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Discussion Starter · #1 ·
Finally, after 6 months I have in hand one prototype header for my V-6 conversion. As I've alluded to before this is a "Trick" setup. As with others doing this mod, a Fiero type manifold is needed. I chose to go with a similar, but different approach for a number of reasons. First I wanted to cut as little sheetmetal from the foot well as I could get away with. That meant the manifold had to be as close to the head as possible. Second, I wanted to try the rapid expansion of exhaust gases and try to cool the manifold down using that basic law of physics. The third reason of using what I did was really simple, a 1 1/2 square tube has more area than a round tube by almost 25%. Which goes back to reason 2. Also, by using the square tube, I didn't have to worry about stub ducts from the exhaust ports to the log manifold, which goes back to reason 1. Now all I have to do is come up with a dozen 5/16 X 20 bolts with a 1 inch shank length. Back to the internet for exhaust bolts that will be useable. It's getting closer. :)

Ron
 

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Looks neat... I wonder if the square tube will flow as well as a round one. Even with the additional 'space' the added angles may not help if flow better. Just a thought.
 

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Totally newbie question here, but shouldn't headers or exhaust manifolds have some sort of runner between the ports and the collector? I know that you used to maintain aircraft, I was a jet engine tech in the USAF as well, but when it comes to auto mechanics, I don't know very much. I'm basing my question on the fact that because of the timing, in my mind it would allow for exhaust gas to enter the exhaust port of the next cylinder down the line, from the looks of your picture.

Dave
 

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Discussion Starter · #4 ·
Husker, it's a prototype, hopefully it will flow fairly well. The exhaust ports are 1.125" diameter and the exhaust will literally dump into the 1 1/2" log, then go to the 2 1/2" down tube, going from high pressure to a, hopefully, low pressure. Because the area is so large outside the port, I'm hoping there won't be too much restriction. One thing the pic doesn't show is the rear port on the log is rounded to divert the exhaust to the front of the engine.

Taavetti, the firing order is 1,2,3,4,5,6, with 1 and 2 at the front of the engine, so theoretically, the exhaust from the rear cylinders will slide past the exhaust ports up front, after the valves close. At least thats what it says in the fine print. :D

Ron
 

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Hi. Unless you retapped the threads, you may want to try 8mm bolts. The GM 60 degree V6s were all metric.
Tazlo
 

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Discussion Starter · #6 ·
Tazlo, that's what I thought too, but I can not run an 8 X1.25 nut down the original exhaust bolts and I can not run an 8 X 1.25 bolt into the head where the original bolts went. So I got out my trusty thread gage and vernier caliper and found the bolts are a 5/16 X 20, which is real close to an 8 X 1.25 metric. A phone call was made to a supplier on the east coast and I'll have an answer from ARP tomorrow for a dozen stainless steel header bolts with either an allen head or a 12 point socket head. So now I have to wait on the bolts so I can figure out where the EGR valve and the oxygen sensor will be located. So close and yet so far. :rolleyes:

Ron
 

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Discussion Starter · #7 ·
Today's update. APR does not stock a 5/16 X 20 bolt and says they have no idea what's up with this engine. I finally got it figured out after doing a little research in my machinists handbook. GM in their wisdom made the exhaust bolts and the threads in the head, an interference fit. The threads are actually 8 X 1.25 metric. I bought some bolts from Kragen and they screwed right in although a little snug going in, but they bottomed out and when I took the bolts back out, there was no distortion on the threads. We're back in business, kinda. The EGR valve does not like the position of the square tubing, so it's back to the drawing board, again.:rolleyes:

Ron
 

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Ron,
A relatively simple way to make shorty 'headers' is to use weldable cast-steel elbows and tees. I just finished making a manifold using such fittings for my friend's rallycar (turbo VW Golf). They're fairly thick, pre-chamfered for welding, and cheap.
They're also consistantly sized internally, and have compact bends. Just thought this might be an alternative...
 

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Discussion Starter · #9 · (Edited)
I was hoping you'd give some critique on this, Bob. The system you attached just won't fit in the confines of the GT engine bay on the left side. As it is now, I'm going to have to weld a section of exhaust tubing to the vertical walls of the foot well and make it removable to get at the manifold bolts. If Gary gets around to loading Phase III, and I understand he's really busy with this site's mods, I have a pic in there somewhere with the Fiero manifold attached to the engine and it protrudes inside the footwell. The reason for a section of round tubing and very visible of how tight the exhaust is to the footwell. I really appreciate the input though, if I could use something close to that, I would. It appears that it would flow a lot better than what I'm putting in. But in my estimation, going from 1.125 diameter exhaust port to 1 1/2 square to 2 1/2 round should flow fairly well. The final 2 1/2" size is what was originally on the engine exhaust manifold. Just out of curiosity, what is the distance from the flange to the collector and how close could it be made to the log manifold I've got?

Ron
 

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namba209 said:
Just out of curiosity, what is the distance from the flange to the collector and how close could it be made to the log manifold I've got?

Ron
Well, the application was entirely different, so I wouldn't use this flange-to-flange dimension (3.5").

Instead, you could simply run one 90 degree elbow, then two 'T's, then a curve downward as you've done. At the same time, they could be cut down a bit to make them fit closer to the head. I imagine you could put the outermost part of the tube about 2" to 2.5" away from the head surface.
 

