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Blue Bullet Blog-The C6 Ownership Experience

I have the report from Katech. It came as a .pdf and has "Katech Confidential" displayed on every page, so I can't post the specifics, but I can summarize parts of it.

In mid-May, just before I shipped the car back there, I ran an oil use test lasting about 300 miles. I put a quart in 200-mi after the test started and then another quart at about 100-mi after that. Katech confirmed that level of oil use just prior to their teardown with a road test of their own which showed about 100 miles per quart.

Katech ran the car on the chassis dyno and found it down on power. They put the original calibration back in the ECM and some of the power loss came back, but it was still 50-hp down from what it was when the car left Katech last on 7DEC2017. They also noted the engine exhibited knock retard.

The report states the MAF and spark table calibrations which were problematic. Starting on 28FEB2018, after Katech emailed me that they were unable to continue to send me revised calibration files, I made changes to both those tables. Prior to that, starting in early January, I had, also, made calibration changes, but none were with MAF or spark. Any calibration change voids the warranty Katech extends to Street Attack LS7 customers.

They ran an exhaust pressure test and found excessive back-pressure on both sides. Both cats are restricted. They borescoped one of them and observed spots where the substrate had begun to melt, an indication the air:fuel ratio was lean under high load. No oil residue was observed.

After getting the engine apart, Katech found the crankshaft, bearings, connecting rods and the valve train are all in good condition.

The crosshatch in all bores is just about worn away leaving a near-mirror finish. Bore wear is about .001-in. on all cylinders. All the piston tops were wet with oil. All the rings were severely worn. The Katech guys told me that an air:fuel ratio under load which is excessively lean or excessively rich can cause that type of bore and ring failure. Poor air filtering can, also, cause that level of wear.

Combustion chambers and valve faces are wet with oil and sooty.

The Intake manifold had dirt/debris inside. The air filter had been damaged, by my blowing through it with shop air when I cleaned the filter about a month before shipping the car to Katech. In talking with them and the filter vendor, I found out doing that to oiled-cotton filters is a bad thing.

Katech uses GM's warranty benchmark for excessive oil use which, in brief, states that oil use by engines subjected to "normal" duty cycles more 2000-miles-per-quart indicates an engine mechanical problem.

My "Street Attack LS7" has 4873 miles on it since it was built by Katech in late 2017. In the first 3021 miles of operation, before I violated Katech's warranty by making calibration changes in early January, the engine used two quarts of oil. From then on, oil use accelerated until I shipped the car back to Katech in mid-May.

In a conference call I had early last week with Katech's top managers, they were unable to explain how the oil use got started in the first 3000 miles. Katech's guys said that they have built many Street Attack engines in the last 12 years and have never had an engine with a problem like that.

The next step is for Katech to send me a quote on what's necessary to repair the engine and what it will cost to do that.

Stay tuned....
So, bottom line is that Katech is not gong to warrant the engine damage because their tune calibrations were removed and someone else's were installed?
Distilled way down...that's correct.

The "someone else" was me.

In a conference call with them week before last, I raised the issue of the engine going its first 3000 miles with their calibration and using 2-qts of oil, then suggested we split the cost of the rebuild.

They turned me down.
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Distilled way down...that's correct.

The "someone else" was me.

In a conference call with them week before last, I raised the issue of the engine going its first 3000 miles with their calibration and using 2-qts of oil, then suggested we split the cost of the rebuild.

They said they turned me down.

Yeah, OEM's would have probably done that also.

The cat's melting substrate makes sense for a lean condition, but the missing crosshatch is a little fuzzier...............
I'm curious as to why you changed the tune parameters? Were you aware that would be warranty problem? I have been thinking about having Katech do some work on my car..... but am rethinking that now. Clearly they screwed something up on the initial build.
When I began changing calibration, I was unaware of the language in Katech's warranty which prohibited that. After I had already made changes, I became aware of it but the "damage" was done and the warranty was void.

I began changing the calibration because, as calibrated, the car would not pass a state emissions test and it had driveability problems. Eventually, I had the cal such that most of the driveability problems were solved and the car would pass the state emissions test.

My first mistake was not returning the car to Katech early-on when I determined the oil use was about 1-qt. per 1500 miles. Initially, I thought the problem was with PCV and crankcase venting which I figured I could fix myself. The second mistake was not borescoping the engine at the point. Had I done that, I may have detected developing problems with cylinder walls and, knowing about that, would have disproved the idea there was a PCV problem and pointed at a wall/ring wear issue.

