331/347 stroker

oldschool88vert said:

just a thought but would it be feasible to run higher compression and have fun and when ready to run forced induction to just swap in some cometic head gaskets since you can choose thickness? i don't know much about those but i thought i read something like that??? just an honest question to learn more.

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btw, i realize there are more proper ways of doing this, as in buying the right parts, but is it possible to use the cometic gaskets to adjust/lower compression ratio to safely run forced induction? any input from anyone is appreciated!

I HIGHLY DOUBT that that combo above dynoed at 500rwhp

The 3.25" stroke (331) and 3.4" stroke (347) both make similar power numbers.

The 3.4" stroke DOES have a steeper rod ratio.

A stock 5.0L displacement is 302 cubic inches. It consists of a 3.00” stroke and 4.00” bore. The stock rod is 5.090”.

A 306 is created by reusing the stock 3.0” stroke but boring/honing the cylinder walls .030” to create a 4.030” bore. It necessitates an oversized piston, larger than the stock 4.00” stock bore/piston. A 306 is a form of a budget build and is not intended to make extra power, but more to create fresh cylinder walls for longer engine life and revive lost compression through high mileage engines.

Both the 302 and 306 reuse stock 3.00” crank and stock 5.090” rods. The 306 needs new oversized pistons.

A 331 cubic inch engine (stroked 302), consists of a new crank of 3.25” of throw, and the 4.030” overbore that creates fresh cylinder walls. To get the 331, you need a crank, of 3.25”, new rods of 5.315” or 5.4” length, and a .030” overbore from stock bore.

A 347 consists of a 3.4” stroke, 5.315” or 5.4” rod, and oversized pistons of 4.030”.

Most 347’s need extra block clearance to clear the rod bolts as a crank rotation is being made. The throw of the crank is too large to have safe tolerances to rotate.

Piston speed in feet per minute:

A 302 with the 3.00” stroke moves 3,000 feet per minute.
A 331 with the 3.25” stroke moves 3,250 feet per minute.
A 347 with the 3.40” stroke moves 3,400 feet per minute.

Excellent info and unbias below:

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

If you want to read about how rod ratios effect performance...read this:

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

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/5197_331ci_stroker_engine/photo_07.html

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.

Remember it is your money that you are spending.

Good Luck!

331 all the way!!!!!!!!!!!! Im bias though (check sig)

To be honest...if i could do it over again...I wouldnt have wasted my time with a 302 based stroker. It would have cost me the same to do a 393 and i wouldnt be as close to pushing the blocks limits like i am now!!!! Im expecting my block to split any time now I have been thinking about yanking the shortblock in selling it if anyone is interested

5spd GT said:

I HIGHLY DOUBT that that combo above dynoed at 500rwhp

The 3.25" stroke (331) and 3.4" stroke (347) both make similar power numbers.

The 3.4" stroke DOES have a steeper rod ratio.

A stock 5.0L displacement is 302 cubic inches. It consists of a 3.00” stroke and 4.00” bore. The stock rod is 5.090”.

A 306 is created by reusing the stock 3.0” stroke but boring/honing the cylinder walls .030” to create a 4.030” bore. It necessitates an oversized piston, larger than the stock 4.00” stock bore/piston. A 306 is a form of a budget build and is not intended to make extra power, but more to create fresh cylinder walls for longer engine life and revive lost compression through high mileage engines.

Both the 302 and 306 reuse stock 3.00” crank and stock 5.090” rods. The 306 needs new oversized pistons.

A 331 cubic inch engine (stroked 302), consists of a new crank of 3.25” of throw, and the 4.030” overbore that creates fresh cylinder walls. To get the 331, you need a crank, of 3.25”, new rods of 5.315” or 5.4” length, and a .030” overbore from stock bore.

A 347 consists of a 3.4” stroke, 5.315” or 5.4” rod, and oversized pistons of 4.030”.

Most 347’s need extra block clearance to clear the rod bolts as a crank rotation is being made. The throw of the crank is too large to have safe tolerances to rotate.

Piston speed in feet per minute:

A 302 with the 3.00” stroke moves 3,000 feet per minute.
A 331 with the 3.25” stroke moves 3,250 feet per minute.
A 347 with the 3.40” stroke moves 3,400 feet per minute.

