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max effort 993 V 291c heads (Read 4326 times)
amxlonnie
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max effort 993 V 291c heads
05/09/11 at 11:45:24
 
Just curious here.  
  I was wondering if there was any appreciable difference from the 291-c heads compared to a set of 72   993 heads with the porting maxed out .  
   I guess what Im asking is can a 993 be ported as big as a 291-c can be ported without  hitting a water jacket.  
   Are the 993's ports  smaller to start with or are they basically the same?
 
 I know the 291-c's have smaller chambers but for max flow the chambers would be opened up to unshroud the valves.
  thanks---Lonnie
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Re: max effort 993 V 291c heads
Reply #1 - 05/10/11 at 02:11:54
 
I have always been told that you might as well start with the larger heads for major porting because people want the 291s for a compression bump on later motors or for stock 70 390s 71 401s  and when you massively unshroud the valves you destroy the value for those people.  If you are going to that much effort one would assume that you are ordering custom pistons anyway so you don't need the small chamber.
 
 
 
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Re: max effort 993 V 291c heads
Reply #2 - 05/10/11 at 19:36:24
 
I know why the 291-c are wanted for the small chambers but my question was relating to porting one to the max.  
  Such as needed for a 600+ hp engine with factory heads. does anyone know if the ports on a 72 993 head could go as big as a 291-c could go.
  Im thinking 280+cfm Intake possibly.
 Or are the 993 heads ports physically smaller,shaped different, or not able to go that far flow wise ?
 
I know this should probably be in High performance but Iv'e not been invited there  Huh
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Re: max effort 993 V 291c heads
Reply #3 - 05/11/11 at 03:09:03
 
Lonnie you might find what you are looking for here
http://theamcforum.com/forum/cylinder-head-flow-numbers-factory-aftermarket_topi c159.html
Dave ----
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Re: max effort 993 V 291c heads
Reply #4 - 05/11/11 at 10:54:37
 
Thanks Dave...
lots of excellent info there nut no answer to my question . . . undecided
 
-----Lonnie
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Re: max effort 993 V 291c heads
Reply #5 - 05/11/11 at 12:39:25
 
You should be able to port them the same as the 291's. They are replacement heads for the 70 heads. Just have someone that knows what they are doing or you may have to use epoxy.
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Re: max effort 993 V 291c heads
Reply #6 - 05/12/11 at 21:54:16
 
here are a couple pics of the 291 heads i have been working on..not very good pics but I basically copied a set of 090 heads that worked real good for me...
the 090 heads have 2.125 intake valves and they had went through in the bolw area and have been welded...I got lucky on the 291 because they have 2.08 intake valves..

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Re: max effort 993 V 291c heads
Reply #7 - 05/15/11 at 04:18:50
 
Plain and simple yes, you can port the 993 heads just like the 291 with no surprises. I prefer the 993 over the 291 in my superstocker.
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Re: max effort 993 V 291c heads
Reply #8 - 05/15/11 at 04:24:09
 
Quote from ssAMX3002 on 05/15/11 at 04:18:50:
Plain and simple yes, you can port the 993 heads just like the 291 with no surprises. I prefer the 993 over the 291 in my superstocker.

 
 Hemi, in you're experience what't the most you get out of OEM heads without welding or epoxy?
 
 SKeown
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Re: max effort 993 V 291c heads
Reply #9 - 05/15/11 at 10:21:48
 
Thanks Hemi,
  I was just trying to determine if the castings had enough material to port and match to a set of maxxed out 291-c's.
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Re: max effort 993 V 291c heads
Reply #10 - 05/15/11 at 11:48:08
 
just for some info,the 993 flow better than the 291c in stock form by 4% ,i can run either set on my g/sa machine and with the 993 heads we made 462 hp on the dyno (4300 carb,stock 762 casting intake ,993 stock heads)  no porting allowed in stock eliminator the engine is a 70 390 and the block is a 529 block,,car ran 11.23 @ 116.00  last month at epping nh    gman
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Re: max effort 993 V 291c heads
Reply #11 - 05/15/11 at 17:46:54
 
G-man the 993 heads do have a better combustion chamber in stock condition.  If you know what you are doing you can obtain 300 cfm air flow @ .700" lift and the port volume will end up at around 295cc . No epoxy, no weld. Just a warning if you start losing air flow at .300 , .400 , .500 lift to obtain high lift flow you will not be happy with the end result.                              
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Re: max effort 993 V 291c heads
Reply #12 - 05/16/11 at 00:44:26
 
Quote from ssAMX3002 on 05/15/11 at 17:46:54:
G-man the 993 heads do have a better combustion chamber in stock condition.  If you know what you are doing you can obtain 300 cfm air flow @ .700" lift and the port volume will end up at around 295cc . No epoxy, no weld. Just a warning if you start losing air flow at .300 , .400 , .500 lift to obtain high lift flow you will not be happy with the end result.    

 
in the stocker rules for amc i have .472 of lift  and i am .020 short of that number of lift(nhra made this a change for 2011)   ,the best flow #'s on the 993 was 241cfm @ 600 lift on the intake and 170 cfm @600 lift,,the 291c where alot less due to the shrouding on the intake vale ,as you know the poured volume has to be held to be legal,,   a little more r&d and 500 hp is not out of the question     gman
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Re: max effort 993 V 291c heads
Reply #13 - 05/18/11 at 12:58:42
 
I found a set of the 993's for sale on a running 360. What would be a good price to offer? I run the 502's for now and looking to have a set of heads ported before I remove my heads.
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Re: max effort 993 V 291c heads
Reply #14 - 05/18/11 at 13:06:19
 
The 090 heads are identical to the 993 heads on the bench.  Too bad NHRA doesn't allow them as replacements, too. That would give more choices.
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