Woody at fordstrokers.com says the is no reason not to go with the longer 3.40” stroke on the 347/363.

 

And if you’re willing to spend the coin on a Dart block 347/363 ($$$$$)and go 4.125” bore, that helps to unshroud the valves for better airflow. But if you’re staying with an OEM block($$), this doesn’t apply.

 

3 + 3 + 1 is 7
3 + 4 + 7 is 14

So the 347 is twice as good as a 331🤣

I've been waiting for a chance to use that. Years ago I remember some guy was trying to say how much better a 347 was than a 331 and that it magically always produced more horsepower per cubic inch.

 

Even if they produced the same "horsepower per cubic inch", you'd end up with more w/ the 47.

 

Hipojoe1.......Come drive my 347😁 (32nd st and Ray road - PhoenIx)

 

If you want the honest truth, we're talking about percentages here. The difference between a 302 and a 289, really.

331 makes a little less torque (the crank throws are .15" shorter, so less leverage). But it holds power to higher RPMs for the same reason. 347 has a worse rod ratio, and more side-loading, but we're talking a couple percent difference in friction at the most?

A lot of people believe that more cubic inches = more horsepower. But it's not true. Your peak power is almost always limited by flow. So if you put a 347 crank in a 289 block, and change nothing (let's pretend the compression ratio magically stays the same here in this example) you wind up making max torque very early, and then it poops out much sooner. Peak flow in and out of the engine are what determine peak power.

You can use more gear with a 289 and get basically the same performance curve as the 347 in this example.

There's other things that can come into play. If, for example, you are using 220cc heads and a huge cam for monster peak power, putting those with a 289 would put the peak horsepower at such high RPMs it would be hard to keep the engine together. The same parts on a big displacement motor would hit their peak at a lower RPM, because the larger displacement would hit peak flow on the ports sooner.

I felt like the 331 was nice and light, had better rod ratios, and was going to make more torque than a 302 or 289 (which I thought would be fun for making tire smoke sometimes). At the time I chose it, I was going to be running a 3 speed C4 automatic with 2.79 rear gears. I needed more torque, but didn't want an all-out monster. I absolutely could've gone 347. But I didn't.

I don't think the differences are big enough to really say that either is a 'wrong' decision, here.

 

I went the 347 route because I wanted the extra torque at a lower RPM. It should pull the 3.50 gears I'll be switching to and help keep some punch off the corners.

 

I've got a 347 at the time it was a toss up between a 347 and a 331. What is surprising because it's my first stroker is how quickly it spins up. I have to watch my rpms and not overdo it before shifting. I probably should install a rev limiter. In tje old days Id wait till I got valve float. Not with this engine.

 

Im with Grimbrand 331 better rod ratio. More science than I totally understand but the bottom line if you build it rt it will quick. I'm sure some will get on the band wagon that there's no difference in block stress between the two. Well working with a TRD guy dynoing supercharged Toyotas I learned some things and rod ration has its place. I built a 351 for my FFR Cobra went 383 verses 408 [rod ratio] car was faster than me.

 

Seasoned 302 block... 400ish HP. 6500 rpm, pump gas, maybe get 30-40kplus miles out of it, and I dont want to fiddle with valve train. Also best builders, warranties, and if we are getting technical... Best price for a given package!

 

My standard response. New block cast in Indiana. Has gone up $200-300 in the last few weeks, like everything else. Ford Small Block Compatible 347 c.i. Engine - 415 Horsepower - Long Block

 

+1 that it's percentages and rpm for equivalent combinations. For street/strip, you would never know the difference, if well planned and built for your project goals. Once upon a time, a big issue was about the rings intersecting the wrist pin hole, but uncommon today.

Also, at some point it's better to cuss at spark plug changes on a 421 stroker, than try to get 30 more HP out of an 8.2 deck. Or yet another direction - build either one for 5500 rpm limiter and juice it past 500hp reliably. More, for less. You have many, many options, and your goals list will highlight better paths. 👉Where is that list? Guesses and favorites are useless without specific goals.

For me, that makes it more a choice of what parts and pieces will be available that best fit your build goals, at what cost, when you click 'buy'. Keep your options open, and best choices will float to the surface. Have fun with them!

 

I personally leaned to the 331 but...

I had a very experienced, very well respected, very popular ford builder tell me 347 every time.
"In his words, It will spin just as high as a 331 and make more power. There are zero issues with a 347.
Then he asked how many motors has anyone on the forum built, because I have built hundreds of 347's" and know what I am talking about".

I say, pick a builder and trust them & if you are building it yourself you will be happy with either choice.

 

I personally leaned to the 331 but...

I had a very experienced, very well respected, very popular ford builder tell me 347 every time.
"In his words, It will spin just as high as a 331 and make more power. There are zero issues with a 347.
Then he asked how many motors has anyone on the forum built, because I have built hundreds of 347's" and know what I am talking about".

I say, pick a builder and trust them & if you are building it yourself you will be happy with either choice.

He's right. There is nothing at all wrong with a 347. It will make more torque than a 331.

However, - he is also wrong about it spinning "just as high". Geometry and math tell us it'll lose a few hundred RPMs. (Like that's a big deal? Who cares?)

