Will the addition of a header on a stock B18 engine with an electronic ignition change the performance (running, gas milage) enough for the cost? Karl

Getting rid of the old style single downpipe manifold is a good thing. Putting a slightly larger exhaust on back to the tail pipe is a good thing (although a stock B18 probably doesn't need too large - 1 3/4 perhaps?). A 4-into-1 header will be an improvement over the single downpipe manifold, but not really any better than a much cheaper stock dual downpipe and matching manifold.

And even if you do have a tiny exhaust system and a single downpipe manifold you won't notice much of a difference below 4000 rpms or so. But from there on up to the redline it will pull harder with a more open exhaust. Swapping the cam (assuming you have a 'C' geind') for a 'D' grind will help you in taking advantage of the improved breathing.
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I'm JohnMc, and I approved this message.

Karl

Emphatically no, unless it is a KGTrimning like John Parker sells. Most steel tubing headers are noisy, too often hard to keep sealed, and with the exception of the KGT part not performance enhancing.

George is absolutely right. I will send you mine when I get my cast iron manifold installed!!!! That way you have something you can cuss!!!

The money you spend on a header will pay for a set of Bilsteins for the front, or a bigger front sway bar, or a pair of cool wheels, or if ya get a good deal an overdrive tranny. Even a peace offering for the significant other if you spend too much time with the car!!!!

It is a well support fact that the combo George suggested flows very well and is perfectly matched to the vast majority of 122 enthusiasts needs and far less maintenance.

Twombo

You'd be better off to get a late model B20 FI exhaust manifold and
a dual downpipe for a FI car (bigger than the ones for carbed cars).
Even a dual downpipe for a 67 122 would be better than the single
one you've got now.
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George Downs Bartlesville, Heart of the USA!

George, do you mean the (dual) FI exhaust manifolds are bigger then the (dual) carbed exhaust manifolds ?? I thought there was no dif between them.
(Or did you just mean to compare the (dual) FI manifold with a single carb version?)

Thanks, cheers, ben
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P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)

I have not measured but the FI manifold looks bigger. The FI exhaust pipe
is definitely bigger than the carb exhaust pipe.
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George Downs Bartlesville, Heart of the USA!

The pipe? The amazon never had an injected version, so there is no FI-exhaust (I think...) Or is the first bit the same as a P1800 or perhaps a 140?

If you feel like it, can you do a measurement some day? I just cut of the exhaust part of a single carbed combi manifold, thinking the exhaust part would be exactly the same as a FI one...

thanks, ben
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P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)

You have to get the FI components for later models. I will be able to
comment more authoritatively on how the latest FI B20 pipe (1975 B20F)
fits when I get around to installing it. I got that one because shipping
was cheaper than the 144 FI pipe because the pipe is shorter (made to
connect to a CAT) and I will have to fabricate much of the exhaust from
the front pipe back anyway. My exhaust guy prefers not to make the 2-into-1
pipe if he can avoid it.

I don't have a combined B18 intake/Exhaust manifold so I can't measure one
for you. I do have an FI exhaust manifold. What dimensions would be useful
to you?
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George Downs Bartlesville, Heart of the USA!

What dimensions would be useful to you?
Inner diameters I'd say. Diameters of the two 'rounds' where the pipe bolts on, and perhaps height and witdh of the 'squares' where the amnifold meets the head? I'll measure the one I cut of a combi manifold aswell, then we can compare.

My exhaust guy prefers not to make the 2-into-1 pipe if he can avoid it.
Does that mean running a double exhaust system al the way? Or do you make the 2-into-1 just before the mufler or so? (or a mufler with 2 'ins' and one 'out')

thanks again, cheers, ben



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P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)

the secondary pipes are 1 3/4" in diameter... And in that regard, John, what are the secondary diameters of your headers? Ooooh, and this also made me take a measure to my 71 integrated carb manifold... Of which I only have the top, primary part, and it is about 1 5/8" in diameter I think... Hmm.. I didn't know there was a difference! I wonder what diameter the pipes are on my car's current setup... I got a new exhaust a while back that came with the dual downpipe, and I wonder if it is also 1 3/4" in diameter like the one I pulled off my old engine... Hmmm... And also that makes me wonder which primary half I have on my current setup. And stuff. I need to take a look at that and measure the diameters next time I have the exhaust manifold apart...
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I just measured my exhaust manifold secondary pipes (which I cut of combi manifold) and they are 1 5/8". So there is a difference between in size betwen the intergrated and the seperate exhaust portions. Too bad. I thought I could get away with cutting that exhaust portion of the combined manifold...

cheers, ben
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P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)

George;
Is a stock '71 1800 going to have the exhaust system you are talking about? If so, I am going to kick myself, HARD, as I have just spent this evening trying to track down a dual downpipe exhaust you and other knowledgable gents talk about, and it just occurred to me I have an intact 71 1800 under wraps behind my garage. Its too dark to check right now, but for sure I will be out there tomorrow having a look. I just dropped off an E head for machining 5 hours south of here, and didn't have the correct manifold for them to match to!
Duh! JD
Fort St John BC

If it is an 1800E it certainly is. If it has the combined cast arn manifold
with 2 carbs, not exactly but the exhaust section is pretty good. If it has
separate manifolds and a dual downpipe it is certainly better than the single
downpipe. I'm not sure how much difference there is between that manifold
and the FI manifold. The FI exhaust pipe is indeed bigger than the carb
exhaust pipe. Have to use a different muffler with it though, and rig
some mountings for it.
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George Downs Bartlesville, Heart of the USA!

Thanks George, right as usual. I went out this evening and checked to parts car, and sure enough I have the exhaust manifold I was after. Now I will send it by greyhound down to the machine shop for matching to the E head.
Thanks
JD