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:dunno, 3.4" is a lot of stroke to be squeezing into an 8.2" block . . . something's got to give, whether that involves rod/stroke and rod angularity, piston pin location, or some of each. I can't make pushing either of those compromises that far sound like good things for a respectable street engine, long-term.


Norm
Yes.....there are hundreds of thousands of 347s that have been built over the past 30 years that couldn't possibly work.
 

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Yes.....there are hundreds of thousands of 347s that have been built over the past 30 years that couldn't possibly work.
Nobody is trying to claim that they don't/couldn't/wouldn't. Only that they're not everybody's choice. 4" bore 383's are common over on the Bowtie side of the street, and I wouldn't build one of those either.


Norm
 

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If you are concerned about 3.4" vs 3.25", why not just keep it at 3"?
 

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There's a seat for every butt. But that statement is a long way from "dunno, 3.4" is a lot of stroke to be squeezing into an 8.2" block . . . something's got to give, whether that involves rod/stroke and rod angularity, piston pin location, or some of each. I can't make pushing either of those compromises that far sound like good things for a respectable street engine, long-term. "

The new version is "I know it works, but I don't like it." Kool, everyone discriminates. But nothing has to give. Both the 347 and the 383 will last as long as any engine out there. There are no inherent geometric, or trigonometric problems that would cause them ot wear out prematurely. Bot the 347 and the 383 are perfectly "respectable" street engines....long term.
 

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Discussion Starter #26
Great information here .For me I'm just trying to swap a Dss 347 with 2000 miles on it upgrade to a dart block and turn up the boost on some corn.
I figured know one will pay me much for that in a short block so why not swap it over to a Dart and keep it a 347.
 

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No real reason not to, you can always go to 4.125 later when you need to rebuild. The only think you'll lose is the increased flow you get from unshrouding the intake valve.
 

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No real reason not to, you can always go to 4.125 later when you need to rebuild. The only think you'll lose is the increased flow you get from unshrouding the intake valve.
How much would you think the unshrouding is worth, versus the gain of 15ci or so?

I'm aiming for near 550hp, with boost, so I don't think mine will need the larger bore, or stroke. So my intention is a 327 or 333(whatever bore that is) in a Dart block, with KB and intercooler. As said, everyone has their preferences.
 

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There's a seat for every butt. But that statement is a long way from "dunno, 3.4" is a lot of stroke to be squeezing into an 8.2" block . . . something's got to give, whether that involves rod/stroke and rod angularity, piston pin location, or some of each. I can't make pushing either of those compromises that far sound like good things for a respectable street engine, long-term. "

The new version is "I know it works, but I don't like it." Kool, everyone discriminates. But nothing has to give. Both the 347 and the 383 will last as long as any engine out there. There are no inherent geometric, or trigonometric problems that would cause them ot wear out prematurely. Bot the 347 and the 383 are perfectly "respectable" street engines....long term.
Nothing changed; the 'new' is the same as the 'old', just stated a little differently. I know that 347's and 383's work; just that they aren't built the way I feel engines of those displacements would be best built to. You were close with "displacement-limited", where for any given displacement target you'd tend to choose the more oversquare starting point.


Norm
 

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1990 Ford Mustang LX 351M powered!! Project Cherry Bomb!!
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Gee, I wonder why Ford never made a stroker besides the 400?
 

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Gee, I wonder why Ford never made a stroker besides the 400?
They did. The 410 MEL engine for Mercurys. It was a stroked 390 straight from Ford. Quoted from Wikipedia:

"The 410 engine, used in 1966 and 1967 Mercurys (see Ford MEL engine regarding 1958 senior series Edsels), used the same 4.05 inches (102.87 mm) bore as the 390 engine, but with the 428's 3.98 inches (101.09 mm) stroke, giving a 410.1 cu in (6.7 L) real displacement. The standard 428 crankshaft was used, which meant that the 410, like the 428, used external balancing. A compression ratio of 10.5:1 was standard."
 

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Ooohhhhh good catch!!!! Also the second longest stroke of any production Ford engine on those two engines!!
And yeh I know the 302 was essentially a stroked 289 too...
 

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How much would you think the unshrouding is worth, versus the gain of 15ci or so?

I'm aiming for near 550hp, with boost, so I don't think mine will need the larger bore, or stroke. So my intention is a 327 or 333(whatever bore that is) in a Dart block, with KB and intercooler. As said, everyone has their preferences.
:D :D :D......not much with that blower. I made 554 at the wheels with a 9.0:1 347, ported Windsor Jr heads (251 @.600) and an OTS Comp cam...and 8 lbs of boost.

The blower IS cubic inches, want more cubic inches, change the pulley. I made a pulley hub and a bunch of different size pulleys so I could put the boost anywhere I wanted. Took about 5 minutes to change over. As one might expect though, I ended up with bigger heads and 12 lbs.
 

