jnsnams

i have a 331 turbo i drive daily and to me its streetable, and ready for the track when i get there..lol...but really i would do 331, its alot less trouble and parts are more likely to get now a days..

my77stang

Vig, the rod : stroke ratio has to do with the angle of the rod as its flinging side to side while the crank is spinning. First, lets look at a short rod vs. long rod design (same bore and stroke, like a "long rod" 302). Forgive my crude MS Paint illustration.



You dont want to sling a rod thru the side of the block right? Neither do I. Imagine if you will that the piston is at the top of the cylinder (as shown) and the spark plug fires..... now that piston is getting jammed back down the cylinder under exteme force. Do you think it is better to have the rod on a steeper angle as its getting forced down? The answer is NO. The closer that rod is to being vertical the better. The internal stresses on a longer rod design are inherently less. This is not an opinion, its fact. I'm pretty sure we can all agree that stress on internal parts is a bad thing. It leads to faster bearing wear, faster cylinder wear, and increases the chance of metal fatigue related failures (ripped out wrist pins, snapped rods, bolts, blocks, cranks, etc)

So lets look at stock ratios....... a 289 has a 1.7962 ratio, a 302 has a 1.6967 ratio. Ford used the 289 rods when they built the BOSS 302 to try and keep them from exploding at high RPM's (289 rod with a 302 crank = 1.7183, not much better than a 302 but something is better than nothing).

Now, look at the stroker ratios. All of them are worse than even a 302, but if you wanna play you have to pay (somehow) right? I think most of us understand that when we build for power we take something away from longevity and we are ok with that fact. Taking that into consideration we must ask ourselves how much we are willing to give up. Personally, if I were to build a 302 based stroker I would want to use the 331 because the combination is more favorable. Sure, I would lose 16 cubic inches over a 347 but I would have a motor that would rev up quicker, and be able to rev it up higher without fear of it planting a rod in the asphalt.

Does that explain my position better? [8D]

ncplaya88

Thanks for explaining R:S, that helped a lot. I have been looking around and I do like the twin turbo set up from pony down, well I just like turbos lol. That set up, with a 331 from fordstrokers seems nice, butI hear all this about cracking the block on a 302 engine. I would hate to do all that and get out one day and have that happen. That set up has to put out close to the limit if not over(i think). When I could just swap in a 351 stroked and not have to worry about cracking the block. But if the 331 could hold up to 100k plus miles with that setup, then I would like that.

Joel5.0

I still have to see a SBF stroker with a rod through the side of the block.... cracked blocks?..... yeah...... Anyway.....yes, stroking an engine does increase piston side load, but again, how "important" is that increase over the benefits in performance it will produce?..... the difference in the rod angle between a 302 and a 331 is .39°...... between the 302 and a 347 is 1.19°, and .8° between a 331 and a 347. A 347 will make more power (set right, of course) over a 302 or a 331...... so what is the priority? R:S ratio for durability?..... why?... specially when OEM engine setups have proven to be as, or more reliable than higher R:S ratio setups like:

I4 1.9L= 1.49 R:S
I4 Zetec 2.0L = 1.55 R:S
I6 250CID = 1.50 R:S
I6 300CID = 1.56 R:S

Why is R:S such an issue for stroker setups, but not for OEM setups that have proven themselves to last 400K+ miles? A 347 stroker will last as long as a 331, a 302 and even a 289 when built right, and I will choose its performance capabilities over a concern regarding R:S stresses....in your case ncplaya88 (as in any other case)...... like I always say, YCYDYP (=Your Car Your Dough Your Prerrogative) though.

my77stang

joel, your missing our on a key point here. a high performance engine is producing ALOT more stress than a stock motor. so yeah, a 300 I-6 will run forever and a day. part of that is because its a I and not a V, they just run longer. i dont know of any that have gone 400k altough i had one go 365k (or 1.9's or 2.0 zetecs either.... 1.9's are actually a crappy motor).

anyways the point was if you built a 250 or 300 hp 347 it would probably live a very long time, but none of use build that kind of motor with a low HP goal like that, we push things to the brink and we drive them hard.

also, i have seen rods break, i have seen LOTS of bolts break and caps rip off, wrist pins getting ripped out of pistons, etc. and yeah, the #1 main breaks off the block up about as high as the bolt holes are drilled and tapped into the block.

i just feel that a 347 is pushing the envelope futher than i would want to, especially on a stock block.

8banger

A short rod motor does increase side load on the cylinder wall...and increase wear...somewhat(more so on a high RPM motor)...But then again I've never built a performace motor with any real H.Pwith the goal of making it last 100k..or more....I builtmany of 1.50ish rod ratio SBC's with rpm in 7k plus rangewith out an issue.....I do however try and use the longest rod availble for a given stroker..
http://www.hardcore50.com/Articles/g...greatmyths.htm
http://books.google.com/books?id=dc7...NVcs#PPA179,M1

Joel5.0

That's what high performance setups do, take the parts a step further in the stress area...... R:S and rod angle is R:S and rod angle regardless of block configuration, OEM or stroked...... lack of stress in a 300 I-6?..... the examples I mentioned are commercial units towing equipment all day + 24hr. work shifts in some cases.

A 250-300 HP 347 stroker?...[:'(].... why would anybody build/waste money building something like that? Drive them hard?.... isn't that what this hobby is all about? My point is, a well built 347 stroker in a stock block, will outperform a 331 and live a long life..... but it has to be built right. here's an example, a 347 N/A vs. a 331 w/NOS...... similar peformance numbers, don't you think the NOS will add more stress to the 331 over the 347 so it can beat it?


Grant 331 nos Mustang vs. Dan 347 N/A Mustang With in car cam

Isn't that what this hobby is all about?.... ....when performance building/racing looses the risk talking part of it, that would be the day it will become boring..... but choosing a performance setup over another based only on R:S and stress, when there are other OEM setups that have proven to be as reliable as higher R:S stroker setups...... I just feel is choosing based on the wrong reasons.

stangman94

With a good hci what kind of numbers can you pull out of a 331? I know the 347 usually comes out around 400rwhp whats the 331 like?

my77stang

so im guessing you'd take a 302 over a 289?

its funny, because you go talk to any "ford guy" who has actually built and drove both and they will ALL tell you the 289 is a better motor.