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Unread 10-17-2015, 03:55 PM
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Default Re: Vorshlag Budget TT Build: Project DANGER ZONE

Project Update for October 16, 2015: Its been another 6+ weeks since my last post, and it has been a roller coaster ride of ups and downs. The rebuilt motor finally showed up on October 6th and was a week long thrash to try to get the car together for a track test October 10th at ECR and a NASA race weekend Oct 16-18 at TWS. We had already missed the September NASA event at MSR-H so we are really pushing to get the car to the last 2015 NASA event in Texas. Unfortunately things did not go to plan and we're scrubbing this race. Let's cover what has been done since my last update to explain...

Note: After writing this update over the course of 2 weeks of work on the car, I had my thread update completed in a private section of our forum - which we use to compose and edit these mega sized build thread posts. Jason had edited everything the night before I scrubbed the event, and the morning I was going to post this (Wednesday the 14th) our forum crashed and has been down ever since. Its so borked that the server is auto-generating 20,000 error message emails a day, driving me nuts, and I have two teams of tech gurus working on fixing it (we've had that forum operational for 13+ years and its never gone down like this). Luckily I had this post open on a window on my pc, so I could copy the text, but it lost all of the UBB code for formatting, images and links. In a rush to rewrite this post now I won't link all my pics to larger images like I normally do and might miss some links I had in here before.



You will notice in this series of posts that I'm not sharing any pictures of the inside of the rebuilt motor and censoring some images where those bits are visible. I'm not going to stop sharing pictures in this build thread, as it is still part of showing "what can be done on a budget" and "what race prep we can do" at our shop, but I'm not giving any more ammunition to our competition!

Rebuilt Motor Arrives

Let's talk about TT-letter class allowable engine rebuild rules. Here they are:
Quote:
Originally Posted by NASA TT Rule 8.3.i.c
18. Engine rebuild with head shave, block decking and 0.020 overbore provided that compression ratio is not increased by more than 0.5 and displacement is not increased by greater than 1.49%. Forged pistons and internals are legal; however, they must be of equal or heavier weight than the BTM parts, and points must be assessed for de-stroking, and/or increased displacement and compression ratio if greater than the limits listed above. (Note: 0.020 overbore with OEM rods and overbore pistons will yield an increase in displacement of approximately 1.1% for most engines.) If forged internals used are lighter than the BTM internals, then Dyno Re-classing (Section 8.4) should be used to prevent disqualification.

19. Engine balancing and blueprinting

20. Removal of the engine balance shaft and/or balance shaft drive mechanism

21. Non-BTM valve springs and retainers, piston rings, and rotary apex seals
My engine builder worked with me at length throughout this build, and sent plenty of images during the rebuild process, but I'm not showing any those here. NOPE.

This engine is a NASA letter class legal rebuild, with nothing out of the ordinary. I'm not going to get into the specifics of what we had done to this LT1 engine, but I will say that it was a 100% legal rebuild. No grey areas, no loopholes, just a solid TT-letter class legal engine rebuild that will likely pick up zero horsepower, only reliability. This engine would survive the most brutal tear-down protest. It is also very well built, uses all new parts, and was not cheap. The engine builder even made fun of the fact that we were having to use OEM rockers, pushrods, rocker studs, guide plates, etc. "I've never had anyone ask to use the stock stuff before!" We went over the rules with him in detail, and he is a racer himself and understands how important rules legality can be.



The engine took over 5 months to be rebuilt partly because so many of the 1992 model specific OEM parts were tough to procure (this "GenII" V8 engine family was only used from 1992-96 and the Corvettes used different parts than the Camaros or Impalas of this generation), and there were parts changes for almost every year of this LT1 - we can use any 1992-96 LT1 Corvette engine, but only as a complete assembly - no mixing and matching of parts like camshafts, heads, etc. We stuck with all 1992 stuff, but it wasn't necessarily the best choice.

There were nationwide searches to find some of the items needed, which took a lot of time. I'm not going to bore you with the trials and tribulations of building a 25 year old motor with many of the OEM parts, but it was a bit of a nightmare. And the engine builder admittedly had some inexcusable delays on his part, but it finally got here as an assembled longblock at the 11th hour, just in time to make the last NASA Texas race of 2015. Yes, this was long after 3 more NASA Texas events passed + NASA Nationals East was missed, which I was none too pleased about. We missed almost the entire NASA race schedule, but we hoped to make the last event here...

Parts Cleaned, TB Airfoil Removed, New Plug Wires + Wrapped Manifolds

The longblock was placed on the engine stand mid-day Tuesday October 6th and then the washed and cleaned Moroso oil pan was installed with a new FelPro gasket and some RTV. Then it was onto several other checks, then the intake manifold and valve covers were cleaned up on Wednesday...