The latest report from Katech is they received my deposit check and are starting the rebuild. I suspect I'll have the car back in early October.
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Hurrah and yippee. The Bullet is back home again in California (to paraphrase Indiana). I sucked in a few cubes of air when I read that you had used over a quart of oil in that leg. Glad to hear it leveled our. Just break in period I presume? Question, did you get a new warranty with the rebuild? Keep us all updated on future performance and reliability.
Back from Katech, Again. Second Time a Charm?
For the last three months there hasn't been any Blue Bullet blogging because the car was at Katech a lot longer than expected. Last summer, after they pulled the motor out of the car and tore it down, Katech decided to set the rebuild aside while they embarked upon a program which researched improvement of oil consumption of their "Street Attack LS7" engine packages. To do this they built an in-house test engine and tried different cylinder wall preparations, different pistons, different piston-to-bore dimensions and different oil ring tensions to see what affect those changes might have on oil use. Compared to how they have done Street Attack LS7s in the past, They settled these four updates for my engine:

1) Pistons made of 4032 forged aluminum rather than 2618 forged aluminum.
2) Different cylinder wall finish
3) Revised piston-to-bore clearance
4) Higher oil ring tension

In late September, they emailed me saying the engine would be done at the end of October, so I got on the Southwest Airlines site and booked a one-way ticket to Detroit Metro. On 30 October, I caught a Jet to Detroit and got a room in Clinton Township, right near Katech. The next day, I went over to Pontiac to do lunch with Tom Read, the media contact at GM Global Propulsion Systems to discuss some future writing work I may do on the 8L90 eight-speed automatic transmission. After that, it was over to Katech to pick up my long lost Blue Bullet. Then, I returned my Hertz car and retired to my hotel with a take out burger and fries from Mickey Ds. Munching on a Quarterpounder, I sat at the desk reading tomorrow's weather forecast on my laptop.

On the Road, Again
The trip back to California would start the next day with a run south to Cape Girardeau, Missouri to take care of some business relating to the 2019 National Corvette Caravan. Cape. G is on the Mississippi in the southeast corner of the state. I would drive southwest from Clinton Twp. to Indianapolis to pick up Southwest Caravan Section Captain, Tony Megowan. He and I would continue on to Cape Girardeau where, the following morning, we'd meet with members of Corvettes of Southeastern Missouri and the staff of the Cape Girardeau Convention and Visitors Bureau. Those folks are planning an event on the sixth and last night of the trip for Caravaners in four Sections: our Southwest along with the Pacific Central, Oklahoma/Texas Pan Handle and Kansas/Missouri.

It rained for almost the entire drive down to Cape G. Fortunately, "real" winter weather had yet to arrive in the upper mid-west, so while we got wet, there was no snow or freezing temperatures. The Blue Bullet is a '12 ZO6 w. the ZO7 performance package which normally has the car on Michelin Cup tires, which are ultra-performance, "almost race tires" with limited rain grooves, reduced tread depth and a soft tread compound. Because Caravans and their pre-run trips can require driving in bad weather, about a year ago, Michelin supplied the Southwest Caravan Organizing Team with a set of Michelin Pilot Super Sport tires to put on my car. PSSes have full-tread-depth with a tread configuration much better suited for wet weather driving. We'll, also, use Pilot Super Sports for the Caravan next year.

The following day, after our morning meeting, we began "PreRun4", a recon trip over five days worth of the seven-day route the Southwest Section would take in 2019, but going in the opposite direction. From Cape G., we headed back north to Kansas City, Missouri for a meeting the next day with people at the National Airline History Museum. The Southwest and Pacific Central Sections will come to the Museum for a catered, sit-down dinner on the fifth night of the Caravan. Following that will be a presentation about the Museum's Lockheed Super Constellation, a long-haul, airliner which first flew in 1956 and was the state-of-the art at the end of the propeller-driven era when air travel was a more unique experience than it is, today.

Tony Megowan and the Airline History Museum Events Director,
Hillary Dunnegan, discuss the Caravan in front of the Museum's Connie

On Sunday morning, 4 November, we scouted a large large parking area near our hotel to use for Caravan Departure. After that, we bid farewell to K.C. and were rolling west on I-70 headed for Colby, Kansas to try out a hotel the Southwest Section will use on Night Four of the Caravan and to inspect a departure point at a nearby Walmart parking lot.

