Need A Recipe For A 273 Rebuild

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poisondart64

poisondart64

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Looking for a parts list from anyone who has built a performance 273.

What did you choose for pistons, heads, cam, intake, carb, etc. Looking for the right mix to get 250-275hp. This is in a driver, not a racer.

Thanks!
 
Lets work on this together. I will need a combo when it comes time to rebuild my 273. First of all if you have a 2bbl engine you have low compression and need to bump up to the 10.5/1 compression that the HP273 engines have.
The pistons create the compression not the cylinder heads. We need to pick a camshaft and have BJR Racing port some heads for your project. The next step would be a intake and carb. There are a few choices so it shouldn't
be a big deal. The ignition should be as simple as what you want to run from
factory single point distributor converted to Petronics with a hot coil to a oem Chrysler Electronic setup to a full blown MSD. I think the cam and intake/carb will be the hardest combo to settle on. The headers/exhaust are a matter of preferece and your budget. The 273 is allready set up for performance with a forged crank, lightweight rods with full floating pins,
solid lifter cam, the stock 4bbl intake is an open plenum design that can be ported to flow or replaced with an a aluminum for less weight....................
Boy I should quit rambling on and let someone else talk. Your turn!!!!
toolmanmike
 
Replace everything from radiater cap down with 360 is probably the best route. The 273 commando only produced 235 hp at 10.5:1 , fat cam, 4 brl. etc..
200 hp is fine with me so I'll keep my 273. It's bores are too small and its stroke too short to spend performance money on.
 
Oh yes but with some simple performance upgrades like cam, headers, carb,and valve springs the little 273 evolved into a 1hp/cu. in. screamer. Will it make 500 hp? I doubt. Call me old fashioned but I would rather have a 300 hp. 273 than a 400 hp. 360. toolmanmike
 
toolmanmike said:
Oh yes but with some simple performance upgrades like cam, headers, carb,and valve springs the little 273 evolved into a 1hp/cu. in. screamer. Will it make 500 hp? I doubt. Call me old fashioned but I would rather have a 300 hp. 273 than a 400 hp. 360. toolmanmike
Click to expand...
There is nothing simple about headers in an A-body.
A 360 can produce more hp and torque between stock manifolds, plus perform street friendly at any rpm range. I shouldn't knock the 273 since I own 2 of them but even ma mopar found a better way.
 
There's no substitute for cubic inches that's for sure. I like the underdog. I just about jumped and cheered when Mopar Muscle Magazine got 400 hp out of a 318. toolmanmike
 
Toolman, sounds like we have the same ambitions. I am trying to keep it "sorta" time period correct and stay with the 273. Right now she's a /6 w 904 pb auto. Looking to keep the pb by going with a similar 904 for v8. I would be really happy with 275 ponies and ecstatic with 300. Nice to see you are in Iowa. I am in the Quad City area.
 
Thanks for the PM! I'm from Waterloo, home of the John Deere Tractor. I wish one of the Mopar magazines would build a 273 and put on the dyno. I'm not talking about a 1 time shot, maximum horsepower pull but a strong but long lasting 273 that anybody could put in any a body without a 4000 stall convertor and 5:13's in the rear. toolmanmike
 
I understand you want period correct engine so staying with the 273 is wise. Take in consideration of .. is the car going to be judged on original condition? ... is the car got all of the original parts? hub caps, radio, etc.. Now here comes the kicker .... for what you are going to spend on the 273 you could spend on a 360 and be farrrrr ahead of the game. It will be a difference of just a motor pushing the car down the road or throwing the car down the road. LOL!

I know you might want something just to cruise around in and that's it but you can still cruise around with a 360 AND have some horsepower IF you need it. Kind of like a ace in the hole.


I have had both. I bought my 67 cuda with a 273 and tried everything under the sun to get the car to "move". I tried 3 different cams, 2 sizes of carbs, heads, etc.. and it didn't do a bit of good. The motor was even bored .060 over! I knew that the short stroke motor was not a beast put I just wanted extra pep.

Then came the planned out 360. Bored .030, 10.7 compression, better heads, etc.. and it so much better. Longer stroke made a word of difference. You could put a plain old 360 in her and without the bells and whistles and it would be better than the 273. The motors look the same unless you tell someone.

Just trying to save you some money and time. I wasted alot of money trying things on the 273. Oh if you keep the lil 273 a good cam is the Summit cam with .441/.441 lift. I got the part number around here somewhere.
 
I am torn between keeping my 66 as original as I can and turning it into something like this:
 
Thanks for the advice mullinax95. Deep down in my heart I know you are right and that would be the smart thing to do. But hey, if I was really smart I would still own all the cars that I drove from the age of 16-28 (when of course, I got married!). I'd be friggin' retired off the money I could get for them now. We can probably all say that. I appreciate the info on the cam. Any vendors you suggest that offer stuff for the 273? (pistons, rebuild kits, etc.).
 
Might want to look into a set of 302 heads from a mid-80's 318. Yes, they they have smaller valves, but they'll raise your compression ratio significantly and there's less valve shrouding than with heads from a larger-bore engine.

