273 vs 318

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sureshot43

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I will be starting a '67 Cuda Convertible soon. I just read the NHRA rules as far as convertibles and roll-bars. If the car runs quicker than a 13.49 it must have a roll-bar. I don't want to put one in an 83k all original car. So...
The car has the original 273 2 barrel/904.7 1/4" combo. I also have a "77 318. What are the pros and cons of putting the 318 heads on the 273(for unleaded gas and a modern aluminum 4 barrel)? I will use a fairly mild Hughes cam and the goodies that go along with it, a low rise dual plane intake, and at least dual exhaust(probably TTI headers). Was also thinking of keeping the 904 to keep things simple,but I also have a 727 that is in great shape. Will this combo have too much snot for the stock rear? BTW, It is a 3.91 sure-grip.
I was originally hoping to have the car in the high 12's, but I am starting to think the more practical cruiser route for this car. I don't think I want to cut up a low mileage original.
Thanks for any ideas and in-put.
SS43
 
66 and later 273 heads will mate up to a four barrel intake just fine, it's the 65 and earlier that's different. Personally I wouldn't get too radical with a low mile vert as you describe, too much history and collector value as stock. Even if you do alter the drive train put the stock one in storage. Have fun and post some pictures.
 
I will never part with the original engine and/or parts. If I stay with the 273,the cam I select will also have to work should I decide to put the top end of the motor back to original(2barrel and all). Besides, I want to run 87 octane gas in it. I want something that is fun to drive,and can be driven anywhere. I will DRIVE it once or twice a summer to the dragstrip just for fun, but I don't plan on overdoing it. Right now,I figure that the money I was going to spend on the drivetrain can now be spent on body work and other things. No matter which engine I choose(both are in the same shape), I will probably end up putting rings,bearings, oil pump,etc. in there since the motor will be out of the car.
 
Might ty to use the search, there are a bunch of recent posts discussing 273/318 combos.

That being said, find yourself a set of '302' casting heads - there's tons of cars that used them - Dippys, Gran Furys, vans, trucks etc. - basically anything with a 318 made in the '80s. They have 1.78" valves, and are the well-documented closed-chamber swirl port design. They are also legal replacements for 273 cars running in NHRA stock eliminator. Those heads should wakethings up. They are LA series so everything else should basically bolt right up.

Hope that helps.
 
There is a difference in the 67 273 crank so look closely at what torque converter you choose.
 
Like rmchrgr said on the heads. Otherwise, you would mostly be wasting time with the head swap. The 302's need work as would the stock heads to achieve this time bracket. (12's) Though a good prep and valve job for 13's would be adviseable.
A Edelbrock Performer intake is what you'll need.
I'm not so sure I'd do tti's since the header tube is large.
A Comp Cam designed for exhaust manifolds is what I'd run.
I'd also replace the time bomb rear with a 8-1/4 min.
The 727 is slower but stronger. And not really needed.
 
That would be a cool cruiser.....I'm not sure it would even get into the 14's though with that weight/H.P. ratio. If it were mine, I'd stash the 273 and build the 318.....better parts availability and more haulin' *** fun factor.....and for sure 14's or better. Your call.

I know.....I've got a 273 Barracuda and I would say it's......just okay.
 
Here is my take. I have done several cars with the 273 and you can't beat them.


273 2 barrel CR is 8.8 to 1. If you use the 66-67 closed chamber heads and shave the heads you could be looking at around 9.1 to 9.3 CR depending on head gasket thickness.

The 273 heads flow quite well on that small motor with some minor mods. A little porting and clean-up of the bowls, 5 angle valve job and going with a 1.84 intake (cut down 360 MP 1.88 valve) and a 1.72 (ferra valve) will yield some flow and velocity numbers the motor can handle. Intake valves larger than 1.84 will cause shroding problems unless the bores are notched.

The Isky E-4 cam is a good choice. Has a nice idle but will pull hard. Of course it's a solid cam and you will need adjustable valve train. The stock adjustables work fine.

The Edelbrock D4B wins hands-down as far as the 273 in my opinion. There are some mods you can make to that manifold. The Carter 9635/9636 works real well on a 273.

Of course all other mods such as electronic ignition, good plug wires etc. will help. On the converter issue, one way to solve the small centering journal on the end of the crank is to have it machined to accept the larger converter centering hubs.

One thing to remember, this little motor likes low gears, the more, the better. 3:55 up is your best choice. In your car, a set of 3:91's would be killer.

I forgot to mention that the 904 is a killer tranny for the 273. you can put the low 1st and 2nd gear in that tranny with a 2500 stall converter and you'll leap out of the hole with that combo.
 
I am really thinking that with my dream of 12's being limited by the rule book, that I will just build the 273 with the mild cam,redo the heads for unleaded gas,add a 4barrel and appropriate headers. The car won't be a screamer,but it will look and sound good. A buddy of mine also has an A-body 8 3/4" laying around that He said is "workable". Anything I do is going to make the car at least a little better in the performance end.
 
sureshot43 said:
I am really thinking that with my dream of 12's being limited by the rule book, that I will just build the 273 with the mild cam,redo the heads for unleaded gas,add a 4barrel and appropriate headers. The car won't be a screamer,but it will look and sound good. A buddy of mine also has an A-body 8 3/4" laying around that He said is "workable". Anything I do is going to make the car at least a little better in the performance end.
Click to expand...

If you are looking at a 273 powered car that runs in the 12's i would count on it being very streetable. You would enjoy the car more by sticking to your plan.
 
Just a thought here, but when i was racing my 318 dart, I had 302 heads on it to start with, then went with 360 heads, ran quicker, Last set of heads were 273 heads 67 castings with adjustable rockers, went from a 8.93 to a 8.79 with the 273 heads, in the 1/8 mile The 273 heads were polished not ported, really impressed me, But it's all in what your puttin in your engine combo to zero decked, milled rear end gears to what you need,Many will and have disagreed with me but the 3o2 castings never impressed me,
 
The more I think about it,the more I want to use the 273,keep it running 87 octane,and have a fun ride that sounds and runs decent. Besides,no one will know how fast my car is(or isn't) unless I tell them.
BTW, I had a '69 Chevelle SS that was a high 12 second car. My next mopar build will blow the Chevy's doors off. You can count on that.
 
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