CarlC
07-02-2022, 11:41 PM
Going back to One Lap of America 2018, after our day in St. Louis doing drag racing, something did not seem the same with the clutch. It seemed to work fine, but occasionally it was difficult to shift into reverse. It did not get worse, and since the engine must be removed to get the T56 Magnum/bellhousing out, I just let ‘er ride with the understanding that the pilot bearing was a likely suspect.
Fast forward to the Goodguys Hall of Fame Road Tour last September. Hauling a$$ through Texas late at night, go to downshift, and the clutch is ineffective. Get the car to the side of the road, shut down the engine, and pump the clutch a few times. The clutch is working again, but for sure the pilot bearing has been lunched. The car made it home, another 800+ miles, while babying the transmission.
So, what was supposed to be a pilot bearing change turned into a complete drivetrain refresh and upgrade.
Exhaust:
Before tearing into the driveline, one of the big ticket items that needed to be addressed is the exhaust system. It had became progressively louder, and after 21hrs almost continuously driving from Ft. Worth to Los Angeles, annoying. The car has seen many different setups, and unfortunately, failures. The system that was most recently in the car contained the following:
Stainless Works 1-3/4” long tube headers (repaired in late 2018 due to tube-to-head-flange cracking)
Flowmaster 3” ball/socket.
3” flex joints
Exhaust hanger support from the transmission mount
Magnaflow “X” pipe
3” pipes to 18” x 9” Magnaflow mufflers.
3” tailpipes exiting behind the rear tires.
All ceramic coated
The prior system had a 3” Dr. Gas “X” pipe, 3” tubes into reducers that fed 18” x 9” Magnaflow mufflers. No ceramic coatings.
To my disappointment, each of these failed, IMO, miserably. The Dr. Gas part cracked, as did the Magnaflow X-pipe. The back caps of both sets of mufflers cracked most of the way around the perimeter weld and were missing nearly all of the noise absorption material.
Both muffler aft end caps have cracks most of the way around:
https://j.hmjimg.com/2022/07/02/Crack.jpg
X-Pipe has an axial crack on both sides. There are flex joints ahead of the X and it is supported by the rubber hanger.
https://j.hmjimg.com/2022/07/02/Crack-2.md.jpg (https://hostmyjunk.com/image/MVGr4)
It's not known how much packing was originally there, but it seems pretty light with lots of open perforations. The prior set of Magnaflows were the same way when they came out:
https://j.hmjimg.com/2022/07/02/20220216_153110.md.jpg (https://hostmyjunk.com/image/MVXk5)
Time for something new.
With the understanding that supercharging is just hard on things, and that the OEM’s have spent billions on exhaust systems that have to survive extended warranty times, I turned to a few folks way smarter than I and with really good data on said topics and came up with a plan to address not just the noise, but also the associated NVH and hydrocarbons that go along with it. Oh, and all while maintaining performance.
The new setup:
LS7 Z28 1-3/4” tubular tri-Y shorty headers, including the OEM heat shields.
All four catalytic converters from a 1k mile 2021 ZL1. I'll trust OEM validated 650hp rated parts vs. anything in the aftermarket.
2-1/2" flex joints
2-1/2” stainless exhaust, HD H-pipe, feeding big 18” x 9” stainless steel mufflers.
Full tailpipes exiting out under the rear bumper.
With said headers in hand (thanks to a fellow member who had a new take-off set available), test fitment on the passenger side could not have been any easier. It dropped in from the top without issue, the heat shields bolted on, and stock ACDELCO spark plug wires and aluminum shields went on just like OEM.
https://j.hmjimg.com/2022/07/02/20220618_112231.md.jpg (https://hostmyjunk.com/image/MVZvS)
The drivers side did need a bit of persuasion. Several sections near the steering box needed to be slightly adjusted in a hydraulic press. It took about an hour to get sufficient clearance for the tubes, but not all of the heat shields were going to fit. The top portion is fine, but the lower part had to be sectioned into two pieces. The heat shields are so effective that at full temperature I can place the back of my finger 1/4" away with complete comfort.
