Just got my Downey header from the brown truck and cant wait to put it on this weekend. My cat-back is still on order and will arive later.

Does anyone have any tips on the install besides the normal stuff. Talked to a tech at the local Toy dealer and he said my exhaust manifold gasket could be resued because its almost new, is this true?

Will take and post later.

 

It's cheap insurance to get a new exhaust manifold gasket. Besides, and I could be wrong here, I think the manifold gasket has crush segments in it that once smashed when the manifold gets torqued down, stay smashed. Been a while since I had one off though.
If you don't have air injection, check the header flange for holes for air injection. If they do have the air injection holes make sure you get the air injection block plates off the stock manifold and bolt them in place. If possible, even consider taking the flange to somebody that really knows their stuff and having the holes welded shut. I've had more leaks at the air injection block plates than any other part of the header.
Probably the number one thing, make sure the bolts aren't too long! On my LC headers, the flange was thinner and the bolts bottomed out and could easily have warped the flange. One bolt actually wound up breaking
Lastly, although I don't know the exact senquence, cross torque the bolts. Don't just go down the line tightening them. If you start with a top bolt, tighten it then drop down to a bottom bolt farther down the flange. Work your way down the flange then back. That make any sense?

 

Yea I am going to get a new gasket and use alot of the copper seal. The air block off plates came with the header and will be used for now. Is the header bolted on or are there studs in the head?????

 

I have found that OEM toyota gakets work wonders. when i had an exhaust leak, i ended up using toyota gaskets and never looked back

-Casey

 

I realized later I should have made it clearer about the bolts. The headers are held in place with studs, but the block off plates will use bolts and it is the block off plate bolts that can bottom out and damage the flange. If the headers came with bolts for the plates you should be fine. If you have to reuse the bolts from the old manifold make sure they aren't too long. If they are too long, a somewhat thick stainless steel washer should be enough
You don't use any sealant on the exhaust manifold gasket. You only use the exhaust gasket itself. If you use a sealant you most likely won't get a proper seal since it is a very flat surface. Considering the incredibly high heat, the sealant probably won't stand up to it either.

 

The header came with the bolts but will check them anyway before install. So the manifold gasket goes on dry, no hi-temp sealant.

I am going to use my g-tech and do a few runs before/after the change to see what a difference it really makes and then do the same thing againg after the cat-back gets put on.

 

I would take the header down to an exhaust shop and have weld a 21/2" collector flange to the end of the header. This would make it easy to remove later down the road if you have to. You will have to take th truck back to exhast shop to other piece fitted and welded. The clamp joint's that you right now with the downey header will work just fine but will become a pain later down the road.