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Unread 01-16-2015, 11:51 AM
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Join Date: Jul 2004
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Default Re: Vorshlag Budget TT Build: Project DANGER ZONE

Project Update for January 16th, 2015: The first stage of "initial race prep" is completed and I'm going to try to write a QUICK update before we load up and I head down to Houston (in the next few minutes!) for the first NASA Texas event of 2015. We had a lot of parts delays but the crew at Vorshlag got everything on the "MUST HAVE" list completed. They only worked on this car over an 8 day period - due to other cars on the schedule. Big thanks go out to Olof, Ryan, Brad and Jon for all their hard work and long hours over the past week and a half. Thanks also to Jason and Tim for helping pick the mods and source the parts we used. Now all I have to do is drive the thing well... but I have a good back-up driver in Brian Matteucci, thankfully.

Brake Upgrade

The last week was a blur, as we had a lot going on in the shop with other customer cars, the phone rings off the hook in January (everyone waits until now to order parts for the new race season), and we're still gearing up for our new CNC machines - which has been a royal PITA. I had a birthday this week, and tons of other crap going on, and I usually work seven days a week playing catch-up on Vorshlag stuff on the weekends. But last weekend I stole a day away to swap on the front brakes.


Left: The 12" front brakes are adequate but can be upgraded to 13" rotors "for free" (no points). Right: The two rotors in question

So the 1992-1995 "Base Trim Model" Corvettes all came with these wimpy looking front brakes, shown above. These include the 12.0" diameter x .810" thick vented rotor and PBR twin piston aluminum caliper, which I detailed a bit in my Dec 29th build thread post (post #5 for most of the forums). And I hinted that we would be able to upgrade from the 12" to the 13" rotor set-up for "no points". Normally this is a +2 upgrade, and we only have 3 total points left to play with. I'm saving those for later so we pulled the trigger on the correct rotors, calipers and caliper brackets back on Dec 23rd.



The measured weights for the two front rotor sizes were pretty close to the spec sheets from Centric. Since nobody seems to want to work the last 2 weeks of a year in the USA, we didn't see these parts until late last week (around Jan 9th), and I started installing them on Saturday the 10th. The right front set-up went on fine, but I got bogged down cleaning the front suspension and wheel well...



It was worth it seeing the beautiful, forged aluminum uprights and control arms after 45 minutes of brake cleaner and WD-40 plus some elbow grease got 24 years of gunk and grease build-up off of the metal. Be careful with brake parts cleaner as it is pretty aggressive, but it cuts through the thick caked on grease well. Once I started to see metal underneath I switched to WD-40, and used WD-40 only on all of the plastics and rubber seals. Decades of road dirt wipes off after a little soak with WD.



Cleaning the gunk showed me a split ball joint boot, which we will replace in another round up upgrades later (along with all of the original, crusty rubber suspension bushings - which can be replaced with any non-metal bushings). The old bits came off easily enough and the new 13" rotor and longer caliper bracket went on. And yes, we gained a solid 7 pounds in the rotor upgrade, but its "good" weight. This is cast iron that can both soak up brake heat and more rotor area and vanes to help radiate brake heat. This car will be 3203 pounds with driver and ballast and that's a lot of mass to slow down for thin little 12" brakes at both ends.



The 2-piston sliding PBR calipers (3.56 pounds) are familiar to me, as I've used them on SN95 Mustang Cobras and 3rd gen 1LE/B4C Camaros in the past, as well as on my 94 Corvette - which had the Z07 package and these larger "J55" option 13" front brakes. The J55 calipers are wider, and the J55 caliper bracket (2.56 pounds) is longer, but neither is much heavier than the "base" brake parts.

How are we getting to use the "bigger" J55 brakes from the Z51/Z07/ZR1/GrandSport models without points? Well the trick is this: all 1996 Corvettes models came with the larger J55 brakes, including the base trim model. And the listing for the car we have (1992 Corvette) is listed as 1992-96 Corvette (non ZR1, non-LT4). So we're updating to the base trim level brakes for the 1996 model car, since the 1992-96 cars are listed on the same line (again, not the 1996 LT4 or Grand Sport). We can also play around with swaybars and springs from the 1996 base trim model cars, which we might do later. Here's the rule that makes it all happen...

Rule 8.5, page 41 of the TT ruleset for 2015:

Updating of parts between different model years of the same vehicle model is legal provided that the competing vehicle is both in the same model group listing (same line) in the Table in 8.2.2, and in the same generation of that vehicle model, and that the entire assembly is replaced. Backdating of parts between different model years of the same vehicle model is legal provided that the competing vehicle is both in the same generation and is in the same or higher base class. No interchange of parts between assemblies is permitted in order to create a new assembly.



Just like in SCCA Solo, this "update/backdate" rule can be exploited to your advantage. It takes a lot of research and sometimes rummaging in junkyards, but it is there as a tool for dedicated racers to use. It helps to have factory manuals as well, which we do (thanks to Matteucci).

Again, this is a simple bolt-on upgrade and we have to use OEM (or OEM equivalent) parts to make it legal. No 2-piece rotors, no aftermarket calipers, this is all real deal GM bits. The brackets are from GM and the calipers are rebuilt GM calipers. So getting the right front corner swapped to the J55 bits took less than half an hour. I added blue loctite to the caliper bracket bolts, torqued it all to spec, re-used the old brake hoses (we will make stainless lines when we have time) with new crush washers, installed new caliper retaining pin and E-clip, easy.



Then a friend stopped by the shop mid-day Saturday and convinced me to go see the Interview at the Alamo Draft House. The movie was hilarious and I'm glad I went, but it put me behind on the right front brakes. No worries, I'll do it Sunday.... nope! Amy made me go write the eBay ad for our TT3 prepped 2011 Mustang, which I did then started writing the massive OUSCI 2014 write-up, which I finished today and promptly deleted (it was too harsh).



