How proportioning valves work in Street Touring
Actually the Camaro’s brake bias was probably too far off to be fixable with a brake bias adjuster, so it’s getting a more powerful prescription:
reduced rear brake piston area.
As you can see, the caliper on the right has a lot smaller pistons. Both have 4 pistons and the same pad area, with the same pad compound (same pad compound used in front).
Going to a smaller piston area may seem counterintuitive if you wanted to reduce force – won’t a smaller piston “move further” than the bigger, thus exerting more force?
In actuality, the pads don’t have far to go, and once they’ve hit the rotors, braking force has to do with the pressure exerted. The principles of hydraulic systems dictate the pressure be equal everywhere, and force can be figured as pressure applied over an area – thus, the smaller the area, the less pressure applied to the brake pad.
Hopefully that equates to less death-rotation under braking 🙂
Like the look and finish of these better anyway, they match the 6-piston fronts.
Rear brakes were definitely locking up
Found some new photos from the SD Tour, and this one:
is especially illustrative. Note how the inside front is still blurry with rotational motion, but the inside rear is nice and sharp…
Looks pretty sharp in the next couple as well, as the car begins to pirouette. Barely caught it.
Looking forward to the lower-piston-area rear calipers. Feels good to have an in-car impression validated with external data.
p.s. I would have bought the digital copy and posted it here – but the photographer wants $40 per digital image? The nice image I used from Late Apex Photo in the last post was a reasonable-for-a-great-photo $7.50…
Many obstacles overcome, still more to go.
About a month ago I posted a list of stuck-points on the project – fortunately since then, with a lot of effort and tool purchases, progress has been made! Have put more time into the car this past month, than in any month so far. First, an update on each of the old sticking points-
Power steering leakage
New pump was purchased and super-carefully installed. All lines cinched up, and no leaks after a couple weeks, yay! Still have to see how it holds up under the pressure of real use with the pump cranking away, but so far so good.
Brake line fitting leakage
This was due to an incorrect flex line in the rear – correct part ordered and installed, and the brakes were bled, no leaks! My brake bleeding assistant, who’s never driven a manual car, had some trouble with my instructions to “push the pedal in the middle” – since the throttle pedal was sunken to the floor, the clutch appeared in the middle of the e-brake, clutch, and brake pedals. I’m going from corner to corner, wondering why fluid is barely eking out as I hear her pumping away! 🙂 A little revised instruction and it’s good to go.
Still had some air after a couple passes, at which point I realized the multi-piston Wilwoods need to be bled at the top of both caliper halves (inner and outer) to get all the air out. Last few bubbles gone and the brake pedal feels very firm inside.
This was a rather labor intensive process. In typical easier-said-than-done fashion they were cut down 2.25″ in length; bushings were trimmed or hogged out to fit appropriate sleeves for mount bolts; the front spring eyes were flipped and ground for clearance; initially the rears were flipped also but it looked like clearance would be an even bigger problem, so they were left upright, but still got some grinding.
This has an ultra-scientific “one to two finger gap” in the rear. Added about 65 lbs. of fuel (more on that later) which only brought it down about 1/8″. Only weight left to go in is the headliner and door glass, so this is where it’ll be for now. It’s not likely this spring rate will be the one I wish to keep forever, so for the next pair of springs, it should be easy enough to request an additional ride height decrease, in addition to the spring length decrease. Bushing work will swap over.
Oh, and in the picture above, the rear wheel has 3/4″ of spacer. There’s room to go inboard or outboard bit if needed, but this provided a more athletic appearing stance, while still providing for tons of wheelwell clearance in all directions. At this setting rear track width is 70.75″, which still, isn’t *that* wide. It’s about 4″ wider than my 240sx was, and about 7″ narrower than the Viper.
