So, this topic may have been be beating a dead horse, but I notice some crankshaft manufacturers, like Eagle for example, list a 273 as compatible with a 4.00" crank. However, I don't seem many people ever mentioning or stroking a 273. Is there some extra machining or clearancing to stroke a 273? Are there interferences in the rotating assembly or problems with flow? I'm just asking for curiosities sake.
273 Stroker, 4.00" Crank
- Thread starter MuuMuu101
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goldduster318
Overzealous Car Modifier
I'm thinking you'd likely have to notch the bottom of the bores for the rods. Probably even with the thinnest rod beams available.
Nobody makes any pistons so they'd have to be custom as well. The cost would be prohibitive I'm sure.
The other thing is...all that work and you get a 336ci engine (at +0.030). Bore size is very small so you won't get very good airflow. You're probably better off overall with a stock stroke 318. Even a 318 block with the same exact crank will make a 390ci engine.
For performance, the 273 is a boat anchor - especially when 318s are almost free and look identical on the outside.
Nobody makes any pistons so they'd have to be custom as well. The cost would be prohibitive I'm sure.
The other thing is...all that work and you get a 336ci engine (at +0.030). Bore size is very small so you won't get very good airflow. You're probably better off overall with a stock stroke 318. Even a 318 block with the same exact crank will make a 390ci engine.
For performance, the 273 is a boat anchor - especially when 318s are almost free and look identical on the outside.
Not any more clearance issues than a 340/360 except for the fact that the 273 bores are smaller and may require more clearance at the bottom of the bores. The biggest problem is the pistons. No one makes stroker pistons for 273's. There are companies that make stroker pistons for the 318, 340, and 360. I don't know the ins and outs of bore vs. stroke when it comes to horsepower and torque but there is a benefit to stroking small cube engines. Hopefully someone will chime in with more information.
tmm
tmm
For performance, the 273 is a boat anchor - especially when 318s are almost free and look identical on the outside.[/QUOTE]
Hey, Hey, Hey! Be nice about 273's. If it wasn't for them you might have a poly in your Duster. LOL (and nothing wrong with those either except for their size)
Hey, Hey, Hey! Be nice about 273's. If it wasn't for them you might have a poly in your Duster. LOL (and nothing wrong with those either except for their size)
So essentially if you want a 273 stroked you should probably take the block and bore it .285" and then throw in a 4.00" crank?
.285? I don't follow you. If you have a standard bore 273 that needs boring you would probably bore it +.030 over.
It was a joke... A 0.285" over bore would give you approximately the same bore as a stock 318.
goldduster318
Overzealous Car Modifier
So essentially if you want a 273 stroked you should probably take the block and bore it .285" and then throw in a 4.00" crank?
Take the forged crank and adjustable rockers from the 273 and throw them in a 318 for a lot less money and go faster
:burnout:Or...just build a 340 or 360. Considering mine is pretty mild and it made 470/455 and still has 13" Hg vacuum at idle with 9.7:1, I'd say they work. I'd have a whole 10ci on a 4" stroke 273 and easily 140 more HP. Head flow matters. Without going 4 valve heads, the small bore will kill airflow.
Ha! I didn't do my math. Goldduster is right. You could do it but the benefits of 390 cubes vs 336 cubes is huge. Now the difference between a 390 and a 408 (360 stroker) doesn't seem so much.
Take the forged crank and adjustable rockers from the 273 and throw them in a 318 for a lot less money and go faster
Or...just build a 340 or 360. Considering mine is pretty mild and it made 470/455 and still has 13" Hg vacuum at idle with 9.7:1, I'd say they work. I'd have a whole 10ci on a 4" stroke 273 and easily 140 more HP. Head flow matters. Without going 4 valve heads, the small bore will kill airflow.
This is all just for information and curiosities sake. I don't think I'd go with a small block for my '68 Dart although if I do, it would probably be a lower compression 408 (around 9:1), maybe with some boost, for driveablility. There are a few people telling me I should keep the 273 in my Dart, but I'm not necessarily a fan. I've got an engine idea for my '68 Dart. It's a bit unorthodox but may fair out well. It's going to be a lot of work (almost Hemi swap work) but it should do well. And it's still a Chrysler/Dodge/Mopar engine so it shouldn't anger the forum peoples. I'm just going to keep it hush-hush for now. ;)
I kind of want to do a 273 build for an early-A in the future basically taking my entire suspension and drivetrain left over from my Dart build and transferring it over. I'm thinking either a wagon of some sort or a Trans-Am "like" car with a Dart or Barracuda. The wagon would just be a car for sharts and giggles. The Trans-Am "like" car would be a loose representation of what I may think a trans am car would be. Both builds would just be for fun, nothing serious.
goldduster318
Overzealous Car Modifier
Curious as to why you wouldn't want to stay with the small block?
