273 with stock 340 cam ?

[toolmanmike]

I looked at your thread. Are you running the 340 performance exhaust ?

It is high performance single exhaust reproduced by Accurate LTD. It was used on the 65-67 273-4 barrel cars.

 

[66fs]

Its a 4 spd and yes Mopar official is the one that will be working on my heads

You should be good to go then. The combo you picked should be great for what you want. I also have the 2.5 straight thru single Commando exhaust on my 66, and I love it. You might want to eventually get 3.23 gears in the rear.

1965-67 273 Hi-po System for Barracuda & Dart

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1965-67 Barracuda w/273ci 4bbl carb in Stainless Steel [7760740202] - $713.00 : Zen Cart!, The Art of E-commerce

 

[66fs]

Hugo; yur in trouble. Big trouble.
Lemme spell it out for you; keep in mind that I am not a 273 hater.
What you propose to do has been contemplated for well over 50 years, and every guy who ever did was wrong.
Yur thinking; the heads will add 50 hp
the cam will be 30.
the headers 25 and
electronic ignition will get you 5,
so that adds up to 110hp, am I right?
Well, it will never work that way, never, never, never.
Firstly;
putting the 340 heads on is +72cc versus 57cc. Put that on a 2bbl 273 and you instantly make a lawn-mower engine out of it, because the compression ratio has dropped to 6.9/1 . Next, you swap a 340 cam in there and change the Ica from 48* to 60*, and the Dynamic Compression Ratio falls to 6.6/1

So what you have built is a slug off the line to say 4000rpm, when it finally wakes up, and then the 340 parts finally kick in. Great,
But here's the deal, even running 3.91s, 4000rpm with 24.5 tires comes to 24mph in first gear with a 3.09Commando 4 speed. So, there is no warrior in that combo.
But wait, the Advertised duration of that cam is 268/276/114 making the Ica to be 60* at plus 4* install. But that is at .008 tappet rise so the valves are still open by .012 inch; and your engine cannot begin to make pressure until the intake valves are on the seat and not leaking. When this is factored in, your Dcr falls even further, to perhaps 5.8/1 and this will turn your 273, at low rpm, into a total lazy dog. The laziest dog ever known to man...... until around 4000/24mph with 3.91s. But if you have the more typical 2.76 ratio, 4000 will be 34mph.
The guys above are trying to tell you this, but you are NOT listening.
But Ok I get that you added a few nuggets, but it will still NOT be enough..
To do it right, with the 340 parts, you will spend a mountain of money in machining, and in the end, have less performance, than a 69 318 with a 4bbl and dual exhaust.
You said;

You're going about it all wrong.
BAR NONE; the cheapest fix is a bigger engine.
But,you can build a fun-to-drive 273, if you do it right. Just ask the 273guys, right here on FABO, how much money they spent on their 273s, and what the results were. Then decide for yourself which way to go.

Ok, just to wrap it up; for your 273 to be fun with all the 340 parts on it, the Scr will need to be raised to about 11/1, and it will still be a slug at below 3000 rpm as compared to that 69 318, gear for gear..
To get to 11/1, the total chamber volume will have to be reduced to 56cc; that ain't gonna happen with 340 heads, and 2bbl pistons. I think, not even with 4bbl pistons. And even if you were able to; everything will have to be custom machined and custom fitted. Your talking multiple mock-ups, multiple trips to the machine shop, and multiple re-machinings. You are likely looking at months of test-fitting.
IMO, there is absolutely NOTHING right about putting a 340 topend&cam into/onto a 273. What I mean is; there is not a snowball's chance in hell, for a streeter, that I would ever consider it. There are just too many easier,faster,better, cheaper solutions .
Sometimes; just because a thing can be done, does not make it the thing to do.

First, the OP never said he was going to use 340 heads. Second, 273 heads have to milled .040 to get down to NHRA minimum of 57.3 cc. I have actually run 273's from stock Commando to 284 duration solid cams including a 340 cammed J headed engine in a 1964 Barracuda 4 speed car. 2 barrel pistons to forged Commando pistons with a 4 speed and automatic transmission. Your conclusions are not accurate. I never spent a lot of money on any engine, as I didn't have a lot. All were fast and I could stay with anything factory up to 100 cubic inches larger than my 273, set up similarly. The 340 top end incarnation, was a whole new level of performance. The 1.88 intake heads were gasket matched, milled .040 and .038 on the intake side to get to NHRA minimum of 64.7 cc. The used 72 340 cam was degreed to 114 degrees. The 71 intake and carb were stock. The 64 273 short block used 10.5 TRW + .040 forged pistons and Speed Pro file to fit rings with the stock rods and crank. This engine was run with a 340 bellhousing, flywheel, and big block clutch to keep the clutch from being replaced every month. All my 273's were street engines behind a 4 speed from 1972 to 1990 with about 200,000 miles on the same short block. Shifts were never below 3,000 rpm. It was a go anywhere, anytime car from Miami, FL to Marion, SD. My current 273 is an Isky E-4 grind, TRW 10.5 forged piston, NHRA minimum cc 273 headed engine with factory carb and intake. The next one will probably be 2 barrel piston, custom Racer Brown cammed, 273 heads, 340 intake and TQ. My brother's 67 Barracuda automatic 273 was a 2 barrel engine that had a Commando cam, carb and intake. It was not as fast but was fast enough to cruise at 100 mph for hours on end and hit 140 mph at the top end with 3.23 gears. That 273 is still in his car today and has 300,000 miles and starts and runs like a new car. You can keep your 318's and 360's.

 

[64whiteghost]

It is high performance single exhaust reproduced by Accurate LTD. It was used on the 65-67 273-4 barrel cars.[/QUOTE
I see, let me check them out

 

[toolmanmike]

It's a $1000 system but nicely built and close to the original system.
Here's my 273-4 with the Isky E4 and the Accurate exhaust.

