Anybody every play with or run a 576 head

Small Block Mopar Engine

  1. pittsburghracer

    pittsburghracer Well-Known Member

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    i was over at a friends house last night and we were talking heads like we usually do (he bought one of my flowbenches) and he grabbed a Mopar performance 576 cast iron head off a shelf. I didn’t get a real good look at them as they were nicely wrapped in cellophane and I didn’t want him to rip them open. He paid some pretty good money for these years ago and never used them. Just curious if any of you guys ever ran a set and what it ran at what weight. He flow tested them and I only now max flow but won’t let that out of the bag yet.
     
  2. yellow rose

    yellow rose Overnight Sensation FABO Gold Member

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    I had 2 pairs of them. Flowed a head. Both pairs got stolen, along with the paper work from the crook who owned the shop. The heads were MY heads, not the shops heads.

    That wasn’t the worst thing that joker did either.
     
  3. PRH

    PRH Well-Known Member

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    Is that the head that’s the MP version of the 308 head?
     
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    • Locomotion

      Locomotion Well-Known Member

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      I ran some earlier in my IHRA crate motor Stock years, but don't recall if there were any obvious differences. It was roughly in the mid-11's at around 3,500 lbs. 1.88" in., .474" lift) But I'd have to do some digging in my records to find more specific details. They are suppose to be an over-the-counter version of the 308 with the most obvious difference being no EGR holes under the exhaust. Always heard mixed reviews. Any other OEM heads in good shape available for a direct same bench comparison?
       
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      • yellow rose

        yellow rose Overnight Sensation FABO Gold Member

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        Yeah, I think so. It had the exhaust port fixed and I forget what the differences were in the intake port if any.
         
      • pishta

        pishta I know I'm right....

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        I have a set on my stroker. have not ran it yet. The PO did some bowl blending and tried to polish the intake port, not sure if he helped them or hurt them. I didnt know if they were a performance head, thought it was just a '308' replacement version. wasnt alot of info on them last time I looked...5-6 years ago.
         
      • pittsburghracer

        pittsburghracer Well-Known Member

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        That’s what it sounded like to me. But with a better exhaust port. I may be going back over soon and may ask to take a better look at them out of curiosity. I guess he bought these before Edelbrock heads were released and paid around 2000.00 for them. They maxed out at 254cfm when he tested time as shipped.
         
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        • pittsburghracer

          pittsburghracer Well-Known Member

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          Man that stinks.
           
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          • rumblefish360

            rumblefish360 So close, yet so far away FABO Gold Member

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            At what lift?
            Doesn’t Edelbrock list there heads to max out there?
             
          • pittsburghracer

            pittsburghracer Well-Known Member

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            Edelbrock heads max out at 243 on my bench. I’m not sure what my buddy flowed these to but I’m betting it was backing up at or before .550.
             
          • Locomotion

            Locomotion Well-Known Member

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            Mopar sold a variety of them in different configurations, bare and assemblies. One was either as-cast or slightly ported while another version was fully ported. There was also a casting for T/A or W-2 rockers. I would guess that the 245 flow are fully ported assemblies. No boxes, "P" numbers to go by?


            From what I know, the 308 and 576 castings are basically the same, except the EGR holes. Same, big pushrod holes too. They've been called "swirl port" or having higher velocities, but don't know if that's accurate.

            Exhaust port floors were raised & flowed better. Had one class racer tell me that they worked so well, they caused overscavenging of the intake flow in the chamber.
             
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            • rumblefish360

              rumblefish360 So close, yet so far away FABO Gold Member

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              *I Think* you are correct.
               
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              • pittsburghracer

                pittsburghracer Well-Known Member

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                My knees were killing me yesterday so I didn’t grab one and flip it around like I would have usually done but it sounded like a limited edition type of deal that came with some porting work. I have to go back hopefully in about ten days as he’s doing something on his mill when I get the parts I ordered yesterday. He’s loving his flowbench
                 
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                • PRH

                  PRH Well-Known Member

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                  I used a set of the MP “308” heads for one of the oval track motors I was working on when those were current in the catalog, but I don’t recall what actually came in the box......308’s or 576’s.