I consider a 273 a straight up hot-rod engine - solid cam, steel crank, floating rods, high C/R... 360's never came with any such equipment!
 
poisondart64 said:
Thanks for the advice mullinax95. Deep down in my heart I know you are right and that would be the smart thing to do. But hey, if I was really smart I would still own all the cars that I drove from the age of 16-28 (when of course, I got married!). I'd be friggin' retired off the money I could get for them now. We can probably all say that. I appreciate the info on the cam. Any vendors you suggest that offer stuff for the 273? (pistons, rebuild kits, etc.).
Click to expand...


The motor was already rebuilt when I bought the car so I didn't buy pistons, rebuild kits, etc..

I would send b67cuda a PM because he just got through rebuilding a 273 not to long ago. Go to post #100 on this thread:

http://www.forabodiesonly.com/mopar/showthread.php?t=27848&page=3
 
Hey Ramcharger, Now you're talkin' my language. Don't forget about the factory dual point distributor,
the open plenum 4-barrel intake, the un-silenced air cleaner, hd (ac) radiator. Not to mention the chrome
air cleaner and the black wrinkle finish valve covers with aluminum heat sinks. Even the pcv and oil fill caps are chrome and are the same part # as on the 426 Hemi. I like my HP273. toolmanmike
 
Personally I would just build a larger motor. Even going to a 318 will be a big plus.

If I were to build a early a body I would start with a 360, nice set of heads, a small solid cam in the 245 @ .050" range, M1 single plane intake, Holley 750 and a set of headers. Paint it all red, Add a set of 273 commando valve covers and air cleaner and tell every one its a 273. Whos going to really know ?

Back it up with a 4 speed and 4.10s for good measure.
 
AdamR said:
Personally I would just build a larger motor. Even going to a 318 will be a big plus.

If I were to build a early a body I would start with a 360, nice set of heads, a small solid cam in the 245 @ .050" range, M1 single plane intake, Holley 750 and a set of headers. Paint it all red, Add a set of 273 commando valve covers and air cleaner and tell every one its a 273. Whos going to really know ?

Back it up with a 4 speed and 4.10s for good measure.
Click to expand...

Save your breath Adam ... I have already tried.
 
I just want to keep mine close to original. I have allways been impressed with the little 273. I would love to have a 64 post Dart with a 408 like the white
66 I posted earlier..........someday toolmanmike
 
Yeah, I know. Some guys like doing things the hard way. Theres nothing wrong with being different.

I would rather have the low end torque of the larger motor then a beable to say I have a 300hp 273.

Remember Chevys 302 ? Theres a reason they only came with 488s and a 4 speed.
 
Ya, I am a bit hard headed...............just ask my wife lol Mike
 
It's true, to get the most out of a 273, it likely wouldn't be very streetable.
Still, the potential is there for a good street engine. 300hp is nothing to sneeze at, especially in an a-body. That's a low 13 second car!

The problem is the bore size, it's very small. You just can't really pack enough in there to make huge power.

They can be made to run though. As an example, there's a '65 Valiant with a 273 in NHRA stock (in the Pac. NW div.) that's run at least an 11.75. Pretty stout if you ask me. But then again, it's stock eliminator, so they have a lot of duration on the cam, high stall converter, steep gears and don't really get going until the upper limits of the rpm range. Again, probably not what you're looking to do, but clearly there's a way to get power out of these engines.

If you're only looking to get 275-300hp out of it, you should be good to go.

See this link for a page about the Commando engines:

http://users.erols.com/dmapes/THIRD.HTM
 
I'm interested in what your uses for the car will be.
Do you want to show it stock with a warmed up motor
and drive it or are you planning to prostreet may race later or
a combination of all.

I'm with the bigger is better crowd but if you want to build a 273
you can come up with a mighty racial sounding motor that will
run good on the cheap.
It's real easy to over cam and carbrate that motor and kill all power potential
on the bottom end.

If your willing to wring it out they take on an eerie sound above 6000 rpm
that scares the competition.

5615.jpg
 
I am in the process of setting up my .040 over 273 2bbl for class specific racing. I know up front that upgrading to a larger engine would be more cost efficient for bracket racing, however. It seems that the biggest hurdle is compression. The 2bbl engine is rated at 8.8:1 with the pistons .011 down. NHRA minimum combustion chamber size is 57.3cc. Mine were as large as 65cc. Head gaskets are another problem. The original steel shim are .020. They also had a small bore for the 273. They are no longer available. Sticking with a solid lifter cam requires a custom grind. Headers are available through Harold at Spitfire. I am waiting for mine. I used a Pertronix setup for ignition. I am optomistic about this build, but also realize that it won't be as fast or as streetable as it would with a stock 360.
 
3404spdvaliant said:
Way to go.
Is this what you call helping?
You know a lil to much about chevys.lol
BTW the reason? remember TA racing??
Click to expand...

Yes, I call it helping. Torque rules the street and a 00hp 360 will make a lot more torque then a 300hp 273 will.

Do I remember TA racing ? Not really. I was born in 78. 9 years after the 69 Z28 raced Trans Am but still 10 years before your wise *** was born. By the way, Those 488 gears probably wouldnt be much use on a real trans Am car.

Yes, I know somethings about GM and Ford. I like Muscle Cars, Just because Mopars are my favorite and thats were most of my knowledge is doesnt mean Im not open minded to like other brands too.
 
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