64 barracuda 273

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Shippy

Shippy

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I’m in the start of rebuilding my 64 273 , i have 2 questions is i have 318 heads available with a 4 barrel intake from a 67 barracuda
I did not get any numbers off the heads yet but is it worth doing ? and will it increase HP at all ?
Any advice will be helpful
 
Shippy said:
I’m in the start of rebuilding my 64 273 , i have 2 questions is i have 318 heads available with a 4 barrel intake from a 67 barracuda
I did not get any numbers off the heads yet but is it worth doing ? and will it increase HP at all ?
Any advice will be helpful
Click to expand...
Make sure the heads are closed chamber or you will be going backwards with compression. 273 and 318 heads aren't much different performance wise but the chambers will kill compression. There is also the early 273 intake bolt pattern which you already know about.
 
toolmanmike said:
Make sure the heads are closed chamber or you will be going backwards with compression. 273 and 318 heads aren't much different performance wise but the chambers will kill compression. There is als the early 273 intake bolt pattern which you already know about.
Click to expand...
Thanks
 
I hate to say it but why not just use the rest of the 318 engine or get a magnum 5.2.
I too had a 273 for in my 1st Mopar, but sometimes it's time to move on, you won't regret it.
 
Well, since the LA318 was not available in '67 (not introduced until '68), it had to have been swapped into the '67 Barracuda- so it could be any year with several different combustion chamber specs. Add to that the fact that 318s never had factory 4 bbl.s until some time in the '80s, and it throws more unknowns into the mix. Is it a factory (cast iron) manifold, or an aftermarket (aluminum) manifold?
We need numbers off the heads, or at least pictures of the chambers/exhaust ports along with the same info from the intake in order to give any kind of meaningful answer.
 
moparlvr166 said:
I hate to say it but why not just use the rest of the 318 engine or get a magnum 5.2.
I too had a 273 for in my 1st Mopar, but sometimes it's time to move on, you won't regret it.
Click to expand...
I agree, unless you are restoring a number matching car I would pass on the 273.
 
Aw, give the 273 some love- unless you have a need to uprate the engine, it will make a fine cruiser; with respectable mileage to boot. It has served well for 60 years now. Freshen it up and it'll love you right back.
Avoid the rabbit hole.
 
The heads won't make any difference (assuming they have the same combustion chamber size as your 273 heads), but the four barrel will. But don't expect muscle car performance. We put a four barrel and dual exhaust on my Mom's 64 Barracuda (using the rare Edelbrock 4-barrel intake for the early 273 heads), with stock 904 trans and 2.94 gears, ran 16.70s. About a second quicker than stock, not as fast as a stock Commando 273 (less compression and milder cam). Since your 273 needs a rebuild anyway, I agree with the above suggestion just to use the complete 318 motor. That's 45 extra cubic inches, more horsepower and a lot more torque. Eazy peazy. . . .
 
Use the 273 with the 318 heads and the "67" 273 4 barrel intake. You need the 318 heads to use the 66 up intake manifold. You can always mill the 318 heads to get the compression you want. Run the Commando exhaust or clone it. Easy to get 265 hp out of a 273 with 2 barrel pistons, a small .425 lift cam and 340 valve springs. Nothing else needed, trans works, rear works.
 
Professor Fate said:
Well, since the LA318 was not available in '67 (not introduced until '68), it had to have been swapped into the '67 Barracuda- so it could be any year with several different combustion chamber specs. Add to that the fact that 318s never had factory 4 bbl.s until some time in the '80s, and it throws more unknowns into the mix. Is it a factory (cast iron) manifold, or an aftermarket (aluminum) manifold?
We need numbers off the heads, or at least pictures of the chambers/exhaust ports along with the same info from the intake in order to give any kind of meaningful answer.
Click to expand...
And I need to add this:
Beware of late model 318 heads with air injection ports, or the expanded exhaust surfaces anyway- there are clearance issues between late heads and the early A exhaust manifolds. Nothing that can't be addressed, but be aware of it ahead of time.
I understand your desire to swap heads and gain the '66 and up manifold bolt angles, I just don't want you to swap one can of worms for another...
 
If the 67's are 920 castings, they have equivalent chambers to your stock heads. No perf benefit, but allows the use of any small port late intake.
 
65 Cuda 340 said:
The heads won't make any difference (assuming they have the same combustion chamber size as your 273 heads), but the four barrel will. But don't expect muscle car performance. We put a four barrel and dual exhaust on my Mom's 64 Barracuda (using the rare Edelbrock 4-barrel intake for the early 273 heads), with stock 904 trans and 2.94 gears, ran 16.70s. About a second quicker than stock, not as fast as a stock Commando 273 (less compression and milder cam). Since your 273 needs a rebuild anyway, I agree with the above suggestion just to use the complete 318 motor. That's 45 extra cubic inches, more horsepower and a lot more torque. Eazy peazy. . . .
Click to expand...
The 2.94 rear will love you more with a 318 in front of it. a "High revving 273" is just a smaller bore "high revving 318". I F'd up my 273-4 and just moved all the parts on to a '68 318 short block. It felt faster than the 273-4. HP sells, but torque wins races. Read the fine print...
 
