How much can valve head OD be cut?

Small Block Mopar Engine

  1. nm9stheham

    nm9stheham Well-Known Member

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    Another silly question: How much can be cut from the OD of a 2.02" valve head? Similarly, what is a good minimum width for the seat for moderate street use?

    The reason to ask: I'm trying to stuff AL heads onto a bored 273 block (like Promaxx or Edelbrock) and am seeing a possible issue with the bore notches for the 2.02" intake valve. The pistons' top ring travel is coming uncomfortably close to the bottom of the bore notch with the valve lift I want to use.... like .010" or less if I have any sort of margin for valve float. So I'd like to see if I can do away with the bore notches, or have just a tiny bit at the very top. There is adequate meat in this block that I can shift the bores over and gain .040" or maybe even .050" on the issue, but wondered if the valves OD can be cut down too.

    Tnx.
     
  2. AJ/FormS

    AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

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    Are you aware that there are 1.88 valve Magnum aluminums at IIRC 53cc?
     
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    • toolmanmike

      toolmanmike FABO Staff Staff Member FABO Gold Member

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      I wouldn't butcher valves to try to put a 202 valve head on a 273. Those 1.88 valve heads that AJ talked about sound like a smarter move.
       
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      • nm9stheham

        nm9stheham Well-Known Member

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        I hate to say this, but no, I was not. Whose are they? That would be a better solution to the valve issue. 53 cc may be a too-high CR issue but I can look at it for sure. Tnx.

        I'd prefer to stick with the shaft rockers, so the initial question still stands is anyone has a good idea.
         
      • mbaird

        mbaird mbaird FABO Gold Member

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        I had a machine shop cut some 2.08s BB valves down to 2.02s once... His suggestion... I had no idea you could do that.
         
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        • AJ/FormS

          AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

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          With aluminum heads I doubt you can make too much cylinder pressure on a 273 no matter how hard you try, lol.

          53+8.8+0deck and 5cc eyebrows totals 66.8 and will give a stock-bore 273, an Scr of a measly 9.416. By the time you put a small cam in it (say 62* Ica) she'll be down another two points to 7.6Dcr (at say 900ft elevation), which being about a full point and a half lower than decent to get your monies worth of performance from aluminum heads. At 7.6Dcr the cylinder pressure is predicted to be 148psi. In my experience, the aluminums work great at over 185psi and mine still burns 87E10 at full timing at .034Q

          Some guys here on FABO claim to be running their strokers at over 200psi on pump-gas, and I have no reason to doubt that. I have seen 200 on my gauge at one time, and it ran very very very nice.
           
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          • nm9stheham

            nm9stheham Well-Known Member

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            OK, I'll spill the beans... it is a 4" stroked 273.... so already 9.5 SCR with 63 cc chambers...

            So, back to the original question, or a source of 1.92/1.88" intake valved aluminum heads. I am having no luck there.....
             
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            • toolmanmike

              toolmanmike FABO Staff Staff Member FABO Gold Member

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              Building a 330 eh? I'm intrigued. Benchmark, 400 horse.
               
              Last edited: Feb 13, 2019
            • nm9stheham

              nm9stheham Well-Known Member

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              LOL, I'll stick to the mid-300's for now. 335 ci as it stands at this moment.
              Status:
              • Pistons found to work off the shelf; cast or hyper options, but not HP hypers, so I am not going to push things hard at first
              • Crank, rods, and pistons mocked up to check piston-crank clearance; all good with no machining except for some very small bore botches at the bottom
              • Pin bushing problem worked over to put pistons on standard Mopar rod lengths and a solution found
              • Bobweight computed, and as of now, is in the low 1600 gram range with SCAT I beams (nice!), meaning that the 4" stoker crank should be balanced by some simple weight removal, no heavy metal
              • Piston valve clearance looks good on a detailed simulation spreadsheet with a .520" actual lift at the valve. The piston heads will probably need a touch-up with the Dremel in a spot or 2 once mocked up and P-V clearance checked.
              So this matter of cylinder bore notching for the intake valves, and not running into the top of the ring travel is the last step in the process. I can back off and use iron Magnum type heads with 1.92" valves and be better off. (Or I just may back off the lift some, but this is a cam I wanted to try.) I prefer AL heads, but just cannot see how to do smaller valved ones with all the 2.02" valved products out there.

              A teaser pix of a piston at TDC; deck height ended up at about -.017" with with no decking done yet:
              DSCN2613 (Small).JPG
               
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              • gzig5

                gzig5 FABO Gold Member FABO Gold Member

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                Can't you have the current 2.02 intake valve seats in the head removed and new seats installed and cut to 1.88" or whatever you need?
                 
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                • toolmanmike

                  toolmanmike FABO Staff Staff Member FABO Gold Member

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                  Next question for me, how large are the chambers on those alloy heads? (diameter wise not cc wise)
                   
                • nm9stheham

                  nm9stheham Well-Known Member

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                  I thought of that, but the throats under the seats (should) have been cut to some extent to match to the ID of the 2.02" seats. So it seems like putting in smaller seats would put an edge right under the valve seat sticking right out into the airflow. I think I'll decline the idea of using JBWeld to fill it LOL

                  I just don't know enough about that area to say for sure what could be done int that regard.....
                   
