Realistic life expectancy of a stroker motor on a D/D???

5spd GT · Jun 6, 2007

juiced_94gt said:
I drive EVERY day, i hate cars that collect dust in the garage, thats why i went 331, from what i hear it has better reliability if it's true or not i will never know.

Yes, technically it is true. It has a slightly less steep rod ratio. The lower the rod ratio, the more 'sidewall loading'. That equals more friction.

Proof: http://www.fordmuscle.com/archives/2003/09/stroker/index2.php

If I was a betting man, and could create an experiment for 150,000 miles I would pick the 331 over the 347 to show a bit less sign of wear.

If you go 347 (not much more power than a 331) just get the 5.315" rod, again to keep the wrist pin out of the oil ring. You'll thank me 50k down the road

A bit over a year ago I tore down my engine and had a basic rebuild done, if I had would have extra money to get the balancer, flywheel, stroker rotating assembly, and custom cam, I would have went with a 347 with the 5.315" rod, just so you know. It was a daily driver then too...

Pokageek · Jun 7, 2007

Thanks 5 Spd GT. I like to know the why and how sometimes. Well said!

Grn92LX · Jun 7, 2007

Ask any top builder and theres nothing at all wrong with a 5.4" rod. I've said this many times but ill say it again, I preferred the 5.4" rod but my builder couldnt get it for me fast enough as it was on a long back order. So He (Rick91GT) called me and asked if I minded switching to the 5.315". I didn't want to but I didn't want to wait longer

Car Nut · Jun 7, 2007

CHP offers many of their 347 longblocks with the 5.315 rods. There's a couple with the 5.400 rods too. I'm not sure there's a real argument on this one, cause both should give good results (an experienced engine builder should have good info on which way to go, depending on your goals/needs/hopes).

CHP does offer an emissions legal 347-e longblock/shortblock and it gets the 5.315 rods.

I would choose a 347 over a 331, especially if the longevity difference was 10% or so. If a 331 could get me 150K miles, but the 347 only 135K miles, I'd take the 10% reduction. I put anywhere from 6K to 10K per year on my stang, so it would take me quite a while to even hit 100K miles on a new stroker (like 10 years or more). 331 engines are not being flamed or bashed on my end, I just want to do the new engine with the mindset that I'll have it for many years.

Pokageek · Jun 7, 2007

I'll bet the difference isn't even 10%. More like 1.5% in my o, lol.

final5-0 · Jun 7, 2007

It has been said there are some factory oem motors that have rod ratios
steep as or steeper than 347's

I like to go WOT as much as the next guy

But ... You just don't do it all that much on a Street Car
however
Something you do a lot is

accelerate from stop lights/signs
accelerate on highway on ramps
accelerate to pass other cars
etc

With a h/c/i 302 you just don't need to go WOT to do those things
and
Even more so on a stroker

Those kinds driving conditions and cruising is where torque makes
itself known in a very noticeable way

I want torque for those conditions
and
IMHO ... the more torque ... the more fun :Word:

That is why I want those 16 additional cubes with the 347

btw ... I'm talking NA combos here

Grady

5spd GT · Jun 7, 2007

Yep, there are engines with steeper rod ratios built from the factory. If I recall correctly, these engines were bigger cube engines and they typically never seen the high mileage like 200k. They were extremely few and far between. I think there is a correlation.

If you are going to build a true street car (daily driver), get the 5.315" rod. The only real advantage the 5.4" rod has is it's longer dwelling time (very very slightly different) at BDC/TDC which gives those drag racer/track kings that very slight edge over the next guy.

Daily Driver = 5.315" rod
Track Car = 5.4" rod

http://www.mustangandfords.com/techarticles/p40345_image_small.jpg

Left is a piston with the wrist pin intersecting the oil ringland. 5.4"
Right is a piston where the wrist pin does not intersect the oil ringland. 5.315"

If long engine life and reliability are your goal (daily driver), keep the piston pin out of the ring area. Having the piston pin close to the hot piston crown is just asking for premature engine blow-by or even failure. The oil struggles to stay on the wrist pin/boss because heat chases it away.

It is a very easy concept.

So in short, to get the cubes and best reliability from those cubes possible, you can go 331 or 347 (5.315" rod). Get the cubes and mileage you are looking for = 5.315" rod.

gcomfx.com · Jun 7, 2007

I went 331 for the basic reason. I picked up the machined block, 331 crank and rods for a good price. Plus, I may add a super charger down the road when I get tired of spraying it. She's ready when my bank account is.

final5-0 · Jun 7, 2007

David

Good info

The pic showing those two pistons side by side is very helpful

Grady

maximos · Jun 7, 2007

So basically as long as it's N/A go with a 347? But blown go with the 331?

