Re: [Amc-list] V8 Cylinder Head Questions

[Frank Swygert <farna@xxxxxxx>]

Greg, the 360 and 401 heads are the same -- they will take up to a 2.080" int. and 1.740" exh. valve. 

A note in "Performance American Style" recommends that 2.02"/1.62"  is the max size for 304 heads due to core shift, any larger and you could hit the water jacket or be very thin near it and have hot spot problems. 

Your local machine shop can tell you how much to shave off the head to bring the compression back up, or you can do the math! You need to lose only 2-3cc... I don't think I'd worry about losing the that little bit of compression. Just use the bore surface area, convert to millimeters, then figure how high a cylinder would have to be to take up 30cmm (cubic millimeters, 10 is 1 cc). convert what you find back to inches for the height. It's not much, might be under 0.010". I'd just have the shop true the heads up and let it go, 0.2:1 or so compression loss won't be noticed! 

What kind of driving are you planning on doing? If this is just a daily driver I'd use the 304 heads as-is. The smaller ports and valves will increase low end and mid range torque dramatically, but it will fall on its face over say 5000 rpm. Top it with a Performer or similar intake and no more than a 600 cfm carb and you'll be all set! That way you get to use all you've got invested in those 304 heads AND get mcuh better street performance. Economy should be good with all the low end power too. 

The best thing to do with the valve geometry is order custom pushrods. They don't cost that much, and you can order one adjustable pushrod, set it to the correct length, then send it to the pushrod company for measuring. Better than taking your own measurements! 

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Date: Thu, 3 Jan 2008 13:40:03 -0800 (PST)
From: Greg Taylor <amundaza@xxxxxxxxx>

  I am also considering pulling the intake and heads while I'm at it and installing some 'built' heads.  I have the '79 304 (59 cc) heads I was building up for the 304 stroker turbo motor.  I have ported and polished them and they are currently machined for CHEVY Milodon Megaflow 1.94 Int & 1.50 Exh. valves (I know, they're smaller than stock 360).  I am considering having them machined for larger Chevy valves, as Milodon makes much larger Megaflow valves.
   
  How much larger can I go on a 360, with intake and exhaust valve size?
   
  The 304 heads had had the combustion chambers opened up as detailed in Performance American style, so they are probably about 61-62 cc's in size now.  How much would this drop the stock 360's 8.4:1 compression?  If it would drop too much, how much can I mill off the AMC heads, to bring compression back up?  IF I could machine 0.100" off the heads, there are 0.100" longer Chevy valves that would make up the difference in valve height so that "theoretically" the pushrod length would not be affected.

-- 
Frank Swygert
Publisher, "American Motors Cars" 
Magazine (AMC)
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