Road Draft Tube
Have to thank my buddy John Coffey for talking me through this one. Tried several different things and took a long time with this, and ultimately found a solution. This item was holding up permanent installation for a lot of simple things in the engine bay, so once it was out of the way a lots fell quickly into place – carburetor, fuel lines, distributor, throttle and choke linkages, etc. The tube coming off the road draft vent hole is the black one fuzzily visible in the passenger side carb photo below-
You may note, the stock-style valve covers. These are actually the third set of valve covers I have for this thing – the first set didn’t fit the bolt pattern (they’re for an even older small block) and the second set were a bit bigger and made of thicker material. They *look* nice and original, but caused all kinds of interference problems with things like the fuel line and the bracket for the power brake booster vacuum line, visible above. While in general I’m not a fan of extra chrome, these are at least very lightweight, and totally stock.
Coolant Temp Sensor Port
This problem begat a bevy of tool purchases. After nothing could convince the old plug to come out, began drilling with ever-larger holes. The largest thing I had on hand for going through metal was 3/8″ (bits and chucks), so it was time for some upgraded hardware. Now have a new 1/2″ chuck drill, and an array of drill bits up to 1″ in size.
Also bought a 1/2″ NPT tap to repair the threads, and a special 45/64″ bit as the final pass before using the tap. After using the 45/64″ bit, all that was left of the plug was like foil and I could pull it out with needle-nose pliers.
Hooray! Coolant temp sensor in its appropriate location!
Also visible in this pic, is the new oil pressure sensor. This is a 1/8″ NPT sensor occupying a small port in the block previously filled with a small square plug. This too necessitated some tool purchases since it was a 7mm square plug, so none of my 6-point sockets would fit it, and the only way to fit a wrench on it, would be to pull off the water pump; no thanks. Ended up buying one of these universal socket things, advertised to work on 1/4″ – 3/4″ bolt heads of all shapes and sizes. After some monkeying, it got a grip on the thing and got it out. The tool earned its keep in that one action!
Perhaps apparent from the way the wires for the oil pressure sensor have been run, am making a big effort to keep the wiring tidy and professional in the car. Bought a ton of heat shrink tubing and overlay sheathing, in an attempt to keep everything clean, bundled, and protected.
No progress on here from last time. The passenger vent window is just about ready to go in, been focused on what’s needed to get it running.
Lots of other progress has been made in addition to getting the above accomplished.
First Fuel Purchase
One of the simpler ones – the fuel line installation was completed, so it made sense to get some gas. We happen to have a very neat retro gas station just a few miles from the house, that sells all sorts of good gas right at the pump, and comes complete with a smiling young man offering to clean your windows or check your oil. It’s mostly frequented by the well-to-do’ers of RSF, topping off their Range Rovers and exotic sports cars. I felt out of place with two crummy 5 gallon plastic jugs in the pickup, but the Camaro will look right at home there.
Oh, and this is the only station I’ve bought gas in, in the last 10 years, where you don’t have to pre-pay. Got a lucky click-off of the pump, no coins! Hopefully a sign of good ProSolo reaction times to come. 🙂
This is another that seems like a no-brainer…which of course wasn’t.
Had the body shop install the wiper motor and attach to the wiper arms at the body shop, as doing so requires having the cowl panel off, and installation or removal of a body panel, is a big opportunity to scratch up the paint on said panel.
Unfortunately the wiper arms were not “clocked” to the motor correctly, causing the wiper blade to want to swing down initially, instead of up. So off came the cowl panel, some time spent futzing with the mechanism orientation, but ultimately, the wipers made it in, and I managed to get the cowl back on without messing anything up too badly.
The car had no wipers when I got it, now it has working ones, ha!
Pedals and Header-back Exhaust
The car has four functional pedals at last! Well, the gas pedal may not make it go yet, but it does open the throttle, now that the road draft tube shenanigans were handled.
Brakes were made ok with the bleeding a little while back, and the clutch was okay, as the pressure plate provides most of the springing, but the complementary clutch return spring that keeps the pedal up against the stop, has also been installed.
