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291c heads

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pnypwr View Drop Down
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    Posted: Jul/14/2011 at 9:55pm
Ive got 291c heads on my amx...what makes these special? I see from posts that they are desireable?  is that way my 360 is "hi compression" small chambers or do they flow well? I know they are square ports not doglegs, have screw in rocker studs but thats all ive seen so far, the intake runners look good sized but im not to fermiliar with the amc v8  ford and mopar yes...ive had plenty but im just learning about the amc v8 engines
70 amx 360 survivor

74 gremlin 360

68 sport satellite vert 440

03 mach 1 4.6 4v with a snail

65 mustang notch 347
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69 ambassador 390 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 69 ambassador 390 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/14/2011 at 10:14pm
You cannot have 291s and square ports also.  The reason 291s are desirable is that they have the small chambers and Dog Legs too.  The valves are actually a little smaller than the later heads and because of the chamber walls being so tight to the valve they are shroude.  In stock form they are actuall slightly inferior to the later heads in flow.  If you install the larger valves you make the shrouding worse and negate the small benefits of the larger valves.  With a little re-working of the bowls and sleeving the guides to reduce the stem size and running undercut race flow valves you end up with a pretty potent set of heads for a reasonable price.  They are actually very much like the camelback or powerpack heads for Chevy guys.  Back in the day they were the hot ticket but with the availability of modern cams and all the pistons out there they are really just cool to have.  No AMC head is actually bad right up till they stopped selling them in 1991.  The later heads have larger chambers and valves and flow a little better.  The advantage of compression is better attained with proper decking and piston design when rebuilding.  That being said.  I have a fresh set of 291s that are going on my Ambo because they are really cool to have.  My 1972 vintage angle milled heads are going on to my 84 Wagoneer for a boost in compression and flow also.  In short.  291s are desirable because they will raise your compression a bit and mostly for a cool factor.  The price is detonation and uberpremium fuel.  If you truly want to run a set I may come out of mine.  Won't be cheap cuase they are cool and I always wanted a set.  no other real reason to need them.
Steve Brown

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pnypwr View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pnypwr Quote  Post ReplyReply Direct Link To This Post Posted: Jul/14/2011 at 10:52pm
i dont have any need  or desire, thats just whats on the car...I m trying to remember when i had the manifold off to regasket I thought they were square port...as the parts store gave me the wrong set the first time...but with my recent valve train failure I have the covers so I can see the cast numbers...im not building a hot rod its just a stock unrestored car im trying to get going to go to the sturbridge show the end of the month...
70 amx 360 survivor

74 gremlin 360

68 sport satellite vert 440

03 mach 1 4.6 4v with a snail

65 mustang notch 347
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 69 ambassador 390 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/14/2011 at 11:23pm
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.
Steve Brown

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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 2:55am
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote pnypwr Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2011 at 6:30am
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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68 sport satellite vert 440

03 mach 1 4.6 4v with a snail

65 mustang notch 347
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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 10:02am
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 10:04am
Dan Curtis, AZ AMC Collector Quality Restorations & Parts - amcmusclecars.com
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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 10:06am
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 10:10am
SC/Hurst Rambler

11.62 120

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