Grn92LX · Jun 7, 2007

maximos said:
So basically as long as it's N/A go with a 347? But blown go with the 331?

No.

BlackVert · Jun 7, 2007

i'm just going to parrot what my engine builder said on this subject. his name is jan norris, and he has been building (mostly) racing engines since the 1960s. i will believe what he says above pretty much anyone else, simply because of the fact that he has built over 1,000 engines.

he says that the steeper rod angle of a 347 will cause the rings and piston bores to wear out more quickly than a 331. similarly, since a 331 has steeper rod angle than does a 302, the rings and bores will wear out more quickly then as well.

my take on it: even if it is a daily driver and you put 10,000 miles on it every year, and if you get "only" 100,000 miles out of a 347 instead of the 200,000 miles like you could out of a 302, you are still looking at 10 years of service, which for me is plenty long enough.

there. i've said it, and i'll go back to the sidelines.

5spd GT · Jun 7, 2007

maximos said:
So basically as long as it's N/A go with a 347? But blown go with the 331?

In most cases that is what I would do.

A 331 piston has more piston material to it. More piston material is less prone to cracking. Just a bit more piece of mind.

Go with a 331 if you plan on lots of boost. A 347 would be okay with mild boost in my opinion and research as long as the block & rotating assembly are up to par

...............................

Thanks Grady

BlackVert - Sounds good to me

juiced_94gt · Jun 7, 2007

Ok i just got off the phone with CHP which built my shortblock, the guy said they dont use 5.315" rods in their 331's only the 5.4 rod, he said that is the rod i want for a street driven car???

5spd GT · Jun 7, 2007

juiced_94gt said:
Ok i just got off the phone with CHP which built my shortblock, the guy said they dont use 5.315" rods in their 331's only the 5.4 rod, he said that is the rod i want for a street driven car???

5.4" rod on a 331 crankthrow is fine, it keeps the wrist pin out of the oil ring land still.

A 5.4" rod on a 347 crankthrow (3.4") puts the wrist pin the oil ring land area.

So for the 347 get a 5.315" rod...and the 331 is fine with a 5.4" rod.

I hope that helps clarify

juiced_94gt · Jun 7, 2007

5spd GT said:
5.4" rod on a 331 crankthrow is fine, it keeps the wrist pin out of the oil ring land still.

A 5.4" rod on a 347 crankthrow (3.4") puts the wrist pin the oil ring land area.

So for the 347 get a 5.315" rod...and the 331 is fine with a 5.4" rod.

I hope that helps clarify

Thank you very much...im a little slow but that put eveything into perspective

5spd GT · Jun 7, 2007

juiced_94gt said:
Thank you very much...im a little slow but that put eveything into perspective

No problem, here is some more articles/pictures about the comparison between the two

http://www.mustangandfords.com/techarticles/5197_331ci_stroker_engine/

http://www.fordmuscle.com/archives/2003/09/stroker/

http://www.strokerengine.com/RodStroke.html

final5-0 · Jun 7, 2007

Sorry about taking things for granted
when I said 347 na ... and ... 331 forced

I should have been more specific about application
and
I took for granted the majority of combos here are street driven
with light strip use

Like David ... I'd have no prob with a forced 347 for street use because
high levels of boost and high rpm are just unlikely

Now ... For something that is more strip minded

I should have said for a purpose built, high rpm, high boost combo,
you will see much more stress, load, pressure, or what ever you want
to call it and I would more than likely go 331.

Honestly ... the whole 347 thing about ........
1) Oil control
and
2) Short life

Well .....
#1 was true in their early days but its been solved for quite some time

A perfect example to show the perpetration of internet myth

#2 While there could be some truth to it
IMHO ... The amount of that truth is highly exaggerated by most peeps

Come on ... Lets get up close and personal with ... R E A L I T Y :Word:

A guy who sinks the money into a:
blue printed & balanced 347 stroker short block
the appropriate heads
the supporting parts
custom tune
etc

I'd be willing to bet 90% or better that does a nice combo like that

They will put between 5K to 10K miles a year on it
and
I'd also bet most of the time ... the value will be closer to 5k than 10k

Grady

1991vert · Jun 7, 2007

it's all in the machine work. im building my supercharged 347 right now and wouldn't think twice about it

Black95GTS · Jun 7, 2007

maximos said:
So basically as long as it's N/A go with a 347? But blown go with the 331?

I would say to you... it depends.

What block are you using?

How much power are you putting out?

How crazy are you getting on your tune?

More stroke = faster piston speed = better spooling. In a forced induction setup I'd try to use as much as stroke with as little compression as I could.

Adam

Realistic life expectancy of a stroker motor on a D/D???

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