The parking brake pedal was the last to be made functional. The Wilwood rear disc brake setup on the car has a complete functional parking brake, but comes without a means of adapting it to the factory cable system. Fortunately the solution was pretty simple, with a pair of Lokar “Explorer style” clevises, drilled out to accept the factory parking brake cable. The entire parking brake system is not entirely new, from the rubber of the pedal pad, to the drum lining at each rear wheel.
As you can tell from the second picture, at this point, the exhaust ends at the mufflers. When I get the car to an exhaust shop, will have to see what can be done to extend the exit either to the traditional location, or out the sides. The panhard rod in the rear suspension complicates things.
They still aren’t right. Rear is too high, as discussed above. I’ve raised the front “2 turns” (haven’t done the math to figure how that equates to inches), but it probably needs to come up more.
This picture was taken a few days ago, before fuel and coolant were added, so both front and rear have since come down a little bit.
You’d think moving the car around a garage floor on dollies like this would be easy – nope, big effort required!
Before trying to drive it anywhere, I’ll probably raise the front another 2 turns.
The Vintage mags with 27+” tall tires will fill the wheelwells better than the Jongbloeds and AD08 rubber. The shorter /35 series front tire vs. the /40 series on the rear, exaggerates the ride height difference.
No problem turning to full lock, even at this ride height-
Pic inside of the front suspension with the wheel turned- contact point at extreme bump, is the lower control arm to the factory bump stop bracket, welded on the frame. At this ride height, it has about 1.25-1.5″ of travel there, equating to about 2″ of travel out at the tire.
Oh, and a funny one-
The family car had to go in for service (Infiniti is paranoid after the Toyota/Lexus unintended acceleration debacle, and is issuing recalls on the new JX35 like crazy. The car needed 5 recalls done, which necessitated an overnight stay) – and since they were busy and out of branded loaners, we got a crummy rental – the Chevy Sonic. The Sonic is one of these economical small cars – not micro like the Smart or Scion IQ, but subcompact like the Toyota Yaris, Mazda 2, or Honda Fit. When my Tundra was serviced I got a Yaris SE loaner, which was actually decent, but this Sonic LT was crap! Anyway, it got to park next to the Camaro one night.
What amazed me was how TALL the Sonic is! Check out this picture-
It only looks a few inches taller than the Camaro…until we see the Camaro is sitting on 5″ tall dollies! Will have to measure the Camaro once it’s back on the ground, but I’m pretty sure its roofline is around 48″, the Sonic (and lots of other cars like it) have rooflines about 60″. Wow.
Ok, so I put it in the trunk, not very exciting. This is an Odyessy PC680, common in the aftermarket. It’s 13-14lbs., vs the 35+ of the stock battery, hanging way out past the nose. Here’s it’s mounted fairly high, but more or less at the rear axle centerline.
Have more thoughts on general battery placement, will have to share another time.
This battery was bought to get the car going (figuratively, not literally) – since in the beginning it is likely to get cranked a lot without much chance to charge normally, and this should stand up ok to that use. The *real* battery I plan on using is the C680 XS Power battery, which is only about 4 lbs., and is the same form factor as the PC680, meaning it will fit in that mount.
The insides of the car received some attention, mostly in the instrumentation area.
Steering was a bit out of whack, had to purchase a puller to get it all apart and re-clocked correctly, but it could at least be buttoned up-
The wrap will come off soon! Still getting my hands dirty doing stuff, just not as bad as before.
Note the cover plate over the center of the dash – bare as a no-option car can be.
Couple other things to see – the switch at bottom left, and of course the DASH2 dash. The switch will be an independent control of power for the DL1 and DASH2. The idea is, I can keep it on, to help let the DL1 keep GPS lock between runs, or any other time I want to have the engine off but instrumentation on. Modern cars tend to have as their key positions, Off -> Accessory -> Ignition -> Run. This car has Off -> Accessory + Ignition -> Run. Want to be able to keep some of the electronics going, without all of it going.
Speaking of the DL1, it got its own custom bracket, just below the dash, to the right of the steering column.
