jdhasa65cuda
Well-Known Member
Rebuilding the Commando 273. Any suggestions to upgrade the intake manifold from the stock cast iron? Thanks.
Upgraded 273 commando intake manifold suggestion
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What year? If 66 and up go with LD4B. If earlier the original heads have different mating angle to the intake(D4B) and bolt sizes.
Looks like you have a 65 according to your avatar. If it's the original engine you will need a 64-65 intake like 4spd suggested. A Edelbrock D4B is a excellent upgrade. They are hard to find and a bit spendy but worth the extra coin. Start a wanted thread here. May be someone has one for you.
dano
Evil Handy Man
What are you planning for a build? A lot of that information will dictate what intake to use.
As per the 66-back intake bolt angle, you can always buy newer heads too to avoid the issue, then your options open up on the intake too.
As per the 66-back intake bolt angle, you can always buy newer heads too to avoid the issue, then your options open up on the intake too.
jdhasa65cuda
Well-Known Member
I’m using swirl port heads from a 1987 318
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jdhasa65cuda
Well-Known Member
jdhasa65cuda
Well-Known Member
Looking for better performance from the rebuilt engine I’m working on than I believe could be had from 55-year-old technology. Looking for more horsepower than stock iron.
jdhasa65cuda
Well-Known Member
1965 block that was upgraded by a previous owner for you and a Dodge dart on the track. He put 340 heads on that little engine and it didn’t Run well for him so he put the engine in storage and I got it for 300 bucks and now I’m making whole again to put in my Barracuda
jdhasa65cuda
Well-Known Member
Thank you for your advice
So with "no heads" theoretically, you can choose either year, 65 and down for D4B. But harder to find= more $$ or go 66 and up with a wider variety of heads and intake.
Good to know. 64 and 65 heads get the D4B and the 66 and newer heads get the LD4B (or comparable intake)
Well Hp is found in the higher rpms. The D4B for LD4B have potential for more hp. May cost some torque on the street - the Hot Rod Magazine dyno test from '68[?] hints at that. Other thing to watch with the dual planes is hood clearance.
Spacer to make a larger plenum should help on the higher rpms with a stock single plane intake.
Years ago David Vizzard tested a bunch of aftermarket intakes and found that many did not have as good fuel distribution or general performance as the factory intake. I'm sure he wasn't testing a 273 but it does serve as a cautionary tale.
Spacer to make a larger plenum should help on the higher rpms with a stock single plane intake.
Years ago David Vizzard tested a bunch of aftermarket intakes and found that many did not have as good fuel distribution or general performance as the factory intake. I'm sure he wasn't testing a 273 but it does serve as a cautionary tale.
Actually the stock cast 273 4bbl manifold is a single plane design and the LD-4B (or D-4B) are dual plane manifolds. I believe that that will mean more low end torque.
The LD4B test on the 340 suggests that generalization probably doesn't hold in this case. The factory needed a low hoodline intake that performed well on the street. The LD series were focused on better high rpm. The LD4B has fat runners (although they do taper down to the 318 port size) and this is probably where at low rpm velocity is lost in at least some of the runners. On the other otherhand If low and mid throttle manifold vacuum is high enough, it might not make a measureable difference.
Thinking about this now, some time back Paul C posted quite a 273 tests. My recollection was they were mostly focused trying differing cams and then running them in the quarter or on an engine dyno - I don't recall which. I wouldn't be surprised if we could find some intake comparisons in Paul's posts. It would be interesting if he had any data on the factory single planes.
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That would be interesting. Damn, I wish our local speed shop had their dyno set up when I got my 273 done. I had a LD4B at that time too. The factory cast single plane manifold isn't much.
Since you are using 302 heads, you will be loosing air flow, unless ported, by 15 to 20 cfm. If you are running 64-66 exhaust manifolds be careful of an interference with the exhaust ports of the smog heads on the rear drivers side. You can run any 66 up intake for a 273,318, 340, or 360. I love the 340 cast iron and a TQ. 340 Air gap would probably work well. Think the whole thing out before you buy any parts. What to you want to do with the car? You can't really get a better short block. The biggest temptation to resist would be too large a cam. LD4B would probably be the best, sold with a Chrysler number for racing, small port intake followed by a Weiand followed by a Performer.
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55 year old technology would typically clean newer technologies clocks for decades.
Can use a simple 2 to 4 bbl carb adapter to go with your Stock 273 intake manifold. Your small port 273 and intake bolt angle setup will be a challenge for the newer more available intakes.
Using your original intake and camshaft, don't have to tear the engine down for starters for the added power 4 bbl upgrade.
Your stock intake runners match the head ports for smooth port flow, and it already bolts up.
Stock 273 and 318s are good low end torque engines that will benefit from the added 4 bbl.
Lots of reasons have done it with success with the stock cams many times for an added boost and the 4 bbl secondaries to play with besides.
Makes them run Happy, giving them the fuel they need.
Even the tone of the engines deepen up with the 4 bbl vs the economy 2 bbl carb.
There you go, Happy Hot Rodding . . .
Edit:
The Edelbrock 1406 Electric Choke carbs work great on the stock 318s as is, just bolt them on and go.
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SpiderHelix
Active Member
I like the simplicity of this idea, but I have to think a stock 4bbl manifold would be much better.
What carb would you suggest for 66 273?
What carb would you suggest for 66 273?
Stock 66-67 273 four barrel intake and 65-67 273 AFB to match your transmission.
@toolmanmike knows 273s, he can recomend a carb.
We use the Edelbrock 1406 on everything here, 318s, 360s, and today just fired up a fresh .060 over 383 and ran that one with the 1406 too. Very Responsive
Ran the same 1406 carb ^^^ on these 2 different engines. Both ran just fine.
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We use the Edelbrock 1406 on everything here, 318s, 360s, and today just fired up a fresh .060 over 383 and ran that one with the 1406 too. Very Responsive
Ran the same 1406 carb ^^^ on these 2 different engines. Both ran just fine.
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dave ellis
Well-Known Member
Any manifo
any manifold can be redrilled to match original heads if needed.
Any good carb will work on a 273. If new, the Edelbrocks are good and I like the Holley Street Demons. I have run TQ’s and Q-Jets on 273,s also.
My original 273 carb was worn out so I put on a 1406. I adjusted the idle mixture, idle speed and hooked up the choke and drove away. That was probably 10 years ago. It will get just short of 20 mpg on the highway. They are good carbs!
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