Stroker Kit Info

[5spd GT]

I don't think the 5.4" rodded 347 is preferred... but probably because that's the rod you had to use in the past.

That was directed to one stanger above.

When done correctly, this is not an issue. If you have restricted oil to the piston pins... there are other issues.
Ring gap and lands are the critical detail to ensure is correct when doing a 5.4" rodded 347.

Heat chases oil away. There is lots of heat in the cylinder. It is well over a 1000 degrees.

Not only are ring gaps important but the machining and correct oil land ring support rail are important.

The use of a good dimpled oil support rail (needed for 1.090" pistons) that can't rotate in the groove (due to the dimple facing down into the pin bore and effectively locking it in place), you can help combat "extra" problems with oil consumption. Bad ones, use what amounts to a 3rd oil ring wiper with no dimple that clamps against the back of the oil ring groove and they can rotate and/or roll in place. Ideally you want a oil support rail to grip, which comes with it being the correct size, against the back of the oil ring groove and also have a dimple. A good builder and parts used are key.

The oil ring support goes underneath the oil control expander on the very bottom, if looking at the piston from it's 'in engine' orientation. The oil support rings go directly above and below the oil control expander, with the oil ring support on the furthest wrist pin side.

Explain this... because boosted and bottled applications don't require much but a nicely matched camshaft.

A longer rod makes the engine more likely to detonate. Think about how the longer rod acts compared to the shorter rod. The long rod is sitting at TDC for a small amount longer. This is a longer state of compression. Do you need excess compression at TDC when forcing air in? Yes, a camshaft is big as well. All else being equal, the longer rod will be more likely to detonate.

Why does this matter? All I see is a heavier piston... although I'm not promoting the 5.4" rodded 347 sbf. I actually have the Probe 3.315" rodded ProStreet version.

A taller piston height directly helps strengthen the piston crown area. There is also more piston skirt area. I have a picture of it, in the link in my signature of a comparison picture.

Shorter piston = Lighter piston
Shorter piston = Longer rod

They both have roughly the same weight because they cancel each other out. But I like the "rock in a sling" more so.

If I built the 3.4" rodded 347ci sbf... I can assure you I will not have oiling nor longevity issues.

Probe is one of the premier 3.315"/1.175" 347ci sbf rotating assembly manufacturers, and should PROMOTE their product as such.

Your right, they are, but as I listed, there is more than just Probe promoting it. They sell the 1.090"/5.4" combination as well

Yes, the smaller rodded setup IS nice... my choice because it's my first 3.315" rodded 347. Will it perform better than the other... probably not.
My opinion as well as many, many others; the shorter rodded setup is easier for the novice or beginner builder/assembler as there are more details that can be "overlooked" and still perform well.

I'm not disagreeing with 5spd, I just see things from a different angle and experience.

You are not going to notice any difference in power between the two. I am not sure why you think that your engine can not perform better than a 5.4" or atleast, just like it. Try upgrading your heads, cam, and intake and get that thing moving

You are going to get 347 cubic inches with either combination. One has a more reliable track record.

 

[5spd GT]

1991vert - This may be a good read for you since you are speaking of repositioned rings...

Ring Location Changed by Stroke:

A post by FastDriver:

Here is some info posted by FastDriver about picking a 3.25 inch stroke over a 3.4" stroke:

"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.

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."

Grn92LX - How many miles do you have on your 1.175"/5.315" combination?

I say skip the 347 and go with the 408-427

As for the heavier piston argument, what about those big bore pistons we all like?

I have driven, rode in my fair share of 347s or similar. I have helped put some nice top-end pieces on them. I have been through my own rebuild process. I have spoke with many HIGH UPs about these topics at hand.

 

[1991vert]

i can't wait for mine to fail!

 

[5spd GT]

i can't wait for mine to fail!

Show me who said it will fail

 

[347HO]

A longer rod makes the engine more likely to detonate. Think about how the longer rod acts compared to the shorter rod. The long rod is sitting at TDC for a small amount longer. This is a longer state of compression. Do you need excess compression at TDC when forcing air in? Yes, a camshaft is big as well. All else being equal, the longer rod will be more likely to detonate.

Slightly off topic but still useful information;
The "dwell" of the longer rod is almost unmeasureable and has almost zero affect on performance.
To a limited extent by themselves, but affective as a sum... ignition timing, camshaft timing, and camshaft events can manage detonation from occuring.
A custom camshaft is one of the most important factors here.

You are not going to notice any difference in power between the two. I am not sure why you think that your engine can not perform better than a 5.4" or atleast, just like it. Try upgrading your heads, cam, and intake and get that thing moving
QUOTE]

I assure you my "top-end" has almost no equal in the "inline" 215cc - 225cc catagory.

