if you run thicker walled material for a manifold is that going to reduce the engine noise.
the cast iron is a lot thicker than the sch 10 i used for my mani. and now that the manifold
is on its pretty loud (or should i say it vibrates a lot more)
or is it reduced by making equal length runners, resonating sound waves and such.

 

You might get more "light ticking" and "static" noise with a thinner material. Who cares as long as your car is faster than the other guys.

 

well my whole dash is rattling now. and steering collumn too. its really annoying going down the freeway holding that
crap still from making all kinds of noise.

 

when does the rattle occur? tighten up your dash, it seems to be a toyota thing when they get 25+ years old :P

 

holy ---- man, shacking the dash and steering wheel? I'd check and make sure you manifold/downpipe isn't grounding out somewhere. A change in material would not EVER cause enough noise for your dash to shake

 

Did you happen to either put in a set of cusco or other engine and trans mounts at the same time as the manifold or stick it up against the steering shaft or floor? The dash in my old AE86 used to rattle like a son of a bitch and the car was generally loud as hell, but I had cusco engine mounts, a straight through exhuast, open ITBs and all the sound deadening removed from the whole car.

 

actually you know my new downpipe that i made in order to install the whole turbo system
is like less than an inch from the steering knuckle.
thats probably it. although i dont necessarily remember feeling it too much in the
steering wheel.