283 HP Potential

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  • Dick G.
    Very Frequent User
    • June 1, 1988
    • 681

    283 HP Potential

    If I built a 1960 283/270HP 2x4 engine, say punched out 30, and used correct ported heads, and used a roller camshaft, what is the max horse I could hope for in a street engine? What else could I do to raise the Horse for a street engine. Thanks DG
  • Stewart A.
    Expired
    • April 17, 2008
    • 1035

    #2
    Re: 283 HP Potential

    Dick I have a computer desktop dyno I can give you a close ball park figure if you would like a TQ and Hp figure. Do you want the motor to look standard because that will limit the H.p. that you will be able to aquire. I guess you will want to be running normally aspirated so if you give me carb size, valves sizes, bore size and cam specs I can give you a fairly acurate range. Also have a look at what size crank you can fit in it. I'm not sure but I wouldn't be suprised if you can get well into the 300 cubes now. I'm just about to ask my machinest as to the biggest stroke I can use on a 283 because a good old American saying there is no substitute for Cubes, that saying has been around for a million years and it hasn't changed, the more cubes the more torque. If you give me a figure of what type of HP you would like I can tell you what gear you need to run and what works best for bang for bucks. Stewy

    Comment

    • Mike M.
      NCRS Past President
      • June 1, 1974
      • 8332

      #3
      Re: 283 HP Potential

      just finished building a 283 250 hp resto engine for our 57 vette. over 330 ci , stock appearing externally, and pulled 330 HP on engine dyno. mike

      Comment

      • Duke W.
        Beyond Control Poster
        • January 1, 1993
        • 15497

        #4
        Re: 283 HP Potential

        Let's start with the OE gross power ratings; 283 gross ratings are reasonably close to reality - perhaps a bit overrated, but nowhere near as much as 327s.

        Massaging the heads on a 283/270 and raising the CR to about 10.5:1 with the Duntov cam will get around 300 gross HP, and this will yield about 260 net horsepower, which is what really counts, and assuming 15 percent drivetrain/tire loss, this would be about 220 at the rear wheels with SAE air density correction, which is what a good OE L-79 will do. And you need a good enough bottom end to allow 7000 revs. The Duntov cam and OE springs with proper installed height are okay to 7000.

        The effects of a typical roller cam would be to raise peak torque somewhat, but likely less low end torque and probably no more peak power- maybe even less. Peak power is primarily a function of head flow. Valve timing is merely a "tuning parameter" to get a desired torque bandwidth. Given the cost of roller cam conversions, I don't recommend them. Roller (hydraulic) cams require gorilla valvesprings that load of the valvetrain and limit revs to about 6000. One would be much better off using a slightly modified Duntov cam - widening the LSA slightly for less overlap and indexing the inlet lobe a little later. This adds about $100-150 to the cost of an off-the-shelf Duntov cam, which is a whole lot cheaper than a roller cam conversion, and you maintain OE valvetrain reliability.

        Mike's stroker with the "Special Powerglide Cam" (swaps the lobes on the 3896929 with rather late phasing because of the long stroke) yielded a very PG friendly torque bandwidth (about 90 percent at 2000) while maintaining the smooth 500 RPM idle. Massaging the heads and the FI "single plane" manifold architecture allowed very good top end power without killing the low end torque.

        As a general rule, 283s with massaged OE heads, equal or a little more compression than OE, and maybe a special camshaft using OE lobes with optimized timing/indexing will achieve net power equal to the gross ratings - all this while maintaining OE appearance and idle characteristics.

        Duke

        Comment

        • Stewart A.
          Expired
          • April 17, 2008
          • 1035

          #5
          Re: 283 HP Potential

          Mike I presume you got away with using a 327 crank. Can you tell me what brand it was and is it a steel crank. Did you have to grind alot of the block to fit the crank in. Sounds great.
          Duke roller cam shafts are a bit of an expensive addition but for me they allow me to run a more agressive cam because it smooths the low rpm idle alot. I just built a 302 cubic inch ford that made 586 hp at 6500 I ran beehive style springs which had not much more seat pressure than my standard ones. I think it was 120 on the exhaust and on inlet. The cam was 230/ 230 at 50 figures and it runs like its stock. Wife drives to get shopping. It Pulls very strong down low and blows the tyres out in most of the first 3 gears. I think If I was building a 283 hotty I would be looking at a new style stroker crank for it so as to have the bennifit of 45 extra ft/ lbs torque. Don't forget Torque is what makes Hp in my book.

          Comment

          • Duke W.
            Beyond Control Poster
            • January 1, 1993
            • 15497

            #6
            Re: 283 HP Potential

            Like I said, peak power is a function of head flow. You didn't say anything about installed heads. Stroke doesn't make much difference. You can test this on any simulation program. Do nothing but vary the stroke and the engines will make about the same peak power at the same mean piston speed, so shorter stroke engines will have to rev higher.

