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Chevy sb and bhp ratings

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  • Chevy sb and bhp ratings

    I've looked all over the web, or so it seems anyway, and haven't been able to find any info on what kind of hp a stock 400 would've made. Any of you guys got an estimation? It's a 400 cid small block w/ holley 4 barrel, i think 600cfm, with an Edelbrock dual plane intake...dont know anymore about the intake manifold than that, i imagine that the pistons, crank, connecting rods, cam etc are stock but dont know for sure. Any guesses about bhp? I know thats not a whole lot to go on, but its all i got right now! Thanks!

  • #2
    The stock LF4 was about 185hp/300ft.lbs as used in the K20 and K30 trucks. It was cammed for torque though. Much depends on what cam is in the engine. The cam can make all the difference in the world. It's not hard to get 400+ horsepower from the 400 but it will take a few buck$.


    • #3
      Boat anchor from what I remember, the 400 was never paid much attention from the performance enthusiast.


      • #4
        Tim 125,
        I dunno about that! I worked for a fellow in Florida who used to run sb 400's in mud racers. He build carburated alky engines & blew the doors of all those jokers running big blocks. Of course this guy was a automotive machinist & ran an engine shop. Not to mention he was an old time drag racer from way back & knew how to make an engine run for all it was worth.


        • #5
          As the ice in Greenland is melting at an enormous rate and fuel prices are at an all time high and still you talk of 400 cid to move from you A to B.
          Your grand kids will love you for the world you left them!
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          • #6
            Contrary to what many may think, the 400-based small block is VERY popular in oval track racing to this day. We build many carbs for engines based on the 400 block (377ci - 430ci).
            Tons of torque and very good HP numbers when built right, but these are definitely not stock bottom ends with those short rods, dished pistons, and junk heads that were prone to cracking.



            • #7
              Assertions made without being backed up with repeatable measurable results are simply BS.

              There's no way of reliably quantifying engine HP from the add-on goodies alone. Many of the factors they individually introduce are often discovered to be interdependent when the engine dyno readings are interpreted.

              Shade tree car yokels can make statements anent engine HP and what gets it and substantiate their claims from an extensive repertoire of anecdotes. A few of these guys are keen observers of what works and what doesn't and their observations should be seriously considered. However most are simply repeaters of urban legend and their faith based claims and remarks are worth every bit of the price paid for them. How to tell one from the other often takes a world class BS detector.

              Suffice it to say most HP claims are simply that - claims - and most are exaggerated or at least hopeful without quantifiable and repeatable readings from some source be it ET's, time to speed, time to climb a hill, or figures from a real dyno to substantiate them.

              So make your mods and try them on a dyno or at least before and after performance testing. Detailed comparative results counts towards objectivity. Don't forget to include altitude, air temp, and humidity for each trial. They all have an effect on engine performance.


              • #8
                Hold on while I save that information.


                • #9

                  Forest- yeah your right, but you'll notice i asked for guesses or estimations - not actualy figures - an expierenced gearhead has a good idea the difference between a stock 2 barrel and a 600cfm four barrel has on an engine and etc. Thats what i'm looking for, a rough idea of where the engine stands as is. Thank you though for your input, your absolutely right, i'm just looking for the "claims" if you will. They are indicative of dyno proven hp, if usually overrated.


                  • #10
                    I run a 400 in my ol' truck.
                    6.0 inch rods, 10:1 compression, Comp Cam ([email protected]/.440 lift).
                    With a 4 barrel on gas it'd make pretty decent power but I built it for LPG and run a single Impco 425 mixer so it's actually pretty gutless in the upper RMP range.
                    BTW...if you follow a build up from a dynoed engine, you'll be pretty close to ball park horsepower numbers.
                    IMO to dyno the average street performance engine is a waste of money (up here dyno time is big $$$)
                    I've won a pile of races with "copies" of engines that someone else had dyno tested.
                    For what it's 572 Rodeck dynoed 2208 hp on 25% nitro and 50% overdrive...not something you'll copy out of a hot rod magazine
                    I have tools I don't even know I own...


                    • #11
                      Fasttrack, what year 400?
                      With the Holley and Edelbrock, I'd guess it has
                      no more than 25-30 HP over stock, if it's well tuned.
                      Without knowing what the engine has to begin with, such as compression ratio and what heads are on it, that's as far as I can go.



                      • #12
                        Alex- Yeah i understand; i don't even know the year yet. I haven't had a whole lot of time to go over it and haven't really looked for the vin on the block yet. Its a junkyard engine that some yokel "rebuilt" and put in the truck. It sounds nice but they did some pretty shody work. In fact there is gasgainch all over these nice edelbrock valve covers, i dont know how they could've neglected to just run a papertowel over it and wipe the stuff off. Oh well - i was looking for a proj truck!


                        • #13
                          Then ya have these "magic" motors.

                          They ain't supposed to run like that. Take them apart and see what is up, they might not run like that again next time.

                          No clue.

                          But I got this 350 4 bolt main motor out of this old 72 chevy truck, been in seven cars now. Almost hit a WOT viper in the ass in a 77 monza Spyder w/iroc 5 speed, went 160 in a heavy assed 64 el camino.. Magic.. No reason.. It had a Melling cam, junk parts in it, Sig Erson springs on the Monster port 4 barrel heads, torker intake, 650 holley Dpumper *holley's that size will only flow 400 hp or so worth of calories at 85% efficiency.. so HOW did it run so good?

                          So must be Magic.. Steel Crank is scored, bores are wore slightly from original bore size. It'll probably never be magic again. Won't know till I turn it loose thou will I?
                          I priced the machineshop work from the best in the area. After all? I don't want to lose the magic.
                          Excuse me, I farted.


                          • #14
                            i looked it up in 70 265h.p. in 71 with a smaler carb it got 255 hp in 72 when they took it from rear wheels it went down to 170.
                            now if you put a set of heads on it to raise compression and with the other mods you said and some work on the timing you could up it from 25 to 50 hp.
                            one thing to rember is it is tork not hp. that gets a car or truck moving.

                            if you do get it check and make sure you have the right flywheel on it. 400's used their own fly wheel. one from any other motor and it will shake.