It will also move the pistons up and down faster in the bores for a given RPM, and rod angles are steeper. Again, these differences are minute, but it will absolutely wear faster and have more frictional loss. Not speculation, that's fact. At the same time, if it's more than a percent or two I'd be surprised. And it's not as if worn out cylinder bores or rings are the #1 cause of engine failure with a Windsor anyway.

There is no point in trying to say whether a 289, 302, 331, or 347 is "best". It makes a lot more sense to decide if it's best for YOU, and for how you want to use your vehicle.

If your ride is heavy and slow, especially with an automatic, then more torque earlier is 100% better, and a 347 makes the most sense. But what if it's light, and is just a smoke machine, unable to hook the tires, with high numeric rear gears? It would be dumb to go with a 347, when a 289 would help the car get more traction, and could hold each gear longer, going to high RPMs but making the same peak power.

Cubic inches are often a lot of fun, but realistically, there's just a lot of ways to solve any engineering problem. There's a balance of economy, RPMs, how long it will last, and how much power it will make. Picking the right parts for how you want to use it always makes the most sense. If you need every last shred of torque, then you'd be foolish not to go with a 347, because it makes the most. What if you wanted economy for a daily driver though? If you're just rebuilding a stock 289 and decide to put a stroker crank in it without changing anything else, that same 347 lower end would be really stupid.

As I often say - pick parts for your engine's intended use.

 

It always gets back to what one wants from his build. If you want tire shredding capability without regard to those minute, but, important nuggets of wear points(mentioned above), then the 347 +, is your engine. If you want decent power with minimal, if any, accelerated wear points, then the 331. If you want "Ho-Hum", stick with the 289/302 stock build. All three will get you from "Point A to Point B", in time.

 

Since you're asking here, I'm assuming this is intended to be a street/strip engine and not a full on race engine.

There are a TON of 331 vs 347 threads spattered across SBF online forums... The rest of the 331 vs 347 information is just regurgitation of decades old information, which leads me to believe this comparison is purely based on dated forum posts. I wonder how many have actually ran both of these motors before. Its like guys just go back to the old threads and post the same exact response over and over again or they just grab a response from chatGPT.

347 = 1.588:1 - Conrod ratio | 331 = 1.662:1 - Conrod ratio --> Difference = Negligible for street motor

If you don't intend to build a full race motor with a rod ratio north of 1.7/1.8 area, then the rod ratio discussion between the 331 and 347 is rather pointless as both ratios fall within the same range of many common street engines. Additionally, for a basic 331/347 build, any RPM discussion will be primarily focused on the HCI combo and what the bottom end is able to handle. The conrod ratio just isn't going to matter as you can build a 7400-8000rpm 347 stroker, if you wanted to. I wouldn't pay attention to the "technicals" between these two basic SBF motors being compared as if it is NASCAR or F1.

I'm not saying disregard all theoretical technical information, but people get hung up on what doesn't matter. In reality, 347 = More HP, TQ, and same reliability (with all things constant). You'll light the tires up with both the 331 or 347 in these cars so arguing the difference in HP/TQ is also kind of pointless.

 

347-331 = 16

318-302 = 16

I never met a 318 that would give my 302 much to sweat about. It's a Ford, you'll be fine either way

 

Where are all those worn out 347" people talk about? There have probably been built many thousand of those 347s over the years, but I still don't remember to ever have come by someone having one showing serious wear caused by the length of the stroke.

My personal opinion is that you for max street fun want TQ, meaning your car feels powerful without needing to rev it high. The same reason I went for max stroke (347") with a mild performance cam. Focus on drivability and mid range power over a peak HP number. 20hp more at the top will show if you race against the clock, but wont make any noticeable difference in how the car feels driven on the street.

Just for inspirational reasons, here's a stock block 347". 😁 The 1/8 times converts to doing low 8s on the quarter.

 

Get a 351W block and build a 408 or even a 427. Same coin for more bang.

 

The ideal torque curve for an engine is a flat line. All being ideal, the line just moves UP with more stroke at the same bore. 302 gets 15ft/lbs across the board on a 289. 331 gets x over a 302. 347 gets x over a 331. At <7000 RPM, take the torque.

Only reason to build a smaller engine is a unique scenario with big money on the line. The truth is most of us are not smart or rich enough to make a 331 better than a 347 in such a scenario. Even if you were, why suffer the brain damage at the same cost?

Someone pointed out a 331 crank is lighter. To me, that's its huge benefit. Car will be lighter.

Compared to a 302 a 331 makes tons of sense. That would be a big difference!

 

Let's face it...every SBF is a short rod engine. SBCs use 5.7 or 6 inch rods and SBMs use 6.123 inch rods. I had a Chevy guy one say "Man, you guys have short rods" in an online conversation. He's right. I don't think there is anything wrong with that though. SBFs have obviously shown that they don't suffer any ill effects because of rod geometry except for maybe the most extreme applications. They can "cope" just fine. There are advantages to short rod engines just as there are advantages to long rod engines. Short rod engines behave like a larger engine because the piston moves faster downward pulling more from the induction system. F1 engines are very long rod engines with rod/stroke ratios in the 2.5 range. They benefit from this since they turn 18000 RPM or more. Less side loading on the tiny piston skirts and less piston G forces and the longer dwell at TDC probably is a good thing at those crazy RPMs.

