Need some help with a 426 hemi street build

Engine, Trans & Driveline

  1. Dragon Slayer

    Dragon Slayer Well-Known Member

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    I think some of the approach is wrong when you take 12.5 to 1 pistons in a stroker that has piston CD to support the stroke but also the current block deck, then detune it buy adding really thick head gasket to get compression down. The quench will be much different.

    You can mill the pistons to get a lower compression profile, then adjust deck height with a gasket, while retaining a better quench profile. Or find a set of pistons with lower profile.

    I bought a package deal too. Standard bore that had been windowed and repaired, but damaged cylinder never fixed. So I had it bored .030 over to take care of the neglected block that had too much cylinder wall corrosion, new sleeve. Lined hone, a critical thing to make sure you get done with hemi's. Mine was not decked as much but my heads were in the 166-167cc range. I had had to mill them some to clean the surface for sealing and wound up around 165 to 166cc. All chambers not as even as you would expect if you cc all 8 chamber. Which I did. Had new bronze sleeves installed along with the valves.

    I found a complete rotating assembly with ROSS 10.05 to 1 pistons stroked at 4.15. I had to deck the block slightly to square it, and again clean the surface for sealing. At that point I used head gasket thickness to correct compression, considering how much less I had in the heads. Build back to the deck spec for the pistons. I wound up using .080. (Piston spec used .40 head gasket) So I am right about 10.25 maybe a little higher. With sufficient piston to head and valve clearance. Racer Brown made me a SS-H-44 cam. I went Hydraulic for a street car. I Rebuilt almost all of the parts on this, and I tried to use original were possible distributor, fuel pump, water pump, oil pump, alternator etc...). Luckily I had access to the parts and did this under the guidance of a master builder with decades of experience. I did go the big block pulley and balance route. Otherwise your into a grand for parts if you do not have them. Ran great on the run stand, waiting for my modified Hemi K frame, before a transplant into a 70 road runner. One thing about this approach, I can incrementally raise the compression with a gasket change. .020 will yield about a 1/4 pt compression change, as long as clearance are ok which they are. Thick gaskets are expensive though.

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    • Dragon Slayer

      Dragon Slayer Well-Known Member

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      By the way I think I had to go through 5 old heads to get a pair that would work, similar, and that did not have damage. You need to make sure you leak check block and heads if your using original, especially an old race block. Head cracks and leaks are probable.

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      • Dragon Slayer

        Dragon Slayer Well-Known Member

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        One last thought. If you have your heads or get the heads your going to use, dry fit it as is. See how your manifold will sit. If the block was decked correct for the race build, the front and rear walls were also milled. Look around distributor hole to see. If you go back and add deck with gasket you will have a large area to fill under manifold on the walls. IF you are using original heads and do it, chances are the intake port might not match and you milling the intake. Getting a solid seal and port match on the intake is pretty important.
         
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        • Beekeeper

          Beekeeper FBBO Gold Member FBBO Gold Member

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          Yes the China walls have had the same amount taken off them as well. I do have a plan to take care of the gap there and yes intake manifold seal is important on any engine as well as port matching for performance. I’m not a newbie when it comes to engine building just a newbie on
          hemis:thumbsup:

          I did do a dry fit on heads with an uncut intake and it was nowhere close to fitting
           
        • Dragon Slayer

          Dragon Slayer Well-Known Member

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          Good luck, hemi's are unique. Just trying to pass on what I learned doing it myself. Do not know how many times I had the crank and pistons installed checking deck height, clearance etc... before I got near the mill.:lol:
           
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          • Beekeeper

            Beekeeper FBBO Gold Member FBBO Gold Member

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            I greatly appreciate all your help and your experiences with a hemi it’s valuable info. I will not turn a blind eye to it.
             
          • Fran Blacker

            Fran Blacker FBBO Gold Member FBBO Gold Member

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            Mr Gasket makes .125 intake gaskets 313G I think if you want to go that way.
             