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Nothing changed; the 'new' is the same as the 'old', just stated a little differently. I know that 347's and 383's work; just that they aren't built the way I feel engines of those displacements would be best built to. You were close with "displacement-limited", where for any given displacement target you'd tend to choose the more oversquare starting point.


Norm
Pardon me Norm....but I've only been doing this for 50 years. What the heck are you yammering about?

I don't build engine off my "feelings;" I build engines that work. Strokers work. So, unless you have a reason, rooted in physical reality for what your feeling, you're just blowing bubbles. Rod ratios are nonsense, oversquared/undersquared is nonsense. Nothing has changed in 100 years. An engine is an air pump, the more air you pump, the more power you make. Given all else is a constant a 302 and a 305 Chevy will make pretty much the same power and live a comparable life. You might change where peak power occurs, but you won't change peak power.

But, by all means.......build what feels right.

I think I'm done with this nonsense now......
 

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Pardon me Norm....but I've only been doing this for 50 years.
So, not all that much longer than I have. First engine I built was back about 1973 or so, and I've built a few over the years since then, doing everything except the hot-tanking, block/head machining, and balancing. Just for myself or for my kids, though, not as a paying job. I guess I should have better realized that looking at this topic from an engineering/road-race point of view wasn't going to square very well with the more customary "just go get a bigger hammer" drag-race mindset.


Rod ratios are nonsense, oversquared/undersquared is nonsense.
So . . . valve areas to displacement doesn't matter? Unshrouding doesn't matter? But I get it, I guess . . . compromise anything and everything in the name of more displacement. That "no replacement for displacement" thing.


Nothing has changed in 100 years. An engine is an air pump, the more air you pump, the more power you make.
Of course. But did you miss where I said that I'm looking with a more displacement-limited attitude than you do? You were the first here to mention that displacement-limited racing thing . . .

Given all else is a constant a 302 and a 305 Chevy will make pretty much the same power and live a comparable life. You might change where peak power occurs, but you won't change peak power.
I already explained why I'd rather have the power up higher and why I'm willing to give up some down low. Though I'd certainly question the ability of a 3.74" x 3.48" 305 SBC to breathe as well as its 4" x 3" 302 sibling (unless you were going to restrict the 302 to the same heads/valves that a 305 could actually use).


Norm
 
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Everything is a compromise, nothing is perfect. Just like the BS going on all over the US, what matters is the mixture of right and wrong, not the absolute "what's the worst let's condemn that and ignore the rest(good) stuff."

Sure yes there are ideal rod to stroke ratios, there are immeasurable differences in longevity for various combinations. So a 332 should last longer than a 347(if everything else was perfect and you could measure it in a controlled environment). That is meaningless in the real world where countless other things ultimately cause issues far sooner than the ideal scenario.

The goal is power, at whatever desired rpm etc. Any stroker combination is better than the not stroked or bored version, in actual use or testing. Leave out the longevity or whatever your mind feels is better. If there is not a huge proof of breakage or issues with a combination, leave out the negative bashing of that, it's a waste of people's lives(here we are).

Final thought, it's just a flu, go back to living. The longer we(not me) act scared of a little risk, the longer this terrible economic effect, lasts for all of us. They are in the process of destroying the college football season right now. Life is risk, live it, don't be afraid of it.
 

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It is no ideal rod to stroke ratio. It's nonsense.

We also wanted to point out some of the common myths and misconceptions about high-performance motors. For example, I’ve seen dozens of magazine articles on supposedly “magic” connecting rod ratios. If you believe these stories, you would think that the ratio of the connecting rod length to the crankshaft stroke is vitally important to performance. Well, in my view, the most important thing about a connecting rod is whether or not the bolts are torqued!


If I had to make a list of the ten most important specifications in a racing engine, connecting rod length would rank about fiftieth. Back in the days when Buddy Morrison and I built dozens of small-block Modified motors, we earnestly believed that an engine needed a 1.9:1 rod/stroke ratio. Today every Pro Stock team uses blocks with super-short deck heights, and we couldn’t care less about the rod ratio. A short deck height improves the alignment between the intake manifold runners and the cylinder head intake ports, and helps to stabilize the valvetrain. These are much more important considerations than the rod-to-stroke ratio. There’s no magic – a rod’s function is to connect the piston to the crankshaft. Period. - David Reher
 

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Good quote; I too recall the thought of the rod needing to be as long as possible compared to the bore size etc. But that concept of the valvetrain stability makes a lot more sense. Ideals are one thing, actual real critical factors are another, and more important. I understand that thinking.

Now let's go back to Bob Glidden turning a Cleveland 9500rpm, that was a special engine they built back in the 70's.
 

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Engine Masters 54 did a comparison on a BBC with Rod lengths of 6.135" vs 6.800" with custom Pistons to achieve the same Compression Ratio using the same Cam. Long Rod made slightly more Torque under 5K, but the Short Rod mode more peak HP by almost 11HP.. Not exactly a game changer..

I'd find it hard to compare between a 331 and a 347 where the Stroke is only .150" difference.

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