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I don't see any problem matching that manifold configuration. A friend of mine owns 'The Fiero Store', I could get a stock manifold from him and check for sure though.

I get my pipe fittings from McMaster-Carr, they're about $5 a piece for the elbows and $11 or so for the 'T's', with a 1.5" ID. They weld beautifully with either MIG or TIG, and since they're thick-walled (about .130"), they retain heat for more power, as well as less noise transfer than thin-wall stuff. They also have 'step-up' sections that would allow you to increase to whatever sized downpipes you wanted.
 

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Discussion Starter · #13 ·
Bob, I went to their website and found a whole lot of fittings that would work, especially the 1 1/2 elbows and "T"s that have a 1 /12 overall length center to center. I also looked at the stainless and almost had a heart attack, the reducer from 2 1/2 to 1 1/2 was over $70 and a "T" was $64. What type steel did you use on the manifold you made? There is a myriad of different types and coatings on their website. The only problem I can foresee using that type of round tubing is the same problem I've got with the square tubing, the EGR valve is too close to the engine. It will either block access to the manifold bolts or the spark plugs. I will have to reconfigure the setup to get clearance for the valve either way. Thanx for the info so far, it's been an eye opener. There is a company locally that has had exhaust flanges up on e-bay for almost all the engines ever built. He has had a 3.4 set up for bid quite a few times, I'll try to contact him and see if I can get a pair of their one piece flanges. It's getting to be more fun, again.

Ron
 

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Ron,

If you are going to try and make your own headers, you might want to take a look at this product:

http://www.covell.biz/donuts.htm

They are steel "dounuts" that basically have a hole that is the diameter of the tubing, so with 1.5" tubing you can have a really tight radius and keep the header right next to the engine.

I just bought some header flanges and I am going to try and make some "block hugger" headers with the donuts>

Nathan Acree
Albuquerque New Mexico
 

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Ron, those tube pieces I displayed above are just plain steel. Sorry about the 'polished' appearance, I pre-polished the parts so they'd look better for when they were ceramic coated later on.
They are very easy to work with, I made the entire manifold in about 10 hours, and that included making the custom 3/8" flanges and the tricky merge into the turbine housing.

Here's what they look like 'as cast'.
 

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Discussion Starter · #16 · (Edited)
Nathan, I don't know what the overall size of the the donuts are, but it looks to be a fairly large outside diameter. I guess you could cut them in half and use the halves for the stub ducts. But they appear to be too large OD for the bolts in the head at the ports. Wait a minute, are they hollow inside? If they are, they may just be the ticket for the end ports at least, but they are pricey.

Bob, those fittings appear to be cast, how did you maintain the alignment while you welded them together? I wish I was aware of this company a long time ago, it could have saved me 6 months of anticipation and I would be that much closer to finishing this project. Does the company sell to an indivicual or do they only sell to companies?

Ron
 

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alignment

As far as the first two "T"s and the end elbow go, I'd say thead a dowel through them to line-everything up nice and straight, tack weld securely, then remove the dowel for finish welding. The only difficult one will be the elbow on the end for the flange.

You may want to check locally for the "T"s and such too, as my local metal shop gets them for much cheaper. They use them for making hand rails and gates and such.

McMaster-Carr is hands-down my favorite company to order from. I've never waited more than 3 days for anything, shipping is surprisingly reasonable, and they can get anything you could want. I do a lot of business with them at home and at work, although I don't think the Navy will toss anyone an official endorsement.
 

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namba209 said:
Nathan, I don't know what the overall size of the the donuts are, but it looks to be a fairly large outside diameter. I guess you could cut them in half and use the halves for the stub ducts. But they appear to be too large OD for the bolts in the head at the ports. Wait a minute, are they hollow inside? If they are, they may just be the ticket for the end ports at least, but they are pricey.


Ron

Ron,

Yes, you would cut them in half (or quarters or whatever) to make tubes with really tight bends. I think the smallest comes in 1.5" OD tubing so the radius of that bend would be 1.5"

However, looking at the pipe elbows that Bob mentioned makes me think they might be the better way to go, they are certainly cheaper and looks like they might have the same radius as well (1.5" which seems the size tubing that most header flanges call for).

Nathan Acree
Albuquerque New Mexico
 

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Discussion Starter · #19 ·
Stephen, I'll get in touch with the guy that's doing the welding on my GT, maybe he has a local source for the elbows and "T"s. If not, and I can get them from McMaster-Carr as an individual, I'll go that route. I just hate to have waited for 6 months on what I have right now, and wait longer to get the manifolds finished, plus pay for the labor and material. But, at the time it appeared it was the only way to go for what I needed. Now it appears there is a better solution, but I will still have to make an adaptation for the EGR valve.

Nathan, it looks like what Bob indicated is the way to go. BTW, did you get the tach mod from PJ Hall for the V-6 engine? I got two boards from him and a parts list. I also found a company that can reproduce the boards for about $4-$5 a piece in quantities of 12 or more. My only problem is right now the engine is inop so I can't test the board until after I get the rest of the car together, it will take a signal generator to run the frequencies needed. If you need a board let me know. They will have to be drilled for the legs of the IC and pigtails of the resistors, caps and diodes.

Ron
 

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Ron, a thought about the EGR valve. Could you "stove pipe" the valve to either side so you have access and still get function? Or, set it lower on the downspout? You can vac-tube longer if the engineers of our group think it would still work.
 
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