3 to 4 bolt conversion

dank GN

BlackArts Automotive (661)993-8277
Jan 11, 2009
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414
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SoCal the high desert
Hey guys I’m in the process of converting to a 4 bolt turbine housing. It involves a lot more then I first thought . The reason I’m doing this is to lower my exhaust back pressure. With the 3 bolt .85 A/R turbine housing I was close to 2.75-3 :1 back pressure to boost pressure. So I figure going to a .96 4 bolt setup it should bring my back pressure down to something closer to 2:1 or even the magical 1:1 is what I’m shooting for . I want to also add that I’m just learning/practicing Tig welding so please go easy on me and my welds . They aren’t the prettiest but I know they penetrated both metals and will hold . I was lucky enough to aquire another 3.5” down pipe . So I first had to remove the typical 5 bolt flange and install a V band on the pipe . I also had to remove the wastegate plumbing and patch the giant hole that was left . I am now on the part of chopping off the old 3 bolt flange and I have acouple questions about the install of the 4 bolt flange. Is there a particular angle I should install it at . The 3 bolt was around 42* . Should I stick with that angle or does it really not matter and I should just put it wherever I need it ? And another question is where is the best spot to plum the wastegate on the header? Should I go to the crossover pipe? 1/2 way up the passenger side pipe? Please let me know what you guys think and if you have any advice for this conversion to go smoother . Thanks again guys and keep spoolin :)
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dank GN

BlackArts Automotive (661)993-8277
Jan 11, 2009
3,521
414
83
SoCal the high desert
after reviewing some data my back pressure was more arounmd 2:1 not 2.75:1.i wanted to edit my orginal post but for some reason you cant do that anymore which kinda sucks IMO.
 

Chuck Leeper

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May 28, 2001
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Are you set up to back purge the welds? Important, for any welds that are prior to the turbine inlet.
The wg location looks to be decent.
Using the original flange angle should be good.
 

Mr.Spool

Well-Known Member
Nov 6, 2006
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after reviewing some data my back pressure was more arounmd 2:1 not 2.75:1.
yes i didnt think you would be that high on a 3 bolt.not to throw your thread off track but bp can be caused by many things,although guys point to the 3 bolt right away i know on the right combo 1.5 bp at 900rwhp has been achieved.
 

Mr.Spool

Well-Known Member
Nov 6, 2006
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Is there a particular angle I should install it at . The 3 bolt was around 42* . Should I stick with that angle or does it really not matter and I should just put it wherever I need it ?
wherever you need it
 

dank GN

BlackArts Automotive (661)993-8277
Jan 11, 2009
3,521
414
83
SoCal the high desert
Are you set up to back purge the welds? Important, for any welds that are prior to the turbine inlet.
The wg location looks to be decent.
Using the original flange angle should be good.
No I’m not setup to back purge . I actually have to go get more gas . I swear there must be a leak I have to find in my machine or something because it goes through a lot of gas . Anyway I’ll probably open her up and see if I can find anything. How should I set up a back purge?
 

Chuck Leeper

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May 28, 2001
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No I’m not setup to back purge . I actually have to go get more gas . I swear there must be a leak I have to find in my machine or something because it goes through a lot of gas . Anyway I’ll probably open her up and see if I can find anything. How should I set up a back purge?
Some good info, here. https://www.bing.com/search?q=how+to+back+purge+stainless+tig+welding&form=EDGTCT&qs=PF&cvid=9cb87af0c98b402183678f23a5a06eef&refig=35140e5405c74446acd9b81a6de955b3&cc=US&setlang=en-US&elv=AQj93OAhDTi*HzTv1paQdngMqSx94Cxcxl9EvGCoPfrZUHc85iACeImzLx1LUFVy2KVXO6kyv45iwenhspcH3zwWDEd2Swi!uMLerwM9AAUX&plvar=0&PC=ASTS
I have a 2nd hose, to a separate regulator, then into the pipe.
I've also used the paste product, to coat the joint.
What is your gas flow set to? Some regulator gauges are inaccurate, and will waste gas. Soap check all the connections, including the valve on the tank. I've had them leak, and be empty, in a short.
Are you using a gas lens, on the torch? I do, and have the gas flow at 20. However, my bud, who is a pro, has a gauge to check flow. My gauge was off by some 15%, low. Was getting some poor post weld flow coverage. Your gauge could be flowing a lot more than the setting.

HTH,
 
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dank GN

BlackArts Automotive (661)993-8277
Jan 11, 2009
3,521
414
83
SoCal the high desert
Started fully welding the flange on . Welding thick to thin is definitely a challenge. I started running out gas so this is as far as I got .
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dank GN

BlackArts Automotive (661)993-8277
Jan 11, 2009
3,521
414
83
SoCal the high desert
Okay I got the flange completely welded on and got a brace going from the header flange to the turbo flange . Now I have to figure out where and how I want to mount the wastegate. I can go from the passenger side header like most or I can go from the crossover pipe. What is the best place for it ? Thanks guys
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dank GN

BlackArts Automotive (661)993-8277
Jan 11, 2009
3,521
414
83
SoCal the high desert
Okay I think I have the spot I want to mount it . Does the wastegate have to be perfectly vertical or can it be cocked some . I think it will be able to flow nice and easy if I get it welded right and trim it out to match the pipe .
 

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Chuck Leeper

8/10's of a century!
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May 28, 2001
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Madison, Ga.
I don't think it will affect the operation.
I'd just be sure it's not at an angle so severe, that moisture can get trapped in it.
 

Nick Micale

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May 26, 2001
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Impressed with your welding/fab skills. :)

With a 96 A/R exhaust it will take a city block for decent response unless you have a small shot of NOS for it to respond properly?

Sounds like a great runner at Bonneville with 5 miles to take advantage of your turbo!
 
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dank GN

BlackArts Automotive (661)993-8277
Jan 11, 2009
3,521
414
83
SoCal the high desert
Impressed with your welding/fab skills. :)

With a 96 A/R exhaust it will take a city block for decent response unless you have a small shot of NOS for it to respond properly?

Sounds like a great runner at Bonneville with 5 miles to take advantage of your turbo!
Do you really think it’s going to be that bad ? I’m not running it on a 109 it’s a 281CID V6 with a small triple ball bearing 6871 on it . I’m thinking it is going to spool just fine .
 

Nick Micale

Tech Advisor
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May 26, 2001
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Phoenix, AZ
www.ArizonaGN.com
Do you really think it’s going to be that bad ? I’m not running it on a 109 it’s a 281CID V6 with a small triple ball bearing 6871 on it . I’m thinking it is going to spool just fine .
My concern would be exhaust velocity with the 96 A/R housing and the large opening of the flange?

A while back building a set or race 3 bolt headers, after testing we sleeved the flange to increase velocity for better spooling.

What size and stall converter do you plan to use?
 

dank GN

BlackArts Automotive (661)993-8277
Jan 11, 2009
3,521
414
83
SoCal the high desert
My concern would be exhaust velocity with the 96 A/R housing and the large opening of the flange?

A while back building a set or race 3 bolt headers, after testing we sleeved the flange to increase velocity for better spooling.

What size and stall converter do you plan to use?
I’m really hoping that this won’t be to big as I actually went down from a 1.1 A/R because I thought that was going to be to big . I have a 3500 stall 9” non lock up .
 
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