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Discussion Starter · #1 ·
I was looking at Mcjacks headers, they offer 1 5/8" w/ 2" collector, or 1 3/4" w/ 2.5" collector. What would I use on a basic 350 with TPI? Thanks
 

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I was looking at Mcjacks headers, they offer 1 5/8" w/ 2" collector, or 1 3/4" w/ 2.5" collector. What would I use on a basic 350 with TPI? Thanks

To be honest the 1 5/8" - 2" is fine for your SBC. However, keeping possible future upgrades in mind, the latter might be a better building block so you don't have to do this part twice.
 

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Block Huggers I presume? If so are you keeping A.I.R. and emissions or is this a non-emissions engine? If not the latter of the questions I'd go to Summit Racing and get their Block Huggers with 1 5/8 primary and 2 1/2 collector. I put that same size from Flow Tech and had the muffler shop tie my 2" exhaust into those and mine runs just fine. If you're running a stock engine the 2" will be fine as most people "over-exhaust" their engine with big headers and pipes. My brother did this with his (now mine) Jeep and it ran like crap until I converted it to a 4 barrel carb with an upgraded ignition and now plan on putting in a hotter cam to get the dog like performance gone. Before getting anything research as much as possible so that you buy once and not waste money:thumbsup:
 

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Discussion Starter · #4 ·
I cut the A.I.R tubes off the stock 81 exh. manifolds and welded 2.5 collectors on, so right now I am 1 5/8 X 2.5 . They leak at all the flanges!

Would the 1 3/4 X 2.5 be an over kill for my situation?

Stock 81 engine rebuilt
Edelbrock 6073 heads
Mild TPI cam
TPI injection w/ some port work
 

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My engine is midly camed, .468 int., .489 exh. minus the aluminum heads which I plan on getting. I asked my local muffler guy that when I go to aluminum heads what is the best exhaust diameter that wouldn't hurt flow or power and he said 1 5/8" headers with 2 1/2" collector and 2 1/4" pipes. He is a drag racer and a car nut so I'm taking his word for it as he's done this for many years. He said most people over do their exhaust when it's not needed. Think of it this way you're flowing 4 cylinders into one pipe vs. 8 cylinders into one pipe, so therefore 8 into one would require more diameter vs. the 4 into 1. I'd stick with the 1 5/8"x2 1/2" headers and put 2 1/4" pipes on it. Others may say something else but I'd ask a reputable muffler shop in your area and get their opinion on it.
 

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If I can find the header and pipe diameter to horsepower figures for both single and dual exhaust system I'll PM it to you. I have it somewhere in my house but since my room flooded I boxed a lot of things up for storage.
 

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Here's the chart and it's link

http://www.magnaflow.com/07techtips/faq/question10.asp

The 1 5/8" will work perfect. If you went 1 3/4" you'd lose bottom end and gain small top end with the engine set-up that you have. I have the header/hp chart but it's packed away so this info is from good memory. Hope this helps and answers your question:thumbsup:
 

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Discussion Starter · #9 ·
Ok I went back and measured! 1 5/8 X 2 1/4 at best! so The
1 5/8 X 2 Looks like a good match? I dont plan on any major engine upgrades as they done! just looking for something that will come close to my allready exhaust. Thanks
 

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I'd go 2 1/4" and call it good. No more than that though. The reason I say 2 1/4" is if it's a close call or on the border I'd go to the next size and plus this will leave room for slight mods if so desired in the future. Hope all goes well:thumbsup: Let me know what you get and post a video when you get the new system:thumbsup:
 

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My vote is for the 1 5/8 to keep exhaust velocity up, any larger and I think you'll be hurting performance in the lower rev range.





Liam
 
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