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291c heads |
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Boris Badanov
AMC Addicted Joined: Dec/14/2013 Location: NH USA Status: Offline Points: 4209 |
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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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Gremlin Dreams
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Ken_Parkman
AMC Addicted Joined: Jun/04/2009 Location: Ontario Status: Offline Points: 1814 |
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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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WesternRed
AMC Addicted Joined: Aug/03/2010 Location: Australia Status: Offline Points: 5799 |
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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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I've finally given up drinking for good...........now I only drink for evil.
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Boris Badanov
AMC Addicted Joined: Dec/14/2013 Location: NH USA Status: Offline Points: 4209 |
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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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Gremlin Dreams
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70amxvegas
AMC Addicted Joined: Apr/26/2009 Location: Lost Wages Status: Offline Points: 1793 |
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71 or 72 heads that are worked flow much better .
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68Ambler
AMC Apprentice Joined: Nov/04/2018 Location: Milwaukee Wi. Status: Offline Points: 98 |
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God I love this Forum.......
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1968 Rambler American 1964 Rambler Classic Typhoon
1966 Classic Cross Country 770 1969 Rambler American 1965 Rambler American 330 Wagon |
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Hurst390
AMC Addicted Joined: Apr/20/2008 Location: secret Status: Offline Points: 5818 |
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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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SC/Hurst Rambler
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amx39068
Supporter of TheAMCForum Joined: Feb/21/2008 Location: Arizona Status: Offline Points: 11576 |
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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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Dan Curtis-Owner and CEO AZ AMC Restorations; Facebook: https://www.facebook.com/amcmusclecars/ & Curtis Real Estate Development
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pnypwr
AMC Addicted Joined: Oct/11/2009 Location: ct Status: Offline Points: 691 |
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70 amx 360 survivor
74 gremlin 390 69 amx 390 project 68 sport satellite vert 440 03 mach 1 4.6 4v with a snail 65 mustang notch 347 |
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SuperStockAMX
AMC Apprentice Joined: Dec/29/2009 Location: Anthem, Arizona Status: Offline Points: 237 |
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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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