Keep the 273. You have a fine forged bottom end and factory mechanical lifters. Put commando pistons and cam in the old girl and you will be making 5 more horsepower than a stock 318. Or put a d dart spec cam in her and you will be making 45 more horsepower than a 318. The 318 also never came with the sharp valve covers or air cleaner the little 273 did. A 273 is an excellent engine.
 
jeff alder said:
Keep the 273. You have a fine forged bottom end and factory mechanical lifters. Put commando pistons and cam in the old girl and you will be making 5 more horsepower than a stock 318. Or put a d dart spec cam in her and you will be making 45 more horsepower than a 318. The 318 also never came with the sharp valve covers or air cleaner the little 273 did. A 273 is an excellent engine.
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318 was not 230 hp, more like 170-190 hp.
 
Mopar Performance had stock hp for different engines. I'm pretty sure I'm close. My HP 318 four barrel marine engine is rated at 225 and I'd put it up against any stock 318 two barrel engine.
 
we had a 67 Barracuda with a 318 which was actually my first car. We saw it for sale next to a barn on old highway 41 in Indiana near the Morocco Indiana Drag strip. $400.00 cash LOL Those were the good old days. Now a Layson's tail lamp housing would cost that much. The owner was a retired machinist that drove it about a half mile to run a quarter mile just for fun at old 41. It was a 318 with aggressively ported 360 J heads with a matched port dual plane thermal quad intake. And of course the ever popular Quadrajet carb on top. Double LOL Black jack headers, 3 speed manual on the floor with a narrowed Dana...and a quite comfortable Ford Pinto bucket drivers seat. 3x LOL. Machinist's are great people to buy old cars from. That old turd hauled ***!
 
When hp ratings went from gross to net, 318s went from 230 gross to 150 net, despite everything being the same - CR etc. 340s only dropped from 275 to 240 despite losing two full points of CR and having smaller intake valves. From that, I'd guess the 318's gross hp rating was a lot more optimistic than the 340's gross rating, and that 66fs's 318 horsepower guess is pretty accurate (#14). And from my own personal experience, the 340 I put in my 65 Barracuda back in 1973 was a lot more than 40 hp stronger than my original Commando 273.

273s, 318s and 340s all shared the same 3.31 stroke. 273s are no more of a revver than the other two, equally carbed and cammed etc. But it will have noticeably less grunt down low.

I loved my Barracuda when it had a 273 in it, but when I blew that up at 150K (trying to drive 200 miles in second gear after breaking my 3-4 shift lever inside the trans) the 340 I dropped in impressed the you-know-what out of me.
 
jeff alder said:
we had a 67 Barracuda with a 318 which was actually my first car. We saw it for sale next to a barn on old highway 41 in Indiana near the Morocco Indiana Drag strip. $400.00 cash LOL Those were the good old days. Now a Layson's tail lamp housing would cost that much. The owner was a retired machinist that drove it about a half mile to run a quarter mile just for fun at old 41. It was a 318 with aggressively ported 360 J heads with a matched port dual plane thermal quad intake. And of course the ever popular Quadrajet carb on top. Double LOL Black jack headers, 3 speed manual on the floor with a narrowed Dana...and a quite comfortable Ford Pinto bucket drivers seat. 3x LOL. Machinist's are great people to buy old cars from. That old turd hauled ***!
Click to expand...

LOL, Everybody knows a 318 can't be fast??? LOL Sounds like a great car. He knew how to make that 318 sing on the cheap.
 
Last edited:
Shippy said:
I’m in the start of rebuilding my 64 273 , i have 2 questions is i have 318 heads available with a 4 barrel intake from a 67 barracuda
I did not get any numbers off the heads yet but is it worth doing ? and will it increase HP at all ?
Any advice will be helpful
Click to expand...
As has been mentioned so far.......what is the purpose of this car? Cruiser? Drag racer? Pro Street? What rear axle gear are you running? If you still have the stock 7 1/4 rear, it's not suitable for ANY increase in horsepower. The stock 9" brakes aren't either. Which transmission, as there may be some upgrades needed there too? If this is just a stock setup for cruising with maybe a slight increase in horsepower, there's nothing wrong with building your 273. Just keep in mind that pistons are fairly expensive and you're already giving up some horsepower vs. a similarly equipped 318/340/360. With all due respect to Professor Fate, the LA 318 started in 1967, just not in an A-body. The first 318/4 was in 1978. The '66-7 273 intake will be a bolt-on for the earlier 920 (66-7 273 and LA318) and 675 heads ('68-72 318). Same intake and exhaust port sizes with no LH exhaust manifold issues. If you're going to use the 920 casting heads, those are closed chamber and work great with a 273 with whatever pistons you chose. If you use the 675 heads, you may want to see if higher compression pistons are available (Eggy?) or you may want to do some head/block milling for a higher compression ratio....whatever you're trying to achieve. If this is going to be a drag car, or, pro street a bigger cube starting block would be a better choice, and the sky's the limit on what you should get taking your budget into consideration.
 
cudamark said:
With all due respect to Professor Fate, the LA 318 started in 1967, just not in an A-body.
Click to expand...
True, but I stand by my statement that a '67 Barracuda with a 318 had to be a swapped motor, which means the heads could be almost any year.
I guess without pictures or numbers yet, we may never know what it's got... :)
 
Professor Fate said:
True, but I stand by my statement that a '67 Barracuda with a 318 had to be a swapped motor, which means the heads could be almost any year.
I guess without pictures or numbers yet, we may never know what it's got... :)
Click to expand...
The OP's car is said to be a '64 Barracuda, but, I'm guessing you were referring to Jeff's 67. If so, he stated that his has ported J heads on it. My impression is that the OP has access to a '67 273 BBL intake and was considering using it with later heads than what his '64 has. If I'm mistaken, I hope he will correct me and supply some further information.
 
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