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Finished installation of LS430 (3UZ-FE) engine in LS400. Thus far the engine runs great and the LS400 ECU is controlling it just fine.
Installed new OEM exhaust gaskets between catalytic converters and Y-pipe, yet both flanges are leaking...
Externally the flanges appear servicable, yet the area where the gaskets nestle in the flange recess appear enlarged after cleaning old gasket material and rust. ...21 years and 175,000 miles is pretty good service life...had I not disassembled them still quiet
I can fabricate replacement flanges with undercut for OEM gaskets but why reinvent the wheel if someone already producing.
So am seeking recommendations on vendors offering quality exhaust flanges that accommodate the factory gaskets OR if anyone has a flange drawing....unable to ascertain whether undercuts the same on converter and y-pipe.
Use a aftermarket one and RTV, if you don't want to use that then replace the entire assembly or machine it flat/even again.
Careful using that ECU since it's going to likely be trimming in a lot of fuel at the higher TQ parts of the rpm range with a 3uz and may run lean without you being able to see it.
If you want to source a used, good condition and rust free y-pipe, I just wanted to share that the 95-97 Y-pipe has different flanges than the 98-00 Y-pipe.
On my 99 Y-pipe I sourced in Alabama which had less corrosion than pictured below, I used FelPro gaskets that were made in Japan and haven't had a leak since installation a year ago.
98+ flange LEFT and 95-97 flange RIGHT
98+ Y-pipe LEFT 95-97 Y-Pipe RIGHT
Use a aftermarket one and RTV, if you don't want to use that then replace the entire assembly or machine it flat/even again.
Careful using that ECU since it's going to likely be trimming in a lot of fuel at the higher TQ parts of the rpm range with a 3uz and may run lean without you being able to see it.
Recommended brand sealant?
Any P.N. on gasket?
Am comfortable with the ECU's ability to sense and adjust air/fuel mixture and timing.
Depending on author, these ECU's can adjust between 15%-25%..
Here .3 little difference or 18.307 cubic inches so should be fine.
That's engine size not output at part throttle, that value likely exceeds 15% by a large margin since engine TQ is what correlates to cylinder pressure/fuel mix ratio and at peak this may line up well with the two engines but not at other areas where you may be tending lean or too much/little spark advance.
I use felpro and permatex ultra copper RTV on everything with new hardware that is coated and I ignore rated TQ spec and tighten till the gasket is compressed fully to actually get a lasting seal that won't come back in a few years with a pinhole leak.
Are you using the 3UZ factory manifold/cats and LS400 late version Y-pipe? I'll link gasket accordingly
That's engine size not output at part throttle, that value likely exceeds 15% by a large margin since engine TQ is what correlates to cylinder pressure/fuel mix ratio and at peak this may line up well with the two engines but not at other areas where you may be tending lean or too much/little spark advance.
I use felpro and permatex ultra copper RTV on everything with new hardware that is coated and I ignore rated TQ spec and tighten till the gasket is compressed fully to actually get a lasting seal that won't come back in a few years with a pinhole leak.
Are you using the 3UZ factory manifold/cats and LS400 late version Y-pipe? I'll link gasket accordingly
Using 1999 LS400 exhaust manifolds , catalytic converters and Y pipe.
Saved the LS430 upper and lower oil pans, oil pick-up, exhaust manifolds, engine wiring harness, eight ignition coils, knock sensors and throttle body assembly...low mileage all like new.
The LS400 exhaust manifolds and heat shields were coated by Jet Hot.
This one, felpro intentionally makes their gaskets a bit thicker than stock to help correct for the issues you are seeing. The RTV will cover any other inconsistency you may have, in sure you are well aware to wire wheel everything as clean and smooth as you can since you have shown you are very capable mechanically but I figured I would just put the reminder in anyway.
05-04-20, 08:39 PM
Seeking recommendations on exhaust flanges