That silly bracket took a ton of time to measure and bend up, and I’m still not totally happy with how it ended up, as I had to change its position slightly to avoid having to use a serial extender between the DASH2 and the DL1.
With this configuration, the DL1 will be recording information from sensors (like coolant temp, RPM, and oil pressure) in addition to the things it can figure out on its own – speed and accelerations – and present this data to the DASH2, as configured, over an RS232 serial connection. This is handy, because you can’t really look at gauges while autocrossing. You might have a chance to look at the tach when doing an initial 1-2 shift, but that’s about it really. On the track you can take a glance for a second or so while on a straightaway, to ensure systems are still healthy, possibly even changing your approach if you see oil temps climbing, or something like that. In autocross you go out and hope the car makes it through the run without self-destructing. If you are having momentary drops of oil pressure, there’s no way you’ll see it, without some kind of alarm light programmed in, but that can be tricky, since 20psi might be OK at idle but death at 6k RPM. With the data acquisition, you’re watching the gauges 100 times per second, and if there are any concerning fluctuations, they can be correlated to other events, like hard right-handers following a braking zone, for instance.
In this photo it isn’t yet talking to the DL1, so it only knows to output fuel level, which it will get from the main vehicle harness, and will not be datalogged. Common Camaro Lore dictates one most always autocross a first or second gen Camaro with a completely full gas tank. I’m hoping that’s not actually the case, will find out soon enough.
The DASH2 is mounted to the steering column via a custom bracket I made. When I envisioned the bracket, it had to be carbon fiber, and making it so, took extra time. In trying to get a photo of it tonight, I now realize now silly that probably was, you can only really see it when looking down through the windshield. Here it is, from roughly the middle of the car up against the windshield, looking back and left-
Even if the aesthetics aren’t perfect, pretty happy with how it turned out functionally. The size and positioning of the bracket and DASH2 unit, allow the wheel its full range of tilt adjustment, without bind or interference. Here it is fully tilted up-
With the steering wheel in a normal position, eye level is slightly above the unit, which is supposed to be optimal for its viewing.
Race-Technology was very supportive in sending me out a loaner so I could get the car fired up, while they send my bricked unit back to the UK for repairs. Thanks Al Seim and R-T USA!
Not very exciting, was able to get a good length PS belt on the second try, looks like I’ll need a third attempt to get an alternator/fan belt of the right length, this one is a bit too long-
Looks like I may need to spend some time shimming the PS and water pump pulleys to get perfect alignment. Like so many things, you think belts will be a 5 minute deal, and it turns into hours… 🙂
The plan for the moment is to get it running, and solid enough to not fall apart or puke its fluids out everywhere on a short drive. Want to make sure it builds oil pressure by free-cranking it with the plugs out, before they go in and I try to fire it. It *should* be fine as it ran great on the engine dyno, but that was over 2 years ago, and it has since received a new oil pan.
It’ll need to go to an interior shop to get the headliner put in (it’s a least a 2-person, if not 3-person job on these cars), then to an exhaust shop (have some tweaks to the Magnaflow system I need/want), and to ProParts USA for some shocks. I want to have the car ready for the San Diego National Tour, which is a short three months away!
Rear brakes and subframe connectors
Initial progress over the holiday weekend. Rear brakes (rotors and calipers) and subframe connectors got installed.
Before getting started on the connectors, decided to wax the underside of the car. Not that this is something I plan to do often (or perhaps, ever again), but it should help keep the underside clean, easy to wipe off any dirt and grime that lands there. With it all bare, this presented the last good opportunity for this extra protection before the car’s underside starts to get “busy” with plumbing and other equipment.