Mountain Snows
On Monday, the plan was to drive to Grand Junction, Colorado to both try out one of the hotels and look for a departure point. This part of PreRun4 was an adventure as we crossed the Rocky Mountains on Interstate 70 in a snow storm. The weather around the Eisenhower/Johnson Tunnel and Vail Pass was forecast to be: snow showers with up to half-an-inch accumulation and temperatures in the low-30s. I knew, once we got as far west as Aspen, the snow would stop and the weather for the rest of that day's run would be ok. I, also, knew the Blue Bullet, with its Pilot Super Sports, would be fine driving through snow showers as long as we traveled at a safe speed and the snow turned to slush once it stuck. Since it was not supposed to go below 30°, I didn't think ice would be a problem because the road stays warmer than the air. Not wanting to use two days to detour south into New Mexico and Arizona, I decided before we left Colby Monday morning to trust the "weather guessers" and stick to the Caravan route, going right up I-70 through whatever show showers we found.

Just east of the entrance to the Eisenhower/Johnson Tunnel
Now we're parked just past the west-bound exit from the Tunnel and, baby, it's cold outside.

The forecast was spot on. As we approached the Eisenhower/Johnson Tunnel, it began to snow and when we came out on the west end of the tunnel, there was definitely a show shower, but it was slushy on the ground and there was no ice. We drove through the snow shower to Vail where we got gas. As we continued west, snowfall lessened and once we got to Aspen, it stopped.

In Grand Junction, after 1951 miles, I checked the oil for the first time. I added 1.5-qts of Mobil 1 5W30, the oil Katech put in the engine. The engine had averaged 1300 miles per quart which didn't make me very happy as it was actually worse oil use than the same trip almost a year before after the original Katech build, but...there would be better news when I checked the oil, again, at the end of the trip.

Utah Eye Candy
On Wednesday, 7 Nov., after the "PreRun4 snow adventure" the previous day, we crossed the high desert of eastern Utah on I-70. I've been over this route three times since 2016 on Caravan pre runs and, prior to that, almost a dozen times, but I can never get enough of the exceptionally beautiful, 105-mile stretch of highway between Green River and Salina Utah. Caravaners are going to love this part of the trip, not only for the fantastic eye candy but, also, for the 80-mph speed limit the State of Utah has on most of I-70 from the Utah/Colorado line to where it ends at I-15 about 25 miles north of Beaver, Utah and then continuing on I-15 most of the way to St. George.
Not many parts of the Interstate Highway
system have 80-mph speed limits.
All along the 105-mile stretch between Green River
and Salina are Utah Highway Dept. rest stops and
everyone has beautiful scenery.
I-40 in east-central Utah has some pretty
deserted stretches of road good for driving
a Corvette the way Zora intended.

We overnighted in Henderson NV and on the last day on the trip we drove to Tony's place in Ventura, where I dropped him and then I made run north on US 101 to Goleta. After 2866-mile trip home was over, I checked the oil. The oil level was the same as it was after I added oil in Grand Junction two days before so, on the final 915-miles the engine used no oil and its average oil use for the trip was a little under a quart every 2000 miles–definitely an improvement.

More Testing Needed
At this point, the oil consumption of my rebuilt Katech Street Attack LS7 is better than before. Interestingly enough, according to data the Katech people supplied me back on 31 OCT when I picked-up the car, the engine is, also, making a little more power, surprising since the changes made to improve oil consumption sometimes cause slight friction increases which costs a little power. On Katech's engine dynamometer, the Blue Bullet's Street Attack LS7 made 614-hp@6900-rpm SAE corrected, about 15-hp more than the same engine produced after the original build up.

I have another about 1000 street miles to put on the car before I can establish a good number for oil use going forward.
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Just posted some new imagery from the last road trip.
Today, I have good news and bad news to report.

The good news is that, now that I've got nearly 4100 miles on my rebuilt Katech Street Attack LS7, I'm starting to hammer it andthat motor is bad-assat wide-open-throttle.

It pulls hard to the rev limiter with little or no knock retard which is amazing considering my testing was on 91-oct fuel, at sea level with a 66° IAT. Injector duty cycle peaked at 92-95% at 6800-RPM. I'm ok with that, now, but if I were to start tracking the car a lot, I'd need an injector change. After the original build, the engine was ingesting a lot of oil and there was a lot of KR as a result of oil's very low octane.

Here's a link to what I saw behind me once I had 3000 miles on the original build. The footage was shot one year ago on 14JAN2018, before I started screwing with WOT fuel and spark.

Pretty ugly, huh.