                  The valve size rules were 1.88/1.50, so I had to put ex seats in them.
                  No porting allowed.
                  Nothing mentioned about valve stem sizes, so I didn’t ask any questions and installed bronze guides and used 11/32 stem valves.
                  For the intakes I just cut down .100 long 1.94 SBC stainless valves to 1.88.
                  Exhaust valves were ootb.

                  I don’t recall what the numbers were, but I do remember them flowing more than the 596’s we had been running.
                  In that application, they did make more power too........ running an RPM intake manifold with an adapter and a 4412 carb.
                   
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                  • perfacar

                    perfacar Well-Known Member

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                    the exhaust port out flows the intake from .050 to .250. which is the overlap area, it pulled intake charge out, headers turned red, lost power, ended up making a cam with less duration on the exhaust lobe, it helped some , installed old 587 heads, went back to going faster,
                     
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                    • PRH

                      PRH Well-Known Member

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                      Below .250 lift, flow is mostly reliant on the curtain area and valve job.
                      It seems like there would have to be something out of “ordinary” for a 1.60 valve to be flowing more than a 1.88 valve in those lower lifts.

                      Something along the lines of the intake valve being lowered in the chamber to help facilitate a valve to piston clearance issue........ which would def kill off some low lift flow.

                      I don’t know how much better a 576 ex port is than a 308 head, but I prepped some 308’s for a NHRA stocker, and on those the ex port was never better than the intakes.
                      At .100 lift they were basically even when a back cut was added to both valves.
                      With the back cut on the intake valve only ....... the ex flowed less at all lifts.

                      Intake flow over exhaust flow with back cut on intake valve only:
                      .100 - 10
                      .150 - 13
                      .200 - 19
                      .250 - 30
                      .300 - 40
                       
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                      • Locomotion

                        Locomotion Well-Known Member

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                        I believe the term "outflowing" is in reference to the theoretical ideal ratio of intake to exhaust flow, which has the potential of overscavenging during overlap. But as mentioned earlier, I've heard mixed opinions on the 308/576 heads vs earlier versions and both sides have had respectable performances. Different cam and exhaust specs may be factors.
                         
                      • PRH

                        PRH Well-Known Member

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                        Stock untouched 308 vs 915 ex ports, both with OE valve job and valve:

                        Lift— 308/915
                        .100 — 43/45
                        .200 — 90/90
                        .300 —122/121
                        .400 —141/140
                        .500 —147/147
                         
                      • perfacar

                        perfacar Well-Known Member

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                        the exhaust port is raised on 576 head, more like a W 2 port. theses were tested on flow bench and installed on a stocker elim 340. since the cam has 265 dur @ .050. that does not help . not some farm boy here. ok
                         
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                        • pittsburghracer

                          pittsburghracer Well-Known Member

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                          So what are you trying to say. Are they good or junk.
                           
                        • yellow rose

                          yellow rose Overnight Sensation FABO Gold Member

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                          They have issues because the exhaust port was improved, but the intake wasn’t.

                          I suspect that a 55 degree seat on the exhaust and a 50 degree seat on the intake would help with the over scavaging issues. Plus the widest top cut you can get on both, no back cut on either valve and using a tulip valve rather than a nail head.

                          All those help reduce reversion at overlap.
                           
                        • perfacar

                          perfacar Well-Known Member

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                          in stock elim, have to run stock angles on seats and valves 45 Deg. my old 587 heads out perform them by a bunch. the 576 head felt very lazy, also the intake port is narrow and tall, doesn't match up to a stock manifold port , which is more square. I've tried 915, 576, 974 heads, 587 performs better. just food for thought.
                           
                        • yellow rose

                          yellow rose Overnight Sensation FABO Gold Member

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                          Yeah, you guys in Stock Eliminator have to fight for every single HP. Way tougher than it looks.

                          I thought you could run steeper than 45 degree valve jobs in Stock, but maybe that was Super Stock.
                           
                        • RedB.

                          RedB. Well-Known Member

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                          Was the 576 head bumped from stock/superstock because of exhaust port volume ? { to big/much } ?
                          Is the 576 head the head used on the old LA 360/360 hp crate motors ?
                           
                        • pishta

                          pishta I know I'm right....

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                          Ill have a look at my heads tomorrow and see if the intake port is a different size. Thy are on the floor so EZ to look at. I dont remember them looking any different from ant other LA head. Have to see....Will give me a chance to dust them off too....:rolleyes:
                           
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