‘66 Barracuda

My ‘66 Barracuda.. it has the 273 2bbl. It starts and runs ok. It looks to have the original engine and trans but being new to the Mopar world, I’m debating on whether I should keep it all original & just rebuild what I have or is it time to swap out the engine for a 318, 340 or 360... I appreciate any suggestion from my Mopar friends.

Welcome! That's a really nice looking car you have there. Your question is answered by what YOU want from the car. It certainly looks to be a nice original car so to keep it as it came from the factory is certainly a great option. If you feel you need to have tire roasting capabilities with your car , then an engine upgrade would be the plan. A good running 273 is a very respectable engine and a few minor upgrades can get a little more potential out of it. But, if you feel the need to break the tires loose on demand or plan to race it, the larger engines would probably be a better option. A swap is fairly easy but there are a few details you need to be aware of before doing so, so do some research on this site before jumping into anything.

Welcome to FABO. Early A bodies are fun cars and I think are pretty cool no matter what is under the hood. You have a 273-2 barrel which isn't a bad engine. Now, if you want more performance you could hot rod what you have or install a 318/340/360. You can use the existing transmission but if you only have a 7 1/4" rear end you may want to upgrade that to a 8 1/4, 8 3/4, or a modified Ford rear. Along with that swap you may get big bolt pattern wheels.

Welcome to FABO, looks nice! It’s your car do what you desire but I like em stock myself

First of all, welcome to FABO, we’re glad to have you with us. Now, as stated above, what you want out of your car is your choice, and it may make it easier to know that the original drivetrain is ok to have, but ok to change as well. You can always keep the motor, but it is not numbered to the body in any way. In it’s place could be the above mentioned choices of small block wonder, all dressed up like your 2 bbl motor. That’s what I’m doing with mine, I had it dressed up like a Formula S because I liked the dress up kit that makes the commando motor look so nice. My car is a 2 bbl car, so I’m dressing up a 340 to look like a 2 bbl motor, using a trans from a 72 car for the comparability, and it has an 8 3/4” rear. All this car will ever need. What you decide to do with your car is your choice, but I would suggest at least a refresh of your motor, you will find some ponies from freshening it all up I’d bet!

I appreciate the feedback.. I’m not planning on any racing.. just a classic car to drive around. But it would be nice to have a little extra power. Again thanks for the suggestions.. I’m glad to be part of the FABO family

318 all the way. 5.2 even better (heads). Loads more torque and HP than a 2bbl 273 and cheap as dirt. Cheaper to build too (almost no 273 pistons available cept stock replacements and the 1-2 4bbl options that are >$400 a set.) . Small bore V8 offers nothing a 318 can do better, cept maybe mileage at the cost of HP and torque. Keep the forged crank and put it in your 318 so it fits your convertor. 273 fast revving? 318 has the same stroke.....rev away. 360 will be more to buy initially but the same to build and will wallop a 318 in every aspect. 340s cost too much to buy nowadays for what they offer 'cept bragging rights. If you keep the 273, spend money on 3.55 or higher gears. And you can keep all the 273 stuff for all the blocks, no one will know the difference unless its got Magnum valve covers and even LA covers fit Magnum heads using 5 of the 10 bolts.

Look at it this way: a 318 has 45 more cubic inches than a 273, and a 360 has 87 more cubic inches. Both can be dressed to look exactly like a stock 273 2-barrel. The extra cubes means more torque, i.e., more low and midrange, and that extra low and midrange is what you're gonna feel in moderate, part throttle driving. In short, the larger motor will feel a LOT peppier, even if the peak horsepower doesn't increase that much if you want it to look stock. And if you make just a few upgrades (four barrel, etc), the power increase will be huge. The 318 would be a more directly bolt-in swap, but the 360 has almost as many extra cubes over a 318 as a 318 has over a 273. Your choice.

Welcome to FABO. You have a nice looking car. Its your car if you want more power do the engine change. The 273 in mine has plenty of power for cruising.

Dwayne Fairchild said:

I appreciate the feedback.. I’m not planning on any racing.. just a classic car to drive around. But it would be nice to have a little extra power. Again thanks for the suggestions.. I’m glad to be part of the FABO family

Click to expand...

A lil extra power ...... when?
1) Off the line, or
2) at 30 mph? or
3) passing power? or
4) All the time?

Each of these has a different solution, that yes, can be solved with a bigger engine. But only #4 demands it.
#1 starts with the Convertor
#2 Starts with gears
#3 is again gears, and a 4bbl, but a bigger engine is an good option
#4 demands a bigger engine, but if not big enough, then might still require a TC and gears to satisfy the requirements of 1 and 2

If you're gonna build an engine, the 360 is as cheap as a 318 to build, and cheaper than a 273. A stone stock 5.9 will kill about everything but a hi-end 360, for street use.