These would be installed after the motor was back in the car, to save time. Some deadlines were looming: be at True Street for dyno checks and possible re-tune that Friday, then out to ECR on Saturday for track testing, then any last minute updates the following Monday-Thursday, then load up and head to TWS for a NASA weekend the next Friday-Sunday. Plus our shop was full of customer cars that all had their own deadlines, many going to the same TWS race weekend.



While the guys were putting the LT1/ZF6 drivetrain in the car Wednesday morning, I took the intake and valve covers to Friction Circle Fabrication in Lewisville to have these 25 year old parts cleaned in their UltraSonic parts cleaner. These dirty bits were soaked in the 155F degreaser solution and agitated for 90 minutes, but they came out super clean. In hindsight we should have scraped more of the burned oil residue off the valve covers mechanically before going in the ultrasonic - would have saved a lot of time.



It is a good feeling to know your new engine isn't going to be filled with trash that fell off of some dirty part you reinstalled. And there was some serious crusty, nasty stuff on the bottom of the valve covers and inside the intake. Old, burned-on oil residue plus liquid oil in the intake - from the massive blow-by - which was being pumped back into the intake via the PCV system.



When I returned with the cleaned parts, Ryan installed the intake manifold (which was a chore - long story) plus the 25 year old OEM injectors. The stock injectors were cleaned and flow bench tested at InjectorRX in Houston back in August, and as you can see with the test results above, the flow rates were all over the map. Three of the units were also leaking and all of them were clogged before, but after they were (ultra sonic) cleaned and rebuilt they all flowed the same. Good insurance on a set of OEM injectors this old - and yes, we have to use the stock parts here, or take more class points we don't have.



The aftermarket throttle body airfoil, which we didn't know was installed until someone noticed and pointed it out from one of my build thread pictures earlier this year, was removed when the intake manifold went back on. The one NASA event where we (unknowingly) ran this airfoil on the car and actually got a class win, we had the points for it (+2 points), as we hadn't done spring upgrade yet (+2). These throttle body "air smoothing" airfoils were super common to run "back in the day" on the TPI and LT1 V8s built from 1985-1996, due to the abrupt shape change of the twin throttle body set-ups GM liked to use back then. Nowadays the LS-series GM V8 engines use a single round throttle blade, which feature smooth inlets and MASSIVE throttle blades (and flow) in comparison.



Anyway, the airfoil is no longer on the car, and is sitting on my desk as a paper weight.


With the valve covers and intake off, you get a big helping of NOPE

Before the motor went going into the car we replaced the AutoZone plug wires with some 8mm Taylor wires made for this LT1 Corvette - these are a bit easier to change with the engine out of the car. The old plug wires were still fairly decent looking, but why chance it when the motor is out? Spark plug wires are "free" per 8.3.I.c.6, for any rules lawyers that are reading, and the costs were around $65. I tend to use Taylor plug wires on everything we build around here. New NGK split electrode spark plugs were also used - we've seen good results from these and they don't have itty-bitty iridium or platinum tips that can fall off.



The OEM exhaust manifolds were also wrapped with DEI header wrap before going on, to keep a little heat out of the engine bay. As we've done throughout this build, if it has to come off or for some other reason we have to touch a part, we're going to make it better - to the limit of the rules and within sane budgetary constraints. Header wrapping the manifolds is legal per NASA TT rule 8.3.I.c.23. Ryan used an old hot rodder trick to wrap these manifolds - he pre-soaked the DEI wrap in water, to make the material more pliable during installation. It was wrapped tightly around each tube tightly then secured with safety wire at the ends. The water boils off quickly during start-up, if the wrap hasn't completely air dried by then.

Drivetrain Installed + Oil Catch Can/Breather Install

The re-installation of the engine is pretty boring work, but it does eat up time. And like everything else, doing this work on a Corvette is more cumbersome than most cars. The ZF6 speed was pressure washed and cleaned up (previously covered in oil from the old RMS leak) before it was bolted to the motor. Everything we touch on a race car goes on clean, even old OEM parts. Dirty parts help hide leaks, cracks and other issues.



Assembling the triple disc clutch to the flywheel, stabbing the transmission and hydraulic TOB, and getting everything into the car was handled by Ryan and Brad. It takes more time to line up the clutch plates and get all 6 pieces lined up together, but this is not hard for our crew. A metal clutch alignment tool is a must for these multi-disc clutches, by the way - we use an old T56 input shaft.



After the drivetrain is in place, the big aluminum C-channel that connects the diff to the transmission goes in (which also functions as the transmission mount, just like on a Miata), as well as the stock aluminum driveshaft. Then the OEM exhaust system goes in, the stock shifter is installed, various wiring harness plugs are attached, etc. No pics of that as Brad was helping and I was across town. This car still has the original OEM mufflers and catalysts, which we visually inspected very closely before the motor went in - the catalyst matrix is still intact after all these years, somehow. Changing the manifolds, cats, mufflers or even the tail pipes costs points in TT-letter classes, so it all has to stay bone stock.



