header question gs300
06-30-16, 09:40 AM
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header question gs300
hello everyone so this is my second post on CL , just bought a 1998 gs300 almost a year ago. i wasnt planning on doing anything to the motor other than cosmetics but unfortunately i got a CEL a few days ago. i rang in code that my cat (bay 1) went bad. checked it out with my mechanic and said it was a bad cat that had to be replaced. not knowing since this is my first lexus that the header and cat were all one piece. ive done some research and saw most cats are 400 or more. i saw the company obx produced a "race" header for our cars only problem is that no one has it not even obx it self all the companies i ordered from refunded me for my purchase. the only other cheaper replacement is pacesetter from jegs. if anyone can guide me to a good site to find the obx ones pls let me know or what you would do in this situation. i tried the marketplace with no luck. thanks again 
06-30-16, 11:32 AM
#2
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Welcome to the forum!
A money-saving tip for buying exhaust manifolds... Buy an IS exhaust manifold! The 98-05 GS300 and 01-05 IS300 share the same exhaust manifold from the factory. Aftermarket IS300 headers are around $150, and I have the "OBX-style" headers on my GS300. I bought mine on eBay. If I were you, I'd just find a shop through google if I could.
The header I bought had the lovely Chinese welding teqnique... MIG weld everything, grind down the welds and TIG over them so they looks nice, and then polish the piece up. It doesn't look top or anything but does the job.
I've run into 0 problems so far. No leaks, no heat issues, and no modification needed to fit the headers.
A word of caution, though. If you will be installing them yourself, have at least one buddy help you out. Oh, and there is an exhaust mount/hanger of sorts that connects to the transmission housing that might cause issues while you remove and install headers. Remove the mount and it makes things a little easier. Consider buying new OEM (or better) exhaust gaskets. The ones that may come with headers you purchase might be of questionable functional value.
A money-saving tip for buying exhaust manifolds... Buy an IS exhaust manifold! The 98-05 GS300 and 01-05 IS300 share the same exhaust manifold from the factory. Aftermarket IS300 headers are around $150, and I have the "OBX-style" headers on my GS300. I bought mine on eBay. If I were you, I'd just find a shop through google if I could.
The header I bought had the lovely Chinese welding teqnique... MIG weld everything, grind down the welds and TIG over them so they looks nice, and then polish the piece up. It doesn't look top or anything but does the job.
I've run into 0 problems so far. No leaks, no heat issues, and no modification needed to fit the headers.
A word of caution, though. If you will be installing them yourself, have at least one buddy help you out. Oh, and there is an exhaust mount/hanger of sorts that connects to the transmission housing that might cause issues while you remove and install headers. Remove the mount and it makes things a little easier. Consider buying new OEM (or better) exhaust gaskets. The ones that may come with headers you purchase might be of questionable functional value.
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QLex300 (09-06-22)
06-30-16, 10:03 PM
#3
Carlos,
I do not want to contradict crunchee, but this was my experience. Check this thread.
https://www.clublexus.com/forums/gs-...00-header.html
I do not want to contradict crunchee, but this was my experience. Check this thread.
https://www.clublexus.com/forums/gs-...00-header.html
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QLex300 (09-06-22)
06-30-16, 11:12 PM
#4
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Thanks for the addition Mcon!
I will add that I am running fleaBay headers with a Megan gs300 downpipe, and I have noticed that the exhaust is a little passenger side biased if you will. Enough so that the resonators are actually shifted an inch to the passenger side. Other than that - no catalytic converters, no complaints. It looks OEM.
The IS300 mid-pipe WILL NOT fit the GS300 as an OEM replacement without exhaust work. The IS300 mid-pipe is shorter than the GS300 one.
I'm planning on ditching the OEM resonators and mufflers for a single pipe exhaust from the mid-pipe back. Without cats, mufflers, and resonators, my friend could hear me do a pull from 4 urban miles away. I would not recommend that kind of set up.
I will add that I am running fleaBay headers with a Megan gs300 downpipe, and I have noticed that the exhaust is a little passenger side biased if you will. Enough so that the resonators are actually shifted an inch to the passenger side. Other than that - no catalytic converters, no complaints. It looks OEM.
The IS300 mid-pipe WILL NOT fit the GS300 as an OEM replacement without exhaust work. The IS300 mid-pipe is shorter than the GS300 one.
I'm planning on ditching the OEM resonators and mufflers for a single pipe exhaust from the mid-pipe back. Without cats, mufflers, and resonators, my friend could hear me do a pull from 4 urban miles away. I would not recommend that kind of set up.
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QLex300 (09-06-22)
07-01-16, 01:15 PM
#6
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Yes there is a CEL, because the catalytic converters are removed with OBX and similar headers. You will need O2 Sensor simulators of some sort if you can't live with a CEL. The car does not suffer from any issues and runs normally without catalytic converters, even with the CEL for cat inefficiency.
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QLex300 (09-06-22)
09-06-22, 02:36 AM
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Welcome to the forum!
A money-saving tip for buying exhaust manifolds... Buy an IS exhaust manifold! The 98-05 GS300 and 01-05 IS300 share the same exhaust manifold from the factory. Aftermarket IS300 headers are around $150, and I have the "OBX-style" headers on my GS300. I bought mine on eBay. If I were you, I'd just find a shop through google if I could.
The header I bought had the lovely Chinese welding teqnique... MIG weld everything, grind down the welds and TIG over them so they looks nice, and then polish the piece up. It doesn't look top or anything but does the job.
I've run into 0 problems so far. No leaks, no heat issues, and no modification needed to fit the headers.
A word of caution, though. If you will be installing them yourself, have at least one buddy help you out. Oh, and there is an exhaust mount/hanger of sorts that connects to the transmission housing that might cause issues while you remove and install headers. Remove the mount and it makes things a little easier. Consider buying new OEM (or better) exhaust gaskets. The ones that may come with headers you purchase might be of questionable functional value.
A money-saving tip for buying exhaust manifolds... Buy an IS exhaust manifold! The 98-05 GS300 and 01-05 IS300 share the same exhaust manifold from the factory. Aftermarket IS300 headers are around $150, and I have the "OBX-style" headers on my GS300. I bought mine on eBay. If I were you, I'd just find a shop through google if I could.
The header I bought had the lovely Chinese welding teqnique... MIG weld everything, grind down the welds and TIG over them so they looks nice, and then polish the piece up. It doesn't look top or anything but does the job.
I've run into 0 problems so far. No leaks, no heat issues, and no modification needed to fit the headers.
A word of caution, though. If you will be installing them yourself, have at least one buddy help you out. Oh, and there is an exhaust mount/hanger of sorts that connects to the transmission housing that might cause issues while you remove and install headers. Remove the mount and it makes things a little easier. Consider buying new OEM (or better) exhaust gaskets. The ones that may come with headers you purchase might be of questionable functional value.
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