After checking it out some more Im pretty sure its the manifold touching the engine mount or the manifold touching its self in a way

 

After beating in the headers more to ensure that they didnt hit the motor mounts and beating in a portion near the transmission(near that bracket I removed previously, the header was still 1/8th of an inch away from the tranny) I conclude that the noise (honestly sounds like I have a glass pack or a screaming v8 haha) the noise is either how the engine sounds with these headers, or that my muffler has seen better days and is "screaming" so to speak. Maybe I have been describing the noise wrong its not really a rattle its more of a "screaming" sound like a v8 or like your typical glass packed exhaust. If there is a way I would like to send one of you guys a video so you can hear it and get your opinion if you want to PM me.

Thanks

 

I would double check all your flanges to make sure they are tight and double check for any exhaust leaks around there. You should upload a YT video.

This is the bracket you can see under the Lexus that I am talking about around 00:40 , check that to see if the exhaust is hitting.

 

I will upload a YT video when I get a chance next, I removed that bracket and also all of the heat shielding except the ones above the mufflers, the sound seems to be coming from the engine bay near the end of the manifold. I'll check for exhaust leaks, it kinda sounds like one where the manifold meets the midpipe.

 

I am not sure if this is the issue yet, but the flange gasket on the midpipe blew out the top... I am considering just using those ring type gaskets even though the manifold doesnt have those grooves anymore.

 

The OEM doughnut exhaust gaskets works good with OEM exhaust pipes with the indents in them but for these aftermarket pipes with flat flanges, you definitely want to use flat exhaust gaskets for those. Another tip that I do for exhaust gaskets is use copper spray on both sides and that helps provide a better lasting seal.

 

The noise is still there even after replacing and fixing the exhaust leak. I am stumped on this one

 

That is a wired one. If you do not hear it under the hood my best bet is that it is under your Lexus somewhere at either end of your midpipe flanges which those bolts need to be super tight. After a few heat cycles those flange bolts need to be tightened down again.

 

It would suck to have to unwrap your headers, but maybe you cracked them somewhere during install by having them stressed by tightening while they were up against the mount. You may be hearing a screaming noise from a crack. Or maybe it was there already and the header is defective. Like where the primaries meet the collectors. They might have bad welds. You might remove it and if you could find a way to smoke it, you could see if there are holes somewhere without unwrapping it. Maybe a shop will help you tape off the ends and put a smoke machine into an o2 port.

 

By the way Shwalker07 , you seem to have gotten lucky because I got the same header you have (ordered from your link) and I definitely had to grind down the mount to fit also. However I have zero noises or issues after the install. I guess sometimes every car/part is different. I didn't have to dent the pipe, so my clearance issue wasn't as serious as Moses'.

 

That might be a possibility, thanks for the heads up. I think it could be an exhaust leak past the OEM metal gasket, and the gas being pushed past it under load is causing the rattle. Here are the videos, the noise is not as loud as in person but you can hear it.

Windows Down, noise starts around 0:11 the vibration:
Windows Up, noise starts around 0:13... :

 

My IS300 headers do not make that kind of sound. It sounds like a slight exhaust leak to me. I would double check every exhaust gasket and exhaust bolts again including the cylinder head. When you torque down the 3 bolts on the bottom flange make sure you tighten them down evenly in a few stages across all 3 bolts. The same goes for the cylinder head exhaust manifold stud nuts as there is a pattern you are suppose to go by for installing the exhaust manifold nuts and I would recommend you do that in stages also.

 

I will keep looking, I have done all of what you described 3 times now haha, I will keep you posted if I find anything. I may also undo the wrap for the slight chance the metal tie wraps are causing vibrations or something haha

 

Are you sure you are no longer wedged up against the mount or anywhere else? You can see space around it? If not you will likely not be making good contact at the head. The under side of the manifold will be held away from the mating surface and give you a leak. I'd also change the gasket if you are still using the oem. It might just be time. I did have to shave the mount down, but it took a few times of putting the header in and out and making sure when you run a nut down that it's still not touching.

Now for my thoughts. I am very happy with the upgrade. The car sounds the same as before except at WOT when it really screams. Im good with that. Idle and normal driving is just as it was before. Deep and smooth. The car is noticeably more powerful. Especially on the mid-to-high end. It really continues to pull noticeably more than it did. There are several benefits that this $100 mod does.
1: It drops weight
2: It lowers under hood temps. It removes the hottest part of the exhaust system (the cats) which happens to be right in the engine bay) and furthermore on the same side as the intake.
3: It raises horsepower and efficiency (the most obvious reason people do headers)
4: The exhaust wrap further decreases under-hood temps and more importantly, by keeping the heat in the exhaust, it increase the velocity of the gases leaving the engine, further increasing power output.
5: You will put less wear on your cats (if you need them for smog testing) meaning they will always be good when you put them back on for testing. They will now see a couple days of use every year or two instead of all year long. My car had bad cats when I got it and was lucky to locate a good used set for cheap. I have no idea many miles are on them. But they passes the sniffer and I know they are good. So it will be nice to stop using them and know I have a good set.

 

I can put my pinky under the manifold where the mount is now, and also after going through a few heat cycles the manifold bolts up properly to the block with no issues. Ill replace all the gaskets to rule that out, and go from there. Thank you