The good news–no, actually it's greatnews–is with the rebuild, there is no oil smoke at any rpm under high load..nada, zilch. Whatever Katech did differently during the rebuild solved that problem. My compliments to Dean at Katech who assembled the engine.

The bad news is that when I pulled the throttle body, I found some oil inside the intake manifold. Rather than removing the intake to drain it which is a lot of work, I decided to jack the back of the car way up high, set it on my tallest jack stands and let whatever oil was in the manifold drain to the front of the manifold where I placed several lintless paper towels to absorb the drain oil.

Steve Spurr, Katech's President and Jason Harding and I did a conference call last week. They asked me: 1) to continue the oil use test using Mobil 1 5W30 for another 1000 mies, 2) before doing that, remove the TB, again, and try and "soak up" as much oil from inside the manifold as I can, 3) use a revised oil level of between the bottom mark and the middle mark on the dip stick and 4) not install a catch can, yet. All of these are reasonable requests with which I'll comply, but on #2, I think a better solution is to just pull the manifold and drain it. I'm, also, going to delay installation of a set of JoshB mufflers and my Zip Products Mamba air filter assembly.

During the conference call, we had a discussion about my calibration changes to idle speed, idle spark advance and adaptive idle spark timing. Steve Spurr was disappointed that I had violated our agreement that I would not change anything in the engine's cal. My position was: 1) that agreement applied only to the first 4000 miles of oil use testing and 2) since the only changes were to idle speed, idle spark and adaptive spark and the engine spends so little time at idle, changes to idle calibration have no practical effect on oil consumption.

The last piece of news is, now that I've got 4100 miles on the engine, I'm going to schedule chassis dyno time at my normal test venue, Westech Performance Group in Mira Loma, California. I'll post the results after I run on Westech's dyno.
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How much oil has been used in your 4100 miles?

Oil inside a dry fed intake manifold is not uncommon as there is no fuel to flush/clean it out. I see it all the time.
The last time I checked the oil, was at 4046 miles and the engine had used 3.5-qt. of M1 5W30.
My oil use testing is still going on, but only kinda-sorta as I have not driven the car much in the last six weeks or so due to 1) weather–I have Cup tires back on the car which are not good in the rain at all and, in California, we've had lots of rain so far this Winter and 2) too busy to take a 1000-mile trip. Hopefully, those situations are going to change in the next 30 days.

In the meantime, I found some used parts at a good price: a set of Katech carbon fiber rocker covers and a pair of "JoshB Mufflers". The CF rocker covers are super light and look absolutely cool as hell. Like other Katech rocker covers they come with the necessary rails to mount coil relocation brackets. The CF rocker covers look great with my MSD intake manifold and MSD ignition coils. Elsewhere on the CAC are product evaluations of both the manifold and the coils.



The mufflers are modified by Corvette Forum member "JoshB". Some people call this the "Muffler Mod". The executive summary is that JoshB cuts a set of stock C6 ZO6 mufflers open and replaces the internal pipes with larger diameter tubing, removes the inlet restriction and increase the outlet size on the bypass side of the muffler. Some CF members insist this is a better performance modification than some aftermarket exhaust systems because it maintains the factory exhaust bypass valves.

When I get to finally installing these mufflers, I'll do before and after chassis dyno tests to assess the performance value of those parts.

Lastly, I changes the oil filter a couple of weeks ago and at the same time took and oil sample and sent it off to Blackstone Labs. The results are attached below.

View attachment BB2LS7-190130.pdf

Let me know what you think.
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I really like the look of the intake manifold, coils, and wires, very cool.

If it makes you feel any better, I just read in Car and Driver that the flat plane crankshaft "Voodoo" engine in the Mustang is ok'd by FoMoCo to use up to 1qt every 500 miles under "severe" use. Not in my $60K Mustang it wouldn't be. But apparently Ford has stated that it is normal.
I've read/heard from several sources about Fords "VooDoo" having high coil use in severe duty, but there is one big difference between Ford's VooDoo issue and mine...my high oil use comes from the "polar opposite" duty cycle, ie: really easy duty, 98% below 3000 rpm and 99% at less than WOT.
What's the latest on the blue-bullet?
The short answer is: the car's going back to Katech for a third visit, this time at their expense. The long answer is coming soon.
The short answer is: the car's going back to Katech for a third visit, this time at their expense. The long answer is coming soon.

