273 with stock 340 cam ?

[64whiteghost]

So I have a 273 2 barrel bored .30 over and I plan on sending the original heads to be ported to match a 340 intake that I have. They will be ported to flow better than the swirl ports. The car is a 4 speed and will have a 8 3/4. So my question is, will a stock 340 cam be mild for my build and still make the valiant a good driver but with good power ?

Also I have a brand new Edelbrock avs 600 cfm carb that will be used

Any suggestions would be greatly appreciated thank you !

 

[4spdragtop]

Not an engine guru here, but we put Comp 270-S in our 273 with 2bl pistons, stock heads, auto, 323 SG. Disappointed.....

 

[RustyRatRod]

I would recommend something in the 252h neighborhood.

 

[64whiteghost]

Not an engine guru here, but we put Comp 270-S in our 273 with 2bl pistons, stock heads, auto, 323 SG. Disappointed.....

2 barrel pistons ? i dont think there is such a thing my friend, but thank you for your advice

 

[64whiteghost]

I would recommend something in the 252h neighborhood.

what is the stock 340 cam at ?

 

[RustyRatRod]

what is the stock 340 cam at ?

Way too big.

 

[64whiteghost]

Way too big.

isnt it close to what the stock 273 commando was ?

 

[64whiteghost]

Way too big.

Ive read that Isky makes a good one. do you have a part number of the one that you recommend ?

 

[4spdragtop]

Yes there is, they will have valve reliefs and NON DOMED. Commandos were domed. Do a search on here....

2 barrel pistons ? i dont think there is such a thing my friend, but thank you for your advice

 

[64whiteghost]

Yes there is, they will have valve reliefs and NON DOMED. Commandos were domed. Do a search on here....

i think you mean, stock pistons. Because if you run a big cam and port your heads those pistons will do just as well

 

[krazykuda]

2 barrel pistons ? i dont think there is such a thing my friend, but thank you for your advice

4 bbl 273's had 10.5 compression, 2 bbl 273's had 9.0 or less compression depending on the year...

The 10.5 compression 4 bbl engines had taller pistons, so yes there is a such thing as a 2 bbl piston....

 

[4spdragtop]

Ok, well you asked a question....you got an answer and now we are all wrong.
Sorry, but I'll guarantee you there were 273 2bl aftermarket pistons lol.
No offense, good luck. Been there done that.

i think you mean, stock pistons. Because if you run a big cam and port your heads those pistons will do just as well

 

[4spdragtop]

273 heads even ported wont flow like 340 heads....

 

[64whiteghost]

4 bbl 273's had 10.5 compression, 2 bbl 273's had 9.0 or less compression depending on the year...

The 10.5 compression 4 bbl engines had taller pistons, so yes there is a such thing as a 2 bbl piston....

oh ok awesome, thank you, that makes more sense

so with 273 heads ported and commando style cam you can still make a 2bbl piston perform like an original 4bbl engine correct ?

 

[MOPAROFFICIAL]

I understand where everyone is coming from. The average garbage old 273, someone tosses a cam in straight and nothing else...and it runs like garbage and all quality it had is gone and is only marginally fun on the freeway...
That's because nothing is done to address existing deficiencies as well as issues introduced by the change in valve timing.
I don't envision doing it wrong. I think it through and address deficiency and necessity. I think the 340 cam installed with 4 degrees advance in a 273 with a milling of the heads to ensure a soild 9.1 or so and mainly... 3.91 gears..and or 4spd would run great.
Its based on the same stroke.
Give it the squeeze it needs and gear. Basic.

 

[64whiteghost]

I understand where everyone is coming from. The average garbage old 273, someone tosses a cam in straight and nothing else...and it runs like garbage and all quality it had is gone and is only marginally fun on the freeway...
That's because nothing is done to address existing deficiencies as well as issues introduced by the change in valve timing.
I don't envision doing it wrong. I think it through and address deficiency and necessity. I think the 340 cam installed with 4 degrees advance in a 273 with a milling of the heads to ensure a soild 9.1 or so and mainly... 3.91 gears..and or 4spd would run great.
Its based on the same stroke.
Give it the squeeze it needs and gear. Basic.

Very well said, I forgot to add that there would be milling of the heads, Thank you for mentioning that

 

[MOPAROFFICIAL]

Very well said, I forgot to add that there would be milling of the heads, Thank you for mentioning that

Let me know when you wanna send the heads. Lol

 

[toolmanmike]

isnt it close to what the stock 273 commando was ?

Oh heavens no.

 

[MOPAROFFICIAL]

Oh heavens no.

Now thats a cam that would not be nice without the proper drivetrain..

 

[toolmanmike]

Ive read that Isky makes a good one. do you have a part number of the one that you recommend ?

E4

 

[64whiteghost]

Hey

Let me know when you wanna send the heads. Lol

Hey Brotha, I figured that was you, lol very soon. Just gotta finnish my brothers Cuda, we are getting his 340 back from the machine shop tomorrow. So we will be assembling and installing over the holidays

 

[krazykuda]

oh ok awesome, thank you, that makes more sense

so with 273 heads ported and commando style cam you can still make a 2bbl piston perform like an original 4bbl engine correct ?

Yes and no...

The commando cam came in engines with 10.5 compression... Putting the 4 bbl commando cam in a 2 bbl engine may not make as much power as the 4 bbl because of the lower compression...

The commando cam was designed for engines with higher compression and had more overlap, the 2 bbl piston may not make the 4 bbl cam happy because of the longer overlap of the commando cam and lower compression pistons won't make as much cylinder pressure... Cams have a recommended minimum compression requirement for them to work efficiently.... The more overlap, the higher the compression you will need is a rule of thumb...

Also keep in mind that the early 273's had solid cams and lifters where the 68 - 69 273 had hydraulic cams and lifters...

 

[toolmanmike]

oh ok awesome, thank you, that makes more sense

so with 273 heads ported and commando style cam you can still make a 2bbl piston perform like an original 4bbl engine correct ?

Not really. Small cube engines need compression to make up for their small size.

 

[MOPAROFFICIAL]

There are better cams, in this range..and solid would be preferred... its more of a 'what are we doing with this motor that it warrants this or that'..

 

[4spdragtop]

Really? I'll "answer" any questions I prefer to.....keep twisting **** around.
You were the one that stated "no 2bl pistons" lol wrong.
Then 273 heads ported to match 340 intake, so I assumed you were hoping for 340 head flow seeing as how you're talking 340 cam....

Lol your one of those that shouldnt be responding to a question. like you said " your not an engine guru. Ive read enough threads to know that if you build a 273 correctly it will run great. I never once said i was trying to make my 273 heads flow like a 340 lol. thanks but no thanks buddy.