https://j.hmjimg.com/2022/07/03/20211211_145230.md.jpg (https://hostmyjunk.com/image/MVS1Z)
https://j.hmjimg.com/2022/07/03/20220618_112243.md.jpg (https://hostmyjunk.com/image/MVhud)
Since the LT4 that the cats came from have a different flange size and location, hacking began in earnest to make all four line up, clear the floor, bellhousing, crossmember, etc. Since the LT4 has a dedicated primary cat support structure that attaches to the driveline, I tried to mimic that by adding supports from the large tabs on the sides of the T56 Magnum. The idea is to relieve bending stresses caused by unsupported lengths of heavy components (cats). Here’s what the nearly finished system looks like:
https://j.hmjimg.com/2022/07/03/20220202_170046.md.jpg (https://hostmyjunk.com/image/MVu5o)
LH and RH sides.
https://j.hmjimg.com/2022/07/03/20220228_101033.md.jpg (https://hostmyjunk.com/image/MV3Ti)
https://j.hmjimg.com/2022/07/03/20220228_101026.md.jpg (https://hostmyjunk.com/image/MVVwp)
To help protect the starter an OEM LS3 starter heat shield was modified and bolted to the aluminum starter mounting plate. The heat shield is made the same way the exhaust shields are, and for the price are less expensive than many aftermarket offerings. The had to have significant "adjustments" to make work but are completely hidden from top viewing.
There’s lots of rubber hangers in the system, along with commonality of flanges. Since I’m not trusting the mufflers to last forever, they have been set up so that they can be easily removed and replaced. When the time comes, each will have a fixture made so that the mufflers and flanges can be built on the bench and easily installed.
Speaking of mufflers, after much investigation, it was decided to use parts made by AP Exhaust. Though not well known in the aftermarket world we play in, they are huge in the standard replacement world, and look remarkably similar to those used by well-known high-performance aftermarket suppliers. Best of all, $37 each from Rockauto: AP / EASTERN XS125
https://j.hmjimg.com/2022/07/03/20220228_101114.md.jpg (https://hostmyjunk.com/image/MVckR)
The common flanges used, except for the manifold/collector flange, were used to make work on the car easier. It meant increasing the size of the holes in the manifold and collector flanges to 1/2". So, lot's of new common length bolts were ordered from McMaster Carr. Skipping ahead a bit, after taking the car out for the first time with the new exhaust, after stopping an letting the car sit for a few minutes, there was a loud PING and the jingling of hardware hitting the ground. Here's the culprit from the manfold/collector flange:
https://j.hmjimg.com/2022/07/03/20220210_203438.md.jpg (https://hostmyjunk.com/image/MVgv7)
I was hopeful that the inclusion was just an anomaly, but after several more heat cycles another bolt failed, and it too had the same inclusion problem. All the bolts had to be changed to a different type to avoid getting another bad batch. Whenever somebody states you must use Grade 8 bolts for chassis work, I'd much rather choose a G5 from Aircraft Spruce than rely on these from what should be a decent supplier.
Driving impressions:
This is an apples and oranges comparison. Think Dr. Jekyll and Mr. Hyde. Plus it can be difficult to be objective. Loud exhaust systems can have a placebo affect. If it sounds loud, it must be fast. If it's quiet, it must be holding back lots of power.
The new version does have a nice mellow exhaust tone at idle, but during cruise and acceleration it is a quantum leap quieter combined with a large reduction in NVH. Think of a modern OEM supercharged car with a stock-ish exhaust. Now I can hear the supercharger whine.
Changing the exhaust has become a good, but challenging, exercise. Good because of the noise and smell reduction, but loud exhaust systems mask other noises. Little noises not heard before now become the task of the day.
From a performance perspective, a back-to-back dynamometer test was not done. My seat-of-the-pants / known traction limits under acceleration/etc. tells me it’s still silly fast. Since it's so much quieter, I have to be careful when applying lots of power since the speedometer is racing upward at a furious pace.
