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291c heads

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Boris Badanov View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Boris Badanov Quote  Post ReplyReply Direct Link To This Post Topic: 291c heads
    Posted: Jan/12/2020 at 12:01pm
The short side radius is too tight for high speed operation.
modding it might best be left to an AMC head specialist.
 
AMC heads flow great.
 
SBC heads are better for very high speed operation.
 
it's all about the short side turn.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken_Parkman Quote  Post ReplyReply Direct Link To This Post Posted: Jan/12/2020 at 10:02am
Unshrouding the valves is not a big advantage. This is an 18 degree head and the shrouding has minimal affect on flow, particularly with a stock valve. Not at all like a crapy SBC. Pay more attention to the valve job and the bowl/short side radius.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Jan/12/2020 at 3:33am
This thread is a blast from the past, just contemplating what to do with my set of 291C heads at the moment, I suspect it will involve some work with a die grinder. What sort of chamber cc do you end up with by the time you unshroud the valves?


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Boris Badanov Quote  Post ReplyReply Direct Link To This Post Posted: Jan/11/2020 at 4:52pm
All large valve AMC heads flow about the same
on the intake side. Dogleg heads out flow square
ports on the exhaust side.

Yes, there are odd race heads made by AMC, but these are rare.

Bottom line is the only reason to think about
seeking out a set of 291s is the combustion chamber
size.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 70amxvegas Quote  Post ReplyReply Direct Link To This Post Posted: Jan/11/2020 at 12:37pm
71 or 72 heads that are worked flow much better .
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 68Ambler Quote  Post ReplyReply Direct Link To This Post Posted: Jan/11/2020 at 10:56am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hurst390 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2011 at 9:06am
here is before and after pics of the 291c head after the chamber mods to unshroud the valves 
 *edit* actually the exhaust had already been opened up in the 1st pic but you get the idea...with 2.08-1.71 valves


Edited by Hurst390 - Jul/15/2011 at 9:10am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amx39068 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2011 at 9:02am
pistons and heads are unique to 1970 390 and 360 and 304s, 71 and early 401s, and all later 304s, 360s and 401 had large dish pistons for a combo of bigger dishes in the pistons and bigger chambgers in the heads. 
 
For example, 70 360 4bbl had 18cc valve reliefs while the 2bbl had 28cc reliefs (IIRC) but both had 50.6 cc head chambers for 10.04 and 9.05 compression ratio respectively.  In late 71 for the 72 model year they switched to all 360 engines having 28 cc pistons dishes and then in 72 also swithed to 58cc heads for a a 9.058 adn then 8.455 compression ratio respectively.  The first 58cc heads for either 090s or 993s (I can never seem to remember which was first without consulting a TSM) which still had indivdual stud rockers and then when the 502-2s cam out they went to brigded rockers which can be reworked by a machine shop to go to individual stud rockers with pushrod quide plates.
 
The total cost of the HS bridged rollers and the cost to convert to individul stud rockers is about the same.  I limit the bridged rollers to cams of no more than a .500 lift.  Others have gone higher but that is the limit I have set for any engines I have built for others or build for myself and seems to be a good rule of thumb as they are all still together and operating as intended.


Edited by amx39068 - Jul/15/2011 at 9:04am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pnypwr Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2011 at 5:30am
Originally posted by 69 ambassador 390 69 ambassador 390 wrote:

You are looking at the wrong side of the heads.  The Dog Leg is on the exhaust.  Your original heads would have been 291s fron the factory.  How did the parts store give you the wrong intake gasket.  There is only one.  They must have given you a Dodge 360 gasket set because thats where they lump us now.  Most parts store guys can't read anything with more than two sylables or form a full sentence anymore.  Be wary of any advice or "knowledge" you get from them.  Come here and ask first.  Trust me if you like your car.  With 5000 members now there must be a 100,000 years of experience all together and the kid behind the counter has dreamed of more engines than he has actually touched in his life.  Usually while reading HotRod on the pooper at school.
really?  I know its the exhaust port...i seem to remember it was square, but it was yrs ago I had the manifolds off.  I dont go to auto zone or any of those places, I go to the local car quest where the counter guy there, has been doing it since these cars were new, he actually trained me when i worked in the parts world...1996-2003 hes been doing it since 71. I cant stand going to the parts store and they counter guy says whats a gremlin or american who...autozone is good for oil and car wash...thats about it.  so are the pistons the same as the later engines? and the compression derived from the smaller chamber?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SuperStockAMX Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2011 at 1:55am
In a nutshell, the smallest combustion chamber offered in a "dog-leg" cylinder head for 360-390-401 was the "291" cylinder head for the 1970 application. It also offered screw-in studs. But the real reason the prices are high is that this is the head the restoration crown needs for their 1970 MD Javelins, Javelin, The Machine and AMX. 
The cylinder heads that followed were basically the same but had a different rocker arm (after 1972 with press-in studs and larger combustion chambers for low-compression mid-'70's vehicles. 
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