 

[RustyRatRod]

Its a 4 spd and yes Mopar official is the one that will be working on my heads

Then you need to let Justin tell you which cam to choose.

 

[64whiteghost]

Then you need to let Justin tell you which cam to choose.

yea thats what it looks like. I just started the Thread to see what other guys would recommend. But he is going help me with that

 

[RustyRatRod]

yea thats what it looks like. I just started the Thread to see what other guys would recommend. But he is going help me with that

Well, he has the heads. He will know the port shapes. He'll know the port flow. He's a genius guy. I'd let him handle it. He'll make you a great choice.

 

[ir3333]

140 mph with a 273 ci engine...Wow!

 

[66fs]

140 mph with a 273 ci engine...Wow!

Easy, that was with 273 heads and 2 barrel pistons. That was not top end for my 64 Barracuda.

 

[ir3333]

I don't know about easy? I lived through the 68 - 70 era and all the 340 cars with 3.23 gears
topped out at 133 - 135mph.
So a 273 at 140 would be very exceptional!

 

[toolmanmike]

I don't know about easy? I lived through the 68 - 70 era and all the 340 cars with 3.23 gears
topped out at 133 - 135mph.
So a 273 at 140 would be very exceptional!

It probably had a 2.78 gear or so. LOL

 

[66fs]

I don't know about easy? I lived through the 68 - 70 era and all the 340 cars with 3.23 gears
topped out at 133 - 135mph.
So a 273 at 140 would be very exceptional!

Think smaller engine, solid cam, rev higher, 67 Barracuda, Midwest straight flats for 100's of miles. My 64 was run up to 140 every month and still had room to go. But by then the 273 had 340 heads, TQ and dual exhaust with factory early "A" exhaust manifolds. The 340 would be quicker by a bit, but would not rev as high. I had both.

 

[ValiantRacing]

isnt it close to what the stock 273 commando was ?

The Stock 273 commando cam was .415/.425 lift.

 

[ir3333]

Could you get a '64 barracuda with a 150 mph speedometer?

 

[AJ/FormS]

First, the OP never said he was going to use 340 heads.

You are right, I screwed up.

as to a 273 going 140; not sure that's brag-able.
What I was taught is that to double your speed, takes about double-double the power. So if it takes 40hp to go 60, you can approximate 160hp to go 120; and 200hp might get you 140. But you know, there are a lotta factors at play there.
I've been to 140 a few times with stock-suspension A-bodies in my younger years, and it was not pleasant. And there is not a chance I would ever do it again.
Having said that, my decidedly not stock suspension, 1968 Barracuda ,is quite stable at 120; so long as it is in a more or less straightline,lol.

Calculate HP For Speed

 

[66fs]

Could you get a '64 barracuda with a 150 mph speedometer?

Right away I knew the stock speedo would not work, plus I wanted a good tach and a vacuum gage.

 

[66fs]

You are right, I screwed up.

as to a 273 going 140; not sure that's brag-able.
What I was taught is that to double your speed, takes about double-double the power. So if it takes 40hp to go 60, you can approximate 160hp to go 120; and 200hp might get you 140. But you know, there are a lotta factors at play there.
I've been to 140 a few times with stock-suspension A-bodies in my younger years, and it was not pleasant. And there is not a chance I would ever do it again.
Having said that, my decidedly not stock suspension, 1968 Barracuda ,is quite stable at 120; so long as it is in a more or less straightline,lol.

Calculate HP For Speed

The 64 Barracuda was stable enough, but I always had the best suspension parts and tires I could get. It is amazing what it feels like doing 140 mph, like the song "Hot Rod Lincoln".

 

[66fs]

It probably had a 2.78 gear or so. LOL

I sold the 64 Barracuda to my cousin for a while. He told me the coolest story. We had put 2.76 gears in the 8 3/4 and he was driving from SD to WA state when some Dork started messing with him on the highway. His wife is with him and the Barracuda is loaded with luggage. After awhile he finally has enough of this Dork and winds the 273 up, pulls beside the Dork at 100 mph and shifts into 4 gear. At that point the Dork knows he has no chance and leaves him alone...

 

[toolmanmike]

I sold the 64 Barracuda to my cousin for a while. He told me the coolest story. We had put 2.76 gears in the 8 3/4 and he was driving from SD to WA state when some Dork started messing with him on the highway. His wife is with him and the Barracuda is loaded with luggage. After awhile he finally has enough of this Dork and winds the 273 up, pulls beside the Dork at 100 mph and shifts into 4 gear. At that point the Dork knows he has no chance and leaves him alone...

I love that story.

 

[64whiteghost]

Update ! I sourced some 302s. For the 273 I plan on porting them and using my stock 340 4bbl intake. My 273 is already bored.30 over what cam do you guys recommend ?

 

[MOPAROFFICIAL]

Update ! I sourced some 302s. For the 273 I plan on porting them and using my stock 340 4bbl intake. My 273 is already bored.30 over what cam do you guys recommend ?

.470-.500 lift, to start.

 

[Jim Lusk]

We ran a stock 340 cam in a low comp 273 several years ago. Car had a stock 904 and 3.23 8-3/4. Ran just fine. We also ran a 340 intake with the mismatched ports. It wasn't fast, but it was decent.

Years ago I ran a Crower .427"/264 duration hydraulic cam in a 10:1 (Jahns cast pistons) 273. In my old '66 Dart with a 904 and 2.94 gears it was lacking a little something. When I put that engine in my old '66 four speed/3.23 geared Barracuda it perked up quite a bit. I ran stamped rockers on stock heads with a stock 273 intake and AFB.