After the engine was in place, we did one more (zero points) upgrade I had planned on for a while, and one we do in a lot of customer's race cars (see above) - add an oil catch-can/crankcase breather. This is something smart to add to any car that sees track time or extended RPM use. The way we plumb these, and how we specify the catch can itself, depends on if its an emissions legal street car (above right) or a track-only race car (above left). A street car isn't supposed to have an open vent for crankcase fuel/oil vapors to get out to the atmosphere, so street driven cars are plumbed with a PCV system to pull excess crankcase vapors out during deceleration and route them back into the intake manifold, to burn them in the engine. Liquid oil in the crankcase vapors is trapped within media inside the catch can, which can collect in the can and be drained out after track days. On a race car you don't have to do with a PCV system - and you don't want to.


This is how much smoke was coming out before the engine rebuild... that's all blow-by

One of the main problems we had with the LT1 motor in the Corvette earlier this year was tons of blow-by. Combustion by-products getting past the piston rings and valve guides/seals then pushed into the crankcase. This was only realized after the leaking oil pan gasket and rear main seal were fixed before our second 2015 NASA event in this car. The blow-by was from worn out rings, three valve guides that had lots of play, and valve seals that had crumbled over two and a half decades. It was smoking so badly we couldn't make one lap without being black flagged.


This is the Peterson 08-400 catch can / breather tank we used

Since I didn't want to take any chances after having "that smoking Corvette" for two NASA race weekends this year, I ponied up for a Peterson Oil Catch Can / Breather a few weeks earlier. It has two -12 AN fittings for inlet, a -6 for a drain (which comes plugged), and the built in breather in the cap. Even comes with a nice mounting clamp. So when the motor was back in the engine bay Ryan and Brad mounted the breather can on the firewall, then plumbed some -10AN bulkhead fittings to both valve covers (because that's what fit the OEM hole on the passenger valve cover).



One fitting went in the factory PCV suction line on the passenger valve cover but the driver's side cover had to be drilled. We have removed the PCV valve and function completely. These factory LT1 "center bolt "valve covers are magnesium and tricky to work with, but they were drilled handled properly and plumbed with -12 sized push-lock 300 psi hose and -12 AN fittings into the Peterson tank.



Now both valve covers vent will excess crankcase pressure to this oil catch can, without the need for a vacuum source to "pull" the vapors out. This Peterson catch can has an integral breather in the lid, which is what makes it not street legal. We have completely done away with the PCV system, so now it is less troublesome and won't allow oil and/or unburnt fuel vapors to be returned to the intake track to be burned - which can cause detonation. And if you get a lot of blow-by it won't send liquid oil back into the intake, which is really bad.

First Fire + Weird Ignition System Issues?

After the breather tank was plumbed, all of the engine fluids were topped off and some Royal Purple break in additive (zinc) was added to the 10W40 Mobil1 synthetic oil we used for initial break in (normally I like to run 15W50 in race cars). The ignition coil and the fuel pump relay were disconnected, then the engine cranked for 10 seconds, and it made 20+ psi of oil pressure almost immediately. After that the coil and fuel pump were hooked back up, the fuel pump was triggered a few times (key on/off... on/off.... on/off) to prime the fuel pressure in the lines and fuel rails, and then it was cranked. And cranked. And nothing. No start.



Then began a full day chasing the starting problems. First we assumed the obvious: it was Optispark related. This is the name for the system GM tried (and failed) at making a better distributor with in the GenII V8s, with a weird unit is driven off the timing gear at the front of the motor. This is widely known as a problematic system. The GenIIs camshaft drives the water pump, also strange, which feeds the motor with coolant in the reverse order of any other motor on the planet. The water pump is right in front of the Optispark, and if any coolant/water gets in the Opti, it usually dies. The LT1's two main bad ideas were the Optispark and reverse flow cooling - they were both abandoned in the next generation engines by GM (GenIII LS1).


Checking fuel pressure, computer issues, wiring harness breaks at Vorshlag (left) and True Street (right)

The other issue we kept running into was thought to be VATS related, or Vehicle Anti Theft System. There's a chip in the ignition key that tells the computer "Hey, I'm legit!". Without that handshake the fuel pump won't fire. It intermittently worked, so we have to disconnect the battery to clear it up. Something I thought was removed when True Street tuned the car, but the SECURITY light kept flashing. The VATS on my 1999 GMC truck was doing the same random faults a few months ago and Sean from True Street plugged in and turned that mess off, too. GM "VATS" is pretty much a "leave me stranded in my own car" system.

continued below
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