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Just to clarify that 1.5iches is too small as an external diameter for header primary tubes. I think it is just right for internal diameter. I also prefer to talk about internal diameter as external diameter does not give an accurate estimate of internal diameter due to varying material thickness between products.
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Old 07-14-2017, 08:43 AM
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Why not go to 1 3/4" ID?
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Old 07-14-2017, 09:02 AM
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Quote:
Originally Posted by 911 Rod View Post
Why not go to 1 3/4" ID?
Because based on my calculations on the flow of a 3.4L engine, 1.5id came out the preferred size. Factoring into that was my desire to keep stock redline and stock rpm for peak torque. Why did I do that? Because the intake manifold is tuned for peak torque at a set rpm for stock engines. I could not change that, so I just worked with it. Both the diameter and length of the primaries are tuned to match the intake peak torque rpm.
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Last edited by gliding_serpent; 07-14-2017 at 10:25 AM..
Old 07-14-2017, 09:10 AM
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Quote:
Originally Posted by gliding_serpent View Post
Just to clarify that 1.5iches is too small as an external diameter for header primary tubes. I think it is just right for internal diameter. I also prefer to talk about internal diameter as external diameter does not give an accurate estimate of internal diameter due to varying material thickness between products.
The only issue is when you change how you communicate diameter the rest of ths world doesn't jive. Meaning when all tubing material is ordered it is ordered with O.D. specs. For example when I order my material for my 914-6 heat exchangers I build I order 1.625 with a wall of .0625. Thus 1.5 inch I.D... They are still 1.625 headers.
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Old 07-15-2017, 05:59 AM
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Quote:
Originally Posted by mb911 View Post
The only issue is when you change how you communicate diameter the rest of ths world doesn't jive. Meaning when all tubing material is ordered it is ordered with O.D. specs. For example when I order my material for my 914-6 heat exchangers I build I order 1.625 with a wall of .0625. Thus 1.5 inch I.D... They are still 1.625 headers.
Fair, but I specified my headers to be made with pipe, not tube. 😜
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Old 07-16-2017, 04:23 AM
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It is common knowledge that 1.5" primaries are too small for anything above 3.0L displacement which is why SSI has little advantage when bolted onto a Carrera engine. Tubing comes in finite sizing so it is pretty easy to choose what works best for your application. Possibly the most important picky point is wall thickness. Our 321 stainless primaries use 0.049" walls instead of typical 0.060"+ used by 304 stainless which gives you a slightly larger ID.
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Old 07-16-2017, 04:48 AM
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Quote:
Originally Posted by gliding_serpent View Post
Fair, but I specified my headers to be made with pipe, not tube. 😜


Umm well that is interesting because if you ordered "pipe" then that is an id measurement with a schedule wall thickness. Schedule 10 is light weight as you can go amd very typical is schedule 40..

I must apologize for picking on this detail but this is what I do for a living and though you may have spec d pipe there are just so many less options specific to wall thickness I find it difficult to see how you would have gotten what you asked for..

Tubing is always measured od pipe is measured id until 12 inches diameter..
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Old 07-16-2017, 07:08 AM
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I am just messing with you (everyone) Ben, it is all good. But it just all shows that the devil is in the details.
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Old 07-16-2017, 07:45 AM
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Lol ..its all good.. I was a bit confused
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Current project 73 914-6 Gt project rusteration 2.4
Reproduction 914-6 oil tanks, 1-5/8" 914-6 heat exchangers source call 2623647426 or email mbconsulting21 @gmail.com
Old 07-16-2017, 08:05 AM
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When I built my 3.3SS engine, I decided to keep it using CIS just to see what it could do. And, since I was keeping the CIS, I reused the SSI system that was on the 3.0 engine. Turns out, it runs quite well with lots on the top end. Would it make more hp with ITBs and true, properly sized headers? Almost certainly. However, my car is driven on the street almost exclusively and much more performance would most likely get me locked up and stripped of my driver's license! As is, it will pull quite well all the way up to 7500 rpms where I have the ignition interrupter set. And, someday if I run out of other projects, I just might change over to ITBs or PMO carbs and a propper header exhaust system. It never hurts to leave room for a sequel!
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Old 07-16-2017, 08:36 AM
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With the 84-89 3.2L motor you are best to keep the stock heat exchangers over SSIs. Save the money and simply put in a cat bybass or pre-muffler with a Dansk Sport Pipe or M&K Pipe and call it a day. You need at least 1.5" to 1.625" ID, it's does not matter what the OD is, when calculating exhaust header sizes it's the ID that matters. You pick the ID then the wall thickness dictates the OD to achieve the desired ID spec.
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Old 07-17-2017, 06:40 AM
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Sal, based on what John posted on his motor, any guesses as to what hp Chris Bennet's 3.4 is making with your MAF? I have driven his car and it is fast and fun.
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Old 07-17-2017, 02:17 PM
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Shaun,

I don't want to guess but I'm very curious about Chris' 3.4 twin plugged motor. What has me most curious about that build is that he's using stock 3.2L cams. I do not have any data or ever seen any such motor. It's a twin plugged 3.4L with stock cams intake and exhaust. You ask a very good question but I don't have any answer till it gets dynoed.

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Originally Posted by Shaun @ Tru6 View Post
Sal, based on what John posted on his motor, any guesses as to what hp Chris Bennet's 3.4 is making with your MAF? I have driven his car and it is fast and fun.
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Old 07-18-2017, 06:48 AM
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Thanks Sal, I'm looking forward to his dyno results someday myself.
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Old 07-18-2017, 06:52 AM
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Old 07-18-2017, 07:17 AM
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