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Exhaust flange thickness

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So about ready to make the flanges for my exhaust and want to know what the common used thickness is for 2 bolt flange. I will be positioning the flange off set so one pipe sits half inside the opposite flange if that makes a difference. Also does diameter of pipe change thickness of flange? While the questions are rolling is there a minimum distance to the top/bottom (12 & 6 oclock) edge of the flange from the outside of the pipe with the holes on the sides (3 & 9 oclock)? Thought I better ask this just incase room gets a bit tight and I know how much to leave.

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I bought the flanges off ebay.

 

They are 10mm thick ( prolly a little thick) and the hole alignment doesnt really matter as far as i can see. The pipe diameter i am using is 2 inch and the holes in the flanges are 2 inch.

 

I have just rotated the flanges to the angle which looks neatest ans keeps them tucked up nicely under the car.

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The distance between bolt holes should be kept to a minimum to just fit the bolts and nuts through and be able to spanner them up. Too far apart and your flange can distort and it's leak city. Also once you weld your pipe on, it pays to give the face a grind flat again as welding can distort it a bit. I use the side of a cut-off saw disc.

 

Of course if you have a bit of pipe protruding from one of them, you can't do it.

 

I'd give at least 15mm of flange face from ID to OD, enough to give a decent seal with whatever gasket/putty you want to run.

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Wow for once I was thinking a little thin on the plate size, that's a first. If I used a thick washer that should give enough clearance for the spanner/socket but I didn't even think of bolt size, 10mm should be fine yeah? Does it need to have a locking nut? So many bloody questions over something so simple as an exhaust flange :blink:

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when i received my 10mm ones i thought they were massive. Specially when you look at 2 sandwiched together with the gasket.

 

I guess based on the warpage factor of the welding 10mm would be good as it would be less prone to warping.

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Suppose your right hendrixhc that would make it over 3/4 inch if using 10mm thick which is probably to thick. Weldability of 8mm vs 10mm isn't that much different but 6mm vs 10mm is very different

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i was concerned at the weight they added to the exhaust system cause there are quite a few of them. i want to run the system as a three piece for ease of fitment, removal and replacement.

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I've always used a course thread bolt and normal nut and never had one come undone.  They tend to grow on there so mechanical lock nuts or springs are really not needed.

 

Try your local steel merchant for the flanges. Tonkin Steel up here laser cut them for all the exhaust shops.  If you buy direct from the exhaust shops you get arse raped. 

 

Never tried ebay.  I have bought 3 bolt flanges from summit and they were good quality.  8mm thick would be good and I would not bother cutting them out myself as the steel shop ones are just so cheap and good.  Just make sure you can get access with a spanner to do them up.  Making the top side (closest to the engine) a captive bolt is not a bad idea as it makes fitting a bit easier.

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So do people use metal gaskets or something else cause guessing that making them will depend on the gasket dimensions with bolt hole location. Reason I would make them is hoping to get exhaust done back to muffler over easter

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Just go to the exhaust shop and buy some them mate.  they will have the metal gaskets (like your extractor flange gasket material) and flanges in stock.  will be much quicker and cost effective if you want to get it done over the 4 day break that is.

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Yeah looks a bit that way, never had the intention of doing the exhaust over easter but it pretty much ready to go so I thought I would have a try at getting it done.

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If you buy direct from the exhaust shops you get arse raped. 

 

Your not bloody wrong.

I went to the one of 2 local exhaust shops as both local steel places don't carry any exhaust products. Paid $25 for a pair of 8mm thick flanges with a gasket and a pair of 8 and 10 mm bolts as they didn't know which I would prefer. There is very little meat around the diameter(7mm) but they will do the job I hope. I then as how much for some 3 1/2 inch pipe. I paid $34 for a 1 metre length from the local truck parts place where I have gotten all my pipe, the exhaust place charged $30 for 500mm saying the price difference between 3inch and 3 /12 inch was huge BULLSHIT. But I needed more as them 1 metre I got wont be enough and the truck parts place wont get any more for almost 2 weeks. Ah well it's only money  :wacko: 

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Yeah really wasn't happy but this is the price you pay for not being organised. If I had bought the 1 metre length sooner from the truck parts place they may well have had some in when I needed it but I was very disorganised and is it very much jumped up and bit me on the arse big time

The pipe is going on my roller cam sedan which is a single system but I am trying the 3 1/2 inch from the extractors to the diff to try and quieten it down for the street. The current 3 1/2 muffler is a straight through type but have been informed that other people have used 3 1/2 inch systems with some success regarding noise volume. If I don't have any luck I will change to a 3 inch system from the extractors using a baffled muffler and maybe that will work.

