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AMC Cylinder head Flow data

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  • AMC Cylinder head Flow data

    With the number of cracked 360/401 cylinder heads that I have been finding lately, I thought I would try to use 304 heads with bigger valves in them for the full size Jeep 360's that I build.
    The idea is to use the chevy 2.02" / 1.60" valves in the 304 cylinder heads and hope that we can get the flow numbers to come close to a stock 360/401 head.
    The first thing that I wanted to do was to just have them machined in and then measure the differences in flow between a stock 360 head, a stock 304 head and a modified 304 head with 2.02"/1.60" vlaves.
    To do this we had to install new guides which have to be replaced about half the time anyway.
    Our results for the stock 304 head is really close to what Mr. Parkman has recorded here so, I know that my numbers are fairly accurate.

    The 360/401 cylinder head is a 1977 #3231475-1 and the 304 head is a 1978 #3233324-2.

    I am really happy with the intake side. The exhaust side is not as close but is getting there. This is with no fancy work or anything. It is just what the cutter can do under normal machining.
    I didn't want to have to do any more than that but to get the Exhaust flow numbers up I guess that I will have to.

    304 head 2.02"/1.60" left side, 1.787"/1.406" right side
    IMG_2828 by Rick Jones, on Flickr
    IMG_2836 by Rick Jones, on Flickr

    304 head machined for 2.02"/1.60" valves

    IMG_2822 by Rick Jones, on Flickr
    IMG_2823 by Rick Jones, on Flickr

    Chuck at the Machine Shop spent 45 minutes on each head blending in the short side radius. Looks to me that it was worth the effort.
    This basically exceeds my hope of matching the flow of a stock 360 head with minimal work.
    IMG_3102 by Rick Jones, on Flickr

    Here are the flow numbers from the Edelbrock Performer 401 heads. I port matched these a little better than delivered to match the intake gasket as well as match a header gasket.
    I actually removed a fair amount of material at the Dog-Leg.
    CylHdFloW by Rick Jones, on Flickr

    Interesting that the Edelbrocks pretty much equal the stock 360/401 head but are not hugely better as far as flow goes. Of course the bonus is no cracks and lighter weight.
    Last edited by SC/397; 05-03-2022, 08:39 AM.
    The Squeaky Wheel gets replaced in my world

  • #2
    AMC Cylinder head Flow data

    I like starting with the 304 heads because of the "clean slate" to work with

    Little more work getting to the larger valves but good product in the end.

    The cutters I have show better results on the intake and exhaust with similar work but not far off.

    I usually get low to mid 230's at .400 with minimal work and mid 250's by .450" lift with some pushrod pinch, short turn and runner cleanup

    It does not take a ton of work to match Edelbrock out of the box but the Edelbrocks sure are a heck of a head start to work with and with some work, not maxed out, they can go around 280 at .500 with a 2.02. A similar iron head will do the same if not better due to a better shape on the short turn if you get it right

    Biggest disappointment for me and Edelbrock is the lack of short turn. The heads still work well but the head could have been considerably better with more short turn to work with.

    You can do a multi angle back cut on the vales to pick up the .1-.3"


    • #3
      AMC Cylinder head Flow data

      A chamber cut will help a little also


      • #4
        Like Mr. Parkman says, It is hard to beat the AMC cylinder head out of the box for the times.
        I wish that Edelbrock would have done a better job so that we didn't have to grind on them to be better than the plain old stock AMC head. I guess I should feel lucky that we have the option but at $2,550.00 a pair is is still hard for me to justify.
        I have at least 6 pair of 304 heads. I should send them all to so that you can do them up for me...
        Question: have you ever seen a 304 head that was cracked in the corners?
        The Squeaky Wheel gets replaced in my world


        • #5
          AMC cylinder head flow data

          I have never seen a 304 head cracked.

          I like to use the 086 castings if available and the exhaust side is all 3/8

          Not a big deal making all exhaust threads 3/8 on the castings with four 5/16 threads but it is something else to do

          I was just talking to someone today about Edelbrock coming up short on the short turn. Seems there is more to work with on a factory head than they give you.

          Next time I do a set of 304 heads I will get some flow numbers. I started a set for an upcoming build but I took the guide bosses down on two runners so both heads will have that done.

          I spent thousands over the years developing cutters for machining seats, bowls and chambers and I have a pretty good system now.

          I have done a lot of stock eliminator heads, tons of AMC and many others so it has been a work in progress. I am happy with what I have now and it all works well

          If you want to send some I would be more than happy to do them