I actually kept the stock stroke on the 340 to make sure it didn't melt the tires off 24/7 driving around on the street. It still makes 400 lb-ft at 2800 rpm. If it was me, I'd spend my money on a fuel injection kit and a roller cam over a stroker kit. An over 450hp street car has a hard time hooking up without traction control. I can stab it at 20 mph and blow them off, and a nice healthy bark on the 1-2 shift (4-speed) at 55 mph. I need to do the suspension and install the 275-35-18's I'm planning on to replace the 225-60-15's.
My Friend was looking into vintage racing for a 64-66 Cuda or Dart. Most of them even allow you to use 318's...one had a 100 lb weight penalty, but it's probably still worth it.
The main reason why I don't want to stay with a small block, and it may seem like a stupid reason, is because it bores me visually. To me it's a little overdone (which makes sense since these cars came with small blocks as their primary power source). I'm not a huge fan of the carbureted look either. I like the long intake look of the Hemi's and such. I know it's kind of a weird reasoning, but I like things that are different.
If I were to do an engine swap my 3 choices would be Mystery Engine, SRT4, or 408.
I'm doing my build opposite of how you did it. I'm doing suspension, brakes, wheels and tires first and then moving over to making power.
I'm also aiming for 275/35/18's on my Dart. Hopefully I can make them fit, if not I may just scroll down to like a 255/40 or 265/35 (would rather go with the 255).I wouldn't necessarily try to get into "Vintage Racing" but just build a Vintage "like" car.
I just switched laptops. My old one will still run my Dyno 2000 program. I know, it isn't really accurate but it's a fun comparison. My stock +.030 with a Isky E-4 cam is rated at 286 hp. @5500 with 307 ft./lb. torque@4000 rpm. With nothing else changed except for the 4" stroke, the hp. went down to 280@ 4500 with 354 ft./lb. torque @ 3500. Not a big change for a $1500+ kit...
65Val
Average Length Member
Go get'em Mike!!!!
rayer:$1500+ for less than 50 ft-lbs of torque? Yeah, that definitely doesn't seem to be worth it. I wonder what the limiting factors are that you're importing into the program? Your 273 build doesn't sound all that bad. If I could just barely tap the 300 hp mark in a lightweight car, I think I'd be happy.
Again, I like things that are different.
Is this from experience, or just theoretical?
Everything else you said was true. But the 273 is nothing like a boat anchor. On the contrary, the Commando version is more like a mini 340 -- high compression, high revving, high HP/CID ratio.
But you are absolutely right about a 273 stroker -- it makes no sense and wouldn't achieve anything. The valve and port sizes on a 273 are perfectly fine for 273ci, but are too small for a larger displacement -- that's why a stock 318 is not a hot performer (larger bore, with the same small valves and ports). Adding displacement via stroking would make the breathing restricted (relative to the cylinder volume), with no way to fix it given the small bore. Stroking usually adds torque, but you'd be choking it at the top end, so probably no net gain, and a serious loss of area under the curve.
IMO, the 273 4bbl was pretty much optimized for a production engine of that displacement. It's hard to improve its performance significantly without major changes. and the best way to improve the performance of the 2bbl low compression version is to imitate the factory 4bbl configuration. If that's not enough for you, then yeah, you need to look for a larger bore block, 318 or 360.
To get decent pistons you need custom anyways for a 273 but most I'd go is the 360 3.58" stroke and still have great rod ratio and decent bore to stroke ratios. Out of the 4 small blocks the bores size is the only real differences and limit for power on each. What the limit is for a 273 who knows but probably ain't that many 350 plus hp 273 running around. I sure someone with the talent and equipment probably could squeeze a lot more if they were so inclined to do so.
That's what I was thinking,hence bringing up the question.
You have me scratchin my head, lol.
I know... I know... I'm full of contradictions. Lol. The 408 would be the last resort if the other two engines don't work out.
Did I hear SRT4? I wish I had taken a close up of the engine.
There are a couple members here doing SRT4 builds.
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