Hot Rod Magazine HP 273 build

Small Block Mopar Engine

  1. toolmanmike

    toolmanmike FABO Staff Staff Member FABO Gold Member

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    I don't get the magazine but just caught this. Looks like their dyno numbers were damn close to the factory's 235 horse rating. They added headers and dyno'd it again for a slight increase. There's some D Dart info at the end of the article. @ddartdude Alan,have you seen this yet?

    Testing the Mopar 273 Power Pak on the Dyno - Hot Rod
     
    Last edited: Dec 13, 2019
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    • pishta

      pishta I know I'm right....

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      .012/.014 lifter specs? There are thinner gaskets available, MP made a red one that was .020 IIRC. Thats pretty close to the 235 advertised.
       
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      • Jimmy-James

        Jimmy-James Active Member

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        My 65 Dart GT had the 273 and we wanted to build it for a supercharger... Novi1200, but we could not find any pistons that could handle it. So had to move up the big brother 318.
        Custom cut pistons were cost prohibitive to my budget. (Limited options)
        Was bummed out, how cool would it be to say “it’s got a supercharged 273 pushing 400 plus pony’s” ?
         
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        • toolmanmike

          toolmanmike FABO Staff Staff Member FABO Gold Member

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          Yep. Gotta pay to play! Pistons are he biggest hurdle. I see HR used the Egge slugs. They are good stuff.

          09_24_0.JPEG

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          • 67autocross

            67autocross A new iron curtain drawn across the 49th parallel

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            They should of had that other magazine engine builder do the build...it would have made at least 325hp
             
          • toolmanmike

            toolmanmike FABO Staff Staff Member FABO Gold Member

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            I think HR wanted a stock rebuild they could dyno. They weren't going for max performance.
             
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            • azaustin

              azaustin FABO Gold Member FABO Gold Member

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              Thanks for posting this. I’m always looking for performance articles on the early 235hp 273’s. I read everything I could find about them during my senior year of high school since I owned a ‘65 Dart Go-go with the four-speed. Wish I could remember what my rear gears were, but they were low (high numerically.) The car would easily hit redline in fourth, resulting in an indicated 115mph, running stock tire sizes. I remember setting up the stock dual-point distributor on my school auto shop Sun machine and adjusting the AVS metering rods to settings published in a magazine. Fuel was 104 octane DX Sunray Super Boron, which was what Sunoco 260 was sold as in Oklahoma. I welded a three-inch cutout just behind the “Y” in the exhaust tubing that exited under the fender. Somewhere I found a set of small-bolt pattern 14” wheels and also a set of “cheater slicks” to mount on them. The stock Auburn three-spring pressure plate didn’t last long under this abuse, so I mounted a rebuilt high-performance disc and pressure plate. Much better. I wish I had kept my timing slips, but my recollection is that the car ran in the high 14’s at our local drag strip. It was a real sleeper, and really stood out amongst all the Mustangs and Camaros.
              Makes you wonder what the engine would have done with the original head gaskets. I’m betting that Those other 2hp would have come to the party.
               
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              • toolmanmike

                toolmanmike FABO Staff Staff Member FABO Gold Member

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                That's a great story. Thanks for sharing.
                 
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                • azaustin

                  azaustin FABO Gold Member FABO Gold Member

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                  That’s a picture of the car by my online name. It’s the only one I have. It was exactly like the coupe in the Dart Go-Go brochure. When I’m done with my current project (which, according to Ulf is a real Go-Go by its’ serial numbers) I will have one of each from the brochure, an automatic convertible (which will be a clone, even thought it has the 235hp motor stock), and my coupe which is a four-speed and optioned exactly like my high school car. I am adding period-correct options like the KH disc brakes and sway bars, and both cars will have 7.25 Sure-Grip rears, 3:55’s for the coupe and 2:91 in the convertible.
                   
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                  • Johnny Dart

                    Johnny Dart Well-Known Member

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                    Digging the D Dart write up.
                     
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                    • 65dartcharger

                      65dartcharger Dart Charger 273 Historian FABO Gold Member

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                      Can't wait to see them.
                       