                • gzig5

                  gzig5 FABO Gold Member FABO Gold Member

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                  Not saying that is would be the right way or even possible and it is only money, but i would back cut the seat insert to flow as evenly as possible into the port wall. The other more involved option would be to build the ID up around the seat area with weld material and then blend it all back in. I'm sure if the seat insert had a sharp transition it would hurt but I don't think we are talking about a huge step to blend here. Even I wouldn't try to hack epoxy under the seat, and I use a LOT of epoxy for stuff.
                   
                  Last edited: Feb 13, 2019
                • nm9stheham

                  nm9stheham Well-Known Member

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                  Bigger than the bores.... like the 675's used on 2 BBL 273's. But I cannot give you an exact number as I don't have a set right now. I don't see a reason to fret over the chamber overhanging the block.....

                  Here is how close the valve is; I simulated a 2.02" valve by carefully pasting a 2.02" diameter paper disc to a 1.78" valve in a 675 head. The 273 block is stock bore.

                  DSCN2655.JPG
                   
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                  • nm9stheham

                    nm9stheham Well-Known Member

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                    I dunno, but maybe one could get some heads from Promaxx with the seats not installed and the throats not yet blended and put in the smaller seats like you say.....hmmmm.
                     
                  • AJ/FormS

                    AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s FABO Gold Member

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                    My butt hurts
                    you said 273

                    I still think 1.92s are a pretty good idea and 53cc heads might still work out too, depending on the Ica. I would not be afraid of 195 psi in a streeter. I have run over 185 on 87E10 with full timing and fresh cold air.
                     
                    Last edited: Feb 13, 2019
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                    • MOPAROFFICIAL

                      MOPAROFFICIAL Well-Known Member

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                      Cut any stainless valve down you want.

                      What's the diff between a 1.88 &1.94, .060?

                      Reading a lot of parroting portrayed as 1st hand experience. Seeing my own numbers and things awfully close gives a funny notion...
                      None the less... I have run 184 and 188psi with .030 quench and iron heads.
                      Aluminum heads will not make it detonation proof or any substantial psi ability than iron heads.
                       
                      Last edited: Feb 14, 2019
                    • 604B1duster

                      604B1duster Well-Known Member

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                      • Only $1250 EACH !!!
                      • AB2035CF-9531-4F2B-A4A4-F85A0CEFE3A0.png
                       
                      Last edited: Feb 14, 2019
                    • 604B1duster

                      604B1duster Well-Known Member

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                      Thought you might find this interesting

                      1495A13D-728C-48A0-886B-BBBA4D766A34.png

                      B05E5053-71B6-459C-906B-1D87718CE8A5.png

                      AC3B268D-EEC1-446D-9379-3AD33FC968CD.png
                       
                    • nm9stheham

                      nm9stheham Well-Known Member

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                      Thanks for all the comments... the MP AL heads are 2.02" valves, so no relief there.

                      I just may slide back to EQ/Indy heads and see what that will do to make things easier.... 1.92" valves gives .050" smaller radius on the intake. Part of this effort is to make this mostly an off-the-shelf-parts build and fancy head work doesn't fit in with that idea.

                      I've run 10.3 SCR and 160-165 psi on iron with quench... worked fine and I did all sorts of things with that engine, including towing, but I had to be careful on the tune. This build ought to end up with 9.5-ish SCR and quench with EQ heads, so cranking compression with the cam I wanted to use will be in the 150-155 psi range at local altitudes. So it has that going for it to help with iron heads. Iron just does not give the extra margin that AL does, and I realize I am getting lazier on tuning in my old age LOL
                       
                    • dartfreak75

                      dartfreak75 Restore it, Dont part it! FABO Gold Member

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                      Following.
                       
                    • dirty white boy

                      dirty white boy 47 yr old Juvenal delinquent

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                    • dartfreak75

                      dartfreak75 Restore it, Dont part it! FABO Gold Member

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                      I dont know if this is something you would want to do nm9stheham but in my book I saw where you can notch the top of the block deck for larger valves. Would this be an option here?
                       
                    • nm9stheham

                      nm9stheham Well-Known Member

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                      Hey DF: That was the plan, but then I figured out how deep the notches would go down the sides of the bore; the notch depth for the cam lift I want is such as to get very close to, or even into, the travel of the top piston ring at TDC. So it is a ring-travel-to-notch interference issue. So the options are:
                      • smaller valves, or some combination of that plus other methods, to eliminate the bore notches
                      • lower lift to make the bore notches less intrusive
                      • larger pistons and bores.... (But my next piston choice that does that failed in a couple of ways.)
                      Yes, sir, that is another option, and I have been looking at iron heads today: I have to dig into the Speedmaster 1.92 flows versus the other options. The LA-X is another choice.... but they are out-of-stock all over right now, of course!
                       
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                      • dartfreak75

                        dartfreak75 Restore it, Dont part it! FABO Gold Member

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                        In that case id go with the smaller valve. I dont think that much will be lost from 2.02 down to 1.88 valves
                         
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