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Old 06-14-2010, 08:23 PM   #1
plym49
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Default AMC/Jeep 258 Inline 6 Dual/Triple Carbs

I've been researching the AMC/Jeep 258 (4.2 liter) inline 6 and, strangely, this seems to be about the only inline 6 that does not have an available twin or triple carb intake manifold.

The only thing I found was a manifold that mounts twin DCOE Webers.

But how about two or three single downdrafts? With as many of these motors that are around, I can't understand why the aftermarket is shy on multiple carb intakes.
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Old 06-15-2010, 09:53 AM   #2
nali
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Default Re: AMC/Jeep 258 Inline 6 Dual/Triple Carbs

Maybe because it should be easy to use a 4.0 head and injection .
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Old 06-15-2010, 10:17 AM   #3
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Default Re: AMC/Jeep 258 Inline 6 Dual/Triple Carbs

That and most of these motors bieng "built" are in Jeeps. You dont want a high end screamer, you want low end TQ.

That said, I ve always wanted to build a 80s 2 door 2wd chero with a hot 4.0
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Old 06-15-2010, 10:45 AM   #4
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Default Re: AMC/Jeep 258 Inline 6 Dual/Triple Carbs

How abut a Triple Weber Side Draught Intake Manifold for that 258?

Or if you choose to swap on a head from a later 4.0 engine (which supposedly breathes a lot better) there's this version - Triple Weber Side Draught Intake Manifold 1991-Later w/ 242 cid (4.0L).

Costly, especially after you add in the cost of the carbs, but cool as all get out and seriously impressive looking.
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Old 06-15-2010, 10:53 AM   #5
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Default Re: AMC/Jeep 258 Inline 6 Dual/Triple Carbs

I have the smaller version of that engine, a 2.5 4 banger/5sp. It was EFI/computer controled with all the gadgets. Now it running a 2 barrel Rochester, and a S/S dist with mechanical advance. Runs very strong for a 4 banger, and my 29 PkUp has never run so well. The B engine is for sale, LOL Iceman
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Old 06-15-2010, 10:55 AM   #6
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Default Re: AMC/Jeep 258 Inline 6 Dual/Triple Carbs

Don't be all hatin' on the 258. I have a 258 in a 1980 AMC AMX. The hot setup for a 258 would be to swap on the 4.0 head which flows much better. The factory exhaust manifolds on a 4.0 flow really well too, they pretty much are factory built headers. Even crazier would be to make a 4.0 stroker motor using the 258's crank to make a 276 cubic inch motor. The 4.0 will bolt in place of the 232/258. I helped my friend put in a 4.0 into his AMC Eagle, everything bolted up to it just like the original motor. The distributor and flywheel will interchange with the 258 as will the intake although the exhaust manifolds are different. The 4.0 does seem to rev a lot fast that the 4.2 and is probably better suited for a hot rod because of it's shorter stroke.
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Old 06-15-2010, 11:07 AM   #7
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Default Re: AMC/Jeep 258 Inline 6 Dual/Triple Carbs

see this thread,,,

http://www.jalopyjournal.com/forum/s...ht=tricknology
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Old 06-15-2010, 11:15 AM   #8
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Default Re: AMC/Jeep 258 Inline 6 Dual/Triple Carbs

Jeep 6-banger so here goes, please bear with me.

Can anybody post a link to the SOHC Jeep 6-banger engine's head? The one that has a 6-lobed cam that operates both the intake and exhaust valves with one lobe????

I'm really curious about it to see just how it is designed.

Thanks,

pdq67

PS., years ago, one of the old mags did an article on a hopped up 258 that was direct port injected using a drilled and reworked factory head and I want to say along with headers and a turbo, but it's been years and years.
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Old 06-15-2010, 11:31 AM   #9
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Default Re: AMC/Jeep 258 Inline 6 Dual/Triple Carbs

If you KNOW a good welder , you can take a stock aluminum or cast iron single carb or EFI manifold and adapt dual or triple carbs.

Also call Clifford Research 6=8 and they can send you to someone that will modify a clifford manifold.

IT IS EASY TO DO.
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Old 06-15-2010, 11:35 AM   #10
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Default Re: AMC/Jeep 258 Inline 6 Dual/Triple Carbs

Why would you not just use a 4.0 jeep engine?

they are better and cheaper, you can get a used 4.0 that will not have to be rebuilt, just clean it up and drop it in your Old 50's Mopar.

why use the 258 that will have to be rebuilt and is not as good as a 4.o?
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Old 06-15-2010, 11:38 AM   #11
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Default Re: AMC/Jeep 258 Inline 6 Dual/Triple Carbs

I just crushed a postal Jepp with one of those in it.
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Old 06-15-2010, 11:56 AM   #12
Jagman
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Default Re: AMC/Jeep 258 Inline 6 Dual/Triple Carbs

I saw a guy with an early Cherokee with a 4.0 in it running a 4bbl, it was a stock manifold, he said.......

I know Pontiac offered a 4bbl on their overhead cam 6 also, doubt it would fit, but you never know....
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Old 06-15-2010, 12:05 PM   #13
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Default Re: AMC/Jeep 258 Inline 6 Dual/Triple Carbs

The 4.0 inline 6 in the Cherokee was the last of the OHV inline 6's. And I would say the best one ...You can use the late engine without messing with FI by modifying the intake to take a carb and using an older model distributor.The 4.0 even comes with stock tube headers,pretty easy to get 220 hp too.
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Old 06-15-2010, 12:23 PM   #14
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Default Re: AMC/Jeep 258 Inline 6 Dual/Triple Carbs

Quote:
Originally Posted by pdq67 View Post
Jeep 6-banger so here goes, please bear with me.