The problem guys run into, is trying to install headers into these early As. And without headers, you limit yourself to a power level that is more in line with what a 318 can satisfy. or a detuned 340. or a lo-po 360.

Of course each bigger stock engine will have a stronger bottom end, so that makes reusing the stall and gears you currently have, an easier decision to make.
But; you still have to look at what is going on at 30 mph and when passing, cuz some combos will force your engine into rpms that it could be dead in.

Therefore, I always look at the gears first.

Take 2.73s for instance, (with a regular Torqueflite)
at 60 mph, with a 77" tire roll-out (24.5 tall) the rpm is about 2450 cruising, at zero-slip. If you need to pass someone, and stomping it into second gear the Rs might rise to 3750 , not bad.

At 32mph the rpm in second gear is ~1750 cruising, so going hammer done is 3500 in first, also not too bad.

At take-off, the starter gear is just 2.73 x 2.45=6.69 a pretty small number. To parlay that into rapid transit will take a hi-stall TC or a lotta torque; as in a bigger engine.

With 3.55s
60=2920 @ zero-slip
Passing gear would be 60=4900 in second, and
WOT in first at 32 mpg might be 4400. And
the starter gear is 3.55 x2.45=8.70, or plus 30% over the 2.73s That's a lot! and that, plus 30%, will make your small engine feel a lot bigger than it did with the 2.73s
Now if you're on the ball, you will have figured out that the take off torque is directly related to the rear gear increase which is 3.55/2.73= plus 30%. So how can this be helpful?
Well, if your 273 makes 50hp at 2000rpm stall, that would be 131 ftlbs. Adding 30%, that would then be 170 ftlbs, which maths to 65 hp, and that is what it's gonna feel like!........ with just a gear change.
You can do the same by installing a bigger engine with 65hp at 2000rpm.
Or you can install a higher rpm TC that stalls at 65hp.
So you got like 3 choices right there.

AJ/FormS said:

A lil extra power ...... when?
1) Off the line, or
2) at 30 mph? or
3) passing power? or
4) All the time?

Each of these has a different solution, that yes, can be solved with a bigger engine. But only #4 demands it.
#1 starts with the Convertor
#2 Starts with gears
#3 is again gears, and a 4bbl, but a bigger engine is an good option
#4 demands a bigger engine, but if not big enough, then might still require a TC and gears to satisfy the requirements of 1 and 2

If you're gonna build an engine, the 360 is as cheap as a 318 to build, and cheaper than a 273. A stone stock 5.9 will kill about everything but a hi-end 360, for street use.

The problem guys run into, is trying to install headers into these early As. And without headers, you limit yourself to a power level that is more in line with what a 318 can satisfy. or a detuned 340. or a lo-po 360.

Of course each bigger stock engine will have a stronger bottom end, so that makes reusing the stall and gears you currently have, an easier decision to make.
But; you still have to look at what is going on at 30 mph and when passing, cuz some combos will force your engine into rpms that it could be dead in.

Therefore, I always look at the gears first.

Take 2.73s for instance, (with a regular Torqueflite)
at 60 mph, with a 77" tire roll-out (24.5 tall) the rpm is about 2450 cruising, at zero-slip. If you need to pass someone, and stomping it into second gear the Rs might rise to 3750 , not bad.

At 32mph the rpm in second gear is ~1750 cruising, so going hammer done is 3500 in first, also not too bad.

At take-off, the starter gear is just 2.73 x 2.45=6.69 a pretty small number. To parlay that into rapid transit will take a hi-stall TC or a lotta torque; as in a bigger engine.

With 3.55s
60=2920 @ zero-slip
Passing gear would be 60=4900 in second, and
WOT in first at 32 mpg might be 4400. And
the starter gear is 3.55 x2.45=8.70, or plus 30% over the 2.73s That's a lot! and that, plus 30%, will make your small engine feel a lot bigger than it did with the 2.73s
Now if you're on the ball, you will have figured out that the take off torque is directly related to the rear gear increase which is 3.55/2.73= plus 30%. So how can this be helpful?
Well, if your 273 makes 50hp at 2000rpm stall, that would be 131 ftlbs. Adding 30%, that would then be 170 ftlbs, which maths to 65 hp, and that is what it's gonna feel like!........ with just a gear change.
You can do the same by installing a bigger engine with 65hp at 2000rpm.
Or you can install a higher rpm TC that stalls at 65hp.
So you got like 3 choices right there.

Click to expand...