Excellent info and unbias below:

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

If you want to read about how rod ratios effect performance...read this:

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

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/5197_331ci_stroker_engine/photo_07.html

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.

Remember it is your money that you are spending.

Good Luck!

Click to expand...

i had to notch my cylinder skirts to get the rod bolts to clear on my 331

Modular2v said:

i had to notch my cylinder skirts to get the rod bolts to clear on my 331

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Yep, some 3.25" strokes need it, but you can pretty much bet the 3.4" stroke clearancing cost will be added in...

Are you using the 5.4" rod?

Good articles 5spd. It's nice to be able show people what you're talking about. I hate hearing the "technology today allows 347s to run without a problem." If I feel like being a dick, I'll just ask them to clarify the amazing new technology that has been invented?

Another big thing to consider in the differing rod lengths is the compression height of the piston, which is usually not a big deal on naturally aspirated engines, but on monster boosted engines, the added compression height necessarily strengthens the crown of the piston, which like you mentioned also helps to keep the heat away from the pin. The added length of the rod directly reduces the amount of compression height you can have.

For this reason, CP pistons all but refused to let me go to a 347 with my 5.4" rods. They would've done it, but had sort of an "at your own risk" attitude.

If their attitude is that they want the extra power associated with the dwell time with a longer rod, I understand it. If their attitude is that they already have the 5.4 rods and really need the extra 16 cubic inches for power, that's cool too. I would personally just rather have almost as much power and a lot more peace of mind, especially with a turbo car that will make as much power as the turbo powering the engine can make.

Chris

FastDriver said:

Good articles 5spd. It's nice to be able show people what you're talking about. I hate hearing the "technology today allows 347s to run without a problem." If I feel like being a dick, I'll just ask them to clarify the amazing new technology that has been invented?

Another big thing to consider in the differing rod lengths is the compression height of the piston, which is usually not a big deal on naturally aspirated engines, but on monster boosted engines, the added compression height necessarily strengthens the crown of the piston, which like you mentioned also helps to keep the heat away from the pin. The added length of the rod directly reduces the amount of compression height you can have.

For this reason, CP pistons all but refused to let me go to a 347 with my 5.4" rods. They would've done it, but had sort of an "at your own risk" attitude.

If their attitude is that they want the extra power associated with the dwell time with a longer rod, I understand it. If their attitude is that they already have the 5.4 rods and really need the extra 16 cubic inches for power, that's cool too. I would personally just rather have almost as much power and a lot more peace of mind, especially with a turbo car that will make as much power as the turbo powering the engine can make.

Chris

Click to expand...

I have to agree

Yeah, I should have addressed the compression height 'issue.' For example, the 5.315" rod 347 has a taller compression height piston, while the 5.4" has a shorter compression height piston.

I believe the one of the Ford Muscle articles talked about how they had trouble cracking the 'shorter' compression height piston crowns with boost...

http://*******.com/index.php?topic=6087.0

http://*******.com/index.php?topic=7010.0

Very good info in these threads for those looking to learn facts..

EDIT: s b f t e c h . c o m (no spaces)

The facts have already been covered.

5spd GT said:

I HIGHLY DOUBT that that combo above dynoed at 500rwhp

Click to expand...

You don't think a turbo 347 can get 500rwhp? Maybe you missed that.

With 35# inj. and no tune I see maybe ~250mi to a tank on my 347.

TokyoJoe said:

You don't think a turbo 347 can get 500rwhp? Maybe you missed that.

With 35# inj. and no tune I see maybe ~250mi to a tank on my 347.

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Yep, I missed the turbo part

You can get 500rwhp with a turbo on a 302/306 as well.

Grn92LX said:

http://*******.com/index.php?topic=6087.0

http://*******.com/index.php?topic=7010.0

Very good info in these threads for those looking to learn facts..

EDIT: s b f t e c h . c o m (no spaces)

Click to expand...

Why read that crap? I got through the first one and realized that the only person who has any comprehension of all of the "facts" is Jay. He didn't say anything new, either. The rest of them seem to have trouble distinguishing between stroke and rod length, lol.