Can anybody post a link to the SOHC Jeep 6-banger engine's head? The one that has a 6-lobed cam that operates both the intake and exhaust valves with one lobe????

I'm really curious about it to see just how it is designed.

Thanks,

pdq67

PS., years ago, one of the old mags did an article on a hopped up 258 that was direct port injected using a drilled and reworked factory head and I want to say along with headers and a turbo, but it's been years and years.

That is a very oddball engine. IIRC nothing is the same as the 258. I know it uses 2 different rod bearings. 1-3-5 use 1 style and 2-4-6 uses another.
Mostly used in military applications. Only seen 1 in 20+ years on the parts counter. They also called it the Tornado engine.
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Old 06-15-2010, 01:11 PM   #15
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Default Re: AMC/Jeep 258 Inline 6 Dual/Triple Carbs

Quote:
Originally Posted by nali View Post
Maybe because it should be easy to use a 4.0 head and injection .
Hardly traditional, though.

Anyway, the 258 family of engines has been around forever, certainly before the days of EFI - why didn't anyone ever make multi carb manifolds for them?
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Old 06-15-2010, 01:12 PM   #16
plym49
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Default Re: AMC/Jeep 258 Inline 6 Dual/Triple Carbs

Quote:
Originally Posted by shmoozo View Post
How abut a Triple Weber Side Draught Intake Manifold for that 258?

Or if you choose to swap on a head from a later 4.0 engine (which supposedly breathes a lot better) there's this version - Triple Weber Side Draught Intake Manifold 1991-Later w/ 242 cid (4.0L).

Costly, especially after you add in the cost of the carbs, but cool as all get out and seriously impressive looking.
Yes, as I mentioned in my original post, this is the only alternative. Webers are nice and sidedraft Webers are even nicer - for a sports car. I am interested in a traditional dual or triple downdraft carb manifold.
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Old 06-15-2010, 01:24 PM   #17
plym49
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Default Re: AMC/Jeep 258 Inline 6 Dual/Triple Carbs

Well, I started off by Googling; when I came up dry I started this thread. I've read through all the referenced threads.

Bottom line: there are no downdraft multiple carb intakes for this engine. Never were and probably never will be. The motor is a total intake manifold orphan. The only options are EFI or the hyper-expensive Clifford side-draft Weber setup.

What a shame and still somewhat incomprehensible as this motor has been around forever (Ramblers right on up) and given that you can find a manifold for any other obscure or oddball motor out there.

Thanks to all that replied.
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Old 06-15-2010, 01:43 PM   #18
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Default Re: AMC/Jeep 258 Inline 6 Dual/Triple Carbs

Quote:
Originally Posted by pdq67 View Post
Jeep 6-banger so here goes, please bear with me.

Can anybody post a link to the SOHC Jeep 6-banger engine's head? The one that has a 6-lobed cam that operates both the intake and exhaust valves with one lobe????

I'm really curious about it to see just how it is designed.

Thanks,

pdq67

PS., years ago, one of the old mags did an article on a hopped up 258 that was direct port injected using a drilled and reworked factory head and I want to say along with headers and a turbo, but it's been years and years.
Got 2 in the garage right now and a third head on the bench.
230 ci SOHC 'Tonado' Turns out was quite a popular engine in Argintina, Lots of S.American Mods for it.

Quote:
Originally Posted by plym49 View Post
Well, I started off by Googling; when I came up dry I started this thread. I've read through all the referenced threads.

Bottom line: there are no downdraft multiple carb intakes for this engine. Never were and probably never will be. The motor is a total intake manifold orphan. The only options are EFI or the hyper-expensive Clifford side-draft Weber setup.

What a shame and still somewhat incomprehensible as this motor has been around forever (Ramblers right on up) and given that you can find a manifold for any other obscure or oddball motor out there.

Thanks to all that replied.
Not a complete orphan:

Clifford and Offenhauser made what the customer wanted.....4bbl.

Just make your own.

Jeff

PS. You want to talk oddball, try finding an alum intake or head for the 134 flat four.
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Old 06-15-2010, 03:03 PM   #19
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Default Re: AMC/Jeep 258 Inline 6 Dual/Triple Carbs

My first car was an 88 AMC Eagle with the 258 I6. If I remember correctly, it was very slow, but never short on torque. Everthing behind the engine seemed too weak, at least when used like a truck. I had checked out what was available performance wise, and there was a tubular header and a 4 barrel intake, not much else. The 4.0's were still relatively pricey late model stuff then. (approx. 1998)

The engine itself was reliable and I still wish I would have pulled that aluminum valve cover off before selling it to the junkyard in 2003.

Maybe a carbed 4.0 would make a nice powerful and affordable inliner for an early Chevy like my 48? I love the look of an inline, but the lack of power without thousands of $ is excruciating. This could be a SBC alternative that makes sense, unless you're stuck on matching engine makes.
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Old 06-15-2010, 03:35 PM   #20
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Default Re: AMC/Jeep 258 Inline 6 Dual/Triple Carbs

Quote:
Originally Posted by plym49 View Post
Hardly traditional, though.

Anyway, the 258 family of engines has been around forever, certainly before the days of EFI - why didn't anyone ever make multi carb manifolds for them?
Because, 1. They didn't come out until, what, '65-'66? The mid '60s was when the single four barrel really took over as THE performance carb. 2. Like it or not, AMC sixes were way down near the bottom of the list of engines to spend $$$ on tooling costs for multicarb intakes for. Same reason you'll never see a 3X2 intake for engines like Buick or Olds 350s, the late AMC V8s, or 472/500 Cadillacs; they were just born too late. I think the only reason you saw 2X1 and 3X1 intakes for the 194-230-250-292 Chevy sixes is that it was such a natural on the 216-235-261s that came before them that the same technology was carried over, at least by Offenhauser.
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