View from the rear-
And from the front-
And here, post-installation:
Can see they were painted the same light gray used elsewhere…figured they’d stick out if kept their original color:
From the side:
And the back:
And the brakes. I bought these a while back. Decided to stay with a modestly sized rotor (12.19″) as it allows for use of 15″ wheels for the real vintage look, if the situation ever warrants. For autocross, these are probably overkill, while being a little small for track duty. Thinking I would like to run the car at the track a little bit some day, Laguna Seca and maybe Streets of Willow. With its autocross geared rear end, it’ll only be good for about 115 in 4th gear, not enough for most tracks.
Compare to how things looked a year ago:
Another good thing about this kit, is there are several different Wilwood calipers that can mount in place with no other changes. Because we don’t have the ability to use proportioning valves in ST, changing calipers is a coarse way of adjusting bias. These calipers are 4-piston, but one of the larger 4-piston units; if there’s too much rear bias, I can go to a smaller 4-piston; if there’s too little, I can step up to a 6 piston.
Made some big orders over the weekend, a complete interior is on its way, along with a few race goodies. Particularly excited about the battery; wish this one had been out for the last couple ST cars I built!
Agricultural 12-bolt and down the rabbit hole
Some of the parts needed for this build are getting harder to find, this is one of them.
The GM 12-bolt is an extremely robust rear-end with an 8.875″ ring gear. It is often compared to the ubiquitous 9″ Ford rearend, the GM piece being a tiny bit less stout, but more efficient (less driveline hp loss).
I’ve been looking for one for a while, and one turned up on Craigslist. The price was good, picked it up Friday.
It is a correct ’67-built Camaro piece. According to the owner, it had been sitting in storage for about 20 years, and then in his yard for the past several months. Based on the dirt removed, by several months, he might have meant 120 months!
Inside the brake drums, an entire ecosystem was flourishing, all sort of spiders and insect carcasses abounded. In this pic you can see the huge black spider that “owned” the passenger side drum-
I don’t think I should count all that dirt as weight reduction, pretty sure it wasn’t there from the factory 🙂
Getting this thing in shape is going to be a bit of work.
My plan was/is to get the car minimally prepped, so I could take it to a welder and have all the big on-car welding projects done. I have taken a welding class, and have access to a good MIG, but don’t trust myself to weld anything critical, like a live axle lateral suspension locator.
The lateral locating device will be attached to the rear axle, so the axle needs to be clean and ready for welding. I also wish to package the device towards the end(s) of the axle. The limit of how far towards the end the device can be located will be defined by the brakes. Hmmmm…down the rabbit hole we go………..
So it looks like maybe I should get the rear brakes put together to ensure I don’t get welded into a packaging dead-end. Now, STX does have a “big brake kit” allowance. Unfortunately, like many of the ST category’s allowances, it is a rather Fisher-Price allowance (“My First BBK”). I can say that, having spent a few years on the STAC – aka the Street Touring Advisory Committee, the “subject matter expert” rules making/advising group for the ST category. I get what they had in mind – the blingy cross-drilled stuff you see in the tuner magazines that are easy bolt-ons for popular cars. Nothing exotic, no messing with the hydraulic system, nothing requiring any engineering on the part of the ST car builder, just bolt-on kit/kid stuff.
Now, there are plenty of “bolt on” kits for the first-gen Camaro. However, none of them are really designed to work with the factory master cylinder, which is rather large (1.125″ bore). Those kits all come with some kind of late-model Camaro or Corvette master cylinder, often with a proportioning valve.
Can’t change the master cylinder, can’t change the booster, can’t add a proportioning valve – at least, not in the classic fashion. Some first-gen Camaros came with a proportioning valve, but that was only the heavier cars with A/C, not the Z28, and even if it did, I couldn’t change it.