Overall, the change is so far to the good that another set of new LS7 manifolds was purchased, and I’m on the hunt for another set of cats, all for spares/future projects.
Up next: Gears, clutch, and transmission alignment.
Fast forward to the Goodguys Hall of Fame Road Tour last September. Hauling a$$ through Texas late at night, go to downshift, and the clutch is ineffective. Get the car to the side of the road, shut down the engine, and pump the clutch a few times. The clutch is working again, but for sure the pilot bearing has been lunched. The car made it home, another 800+ miles, while babying the transmission.
So, what was supposed to be a pilot bearing change turned into a complete drivetrain refresh and upgrade.
Exhaust:
Before tearing into the driveline, one of the big ticket items that needed to be addressed is the exhaust system. It had became progressively louder, and after 21hrs almost continuously driving from Ft. Worth to Los Angeles, annoying. The car has seen many different setups, and unfortunately, failures. The system that was most recently in the car contained the following:
Stainless Works 1-3/4” long tube headers (repaired in late 2018 due to tube-to-head-flange cracking)
Flowmaster 3” ball/socket.
3” flex joints
Exhaust hanger support from the transmission mount
Magnaflow “X” pipe
3” pipes to 18” x 9” Magnaflow mufflers.
3” tailpipes exiting behind the rear tires.
All ceramic coated
The prior system had a 3” Dr. Gas “X” pipe, 3” tubes into reducers that fed 18” x 9” Magnaflow mufflers. No ceramic coatings.
To my disappointment, each of these failed, IMO, miserably. The Dr. Gas part cracked, as did the Magnaflow X-pipe. The back caps of both sets of mufflers cracked most of the way around the perimeter weld and were missing nearly all of the noise absorption material.
Both muffler aft end caps have cracks most of the way around:
https://j.hmjimg.com/2022/07/02/Crack.jpg
X-Pipe has an axial crack on both sides. There are flex joints ahead of the X and it is supported by the rubber hanger.
https://j.hmjimg.com/2022/07/02/Crack-2.md.jpg (https://hostmyjunk.com/image/MVGr4)
It's not known how much packing was originally there, but it seems pretty light with lots of open perforations. The prior set of Magnaflows were the same way when they came out:
https://j.hmjimg.com/2022/07/02/20220216_153110.md.jpg (https://hostmyjunk.com/image/MVXk5)
Time for something new.
With the understanding that supercharging is just hard on things, and that the OEM’s have spent billions on exhaust systems that have to survive extended warranty times, I turned to a few folks way smarter than I and with really good data on said topics and came up with a plan to address not just the noise, but also the associated NVH and hydrocarbons that go along with it. Oh, and all while maintaining performance.
The new setup:
LS7 Z28 1-3/4” tubular tri-Y shorty headers, including the OEM heat shields.
All four catalytic converters from a 1k mile 2021 ZL1. I'll trust OEM validated 650hp rated parts vs. anything in the aftermarket.
2-1/2" flex joints
2-1/2” stainless exhaust, HD H-pipe, feeding big 18” x 9” stainless steel mufflers.
Full tailpipes exiting out under the rear bumper.
With said headers in hand (thanks to a fellow member who had a new take-off set available), test fitment on the passenger side could not have been any easier. It dropped in from the top without issue, the heat shields bolted on, and stock ACDELCO spark plug wires and aluminum shields went on just like OEM.
https://j.hmjimg.com/2022/07/02/20220618_112231.md.jpg (https://hostmyjunk.com/image/MVZvS)
The drivers side did need a bit of persuasion. Several sections near the steering box needed to be slightly adjusted in a hydraulic press. It took about an hour to get sufficient clearance for the tubes, but not all of the heat shields were going to fit. The top portion is fine, but the lower part had to be sectioned into two pieces. The heat shields are so effective that at full temperature I can place the back of my finger 1/4" away with complete comfort.
