273 and 318 the same block?

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From what I read I your other threads I'd go with all aluminum 470 big block 550/550 hp/torque
 
273 said:
Depending on desired hp this wouldn't be a bad combo
still would have great rod ratios and still on the over square side ( bore stroke ratio) and with the extra cubic inch it would bring the power band down a little. But without a good head porter it would be hard to get more than 350hp, it probably make a good 1 hp per Cid gas mileage engine but you would be further ahead going larger bore engine.
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Let's just say I dare to be different. I remove the 273 out of my Dart and throw it in something else. Now I've got an entire 273 carb to pan and a spare block sitting in my garage. A cast 360 crank cost what, used? Maybe $50-100, I'd assume. Machine it down so it fits the 273 mains. I know Egge makes some pistons for the 273 if I need to bore it out. Do a classic rebuild with bearings, bushings, gaskets, water pump, timing set, plugs, etc. Install a little more aggressive cam (nothing too wild), a better intake, and a 4-barrel carb and I would assume it would be a great, high revving street engine in a lighter car. Nothing fancy and I would assume it shouldn't cost too much. Sure, a 318 may cost next to nothing compared to a 273 but then again it would be a decent 1 hp per cubic inch engine, or close, maybe?

Now are the 273 and 318 intake patterns different for 67-69?
 
Not to drastically change the subject, but isn't the Mopar Performance Crate 360 still available? For all the coin in machine work and porting, I think you can get a crate 360 that will do what you need it to do rather cost effectively. Unless you have your own machine shop and want to experiment, it wont be cost effective to try and push a 273/318 out to 340/360 performance range. I can understand the shortage of 340's, and the interest in "making" a 340 out of a 318, but I remember in the early 90's 340's were sought after and weren't cheap even then. I just don't think making one is really cheaper than a MP crate deal. I may be wrong though.
 
MuuMuu101 said:
Let's just say I dare to be different. I remove the 273 out of my Dart and throw it in something else. Now I've got an entire 273 carb to pan and a spare block sitting in my garage. A cast 360 crank cost what, used? Maybe $50-100, I'd assume. Machine it down so it fits the 273 mains. I know Egge makes some pistons for the 273 if I need to bore it out. Do a classic rebuild with bearings, bushings, gaskets, water pump, timing set, plugs, etc. Install a little more aggressive cam (nothing too wild), a better intake, and a 4-barrel carb and I would assume it would be a great, high revving street engine in a lighter car. Nothing fancy and I would assume it shouldn't cost too much. Sure, a 318 may cost next to nothing compared to a 273 but then again it would be a decent 1 hp per cubic inch engine, or close, maybe?

Now are the 273 and 318 intake patterns different for 67-69?
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Theres no cheap way to stroke a 273, there's is a cast steel crank the fits 273 mains for around $ 250 - $ 350. For pistons custom would be the best and most expensive option but probably not by much. 2nd option would be to see if there's enough material on the cast replacement pistons to be milled off the top to work, I seen a 318 with a 360 crank done that way think they milled off 0.100". Or 3rd would be to get a hold of Australian hypereutectic pistons for a holden engine which has a similar bore size. They will come out to around zero deck with a 360 crank. But they have Chevy pin size so you probably would have to use Chevy 6.125 rods and have the crank and rods machined to work $$$.

For the few extra cubes I wouldn't worry about stroking unless you plan on custom pistons anyways.

You don't seem to expect to much from the 273 so the stock heads should be more than enough, there good for about 300-325 hp more than that you need to port (look at the sticky for porting stock valved 318 heads ) or notch the block and run EQ'S.

For your build I just go with a 9:1 cr stock heads with a good valve job and at least cleaning up the bowls and port matched a little extra flow makes you able to go with less cam which for a 273 you have to be careful with, with the rule of thumb you would want to run about 15 degrees less cam than a similar 360 build. So probably in the 260-270 range.

Gears wise I wouldn't go under 3.55 but something like 3.91-4.10 would be better.

For my 273 I was thinking of having the block sonic checked To see what would be the best possible bore size and have the crank off set to 92% of the bore supposedly the best compromise for friction to hp. I was figuring I'd be around 292 cubes when done.
I was also gonna run a early Chevy 2" bearing 6.25" rod partially to maintain rod ratio but mainly to be able to run lighter Chevy pin and a shorter and lighter piston. For heads I was gonna go with stock since there closed chamber and I wanted to keep the smallest port posible to maintain velocity. I was gonna run under cut hollow thin stemmed ford 1.85/1.55 valves with beehive springs and titanium retainers trying to keep spring rate low as possible since it's a street car and wanted a 7500 plus red line. Was gonna port the heads myself with a home made flow bench I read where use the block and a vacuum it only measure percentage not cfm numbers but still able to check progress. Was hoping for 200-220 cfms in a 273 bore. Cam would be a custom made solid or solid roller, was leaning towards solid roller cause want to keep overlap small and lift high to build the widest power band possible my dyno program like comp cams 268 solid roller so I'd imagine the cam would of been around that. And a 750, airgap and custom A.R. Headers to top it off and either A833 4 gear and 4.88-5.13 out back or T5 with 3.55-4.10.
 
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