Wow!! I appreciate all of the information. I would like to have more horsepower overall. So this will help me make some decisions for this upgrade... thanks again for all of the suggestions.

Just remember, on the street, horsepower ain't everything; don't get caught up in the numbers.
The biggest problem with a small-engine streeter, believe it or not, is a lack of gears.
A 5-speed would solve most of our problems, or a 4+1overdrive.

Take the Ax-15 manual tran, for example;
The Novak Guide to the Aisin-Warner AX15 Transmission

The AX-15 ratios are 3.83-2.33-1.44-1.00-.79
These are almost ideal for a small engine with a wide powerband...... like a 273/318.
You just put second gear where you want it, cuz most of a streeter's life is gonna be in second gear. and watch the rest unfold.
Say your 273 is stock. it will power-peak at about 4000, and you can probably shift it at 4500. The torque peak will be at about 2500..
It will pull well from 3000 to 4000, so that is where you are going to want to be. In 2.33 second gear 32 mph will need 2.94s, for 32=3006rpm by the math, and 40 will be 3760 and 4500 will top out at 48 mph.you can't hardly get a better second gear than that. The starter gear will be
3.83 x 2.94=11.29/ funtastic. and in .79overdrive, she will cruise at
65=2070 really nice.
Third gear will cruise at 35=2030/ super nice

I'm not suggesting that you drop everything and install an AX-15! Not at all, I just used this as an example of the gearing problem.

The AX-15 ratios are 3.83-2.33-1.44-1.00-.79, and with 2.94s, the road-gears are
11.26-6.85-4.23-2.94-2.32 ;the important ones to see are the 6.85 and the 2.32, as shown above.
My question is; can we duplicate those with an A904; 2.45-1.45-1.00?
Well,l I think you can get the 6.85 in second gear with 3.91s at ~20% TC slip; I get 6.80; so that is doable. First gear will then be 9.58 times the TC ratio , which could be 1.8 at zero mph diminishing to about 1.4 at shift rpm, so 17.25 to 13.41; so that will be a blast.
Third will be 4.30@10% slip
and that's all. lets line them up
17.25-13.41-6.80-4.30
If you had a lock up you can add 3.91, and lets average first gear; So
15.33-6.80-4.30-3.91 compared to the AX-15 below it
11.26-6.85-4.23-2.94-2.32
That's looking pretty good, except, without an overdrive, 65=3674

But here's the deal I chose the 3.91s to make the numbers, so the 273 could be the best that it could be.
If you installed a 318 which is ~16% bigger, then you can easily take out 16% rear gear; so now that would be 3.23s; and the new numbers are;
14.24 to 11.08-5.62-3.55-3.23 in loc-up; well now, that's a whole bunch better even 65=2880. Even tho the numbers are all smaller, by the time you multiply them by the engine torque, this 318 will be every bit as peppy as the 273 was.
But It gets better. You now have a 318 with waaaaay more torque that the 273 could only dream of. What if we installed an A999 with the wider ratios and matched up the second gears. The A999 ratios are
2.74-1.54-1.00, and the roadgears with 2.94s are
14.51 to 11.28-5.43-3.23-2.94 and 65=2620;compare to the A904
14.24 to 11.08-5.62-3.55-3.23 and 65=2880
You can see how I did that by swapping out rear gears to match up second gears.
Is that the best option?
Maybe, but I got another one up my sleeve. All these combos are designed to maximize your second gear WOT power.
We could do a similar thing by putting your 273 on or after the torque peak with whatever rear gear you have and again at 32 mph, by adjusting the stall-speed.
Say you currently have 2.73s, and a 77" tire roll-out just like in all the other examples. Your rpm at 32 mph then, in first gear, will be 2930 at zero slip, say 4100 at WOT So you don't need any TC help at 32 mph. But on the start line with a starter gear of just 6.69 your 273 is gonna need a bit of help to squirt away from the light. So, swapping out the 2000 TC for a 3000 will put your engine on/or close to on, the torque peak, and that 273 will really jump off the line.... because;
first off, the Tc is up on the TM peak of say 1.8, so that lowly 6.69 might be acting like 12.04 at zero mph. and
secondly you 273 might be putting down 20 ftlbs more at 3000 versus 2000!
So here we have same 273 engine, and same A904 trans, and same stinking rear gears, acting with a whole bunncha more attitude, and all it took was a higher stall TC. Will it compete with a 318?
Well, no .
But you said;
Not planning on any racing, and
just a nice cruiser..... with a lil extra power.
IMO
A "hi-stall" TC, is the cheapest, easiest, and fastest way to achieving a performance goal
A 4-bbl/ free-flowing exhaust, would be next, and
then Gears ..
But if it's tire-frying power you're after......... that's a different combo