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What to do with Exhaust

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What to do with Exhaust

Post #1 by peeeot » Thu Oct 25, 2018 9:01 am

I need some insight from you folks with practical experience. My objective is to maximize efficiency and performance up to 4000 rpm; seat-of-pants feel is about as important as actual performance.

My current exhaust is a single 1.75” pipe off the stock manifold. After about 2-3 feet it steps up to 2” all the way to the stock-style muffler at the rear of the car.

I have been considering a few things:
1. Just step the first bit up to 2” to match the rest
2. Step the whole system up to 2.25”—manifold outlet is only 2” so would have to step up just after the flange
3. Split the manifold old-school style, either 4/2 or 2/2/2 and probably join the pipes into a single outlet after several feet or possibly leave separate (very curious as to what 2/2/2 would sound like out of 3 exits!!)

Which of these possibilities would work best for my objective? I’m not interested in Cliffords headers, which are the only header option I’m aware of for a car application.

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Re: What to do with Exhaust

Post #2 by bubba22349 » Thu Oct 25, 2018 8:33 pm

I would go with a 2 1/4 inch system for a single exhaust or you want a duel system then a pair of 1 3/4 to 2 inch would be good. You could port the exhaust manifold to get it closer to 2 inch or you could make a tappered transition piece to help flow, also if you can find a big truck 223 or 262 (F500 or up) exhaust manifold it should have a lager outlet too. A nice mandrel bend system with a free flowing muffler or mufflers (Turbo's, Magnaflow ect.) should get you that seat of the pants feel you want. On the manafold split a 2 /'4 is the easiest better is a 3 / 3 see below link on stock manafold s that were split. And the other link showing an older post of mine with pictures of the best cast iron 223 exhaust manifold these was made by Fenton. Good luck on your 223. :thumbup: :nod:

Splitting a 223 exhaust manifold. ... ld.272374/

Fenton duel exhaust manifold
A bad day Drag Racing is still better than a good day at work!

I am still hunting for a project car to build but with my current low budget it's not looking so good. My Ex- Fleet of Sixes these are all long gone! :bang: 1954 Customline 223 3 speed with O/D, 1963 Fairlane project drag car with BB6, 1977 Maverick 250 with C4, 1994 F-150 a 300 with 5 speed.

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Re: What to do with Exhaust

Post #3 by peeeot » Wed Nov 14, 2018 8:54 pm

Those Fenton manifolds are ideal, but seem to be rather scarce these days. To bad they aren’t reproduced!

I am planning to go with your suggestion of a mandrel-bend 2.25” single, at least to start with. I may have to dimple the pipe at the flange to accommodate the nuts.

I found an article from where they put a 2.5” single on a 225 slant six that had previously had a 1.75” to 2” pipe almost exactly like mine, and it gained 9 hp with just the pipe change. Granted, it’s not the same manifold and it has a true 2.25” outlet, but it supports the idea that it’s possible to make a noticeable improvement even while retaining a 6-into-1 cast manifold. Here’s the link: it’s interesting to me because other articles (horsing around, soup that chev, slant sickness) all show a 10 hp increase from swapping to dual outlet headers/manifolds. I would have guessed that a big single on a stock manifold would not have made so similar a gain to the dual outlet headers. I suppose peak numbers only tell part of the story. Or maybe it’s because the slant started with a 1.75” pipe.

About the larger outlet on the truck manifolds: are you sure? I found an eBay listing for a heavy truck manifold with the right casting number (c3te-9430-c) and contacted the seller to get outlet measurements. The numbers he gave matched my current manifold.

Thanks for your help!

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