https://j.hmjimg.com/2022/07/03/20211211_145230.md.jpg (https://hostmyjunk.com/image/MVS1Z)
https://j.hmjimg.com/2022/07/03/20220618_112243.md.jpg (https://hostmyjunk.com/image/MVhud)
Since the LT4 that the cats came from have a different flange size and location, hacking began in earnest to make all four line up, clear the floor, bellhousing, crossmember, etc. Since the LT4 has a dedicated primary cat support structure that attaches to the driveline, I tried to mimic that by adding supports from the large tabs on the sides of the T56 Magnum. The idea is to relieve bending stresses caused by unsupported lengths of heavy components (cats). Here’s what the nearly finished system looks like:
https://j.hmjimg.com/2022/07/03/20220202_170046.md.jpg (https://hostmyjunk.com/image/MVu5o)
LH and RH sides.
https://j.hmjimg.com/2022/07/03/20220228_101033.md.jpg (https://hostmyjunk.com/image/MV3Ti)
https://j.hmjimg.com/2022/07/03/20220228_101026.md.jpg (https://hostmyjunk.com/image/MVVwp)
To help protect the starter an OEM LS3 starter heat shield was modified and bolted to the aluminum starter mounting plate. The heat shield is made the same way the exhaust shields are, and for the price are less expensive than many aftermarket offerings. The had to have significant "adjustments" to make work but are completely hidden from top viewing.
There’s lots of rubber hangers in the system, along with commonality of flanges. Since I’m not trusting the mufflers to last forever, they have been set up so that they can be easily removed and replaced. When the time comes, each will have a fixture made so that the mufflers and flanges can be built on the bench and easily installed.
Speaking of mufflers, after much investigation, it was decided to use parts made by AP Exhaust. Though not well known in the aftermarket world we play in, they are huge in the standard replacement world, and look remarkably similar to those used by well-known high-performance aftermarket suppliers. Best of all, $37 each from Rockauto: AP / EASTERN XS125
https://j.hmjimg.com/2022/07/03/20220228_101114.md.jpg (https://hostmyjunk.com/image/MVckR)
The common flanges used, except for the manifold/collector flange, were used to make work on the car easier. It meant increasing the size of the holes in the manifold and collector flanges to 1/2". So, lot's of new common length bolts were ordered from McMaster Carr. Skipping ahead a bit, after taking the car out for the first time with the new exhaust, after stopping an letting the car sit for a few minutes, there was a loud PING and the jingling of hardware hitting the ground. Here's the culprit from the manfold/collector flange:
https://j.hmjimg.com/2022/07/03/20220210_203438.md.jpg (https://hostmyjunk.com/image/MVgv7)
I was hopeful that the inclusion was just an anomaly, but after several more heat cycles another bolt failed, and it too had the same inclusion problem. All the bolts had to be changed to a different type to avoid getting another bad batch. Whenever somebody states you must use Grade 8 bolts for chassis work, I'd much rather choose a G5 from Aircraft Spruce than rely on these from what should be a decent supplier.
Driving impressions:
This is an apples and oranges comparison. Think Dr. Jekyll and Mr. Hyde. Plus it can be difficult to be objective. Loud exhaust systems can have a placebo affect. If it sounds loud, it must be fast. If it's quiet, it must be holding back lots of power.
The new version does have a nice mellow exhaust tone at idle, but during cruise and acceleration it is a quantum leap quieter combined with a large reduction in NVH. Think of a modern OEM supercharged car with a stock-ish exhaust. Now I can hear the supercharger whine.
Changing the exhaust has become a good, but challenging, exercise. Good because of the noise and smell reduction, but loud exhaust systems mask other noises. Little noises not heard before now become the task of the day.
From a performance perspective, a back-to-back dynamometer test was not done. My seat-of-the-pants / known traction limits under acceleration/etc. tells me it’s still silly fast. Since it's so much quieter, I have to be careful when applying lots of power since the speedometer is racing upward at a furious pace.
Overall, the change is so far to the good that another set of new LS7 manifolds was purchased, and I’m on the hunt for another set of cats, all for spares/future projects.
Up next: Gears, clutch, and transmission alignment.