tube80z

For the 40 carbs it was straight through with no venturis. It was a no cost test and more of a curiosity for me. You have one of Vizard's graphs a few pages back in your post. So my guess is that you either did see it or some other pub that referenced it. In case you're curious here it is. choke(mm)=(CV x rpm / 2600)^0.5 CV us cylinder volume in CCs and RPM is the point of max power.

Here's what I can add. I haven't dynoed any of this but I used to own a flowbench and did a lot of work flowing things (heads, carbs, mufflers). Some of those things were Weber carbs. When you get to a 40 running a 36mm choke you are maxed for the most part when it comes to flow. Sure you can put in larger chokes but you're only changing how it responds when you're not maxed out. Assuming the engine wants all that air then to make more power you need to move up carb sizes. Here's what I saw on my bench. Weber 40 with 4.5 aux venturi compared to Weber 45 with 4.5 aux venturi. Below is carb and then secondary choke diameter. What seems to control flow is a lot of the shape changes seen by the air when it goes through the carb. 40 -- 32 out flowed 45 -- 32 40 -- 33 out flowed 45 -- 33 40 -- 35 tied 45 -- 35 40 -- 36 lost to 45 -- 36 40 -- 40 lost to 45 -- 36 What you saw for power changes doesn't surprise me. Our old engine that was smaller than your combo worked much better when running the 38mm chokes with the 45 carbs. It gave up a little down low but could pull all the way to 7500 where the limiter was set. When running the 40s with the 36mm chokes it started to give up a little over 6300. Have you ever seen David Vizard's formulas? If I did the math right it claims your sweet spot to be a 37.25mm choke at 7K. So I'd say you're right in the ballpark with what you've got now. Hope this helps, Cary

If you want advice you're going to need to provide more detail on what it's doing. It could be all of the above. How does it upset the chassis? Pull to one side of the other? Does the back want to swap positions with the front? Does the front end wash out? More along those lines would help.

For a racing car you don't want any compliance. Those often lead to weird limit behaviors. If you're looking for advice there's some good info in the online tech section here, http://www.ronsutton-racetechnology.com/pages.item.29/Tuning-Support.html

For a budget chump car check to see if they haven't closed the bump stop rules. If they haven't then you want to look at running either bump springs or some of the softer circle track bump rubbers. Then use packers to close the gap and you now have a much stiffer "spring" and all the benefits. If the penalty is too much for a real 2.5 inch spring then you could cut the coils a lot and raise the spring seat above the tires. You'd probably still use the bump stop of some kind for fine tuning. There are a lot of low buck ideas you can use in the grey areas to get better handling. The bump stop stuff is already being done by a number of teams.

Coleman used to sell a similar item but I can't find it on their site at the moment. You might have to search for birdcage clevis to find them.

I think the big difference is really stability and control. In a street car you want to have a limit behavior that is benign. This gives the driver confidence in their ability to take the car to the edge and still be able to bring it back in one piece most of the time. But often those tricks end up slowing down the ability of the car to provide good feedback when transitioning quickly for a more experienced driver. I once heard an explanation that you have a triangle (or radar diagram) where you have grip, stability, and control. If you want a really stable car then you generally have to give up grip or control and vice versa.

I know this is a few weeks old but I just "discovered" this thread. The advantage to raising the floor is you end up lowering the CG of the car. That's something to think about before you get too far along.

The long links are appealing. I've seen a lot of cars running the bar across like a strut bar and then you have the long link. You could even hang the bar from the strut bar via rod ends to make a nice low friction mount. I've seen a couple of touring cars use rockers on the ARB linkage so you can get long links and mount the ARB down low. You can also fit droop and or pitch limiters this way. As you turn with the strut mounted version you'll see offset that will sideload the strut. Somewhere I read a quote from a touring car driver that mentioned he had fought understeer on their car all year and then it was solved. When he asked the race engineer what the change was he said it was the ARB mounting location changing from the strut to the control arm (same wheel rate was seen). Ideally it would be nice to have some hard data to back this up but I don't. I just wanted to throw this out there as an FYI. I personally was all set to do this myself until running across this. When I took my first class with Rouelle I sat next to a guy who built some really trick cars. He shared in class how changing the rocker geometry so that the pushrod/rocker/shock were in plane from the old setup where the pushrod was out of plane with the rocker made a large difference in front grip and driver feel.

Looks awesome!

Look at used nascar swaybar on ebay or go to Roush's outlet store and you can find anything you want. A friend used one on the front of his 260 EP car. He used the spherical mounts you can get for them and used the straight arms and then bent them to be close to the stock pickup location on the lower control arm.

You really don't want to connect to the struts. I know a lot of production cars do this now but for a racing car you're better off connecting to the control arm. The reason being you increase the side load on your struts and that increases the friction that needs to be overcome before everything can move and the shock can do its thing.

