Anyone want to build a downpipe?

I will be going down to Sarasota on Sunday to talk to Jay(Turbomotion) about a few things, and am going to suggest this to him.
I think the biggest problem here is welding the steel tubing to the modified cast iron elbow. It might last a little while.
i've consitered trying to build a three inch d/p for the hotairs that use external wastegate like my hooker pipe for my i/c motor but in 3 inch.

heres the thing how many like that idea and would you even care if it was mild steel so that cost would stay down some?

it will be alil while (after i finish putting my i/c motor in) but i would put my hotair motor on another car i have with no front clip so i would have room for fitting the pipe under the ac box.

sounds like a winter project to me
dont get too excited but let me know you'lls thoughts on that

Thats putting a lot of pipe in a small area. You might be better off with a 2-3/4". Just a thought.
MIB is right...a 3" DP is about too big for the space that it has to fit into...I've got, as far as I know, about the only TH-style 3" DP made, and it is a tight fit...With the motor in the car, you have to remove the passenger side header to install the DP, then put the header back on...A royal PITA tightening the header bolts back up...Not only that, it's a 2 piece, and getting the top half and the bottom half to seal up and not leak is another PITA...There is no way to make it a 1-piece DP and be able to install it with the motor in the car...And then changing spark plugs??? Forget it if the engine is hot...There isn't enough room to even get your hand down there to pull the spark plug boot off(barely, I've got small hands)...

A 2 3/4" DP would probably fit a lot better...I've also had problems with my 3" DP hitting the upper control arm and also coming close to the frame rail...

Just my .02 worth...
I've got Lee Thompson's 3" DP that eliminates the elbow. Once the stocker is out it's a 30min install max. It couldn't be easer. There's a ton of clearance. I had to modify mine to clear the dual stage headers so I had to cut the inner fenderwell a little. IMO there's plenty of room for a 3" DP but it has to be a 3 peice or it will be nearly impossible to install. Remember, I have dual stage headers which take up a ton of space so I think this thing would be even easier with stock style headers.
I'm making one...... BUT

I am planning on making a new downpipe for the car that replaces the elbow BUT I no longer have the a/c box in the car and I will use that to my advantage while fabbing the new pipe up. Also I am using a external wastegate (Deltagate on the x-over) and again will make things simpler for me. I was also thinking about changing exhast housings completely. I am currently running a Precision .63 stock-style exh housing. I was considering moving to an on-center style housing.... I realize that this really doesn't do ya'll much good but I can say that once I get the new one on the car, the 3" Action-Fab dp I have currently on the car will become available for sale to someone.... blah blah blah....

Drew H. Carlton
'85 GN, 11.918 @ 111.6 , NO IC, NO SPRAY, DAILY DRIVER
I asked Jay today about making one. He is going to look into it, but doesn't promise anything. 2 3/4 would be find be me. I'm not hell bent on a 3 incher. Just better flow is goal.
it probly would be easier to fit the 2 3/4 than the 3 inch ....mught have to try both.

im just thinking as guys are going to the t/m kits and big turbos that their gonna want 3 inch so i'll keep it in mind and if it dont seem too bad of a job may even just do them by order say what size and if you want one piece or not.
from the looks of things im thinking a two piece should be able to go in and out with motor in place splitting it about were the uppipe bolts to the pass. side header where you could take the top half off pretty easy for getting to the valve cover or removing the engine etc..

i really dont see were it would be that hard to make it just depends on material cost to weather it would be worth doing them or not its alot more bends than a i/c car

as far as sealing the joint were the two pipes go together it would be a matter of using a thick enough flage so you wouldnt have to worry about them warping..

well i'll update people when i get the chance to do some test fitting...i may be going i/c with my car but im not giving up hope for hot-airs and while im getting my hotair motor ready to go in my 442 it gives me the chance to use the intake and turbo stuff to test fit with i have a n/a motor to use for a dummy.

Thinking outside the box...

Why not build a fender exit dump tube? One that you can block off and T into the exhaust system? Use the Terry Houston piece that connects directly to the turbo and no more elbow! Weld a length of pipe 3" or larger :) that will exit through your modified inner fender (yup... you'll have to cut something)

A purist probably won't want this... but those of you who want the max flow can definitely get it... larger than 3" if you want.

You could T in your exhaust system to the fender exit piping which could be blocked off for street usage; capping it off or perhaps using one of those manual actuated valve units you see advertised in Hot Rod Magazine from time to time (popular amongst the early rod guys).

I would think for those of you wanting maximum exhaust flow you'd give this one a thought or two. Imagine 4" I highly doubt you'll outflow that.
Re: Thinking outside the box...

Originally posted by IRaceAV6
I would think for those of you wanting maximum exhaust flow you'd give this one a thought or two. Imagine 4" I highly doubt you'll outflow that.