            Since Mike's is a "restoration engine" maintaining OE base cam idle quality is critical. Otherwise it will fail a PV, so the Special Powerglide Camshaft has the same effective overlap as the OE cam. Any increase in overlap would have degraded idle charateristics/quality and unacceptable amount. In addition the PG requires very high low end torque to give good normal road driving performance - like pulling away strongly from a dead stop at part throttle.

            You said your engine runs like "stock", but didn't say what "stock" engine you are comparing. A base engine runs much different than a SHP engine.

            Power is proportional to the product of torque and RPM, so both are equally important for peak power. For best average power from off-idle to the maximum mean piston speed that head flow will support, a large displacement engine is advantageous since torque is primarily a function of displacement and compression ratio.

            Duke

            Comment

            • Stewart A.
              Expired
              • April 17, 2008
              • 1035

              #7
              Re: 283 HP Potential

              Hey duke what is the largest valves you can fit in a standard 283 head
              and what can a standard 270 twin carby setup flow.
              Sorry I realise that changing one item like stroke and leaving the rest would result in a poor hp gain thats obvious, I was thinking that if the crank was swapped the heads were scratched with bigger valves and carby re jetted with a camshaft to match would be the biggest overall hp gain down low and up top.
              Yes my car pulls like a stock engine, the low down air speed is enough for the car to pull fast and cleanly away from a standing position at very low rpm about 1800 -2000 as the rpm increases it obviously starts to come on strong around 3200 and its all over at 7000 rpm. I used an aluminium head from AFR I used the 165's for faster air speed and good street drivability also aluminium lets me run a higher comp. I measured it
              at 10.7 to 1 timing set around 36. I used an rpm air gap dual plane set up to start but changed it to a victor jnr open plenum for an experament.
              The open plane pulls alot harder mid to high end with the dual plane low end to mid. Its a really nice motor to just cruise around in and obviously drive hard in.

              Comment

              • Mike M.
                NCRS Past President
                • June 1, 1974
                • 8332

                #8
                Re: 283 HP Potential

                Originally posted by Stewart Allison (48922)
                Mike I presume you got away with using a 327 crank. Can you tell me what brand it was and is it a steel crank. Did you have to grind alot of the block to fit the crank in. Sounds great.
                Duke roller cam shafts are a bit of an expensive addition but for me they allow me to run a more agressive cam because it smooths the low rpm idle alot. I just built a 302 cubic inch ford that made 586 hp at 6500 I ran beehive style springs which had not much more seat pressure than my standard ones. I think it was 120 on the exhaust and on inlet. The cam was 230/ 230 at 50 figures and it runs like its stock. Wife drives to get shopping. It Pulls very strong down low and blows the tyres out in most of the first 3 gears. I think If I was building a 283 hotty I would be looking at a new style stroker crank for it so as to have the bennifit of 45 extra ft/ lbs torque. Don't forget Torque is what makes Hp in my book.
                cresap machine @ 301 724 8794, ask for dean the owner and tell him i referred you. pretty sure Dean used a forged 350 sbc crank and truned it to get the stroke. had some minimal oil p[an rail clearance problems but they were managable. mike

                Comment

                • Duke W.
                  Beyond Control Poster
                  • January 1, 1993
                  • 15497

                  #9
                  Re: 283 HP Potential

                  Originally posted by Stewart Allison (48922)
                  Hey duke what is the largest valves you can fit in a standard 283 head
                  and what can a standard 270 twin carby setup flow.
                  Sorry I realise that changing one item like stroke and leaving the rest would result in a poor hp gain thats obvious, I was thinking that if the crank was swapped the heads were scratched with bigger valves and carby re jetted with a camshaft to match would be the biggest overall hp gain down low and up top.
                  Yes my car pulls like a stock engine, the low down air speed is enough for the car to pull fast and cleanly away from a standing position at very low rpm about 1800 -2000 as the rpm increases it obviously starts to come on strong around 3200 and its all over at 7000 rpm. I used an aluminium head from AFR I used the 165's for faster air speed and good street drivability also aluminium lets me run a higher comp. I measured it
                  at 10.7 to 1 timing set around 36. I used an rpm air gap dual plane set up to start but changed it to a victor jnr open plenum for an experament.
                  The open plane pulls alot harder mid to high end with the dual plane low end to mid. Its a really nice motor to just cruise around in and obviously drive hard in.
                  Most 283 heads will accept a 1.84" inlet valve (from the 305 CID engines), and the 1.5" exhaust valve is fine, but flow is still restricted relative to later big port heads.

                  The 2 WCFBs provide about 800 CFM @ 1.5" Hg flow and with 3" manifold runners, the induction system doesn't represent a significant flow restriction.

                  You should get a chassis dyno test to see what your engine outputs in the real world. High overlap cams can produce big power on lab dynos with open exhaust, but can take a huge hit in a vehicle when all that exhaust has to be pumped through a restrictive exhaust system.

                  Duke

                  Comment

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