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            • Beekeeper

              Beekeeper FBBO Gold Member FBBO Gold Member

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              RJ,
              I have sonic tested the block and although not ideal in a few cylinders it has been ran in its current configuration. Here’s my results using a Dakota ultrasonics PR-8 tester
              39B65859-759B-47AE-ABA3-B293E69345C4.jpeg
               
            • RJRENTON

              RJRENTON FBBO Gold Member FBBO Gold Member

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              Beekeeper...
              THANK YOU for your insight and sharing your ultrasonic testing results. The thrust side of the bore thickness (outside) of the odd number cylinder bank looks Ok. The thrust side (cam side) of the bores of the even number cylinder bank (#2 - #8 in particular) are becoming, IMO, marginal. Its POSSIBLE, under extreme pressure loading, for the bore to distort slightly, leading to loss of ring seal. Since you are building a "street use application" it is unlikely those thickness readings will cause difficulties. I wish you well and success with your endeavours.
              BOB RENTON
               
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              • PolyJon

                PolyJon Active Member

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                Nicely written piece Dragon Slayer!
                I found several sets of ‘old race heads’ with varying degrees of ‘porting and repairs’. Most were unusable for any kind of street engine, so took the plunge and went Mopar Aluminum.
                Supposedly a copy of the 65 Alcoa head, or some such first gen casting?
                That seemed right as it’s for an A990 clone lol.

                Well done beekeeper for the read out.
                The #6 wall at 0.080 is thinner than I would have expected in hemi block.
                I would be tempted to put a thick wall liner in there myself.
                If you don’t sonic test then you would never know lol...
                The readings quite clearly shows that core shift is common in many blocks.
                The over .300 wall thickness at the rear is an eye opener indeed.

                My 440 race block was ‘fully linered’ and held up very well with extreme abuse!
                If I still had access to a machine shop, I would fully liner my hemi blocks too...
                 
                Last edited: Dec 8, 2020
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                • Draggin

                  Draggin New Member

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                  Thinking of changing my cam. So how much valve clearance do I have in a stock 426 Hemi? Will pressurized oil rollers solid lifters hold up on the street ( just driven to local car cruises and go to church on sundays)?
                   
                • hangn0ut

                  hangn0ut Well-Known Member

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                  I ran a Hemi with a molar duel plane single 4 barrel manifold. Small solid lifter cam and 830 holley dp. Ran strong and very streetable. To the point where my dad drove the car for about 10 years. And as far as compression goes, e-85 might be a solution.
                   
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                  • 70chall440

                    70chall440 FBBO Gold Member FBBO Gold Member

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                    Thats pretty much the plan I am after.
                     
                  • smithchargers

                    smithchargers Well-Known Member

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                    I put together a low mileage virgin 65 race hemi short block and 64 K heads. I retained the original "12.5-1" pistons and used a .098" Cometic gasket. According to my calculations the engine had 13.1-1 compression in stock form but I now have 10.74-1 compression with the cometic gasket. The engine makes great power and I am running 93 Octane pump gas with no detonation. I currently have timing set at 33 total but have not had a chance to play with that yet.
                     
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                    • 6PKRTSE

                      6PKRTSE Well-Known Member

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                      Hemi engines like to breath. Good induction, lots of cfm with carbs or injection and good headers. They do love compression, but it is still possible to make good power and make it live and be streetable. Mine is 528" 10.5:1 on pump gas. Of course use better race fuel (N02) at the track on the spray.
                       
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                      • Beekeeper

                        Beekeeper FBBO Gold Member FBBO Gold Member

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                        Well all my goodies will be shipping out tomorrow from Ray Barton:thumbsup:
                         
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                        • erickson

                          erickson FBBO Gold Member FBBO Gold Member

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                          I had a Hemi that someone rebuilt with 9.5 Compression didn’t have enough power to get away from its own shadow you should be able to go with 10.5. And run it on 91
                           
                        • Bold & Old

                          Bold & Old if its to be......... then its up to me FBBO Gold Member

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                          My build was stroked 476 582 hp 558 torque and 9-1 comp @ 5800 NOS duel point

                          7 25 199.jpg 426ehmi3.jpg 7-Copy.jpg short23 - Copy.jpg block.jpg

                          Scott smith did the special build on the stock looking carbs.... they are the old carter look with eldys interior... http://www.harmsauto.com/home.html

                          He did a great job on mine.

                          I kept mine mild with plenty of punch
                           
                          Last edited: Jan 14, 2021
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                          • 6PKRTSE

                            6PKRTSE Well-Known Member

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                            Mine making some noise.

                             
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                            • 6PKRTSE

                              6PKRTSE Well-Known Member

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                              Out for a little cruise.

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