The 273 Build That Doesn't Suck
WARNING: Reading this article might cause you to giggle uncontrollably with excitement. It might lead to sleepless nights and neglected work-hours spent planning your own 273 build. It might have you scrounging vintage salvage yards, the classifieds and maybe even strangers' back yards looking for neglected 273 cores. It might even lead you to abandon all rational engine building protocol in the quest to create your own dare-to-be-different scream machine.
We are not responsible for any of this. However, if you choose to build an engine like this, we'll be right there to help you build it.
A few months ago, Chris Sockriter stops into our shop with that glint in his eye and a plan in his head to build a hot 273 for his 69 Dodge Dart. Now if this was 1965 and the 273 was still a serious D/Stock contender, we might have been just as excited as Chris to build this engine, but the fact is, MOPAR's tiniest small block is just that- tiny- and as anyone who builds or has had an engine built for them knows, bigger engines make more power for less money. In other words, why build a 273 for power when you can build a 360 that will make more power for less money? While you're at it, why not build a 408? In comparison, they're even cheaper than 360's when it comes to producing power for pesos.
But like we said, Chris had that glint in his eye, a plan in his head and money in his pocket and all of them were targeted to build the 273. So we kept listening. And that's when things started to get interesting. Turns out Chris didn't just want us to build a hot 273, he wanted us to build one with a hair dryer- aka- a turbo (or two), for some stick-shifted silliness in that Dart we mentioned earlier. Now we started getting that glint in our eye too. This could be fun. Sure, the 273 is still small but throw some turbos at it and it gets quite a bit bigger. Factor in the advantage that Chris already had the engine and that its factory forged crank is plenty tough for boosting and beating and the higher costs generally associated with building small engines might not be so high. So we devised a plan to build a simple, stout, small block that's just a huff-job away from becoming a hero.
Building For Boost
With the plan established that this was going to be a turbo engine, we got to work on prepping and building for boost which in this case, like every case, meant first building a solid and excellent performing naturally aspirated engine. To do this, we spec'd out a package that included a mix of tried and true components along with some creatively applied out of the box thinking and parts selection along with our requisite high accuracy prep, machining and assembly procedures.
The Foundation
The Block
Since everything is built to go on or in the block, we started there. From the beginning we were concerned about the 273's small bore- things like bore shrouding, air flow and even basic piston availability were major considerations; custom pistons for example can add huge costs to a build. As it turned out, we had little to be concerned about. Here's why: sonic checking the walls on this particular 273 revealed thrust side cylinder wall thicknesses of about .280. Better yet, core shift seemed non-existent on this block because the numbers were consistent from front to back in both banks. If nothing else, this solved our piston selection, material and price issues because we could safely bore the block to stock Chevy 305 size which meant our piston options grew almost exponentially while the price point dropped with the selection and availability of the much more common pistons.
The Crank
Like we mentioned before, this was almost a no brainer. We know from experience the factory forged steel crank can take a beating thanks in part to its robust construction method, material and relatively short overlap. Provided it was in good condition, this would prove a near perfect part of this build. Fortunately, the crank was in beautiful shape. Done.
Rods
Yes, Chrysler's factory forged steel connecting rods can be excellent choices for high performance engines but the reality is that once you factor in the cost of reconditioning, new, forged steel performance rods are a better and more economical choice. We used SCAT I Beam rods.
Pistons
Knowing we were gonna get blown dictated several custom design parameters be built into the pistons which is why we went with custom designed PIE/JE units. Even with the custom design however, the more common bore size kept costs within reason for this type of build.
Camshaft
One of the great things about turbo engines is their excellent street manners vs performance potential. Turbos make great power while offering unmatched drive ability. Getting blown is awesome! With this in mind, we selected a reasonably mild, off the shelf grind from COMP. It specs out with 218/226 Duration @ .050, .525 I/E lift and it's all built on a 114 LSA. This is a cam we knew would make great power in naturally aspirated tune but also make the most of what the turbo has to offer.
Heads
This was almost as much a no brainer as the crankshaft or conrod selections: we went with the EQ Iron Magnum heads. When it comes to bang for the buck these things just can't be beat. EQ's key durability upgrades that addressed the Magnum's short comings combined with an LA style manifold bolt pattern make these heads outstanding, economical performance pieces. The iron construction also make these perfect for power production and long term reliability in a turbo engine. For our part, we added our exclusive Stage One Porting which includes upsized intake valves and flow bench tuning that help unlock even more power potential. Throw in a set of our adjustable roller rockers and this part of the combo is good to go.
Intake
An Edelbrock Super Victor will help handle the deep breathing induction duties. It will be drilled and set up for EFI once we go boosted. Until then (and for dyno testing) we'll use a 700 cfm carb.
Oiling System
A Melling standard volume pump is all we need to keep everything moist. Remember, staying lubed is a very important feature when you're gonna get blown.
Prep, Machining & Assembly
The reality here is that for most people, machining isn't all that interesting and we get that, so we won't bore you with details here except to say that exciting or not, proper machining is critical to an engine build's success or failure on the dyno, the road or the track. Both power production and durability are greatly affected by the quality of the machine work. With this in mind, all you need to know is that we spent painstaking hours, the way we do with every build, inspecting, cleaning, machining and prepping every element of this little 273. From machining and assembly to inspection and cleaning to fanatical detail of each and every tolerance, we checked everything to make sure we didn't miss anything.
Dyno Time
Let's face it, you probably skipped to the dyno sheet before you read anything else. That's cool, we do that too. In that case, you already know the little 273 made 360 bhp and 355 lb-ft of torque. Stout numbers indeed. Naturally aspirated, this works out to about 1.3 bhp per cubic inch which means this little beast is pretty efficient at sucking air, mixing it with fuel, slamming them with spark and blowing the whole combustive cocktail out the exhaust. And it sounds sweet doing it.
So what's next. Well, we think you have a pretty good idea by now. Soon we'll pour on the boost and see how many more horses we let loose. In the meantime though, Chris is getting ready to drop this little bomb into his Dart and drive it as is for a while. We know he's gonna have blast with it but we can't wait to get those turbos installed. Once they're on, the suckin', squeezin, bangin' and blowin' is going to get really good.
