need advice on a downpipe

[toomanymodz]

I have a Terry Houston 3" downpipe with internal WG that i used on my old combo, which was mostly stock with a PT51 turbo and ported heads.

Now I'll be running a Weber stroker with fully-CNC'd GN1's and a fully-CNC'd Champion intake, roller cam (218/212) and a 6765 billet wheel turbo, journal bearing.

First question is: should i stick with a 3" downpipe or go for a 3.5"

Final question is: should i go external wastegate.

I'll be running around 20psi on the street, and may turn it up to around 22-23 at the track. I expect high 10's on pump gas and low 10's on race gas. Thanks.

 

[machinegun]

Your 3" pipe will be just fine. Keep it and use the money on something else.

 

[Hartline Perf.]

I agree your 3" downpipe will be fine.
But for Better Boost Control, I recommend RJC Larger Puck or External Waste Gate.

 

[toomanymodz]

Well, my TH has two issues. First, someone clamped it too tight at the bottom and now I cannot separate the downpipe from the dump pipe. Second, there was an exhaust leak which grooved the surface, so I'd have to have a machinist resurface it where it meets the turbo.

If I have to fork out the funds for a new one, I may as well go with an external WG. This is my thought anyway. they are about the same cost, or close enough, and I'd hate to discover that the internal doesn't quite control the boost good enough. Good to know that the 3" is sufficient, since the fit is tight and a 3.5 would be even tighter. Next is the challenge of finding a good one. I called Cotton's and their pipe w/External WG uses V-Bands, even though it doesn't show it on their website. I want the bolt-on style. This one from full-throttle looks like the WG bolts on, but the pic is rather small. FULL THROTTLE SPEED - - 3" Down Pipe with a 46mm Wastegate

And this one from TRCustom looks really nice:
DOWNPIPES 3" STAINLESS

I'll have to make some phone calls and see who has any in stock. Seems like everything is back-ordered these days.

 

[84BuickGNYorkPA]

I would also consider RJC down pipe if I was in the market.

Chuck

 

[pacecarta]

Well, my TH has two issues. First, someone clamped it too tight at the bottom and now I cannot separate the downpipe from the dump pipe. Second, there was an exhaust leak which grooved the surface, so I'd have to have a machinist resurface it where it meets the turbo.

If I have to fork out the funds for a new one, I may as well go with an external WG. This is my thought anyway. they are about the same cost, or close enough, and I'd hate to discover that the internal doesn't quite control the boost good enough. Good to know that the 3" is sufficient, since the fit is tight and a 3.5 would be even tighter. Next is the challenge of finding a good one. I called Cotton's and their pipe w/External WG uses V-Bands, even though it doesn't show it on their website. I want the bolt-on style. This one from full-throttle looks like the WG bolts on, but the pic is rather small. FULL THROTTLE SPEED - - 3" Down Pipe with a 46mm Wastegate

And this one from TRCustom looks really nice:
DOWNPIPES 3" STAINLESS

I'll have to make some phone calls and see who has any in stock. Seems like everything is back-ordered these days.

the v-bands are much better seal and allow you to run the pw46 gate

the ones you showed from fullthrottle and mark at trcustoms are the same pipe , they swing way out and as noted on marks site it will require that you cut back the liner.. if you dont cut it away or protect it it will burn its way through .

 

[jasjamz]

I would have the pipe belt sanded to repair the flange and have the bottom fixed. Then do the RJC puck. Its huge and works!
of you go any other route go to the external Precision wastegate.

 

[~JM~]

What is the advantage of the RJC puck & how large is it as compared to the TA Down-Pipe?

Thanks
~JM~

 

[jasjamz]

What is the advantage of the RJC puck & how large is it as compared to the TA Down-Pipe?

Thanks
~JM~

Best I can do for you is show you how the RJC puck in my ATR downpipe covers an unported and mildly ported waste hole on a 6765...
http://www.turbobuick.com/forums/tu.../340786-pte-6265-swap-5857-a.html#post2714113

 

[SHADOWII]

I called Cotton's and their pipe w/External WG uses V-Bands, even though it doesn't show it on their website.
Thanks toomanymodz, I've been looking for a supplier of V-band w/ext gate and I skipped Cotton because I didn't see it on his site, only the 3".
Now I know who to call!:biggrin:

 

[Red C5]

I'd stay with a 3" dp and switch to an external gate.
With your combo I think you'll easily surpass your goals.

Peter

 

[toomanymodz]

Thanks for the replies guys. Hopefully within the next 4 weeks I'll have the new combo going. I'll post pics of the install.

 

[toomanymodz]

New RJC downpipe arrived today. I've placed it beside my Terry Houston downpipe. You can see that it has a more gentle curve.


And the puck is 1 5/8 inch compared to the 1 3/8 in the old TH pipe.


The mounting flange is slightly thicker, 3/4 inch compared to 11/16, and note the more gentle slope of the wastegate buldge how it merges into the pipe


Mocking it up on the new engine. Plenty of header clearance.


Put the pattern of the wastegate puck onto the surface. Seems a little offset to me.

 

[toomanymodz]

Here is the ported WG hole on my old PT51


And this is the un-ported WG hole on the new 6765

 

[blackgn1]

You might loosen the downpipe and move it around a little and get a little more area down low to work with. It's possible.

 

[84BuickGNYorkPA]

Thanks for taking the time to post up the pictures, the RJC looks to be a better product then the famous TH DP IMHO.
As far as the location of the puck is concerned, I think it's fine, you won't be porting to full puck diameter on the exhaust housing anyway.

Chuck

 

[jlat]

hello; That's a good catch Tomanymods and RJC should know about it . They probably do but feel it is OK as more work would be needed to make it right.. IMO the Puck should be symmetrical to the turbo.
I recently got RJC and I'm collecting parts more upgrades. I did call them as the puck control was all flapping around when I got it and suggested to just use a rubber band for shipping purpose to not cause damage.
I have an old BGC 3" on the car now.
IBBY

 

[toomanymodz]

They packaged it very well. Each end wrapped in bubble wrap and taped very well. Yeah, the puck placement is a little offset, but I don't think it will matter much since I can still port the hole quite a bit. It may end up being an oval shape though. Overall it seems the quality is much better than the THDP, although the puck placement on the TH was almost perfectly centered. I'll post some pics after I port the hole.

 

[toomanymodz]

Done porting. I was able to move the puck about 1/8 inch which helped a lot. The hole ended up being a slight oval. 1 3/16 wide and 1 1/4 tall. I smoothed the transition like I would be porting a set of heads. Hopefully this can control the boost down to 20psi.

 

[2QUICK2B6]

yeah ss thdp's are **** i will buy yours for $100 if it is ss ?