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                      • chryslerfat

                        chryslerfat Well-Known Member

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                        Thanks for posting this
                         
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                        • ddartdude

                          ddartdude Well-Known Member

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                          Yes....it's the same article that is in the Feb, 2020 issue of Mopar Muscle. Looked around the Web for Steve Magnante's contact info to correct some of the D/Dart info. No luck.
                           
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                          • toolmanmike

                            toolmanmike FABO Staff Staff Member FABO Gold Member

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                            There is contact info on the Hot Rod site. @ddartdude
                             
                            Last edited: Dec 14, 2019
                          • 66fs

                            66fs Well-Known Member

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                            I thought it was interesting that the Headers only added just under 11 HP.
                             
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                            • toolmanmike

                              toolmanmike FABO Staff Staff Member FABO Gold Member

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                              The stock manifolds are restrictive but it sounds like the small exhaust valve and ports could be a big factor.
                               
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                              • 66fs

                                66fs Well-Known Member

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                                Maybe not as restrictive as one would think? Also note how flat the torque curve is between 2,500 and 4,500 rpm. If you were running a race motor, headers would be different. But I'll gladly give up the header "hassles" for 10 hp and keep my Commando exhaust.
                                 
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                                • yellow rose

                                  yellow rose Doctor of Thinkology.

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                                  How do you know the headers were any good? Ive tested headers that were a 75 HP loss.
                                   
                                • 66fs

                                  66fs Well-Known Member

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                                  I know people using those headers running a 10 second 1/4 mile in a 65 Barracuda.
                                   
                                • toolmanmike

                                  toolmanmike FABO Staff Staff Member FABO Gold Member

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                                  I think a free flowing exhaust is key for these cars.
                                   
                                • toolmanmike

                                  toolmanmike FABO Staff Staff Member FABO Gold Member

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                                  "How do you know the headers were any good? Ive tested headers that were a 75 HP loss."
                                  A 75 horse loss eh? :wtf: They must have been smaller tube than the stock manifolds.
                                   
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                                  • yellow rose

                                    yellow rose Doctor of Thinkology.

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                                    Nope. Name brand junk. I've said this before but it's worth repeating here.

                                    I've seen more headers LOSE power than make it. If you don't put the engine on a dyno and test you wouldn't know. Or worse yet, you dyno the engine with dyno headers (that is just dumb) and then wonder why the dyno numbers don't match what happens at the track.

                                    Testing between good headers there is very little difference.

                                    Testing between a good header and a junk one is huge.
                                     
                                  • perfacar

                                    perfacar Well-Known Member

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                                    back in the early 1970's ran a 235 dart, 5.13 gear, 29.5 x7 " slicks, 2.47 first gear stock trans, 10" clutch, tri y headers, legal j/s, 13.31@ 102.31. still drove it on street. didn't have trick rings back then.
                                     
                                  • 66fs

                                    66fs Well-Known Member

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                                    Also interesting to note how the 273 makes 235 hp with a miniscule cam .425 lift and 248 duration.
                                     
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                                    • MOPAROFFICIAL

                                      MOPAROFFICIAL Well-Known Member

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                                      That's normal for a small motor and considering those 273/318 exh manifolds were designed around the 273.
                                      Some of the expensive off the shelf headers "for most street combos" only add 12-14 hp. I'm sure if you up'd the ante and went next level...that in comparison to the exhaust manifolds , headers would yield 20+ .and so on. Basicaly stick the power range way higher up in the rpms and the increase is greater..cause the manifold cant scavenge .
                                      Near article ..but the thing about the 273...is it's no smaller than a 360 'externally'...so the novelty just isn't there, for me at least. Like a 265 vs 283, are you really gonna choose the 265 block, hell no. I wouldn't even choose a chevy in the 1st place..lol. but hopefully someone gets what I'm saying. Unless you have a special 273 4 brl car..build a 318 or 340...otherwise go 360 or 408...more power in the 'same looking' motor. Always interested in mopar stuff ...so cool article though.
                                      I'd actually like to see more 241 red ram builds, 3 something cid poly truck motor builds with hemi head swaps... lol how about a dyno test of the those weiand multi 2 barrel intakes on a 383 or 361.

                                      Next time ....they should turbo it.
                                       
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