the forum; it seemed reasonable, but lots of things that won't work seem reasonable before you try them.

Here's a picture of a test rally port that I did tonight. I think it looks pretty good. I didn't sand it though.

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-Zack

Did you port the inside curve's edge any closer to the center?

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Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.

No I didn't go inside at all. I have a template from Pineapple Racing, I mainly went up. You can see where (I think) the oil ring rides on the inside, I didn't want to get too close to that.

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-Zack

Good. Very good. It's unfortunately common for people to destroy perfectly good side housings by porting them in. The oil rings do not tolerate sliding over an edge at all. I bought a core engine that some doofus ported that way, the engine ended up sucking down all of its oil and siezing the bearings. Never seen that happen before.

I anal-retentively make sure the side seal coming "up" can't stub itself on the closing edge, and make sure the closing edge's angle is such that the adjacent seal closes it with a scissors motion instead of a flat swipe (or worse, a tip-first angle). But then I've never bought a template, just rolled my own.

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Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.



Edited 1 time(s). Last edit at 03/28/2015 04:42PM by Pete.