Psh! 4.5" will outflow that all day long :D Seriously, didn't some vendor try that a while back? I think Kenne Bell offered fender dump downpipes or some such thing. Never caught on too well, seems they melted tires or something. What we need is a way to relocate the turbo to the front (use '86+ exhaust pieces?) and route that in to a TM V2 style hot air intake. Then we can use Terry Houston downpipes, and get wicked-sweet intake flow from the TM-style intake and after-turbo throttle body. Feasible?
A 3 piece DP would probably fit pretty good...without having to remove the passenger side header...As I had said, my 2 piece, started out it's life as an Action Fab 3" DP, with the upper transformed into a TH-style piece, has a slip joint connection right about where the up-pipe bolts to the passenger side header...I tried the band clamp style of clamp and it didn't want to seal right...Right now I've got a regular u-bolt type of clamp on there and it's sealing pretty good...I know I'm going to have a problem if I ever remove it and then try to re-install it to try to get it to seal again if it will want to go back together again...I may have to get a tailpipe expander and expand it again...I will have to wait and see on that...

As for Drew's new DP, hehehe, he took the easy way out and eliminated the a/c now he can come straight out from the turbo and then follow the firewall straight down...just like Marka Gallina's setup, I believe...:cool:

Good Luck to all...I will say that the place that made mine has said that if I ever have time to take it out of the car and won't be driving it to send it back to them to see about having some patterns made up to reproduce them...BUT right now my car is my daily driver and I can't park it for the time it would take to have my car down...
ya know.. if this was going on a race only car.. you could always just have someone cut a hole in your hood and route the exhaust straight up through the hood.. your new "up pipe" would consist of a flange and a 90 degree bend about 1ft long then.... ya never know ;)
Re: Re: Thinking outside the box...

Originally posted by mike85gn

What we need is a way to relocate the turbo to the front (use '86+ exhaust pieces?) and route that in to a TM V2 style hot air intake. Then we can use Terry Houston downpipes, and get wicked-sweet intake flow from the TM-style intake and after-turbo throttle body. Feasible?

I've often thought about this.....need 86-87 accessories (turbo will be right where the alternator sits)and us hydroboost guys would have fun too (right Louie?).

Nick - you'd need one of those cool tractor flappers too......
Not feasible...

What we need is a way to relocate the turbo to the front (use '86+ exhaust pieces?) and route that in to a TM V2 style hot air intake. Then we can use Terry Houston downpipes, and get wicked-sweet intake flow from the TM-style intake and after-turbo throttle body. Feasible?

I did look at doing this... until the V2 untake is converted to the '87 style water thermostat location it isn't going to happen. You have to use the '87 Alternator bracket and this causes interference with water hose routing. I tried to overcome this issue and it can't be done with air intake hose and MAF routing.

If the V2 can be converted to the '87 style thermostat ('87 stock location) this idea would be feasible. My 3" Terry Houston downpipe is nice... Just gotta love the superior '86/'87 set up! (ooop's did I say that outloud?) hee hee
Ok, ok! Let's revise the plan then (I can just see the cost skyrocket!). So we need '86+ style accessory brackets and exhaust pieces. And an electric fan to give us some room.

Now, can we feasibly relocate the thermostat with a V2 style intake? Jay? Can we? Then we can have the turbo point either:

Down - for an intercooled setup


Up - straight into the V2-spec throttle body/intake manifold

Giving us the ability to choose what we want or upgrade later. Also, with proper thermostat relocation, wouldn't the IC guys get a boost from this style intake? What's the deal? Then we can put those sweet THDP's in there and not worry about turbo elbows and other such crap.

Although, a "race only" hood with an "up" downpipe sticking out of it would really kick ass!
I think you guys are forgetting a lot of stuff. To do what is suggested you would need to move the coilpack, buy ALL the 87 accessories and powersteering, passenger side header, DP, turbo bracket, oil feed and drain, drill a hole in the block or oil pan for the drain, wiring for the relocated alt., and other stuff.

Trust me, the LT 3" DP fits fine, there's a ton of clearance it's not even close to interfering with anything. It's a 3 peice with thick flanges, no leaks ever, took less than 30 minutes to install. The bend coming out of the turbo is gradual, not sharp and there's a ton of room. This is not a problem. The problem is getting someone to build one that will use the stock wastegate. That's the only shortcoming of this pipe. Again, clearance is not an issue with a 3" TH style pipe.
Think we strayed off topic?

I think we are not here to argue about what fits or doesn't fit, we were asked to look for a viable option to be created. At moment you are stuck with ATR's 2 1/2" when your other downpipes corrode, wear, and flake away - that will be in approx 3 to 4 years for those of you with mild steel.

Blowing the exhaust through the hood would be interesting as would be the reaction of the tech inspector checking over your car. Legal?