how large of a carb can perform well on stock 273 commando ?

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stroker402

stroker402

1968 dart GTS convertible
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Just finished installing a ld4b on my stock spec 273 dartcharger .. also intalled a holley 650 dp with stock specs on top of that .. took it for a spin and it seemed like it was way too much carb . What are guys running out there?
 
I started with the stock AFB and have a 600 Edelbrock on now. Both performed about the same but the Eddy runs cleaner because it is near new. tmm
 
I would think a 650 would be ok as long as it wasn't jetted too fat although I've never tried one.
 
I used to run a 650 dbl pumper on one of my 273s. 10.5 motor with a slightly hotter crane cam and headers. It worked ok after I got it tuned in. Definitely needed to be leaned down though .....
Later I put a 600 on it thinking it might work better but it was not a noticable difference.
 
I got the stock jets of 67 and 73 in the 650 holley dp .. just seems real fat with no crisp throttle response like the stock afb had. no headers yet though..dougs headers are coming next week !
do you recall how much you leaned that 650 dp out > jet numbers ?
 
I'm at 4500 ft and think I got down in the neighborhood of 64 and 65s to get decent plug readings. It's been several years so I don't remember for sure.Try something a few steps smaller and watch your plugs closely until you get dialed in. Unfortunately with modern gasoline it's a lot harder to tell when you're "on". I know I had mine leaned down a lot more than you would think you should.
 
650 is a bit too much for a 273. Also, is it 4 speed? If not, get rid of the dbl pump.

Original D-Dart 273's had a 750 Holley, but they are a much more radical engine than street Commando's.

I like the orig carbs...Carter 4295 500cfm (thats whats on mine), or,if you want more modern, 500/600 Eddy.
 
1404 edelbrock would be optimal at 500 cfm near equal to factory AFB. I use a 1405 as I said I jetted down to .98 from .100, and used rods .073 x .052
 
Well ...... after screwing around with larger carb I went back to the original 500cfm afb.. engine just did not like that 650 dp holley.. too much .
after intalling the original afb .. the 273 loved that ..
great throttle response and revved FASTTTTTTTTT.
after I got the carb all tuned in to that new ld4b .... Relashed the valves again .... quite a few were tight after lashing them cold. now they are 21 and 13 HOT. took her for a BEAT RUN .......... AND ...... What a difference with just switching to the ld4b.. More torque and Power... Now at a roll in 1st gear ... just jump on her and it swauk the tires and get rubber out of second gear... never did that before .. All this with just an ld4b intake change.. and you would not believe how it pulls on top end now. This is all with a stock 273 never opened up. right from chrysler. Dougs Headers will go on in a couple weeks and then may try going up on the carb some.. also .......... 2.93 Gears are coming out and 3.55 are going in ... this 273 is going to be a beast !!..
I had a bunch of 340 darts and cudas over the years .this 273 feels just as fast .. think this engine is a littlle freak .. just keeps getting faster as I tweak it.
has a lot of potenial yet.
I'll keep you post on the updates.
john
 
John...sounds like you're pretty stoked! Cool!

I maintain that the 273 is Ma Mopars' most underrated and underappreciated engine of all time.

Go get'em dude!!!! :burnout::prayer:
 
If you spin it 15 grand you can run a 1050 dominator.
 
ANY small fairly stock engine should have a vacuum secondary carb and not a DP or other mechanical secondary design. That's one reason the old venerable Holley "780" was so popular, the vacuum secondaries let you throw it onto about anything.

The AFBs and AVSs are also much more forgiving in that regard

I would think a 600 AFB would be about the top of the max
 
I maintain that the 273 is Ma Mopars' most underrated and underappreciated engine of all time.

Go get'em dude!!!! :burnout::prayer:[/quote]

You are so correct 65val !! wonder why that is >> most people have nothing good to say about the old 273..

john
 
stroker402 said:
Well ...... after screwing around with larger carb I went back to the original 500cfm afb.. engine just did not like that 650 dp holley.. too much .
after intalling the original afb .. the 273 loved that ..
great throttle response and revved FASTTTTTTTTT.
after I got the carb all tuned in to that new ld4b .... Relashed the valves again .... quite a few were tight after lashing them cold. now they are 21 and 13 HOT. took her for a BEAT RUN .......... AND ...... What a difference with just switching to the ld4b.. More torque and Power... Now at a roll in 1st gear ... just jump on her and it swauk the tires and get rubber out of second gear... never did that before .. All this with just an ld4b intake change.. and you would not believe how it pulls on top end now. This is all with a stock 273 never opened up. right from chrysler. Dougs Headers will go on in a couple weeks and then may try going up on the carb some.. also .......... 2.93 Gears are coming out and 3.55 are going in ... this 273 is going to be a beast !!..
I had a bunch of 340 darts and cudas over the years .this 273 feels just as fast .. think this engine is a littlle freak .. just keeps getting faster as I tweak it.
has a lot of potenial yet.
I'll keep you post on the updates.
john
Click to expand...

John! I wish I could see and hear it. You're doing a great work on that engine.
 
enginewithld4binstalled.jpg
[/IMG]Thanks ulf ... I'll get some pics or video up soon.
JOHNhttp://i446.photobucket.com/albums/qq185/stroker402/enginewithld4binstalled.jpg
 
OK............ I think I figured out this picture posting thing...... ..... you can't post a pic on somebody elses
post .
 

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here is another shot of the dartcharger 273 screamer . ...
 

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