Are you planning to buy a C8?
No. In fact, we just took delivery of a C7 ZR-1. After studying the C8 issue, I decided that, for what we like to do with Corvettes–long road trips–the ME car would not make much sense as the rumor is that it has less room for luggage. I was able to find a dealer who'd sell one to us at sticker so we took a Museum Delivery on the Last Great Front Engine Corvette.
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By the time I had 3000 miles on the engine since the rebuild, it was obvious to me, via careful checking of oil levels using the required "LS7 procedure" (run engine until oil temp is at lest 150°F, shut the engine off, wait exactly five-minutes then check the oil) starting as soon as I left Katech with the rebuilt engine, that the engine's oil consumption was, once again, in my opinion, too high.

Katech asked me to observe the oil use checking procedure GM dealers use when dealing with a customer complaint of high oil consumption. One facet of that procedure is there must be at least 4000 miles on a "new" engine before a dealer can conduct an oil use test. Katech and I agreed that I'd continue to monitor oil use until the 5000 mile mark. Actually, I went to over 5000 miles. Oil use worsened after the first 3000 miles and continued to gradually increase until I ended the test at 5358-miles after the rebuild. I should add that in my opinion, for the near $20,000.00 one pays for a Katech engine which is broken in on an engine dyno, from "day one", its oil use in a normal street duty cycle should stabilize at a reasonable rate and do so sooner than 4000 miles.

In reality, since it was rebuilt, in 5358 miles, my Street Attack LS7 has used 7.4995-qts for an average of 714 miles per quart. In the last 764 miles of this test, it used 2 ⅛-qts or 359.5 miles per qt.

When I picked up the car after the rebuild at Katech at the end of October 2018, I promised Katech President, Steve Spurr, that I would not make any changes in calibration for the first 4000 miles. Once the rebuilt engine reached 4000 miles, I began working on idle quality, again. You have to understand that when it comes to tuning, I'm much more into idle and part-throttle drivability that are most DIY "tuners". I started with the calibration Katech put in the ECM after the rebuild, which, I might add, was better idle-wise than was the first Katech cal. The only tables I changed were idle spark advance, tables controlling adaptive spark and adaptive throttle opening, along with re-enabling DFCO. The result was a relatively smooth, 700-rpm idle...not as smooth as a stock LS7, but considering the Torquer 116 cam has a bit more overlap and 5.5° less lobe separation, the idle is pretty nice.

Other than that, I've made no changes to Katech calibration. I did install my wideband O2 sensor and ran some on-road acceleration tests (uphill, third gear, 1500-7000 rpm) which seem to indicate the engine is rich at wide-open throttle but, if that's the way Katech wants it's Street Attack LS7s calibrated, it is what it is.

While it is true that, technically, I've voided Katech's warranty, again, I'm confident that there is no freakin' way that modestly changing the tables for idle spark and adaptive idle functions would cause oil consumption to skyrocket. I defy anyone who feels otherwise to prove that it will.

I've had some PMs from other ZO6ers on the Corvette Forum about pistons which suggest maybe the type of piston, ie: Mahle forged in combination with the required piston-to-bore clearance is causing the problem. GM is using a forged Mahle piston in the ’19 ZR-1's LT5. Over 2000 ZR-1s are on the road at this point. My guess is, of the first 1500 or so, there are enough cars with 4000 or more miles on the engines that if the LT5 had an oil consumption problem because of its pistons in normal street use, we'd have known about it by now. Also, GMs Performance and Racing Center builds 5.5L V8s for Corvette Racing. The cylinder case in the 5.5 is an LS7 block and GM uses a forged piston. At LeMans in 2018, those engines used half a quart of oil in the 3000 race miles run over 24-hours in that race.

My belief is that, this time, the problem with high oil use is related to rings, ring end gap, oil drain back holes or cylinder wall preparation, but that’s just speculation on my part based on some conversations I’ve had with a friend of mine who owns an aftermarket piston company.

I just bought a Snap-On borescope and plan using this this coming weekend to see if I can get a good look at the cylinder walls.

My belief is that getting reasonable oil consumption from a Katech Street Attack LS7 is not "rocket science". Lastly, my definition of "reasonable" is half or better of the oil use a stock LS7 exhibits. When it was stock, my LS7 used a quart of oil every 8000-10,000 miles of "normal" driving, so my hope would be that a Katech Street Attack LS7 could exhibit oil consumption of 4000-5000-miles per quart in a "normal driving" duty cycle.

Katech is aware that the rebuild’s oil use is just about as bad as that of the original build. This time, Katech has agreed to pay to ship the car back to them, again, and further, has agreed to cover the cost of a second rebuild. There is a thread on the CF about all of this which has more detail.

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