Look, the bottom line is that you, Jay, 5spd, and myself all know the facts, and we all make our own decisions. I'm pretty sure we are all happy with the decisions we've made, too, and I doubt that any of us has the capacity to change the others' minds unless some type of new information becomes available so why continue the argument?

I do have a slightly different argument for you if you really want one, though, why didn't you go with a 3.5" crank? You're only running na and it will give you another 10 c.i. As a matter of fact, boring out your mill to 40 or 50 thousandths over would work, too. Just need a decent cooling system and I'm sure at your power level the block would be fine. You could be running a 361 c.i. motor. All of your arguments thus far apply to running at least the longer stroke. Sure, there'll be a little more oil consumption, slightly worse compression height at 1.05" (only 5 hundredths off of the 3.4" stroke), slightly shorter piston skirts, a slightly worse rod:stroke ratio, but they are all even more negligible than the difference between a 331 and a 347's stuff. I know I could put this motor together and bore out the pistons to at least 40 thousandths and run a little more displacement than you, which should make me more power. Why didn't you do this in the first place. 3.5" cranks aren't that hard to find. If I build another na fox, its going to be a 357. I think I'll name it Magnum, and put magnum badges all over it.

Mike, in all actuality, I think a 3.4" stroke is perfectly fine for a naturally aspirated street engine. Wouldn't hesitate to build one myself. Your combination is different than mine. I'll tell you this though, for all the whining people with 347s do, how can they give **** to people who want to use a 5.315" rod? Nobody can show me evidence that there is any power difference. Theoretically, the dwell time should help the 5.4" rod, but that's insignificant. If I put a 347 together, I'd definitely do it with the shorter rod unless I already owned the longer one AND the 347 crank.

Different strokes for different folks - almost literally in this case.

Chris

KdSaint said:

Yes, a 351w stroked to whatever would net me more power in the end, but it would probably be more expensive considering I don't have a 351w lying around. Unless someone wants to donate one, and all those wonderful accessories (i.e oil pan, wiring harness, etc etc) I'm going to have to go with the 302 block. Money just doesn't grow on trees.

Click to expand...

'Wiring harness' WTF???


See my site (in my sig) for a REAL 351w conversion discussion...




jason

Hey, I forgot to mention the biggest reason CP didn't like the 3.4" stroke. The ringlands on high boost application pistons has to be lower, which runs you into a bind if the pin is already intersecting the oil-ringland.

FastDriver said:

Hey, I forgot to mention the biggest reason CP didn't like the 3.4" stroke. The ringlands on high boost application pistons has to be lower, which runs you into a bind if the pin is already intersecting the oil-ringland.

Click to expand...

Can you please elaborate on WHY the ring lands should be lower for boost?


jason

vristang said:

Can you please elaborate on WHY the ring lands should be lower for boost?


jason

Click to expand...

There are three reasons as I understand them:

1. The easy explanation is that the higher you place the rings, the more heat that they are exposed to making more prone to fail - there is a thermal barrier between rings that are lower on the piston and the combustion chamber that is created by less efficient burning of the gasses between the crown of the piston and the cylinder wall 2. The thinnest part of matrial at the crown of the piston is the "meat" between the top of the piston and the 1st ringland making this the most likely part of a piston to fail in many applications, and 3. the higher the ring the more prone it is to fail due to mild detonation. As you can see from the article I quoted below, this is not optimal for a naturally aspirated engine:

The "dead space volume" above the piston up to the top of the cylinder wall usually traps unburnt fuel and burns less completely...producing more emissions. Reducing this volume, by moving the top ring up , decreases emissions. The top ring is now exposed to hotter temperatures and must be stronger.

However, moving the top ring up is not just for emissions purposes either:

Here you see a higher top ring and piston pin location placed at the level of the oil ring groove, both of which allows for a longer rod and better rod ratio in these forged race-only strutted pistons.

Moving the top ring down improves durability but at the same time, creates a situation where more entrapment of unburned gases will occur locally in that area, leading to a less efficient burn.

If you want more technical information concerning the subject talk to a tech named Mike at CP. He once explained the subject to me and at the time, I felt I had a very good understanding and I was in agreement with his assessment that I should go with the 3.25" crank instead of the 3.34, 3.4, and 3.5" billet cranks I could get at the time.

Hope this answers your question adequately,

Chris

Good stuff Chris

David