So on Monday I came in and the guys were working on other items on the Corvette, so I got to work on the left front brake upgrade. As soon as I tried to put the left front caliper on, DOH! It didn't fit.



The box had the correct J55 caliper bracket (which moves the caliper out for the 1" larger diameter) but the wrong caliper casting. It was too narrow by almost .300" and would never fit over the thicker rotor (.300" thicker). Crap. We had ordered the right parts, and the part number on the box from Centric was correct, it just had the wrong damned part in it. Oh well, stuff happens. We took these pictures, sent them to Centric, let them kno how urgently we needed the right part, and hoped for the best.


Left: original Delco/Bilstein dampers. Right: New Bilstein OEM replacements went on

Luckily they got the right caliper to us just in the nick of time (Wednesday the 14th!). The OEM replacement shocks also arrived at the same time (also ordered in December and also very very late) and Olof and Brad got all of that installed when I was out running errands that day. We replaced factory base trim model "Delco Bilstein" dampers with the OEM replacement Bilsteins that were listed in our Bilstein dealer catalog. The two original rears were blown and the new bits matched up perfectly. These are non-adjustable and are considered replacement OEM dampers available, so they are a "zero point" install.



We re-used the Carbotech brake pads Matteucci had purchased for the OEM brakes, which were XP12 front and XP8 rear. A little soft for my tastes but they were brand new so we will use them for this first event. We pushed some Motul RBF600 through the lines and it felt good. Too many other fires to put out to get to brake cooling this time around so we'll keep an eye on the fluid and Alcon temp strips at this first event.

Tires and Wheels Installed

The Hoosiers arrived this week Olof dismounted the 7 year old crusty 275/40/17 A6 Hoosiers that were on Brad's 17x9.5" SSR wheels. Then he mounted the 245/40/17 Hoosier R7 tires and balanced them. They did all that while I was at lunch one day and I didn't get to weigh the wheels without any tires, so I'll have to do that next time, but I can do simple math. Just weighed an old 275 Hoosier that was removed (22.40 pounds) and the weight of the wheels+old tires (38.76 pounds) that puts the 17x9.5" ET55 SSR wheels at about 16.4 pounds each. Not too shabby.



The SSR wheels were a bit dirty so I cleaned 7 year old brake dust off of the inside barrel and spokes with more WD-40 and some elbow grease. The 245 R7 looks so tiny to me, after a season of using 345 A6 Hoosiers, but it doesn't look bad on the car.



We will see if burning 10 of our 13 class "mod points" on tire compound was worth it this weekend. This is an experiment that could pay off big or fail miserably.

Roll Bar, Harness, Seat and Fire Bottle Installed

With only 8 days of shop time we were not able to build a full roll cage (that will be a 3 week job by itself) but Olof did manage to get the roll bar built, reinforced, and mounted.



A big time suck on this job was making the aluminum cover plates. These are necessary on a fiberglass bodied car to cover the access holes in the body to the steel frame.



Again, on a traditional steel bodied/unibody chassis car this step is not necessary at all. But its a Corvette, and has to be a pain int he ass. Olof used card stock to make templates (below) that cover the access holes, then transferred this into .065" thick 3003 aluminum sheet.



The sheet was cut, bent and welded at the joints to make a box-like shape that fit the funky fiberglass tub shape and covered the openings with about a 1/2" overlap. Then a few holes were cut to add small stainless steel button head bolts and riv-nuts were added to the fiberglass (these are special ones we use just for fiberglass, with a different grip length than normal sheet metal riv-nuts)




A silicone bead was added to the perimeters of the fiberglass and these four, somewhat elaborate aluminum covers were then set in place and bolted down. These will now keep water, dirt and debris from spraying up from the tires and getting into the passenger cabin. Olof did a superb job and they look great and fit tight around the roll bare tubes. These can be removed and the roll bar unbolted for when we go back and finish the roll cage. Similar plates will be needed up front at the additional 2 lower points of the 6-point cage design.



We knew we were going to be WAY too light for the class minimum (3203 pounds) and would need anywhere from 90-200 pounds of ballast. On Tuesday we were getting a little tight on time so I asked Ryan to step away from a cage job he was working on and make the ballast weight bracket from some heavy 1x2" tubing. I was thinking of something basic but he made this beefy assembly with a slick, threaded top cap that fits over a 2" tube.



For ballast I purchased new 45 pound "olympic" style barbell plates with a 2" center hole. Typically cast steel weights like this cost around $1/pound, which is what I saw at a few places like WalMart. But after doing some shopping I found the best price at Academy sports, who had a wider assortment of better looking plates to choose from. These 45 pound plates were $31 each, or about $.68/pound. Sure, you can slum around on CraigsList and maybe find some mis-matched weights for around $.50/pound used, but its very hit or miss. Save yourself some hassles and go to Academy. If you want something more compact you can usually buy lead for $1/pound at plumbing supply stores, but just wear a mask when cutting or grinding on this stuff.



I didn't get any detail shots but the factory seat mounting studs (which are reinforced and rated for carrying up to 300 pound passengers) were used with some BIG bolts cut down on the lathe (and drilled/tapped to fit over the seat studs) go down from the top to secure the rack in place. You could pick the car up from this set-up and the 2" tube fits tight to the plates in sheer. At a minimum we will run 90 pounds of ballast here plus 120 pounds of fuel in the 20 gallon tank. Once we replace the 46 pound glass rear hatch with plexiglass we will add another 45 pound plate to the ballast box.

continued below

Last edited by Fair!; 01-16-2015 at 11:59 AM.
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