Sorry to hear Tony. I know the feeling of being violated all too well. For me that was the part that was a little hard to get over. Sending bad karma their way. Cary

Is this a race thing or a street thing? If it's race you really want to look at the Teve's or Bosch units. Motorsports ABS lets you use areas of traction that are forbidden because of stability on a stock car. Take a look at the Bosch PDFs for their ABS system (http://www.bosch-motorsport.com/media/catalog_resources/ABS_M4_Brochure_epdf.pdf) Cary

I have no doubt it will hold up. What I meant is to take it to the next level it's going to require some changes. A big one I haven't seen anyone try yet is reducing the front scrub radius using struts. I'm cheating and using a-arms. Look at what BMW does with dual lower ball joints. Or Ford and GM with a strut that has an articulated upright on the end (superstrut). Technology has moved on, fortunately in prepared you can bring your car up to date. That's what it's going to take to take the fight to Gorman's Porsche or some of the other cars. As they say the first few seconds are easy. It's those last few tenths that get very hard.

That will be a big step forward. Build a suspension to go with that motor and you'll have one of the fastest autox Zs around.

Make sure the subframe is held solid. On the 510 we used to flip the subframe caps to nail them down. You might be able to do that you use washers to put pressure on the rubber bushing. Between that and the trailing arm bushings you should be good. If it still hops after that I'd look at the shocks to see if they have a dead spot in them or are too lightly damped. Hope that helps, Cary

That's the idea. I think you'll find the car is much more stable this way. You'll have less movement on your bumpsteer curve and when accelerating the nose won't raise so much. And at some point you can revisit lowering the nose again. But I wouldn't do that until you get the rest of this sorted. And once the front is sorted then you can look at making some toe-link rear arms that will allow you to mess with rear toe much easier. BTW, I looked for the parts from Dave's car but couldn't find anything but the drilled steering arms. Cary

One thing that will help a lot is what Jon mentioned about raising spring rate. I would start with 400 lbs/in all around and this will reduce the amount of travel you are seeing and that will help a lot to keep you from seeing as much bumpsteer. Ideally you need to get your bumpsteer down to around a 1/16 of an inch over the range of travel. That will make a world of difference. The last batch of AZC knuckles I saw needed a large wheel for clearance. I can't remember if we had 15s or 16s but the wouldn't clear with the wheels and spacers we had. We ended up using a spacer to lower the outer steering arm pickup point. The amount will also depend on how much caster you have cranked in. From what I recall this spacer was about 1.25 to 1.5 inches. It had to be clearanced as Cameron mentions when running a 15 inch wheel. If I still have these parts (knuckles, spacers, bolts) I'll send them to you but I'm pretty sure they were on the car when it was sold.

The only issue is those rod ends are junk. The grease fitting is the giveaway. So add another $40 to $80 for higher quality units are call them to see if that's really the case. Cary

1.3 to 1.5 may be all you can get if the pavement is not really clean and rubbered. It may also indicate that your tires are getting too many runs on them. You'll need a clean surface and the tires up to temp to ever see numbers over 1.5. When a bunch of us used to run our cars in prepared classes in Medford, OR we found that most cars worked pretty well with 550s all round, which is assuming a weight of around 2K pounds. The higher spring rate will help put heat into the tires. I know there are many ways to skin a cat but that resulted in a FP car that took many TTOD and was top on top of PAX. To put that in perspective on the Fall Enduro course it would now lap in 44.75 seconds. Not sure if that helps if you haven't been there with how the car is currently configured. Cary

The only thing I will add to this thread is that I've been seeing a lot more counterfeit parts. So if you see a really low price for what are typically premium brand parts and they are new take a really good look. I got a set of low cost "GM" ls7 lifters that ruined an engine. Cary

There are parts listed in the rule group that are excepted that are contoured. Everything else needs to be a flat plate. Cary

Jon found on off the shelf spacer for the 280 spindle. It' this one if memory serves it's the legends one, http://www.drpperformance.com/resources/bearing-spacers-kits-and-tools-mini-catalog/ Cary

I tested 240 parts and found they would move a lot more than expected. 280 struts will be better but you can create a sheet metal gusset from the tube to the spindle housing. Jon did this on his car and I can dig up some pics I have buried somewhere if you need. You have to figure you are putting a lot of stress on your parts with bigger sticky tires, a lot more HP and torque, and now aero. Here's an image of a Ground Control modified strut. Note the gusset used to stiffen the spindle The next step is to build a custom housing but when you get there it's probably time to start seriously looking at an a-arm retrofit. I have been playing around with a simple design that uses Nascar and dirt track pieces. I can't decide if a 7 inch upper is long enough (allows for 3 inches of suspension travel) or a longer upper is needed. At 7 inches I don't think you have to put holes into the engine compartment for mounts. Cary