The side loading difference between a 331 and a 347 with 5.4 rods is 4.9%. The 347 has a smaller skirt so the difference may be a bit higher overall, but there are many reliable 347s out there so it probably doesn't matter for the most part. My 331 has virtually the same R/S ratio as a 347 (1.586 vs 1.588), but the piston skirt in my 331 is considerably larger than the 347 piston so in essence my 331 has less side load per area than any 347 or conventional 331. It comes at a cost of a heavier piston.

An unforeseen benefit of my unconventional 331 was that I had to remove approximately 1/8" from my crank counterweights so the bottom of the piston would clear. Essentially a lightened crank. The whole assembly balanced without any mallory metal.

Unfortunately, the KB322 pistons are no longer produced so building this engine would require a custom piston. KB informed me some 10+ years ago when they were going to stop production of the KB322 so I bought another set of pistons just in case.

 

Short deck and rods = valvetrain stability.

 

I always remember what the old guy at the speed shop told me back in the 70s when I wanted to hop up my 390 or go get a junkyard 428. He said, 'There is no replacement for displacement.' Speed costs money; how fast do you want to go? I kept the 390 and added the basics. All in a 56 F100 that wouldn't hook up, but could do one hell of a burnout and was scary fast. I only drive 2000 miles or so annually in my '66 K-code. I have a roller 302 90's mustang motor in the corner that I am leaning towards building a 400 hp 347 engine to swap into it. Just for fun and because I want to. I've ridden in a few Fox Body Mustangs that the guys have run 347's in, very exciting! No comparison to my 289 hipo.

 

Stroker? Yawn.

7500+ RPM 302/306? Now that's more like it .

 

Since you're asking here, I'm assuming this is intended to be a street/strip engine and not a full on race engine.

To add to this point of goals, one of my all-time favorite builds was a '69 convertible. Not s/s, not race, just a fun cruiser than I would 'get on' once in a while. I went with a low-rpm 427 stroker that peaked around 5500. Why? With all the wide-band torque, all I had to to was think "pass that car" and it did. Effortlessly. An up-side was the cammed rpm, which gave really good MPG. 😁 It was planned and built to the purposes, and was very satisfying because it hit the specific goals.

SBFs have obviously shown that they don't suffer any ill effects because of rod geometry except for maybe the most extreme applications. They can "cope" just fine. There are advantages to short rod engines just as there are advantages to long rod engines.

+1, rod:stroke is splitting hairs for anything but high-end racing where every ounce of power is worth big money. For street examples, look at the 'horrible' r:s ratio of the Honda 1.6, or the Chevy 454, and yet they are famous for their lifespan. Split hairs if you like, but reality says it's not worth the time or exaggeration for anything we're doing here. An extra hour of tuning will gain more than the r:s difference, in both performance and longevity.

7500+ RPM 302/306? Now that's more like it .

If that's your boogie. As @ Grimbrand originally started this angle with, a 289 or a 460 can run neck-and-neck, if the engine and chassis package are designed well to the goals. Top-down begins with a 200ci at 2x rpm and a 400ci can do the same work – if planned and built for it. But, does that satisfy your goals?

For a street car and 1:1 trans, the performance gearing would mean that engine type would suck at MPG. That's OK, if that part of the plan isn't important to you. Or likewise, highway gearing would make it suck for local driving and strip work. It's all compromises, and to our best benefit to know what we are juggling the compromises toward. Make your total goals list, and be specific for everything you want or need it to do. Then do your thing.

 

The thought being here..... What, Who, Why is the best 331 - 347 engine package. The best Bang for the Buck. No race car stuff, No constant fiddling, Longevity, No extreme RPMS, just a great small block ford. Is it Woody, Blue point, local shop down the street? Then price point break for such an animal.

 

First, I'm a design and build person. If I were not, I'd go with "Woody". Fordstroker's, has a long history and well recommended, just my opinion. I've read here, about BluePrint and many good experiences. MY from signature, you see I went with a 331 w/.040 bore for 333 cu.in. It's been a solid engine since 2007-08. All of my performance goodies are add- ons and have supported the build very well. If I were in the market again, I still go with a 331 (for many of the reasons posted previously) and have "Wood" assemble it with my input. Yeah I know, delivery may be 6 months to 12, but, I'd factor in all of this knowing the results. Some folks here like 500 + HP, that's not me. My build was DYNOD at just under 392 "Peak" RWHP at 6200. I'm fine with this. Just my 4 cents.

 

Woody doesn’t build OEM blocks anymore. Only aftermarket blocks. Where are you located? You can ask local car club members for recommendations, too.

 

I'll have to visit to look over what's up to these days. Thanks for the update.

 

I guess the Blueprint offers are hard to beat, if just looking for an turnkey engine that come with an warranty. They are factory new engines. Built in a factory style environment with assembly lines. But it's not were you get a custom designed engine to you exact specs.