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Yep there is absolutely no need for 3 1/2 inch but there is 2 reasons I went that way 1. I have been told that 3 1/2 will actually have a quietening effect without hurting performance. 2nd is I am trying something with a different brand of muffler hoping for a unique note to the car. Different is not always better but its what I do so will have to find out if it works. And since I have zero experience with this level of engine performance I am relying on other people's experience and knowledge, but at the same time this builds my experience and knowledge. I am running 3 inch up and over the diff anyway so if the 3 1/2 doesnt work out I will just make up a 3 inch section from collector to rear muffler position and have full 3 inch with a baffled muffler most likely a hooker aerochamer. The 3 1/2 inch section will end up costing me less than $100 including the muffler(the muffler is a whole different story) so I really haven't lost anything if it doesnt work. Nothing ventured nothing gained.

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Look @ new 2ltr Subaru's and other modern shit boxe's that come factory with twin 2.25" systems.Big car companies wouldn't do it if it didn't work. Pipe max actually recommends the twin 2.5" exhaust I run on mine (although it says shorter secondaries) and no-one says to me "that exhaust is too big for your car Rob". They all say "that doe's not sound like a 6cyl" lol. If we think a BBC uses twin 3" or twin 3.5" with double the cubes this is half so it needs half as much. In my best Freberger voice LOL

 

But besides that it all about flow and how you use it. He has modded extractors and a custom merge collector to suit. This will enable him to use that pipe size to it's full effect to make his engine efficient. Good exhaust shops will tell you it's all made in the collectors and what happens 500mm after then is based on use/tastes. Long gone are the days of needing back pressure.That is a statement said by people who don't know what there talking about. 

 

Plus this engine WILL use the 3.5" exhaust well :)      

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And some.  Cam and comp need big pipes. 

 

You think 3.5" is big on a tough crossflow.  I ran 4" on the race car and then twin 2.5" with an x pipe.  Did people come up to me and complain my car was too loud? Nope.  They all whinged because they could not hear it and the first time they knew I was there was when I went down the inside them or around the outside. They were all busy sticking with their know it all local exhaust shops and there single 3" systems.  All they did was make a heap of noise and lose power. 

 

Have a think about the size of these engines (per cylinder) and in total ci and then think about increased compression and cam.  Bigger - free flowing pipes are mandatory.

 

Trust me Ryan - there is no way known you will go back to a 3" system and whilst we are both disappointed in the external appearance of the muffler we have chosen for this engine - I can assure you that it will work very, very well. 

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And some.  Cam and comp need big pipes. 

 

You think 3.5" is big on a tough crossflow.  I ran 4" on the race car and then twin 2.5" with an x pipe.  Did people come up to me and complain my car was too loud? Nope.  They all whinged because they could not hear it and the first time they knew I was there was when I went down the inside them or around the outside. They were all busy sticking with their know it all local exhaust shops and there single 3" systems.  All they did was make a heap of noise and lose power. 

 

Have a think about the size of these engines (per cylinder) and in total ci and then think about increased compression and cam.  Bigger - free flowing pipes are mandatory.

 

Trust me Ryan - there is no way known you will go back to a 3" system and whilst we are both disappointed in the external appearance of the muffler we have chosen for this engine - I can assure you that it will work very, very well. 

 

Hey Ando, very interesting interesting regarding exhaust sizes. When you say comp and cam, what size are we talking?

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Ando I lost faith in the muffler when they sent me the second one that was not even welded. Yeah the first one only looked like shit but for the price of it, it should be much much better. It is what it is and at the end if the day I wont be suprised if it doesnt work.

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