The flexible brake lines I can change, the calipers and bracketry I can change, and I can use any rotor equal to or larger than the diameter of the factory rotor or drum. Even the smallest aftermarket stuff is about 12″ (stock drums are 9.5″) so the diameter won’t be an issue. Since the calipers themselves are free, I was thinking I could use one small proportioning valve right at the inlet to each rear caliper. Then I could say it is part of the caliper and thus legal. I expect to receive emails from people saying “hey, that’s not what they had in mind” shortly 🙂
But I’m not totally sure I even want to have a proportioning valve. The Viper had one when I bought it. I ran it that way for a couple events (nothing National, folks). The car from the factory had shorter front tires than rears, and the previous owner raced it with equal sized tires all around. Taking the car back to Stock, I removed the valve as it wasn’t legal, or needed. When the Viper was on the ideal f/r diameter tires, I thought its brakes were the best of any car I’ve ever driven, and a lot of that was the factory blessing the car with a healthy amount of rear bias. When I ran a slightly (.6″) taller front tire, it would try to kill the driver with too much rear bias. So, suffice it to say, there isn’t a ton of room for error in sizing the brake system, but the proportioning valve does give you a bit more leeway.
I won’t go too far into designing a brake system here, but there are several key variables to consider. In my case, some are fixed, some I know or can estimate, and some are free to change.
Master cylinder bore
Brake pedal ratio
Brake booster ratio
Static front weight
Static rear weight
Maximum deceleration (use this to calc load on front and rear tires at max decel)
Front and rear tire diameter
Caliper piston area
…from all this there’s a bit of thinking to do. You can design a perfect system on paper, but if the parts don’t exist out there in the world, it doesn’t do much good. Not going to have custom calipers made for this. Have to see what is available from Wilwood, Baer, Brembo, Stoptech, etc., and piece together a working system from their available components. Also have to consider – is the car going to get track time? Autocross puts much less demand on brakes than does the track. Most of my track experience is in the S2000, which had somewhat undersized and undercooled brakes, a constant problem.
If the car isn’t going to see much hot lapping, then 12″ rotors will probably be fine. If it is going to be tracked hard, I’d probably want 14″ rotors, as I plan to run only 18″ wheels, and they’d provide the ultimate in thermal capacity. The bigger rotors are heavier though, a disadvantage at autocross. 13″ rotors might be a good compromise. The larger diameter rotors also provide more brake torque with all else equal.
Speaking of weight, the stock rear drum brakes weighed 43 pounds between the two sides. In my STX Z28 spreadsheet, was anticipating losing 7 pounds in rear brakes, would like to stick to that if possible. Also have to retain some kind of parking brake, which adds weight.
Browsing Wilwood’s brake kit chooser site:
They ask about the axle offset. Hmm. Didn’t have the axle apart enough last night to get this measurement, and even if I did, am I sure it would be right? I’ll be changing the limited slip, and didn’t know if the axles in there were the stock size and length. So one more trip down the rabbit hole, might as well get my limited slip now, with OEM replacement axles (no donuts here Civic guys! ;)), so I can put all that stuff together and measure my axle offset properly. Will need the measurement to be final and exact regardless of whether or not Wilwood stuff is chosen. They list three sizes, 2.75, 2.81, 2.91. Again, not much room for error here!
Will go into a discussion about the limited slip choice later. One somewhat unfortunate thing, is the GM 12-bolt isn’t the hottest diff out there, so it doesn’t have all the fancy choices some other cars get. I’ve had excellent experiences with ATS/Carbonetic in the IS300 and 240SX, and the OS Giken has gained huge popularity in autocross circles as of late. Still, there are some tried-and-true options for this car I think I can make work fine.
So I got things a bit further along today. Didn’t try measuring the axle offset, figured the bug guts might throw it off by .06″ anyway.. 🙂
Whole thing covered in funk and some kind of white paint, got most of it off. As bad as it looked on the outside, the insides look great. Everything very straight and true, turning very smoothly. It had a 3.07 open diff in it, so it’s not likely to have seen much heavy use. The gears all looked better than any of the Viper diffs I’d worked on!
Oh, and speaking of gears, one cool thing about old cars, is you had LOTS of choices-
…and the Z28 could be ordered from the factory (unlike the dealer-installed cowl-induction or header options) with just about any of them. 3.73 standard. These days, you have to order a whole big option package or something to get a different rear ratio, you never get to choose it individually.