Building a 900 for hillclimbs

[Geoff]

Why not steel?

[KPAero]

it looks like the kind of part that a machine shop could mill out of a chunk of aluminum for you relatively easily.

I thought about that, and I am planning to bring one to the machine shop I work next to and see what they think it would be cost wise.

The box is a 79, so that would fit those using a sand cast aluminum housing.

[KPAero]

I've finally had a chance to get back into the garage and do some work on the hill climb car. Im planning to shake things up a bit this year and am doing the Team Oneil SCCA rally sprint as my first event. With that in mind I need to make some changes to the car for the gravel.

Im undecided on what I might do for suspension. I'd like to do something a little more involved at some point, and given the time constraints between now and the event I might just leave it as is. The roads at Team Oneil are not rough, so it shouldn't be a big issue, and the springs in the car probably have decent spring rates, even if it does sit a bit low.

My main focus is going to be on the underbody. Obviously I'll add a real skid plate and the required mud flaps, and in addition I'd like to add some additional underbody protection for the rear axle etc.

My first project has been the exhaust. The original came with the car, and the 3in diameter and semi-poor quality meant it was vulnerable and sitting rather low in a couple spots. I'd made some modifications to help improve it, but was limited in how nice it could be made. Id wanted to change it out anyway, and figured I'd want a nicely routed, securely mounted exhaust before taking to the gravel. I downsized to 2.5in tube and went for double slip connections, the v bands that were used previously added a low spot. The only thing left to finish it is to add the hangers, and make the transition from the downpipe to the 2.5in tubing. That should be done later today.

Here are the double slips, transition and springs to hold the joints. The double slips came from burns stainless. The rest came from eBay, I went for the cheapest stainless tube I could get to manage cost.


Heres the new and the old.

[squaab99t]

Looks fantastic. That stainless adds up quick and if you do not have a lot of critical bend you can get away with the more economical tubes. I recognized the burns packaging on the hardware; Invoice sleeve from ups.
Good luck on the new race series.

[Geoff]

I saw you were on the entry list. Glad you're doing it! I saw the course and although I haven't been on half of the roads I think you'll probably be pretty good with whatever road/hillclimb suspension you're using. Worst case you could put some SAS spacers in the back and some other spacers in the front (MSS used to sell some). A good strong skidplate is a must to protect that nice gearbox!

I wanted to go up to TON for the day but I can't make it that weekend. I hope they'll end up doing some more of these!

[KPAero]

I wanted to go up to TON for the day but I can't make it that weekend. I hope they'll end up doing some more of these!

As do I, it should end up being very similar to a hill climb, but with gravel. I hope the SCCA program ends up being successful, and can find more locations.

I still have a stock 5 speed in it that I swapped in end of last year, but in anticipation of getting the other gearbox back together at some point, a good beefy skid plate is a must!

[KPAero]

Looks fantastic. That stainless adds up quick and if you do not have a lot of critical bend you can get away with the more economical tubes. I recognized the burns packaging on the hardware; Invoice sleeve from ups.
Good luck on the new race series.

Thanks, the burn stuff is definitely nice. The biggest issue I ran into using the double slips with the cheaper tubing is the inconsistency made the joints a little tight. Im going to try and shave a bit off the middle tube to make them easier to detach. But given the high likely hood that it will get beat up under there, I couldn't justify the extra cost for nicer stuff.

[KPAero]

One change for the rally sprint will be the addition of a co driver. While I always have had a passenger seat, it was not one I intended to have someone in during competition given the disparity between the two seats. I still don't have a replacement, but because the Corbeau seat that was installed was a bottom mount, a new seat won't work particularly well on the existing mount in the car.

So I've been going about changing it. I didn't want to make the new seat rails mount the same way I did the drivers side as that uses the stock front seat rail. While it is plenty strong, it also sits up kind of high and I wanted to get this seat as low as possible.

I decided to make the new rails the way it is outlined in the FIA 253 ap J. documents, where the seat rails bolt into the car using welded in backer plates. Here is the result, I was pretty happy how they turned out.


Here is one of the backer plates with weld nuts on the back.


And the rail bolted in with two m8 bolts. The only thing left is to weld in the threaded inserts to the rails to bolt the seat brackets to. For the Pro ADV and OMP brackets I'll use, those need to be 15" apart on the centerline of the bolts.

[DrewP]

Is that so the rails can be replaced if they are damaged or something? Or so the welds don't pop and the seat comes loose?

[KPAero]

I'm honestly not sure what the exact reasoning is. It does however make it really easy to weld fully around the tube and plates, which was one of my motivations for doing it that way. I've also seen where it was nice to be able to remove them to repair the shell if the floor pan or sill is damaged.

[DrewP]

Those are both good points.

[squaab99t]

Thanks, the burn stuff is definitely nice. The biggest issue I ran into using the double slips with the cheaper tubing is the inconsistency made the joints a little tight. Im going to try and shave a bit off the middle tube to make them easier to detach. But given the high likely hood that it will get beat up under there, I couldn't justify the extra cost for nicer stuff.

Yes we noticed that on lower costs stuff the seam weld is not flat and creates a thicker wall thickness and/or the tube is not perfectly round. Sucks to get a internal and external slip joint to fit. Carbide burr turning at low rpm can clean up the seam weld and dead blow with a panel beater bag to true to round.
Vince at burns stainless talked me out of the bee hive springs, but I was going to use them before the turbo. They had a 4 cyl on the Dyno and had a backfire. Made a metal mess as all the tubes popped out off the double slips because the springs allowed that much travel. He had me go with bolts and min sheet metal saddles.

[KPAero]

Got a couple more items done. Finished adding in a second gusset on my A-pillar supports to get it ready for a logbook inspection. I also started working on skid plate subframe/mounts.

The exhaust is also now done and mounted.


And I also added pin stand mounts. I plated the outer skin, and tied the tube into the top of the inner sill area. The fronts go through the lower leg of the front fender. and the rears just ahead of the rear wheel well.

[Crazyswede]

Not sure if you have sourced a skid plate yet but you can get a 2'x3' 3/8" thick piece of 6061 off of ebay for pretty reasonably money. The 3/8" doesnt weight that much and is a substantial improvement in protection over the Saab stock S&R unit which really isnt thick enough for rough rally use.

[KPAero]

Good to know. I already have a piece of 1/4 6061, but I have thought about having two interchangeable plates depending on conditions. Id also like to leave it on for hill climbs in case of an off road excursion, so maybe I'll have the 1/4 for that and smooth rallies.