 

[5spd GT]

Slightly off topic but still useful information;
The "dwell" of the longer rod is almost unmeasureable and has almost zero affect on performance.
To a limited extent by themselves, but affective as a sum... ignition timing, camshaft timing, and camshaft events can manage detonation from occuring.
A custom camshaft is one of the most important factors here.

I COMPLETELY agree with you

 

[347HO]

That it's slightly off topic? LOL!!

Here I was... puffing up for a really nice debate, how deflating!

Again, I also agree with your tech... I just see/do things from another angle to achieve the same goal.

 

[vristang]

Decent read guys....

347HO ????
Welcome back to town!

jason

 

[5spd GT]

That it's slightly off topic? LOL!!

Here I was... puffing up for a really nice debate, how deflating!

Again, I also agree with your tech... I just see/do things from another angle to achieve the same goal.

I believe there is a big difference between a debate and an argument.

We have did a good job of keeping it objective and on a debate level.

Welcome

 

[wideopen]

Rod Ratio

Here's some interesting information posted on LS1tech.
331 vs. 347 peeps: info inside!

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http://www.ls1tech.com/forums/showthread.php?t=852629

Comments?

Posted by Erik Koenig:

After doing all the research I could for years and years I have found nothing correlating any measurable wear differences for real from Rod to Stroke ratio. There have been numerous studies even on the performance advantages or disadvantages of "good and bad" rod stroke ratios with no change at all as the result.

You can take an old carbureted ford 302 with a super tall "stable" piston and no stroke at 3.000 and a rod ratio that is 1.70 and yet they have horrible bore wear same as the 351W with also a "great" rod ratio and super tall pistons. some times you have to these blocks to .060 to even get them to clean up.

Right when they went EFI and didn't have the old carbs flooding the cylinders with fuel during the choke phase in winter the bore wear has now almost vanished even on 200K engines sometimes when I see these in the core yards. You also have tons of "bad rod ratio" Hondas and late models Fords that last for hundreds of thousands of miles.

Basically you can't really get "bad" enough to make a difference or nothing even fits. The LS7 is the worst rod ratio yet in the LS7 family and I guarantee it will last just as long as the others while making more HP as well.

Posted by Erik Koenig:

Almost every LS1 stroker of any kind already has the oil ring intersecting the pin incuding every single 402 and 408 and 383 deal out there that's built right. They don't have any issues at all and are run everyday on this site.

Posted by Erik Koenig:

I just thought of this here at 5am while getting up to feed some pets bothering me but after honing like a couple of thousand cylinders I have also failed to notice virtually ANY wear down where rod angularity is highest at all. Its highest a little before halfway down the bore and yet there is never really ANY real wear down the cylinders on any engine whatosever at that point or in that vicinity.

95% of the bore wear is all right up at the top withing the top inch of bore.

The whole cylinder has crosshatch generally from the top inch down unless again it's an old old carb engine and even then it still cleans up in the hone within a few thousands except for the ring grooves right up at the top which can take up tp .060 sometimes to clean up. So again if the rod ratio is so important why don't we see bad wear here really ever instead of almost only up at the top where the cylinder pressure is much higher.

Also on virtually ANY extreme power adder engine no matter how short the stroke is the ring groove and bore wear right at the top is again much worse than any NA engine again also reguardless of rod ratio.

Just the move to EFI, Plasma Moly top rings and plateaued hone jobs has increased bore life by a factor of 4-10 times or more whereas even the wrong air filter can cut in right back down again.

We have honed high mileage super charged Ford 5.4s that have been toasted with big NOS and have a 4.165 stroke right from Ford and yet after 150K miles they also do not have any bore wear in the middle of the cylinders either.

Now I know why even Ron Sperry and the GM guys I talked to at Superflow didn't even seem to care about rod ratio at all. They said it's just a by product of packaging 90 per cent of the time and has only tiny negligible effect with several good pumping effects going to the lower rod ratios favor even.

 

[dadslx]

if your spending that type of cash on building a motor why not get every penny worth?..i have a 347 and really thought about a 331 because some guy told me the 347 was a 50k mile motor. well i did some reading and bought the 347 with the longer rod length. i added a high flow oil pump, 7 qt oil pan and run high grade oil. will that help me? who knows but dont listen to people on here get what you want. and yes my 347 loves the high rpms i tried turning it to just 6k but it only wants 7k or nothing...ps i am running a complete forged bottom end made by scat..i did take one persons advice and that was dont piece together a kit buy a complete kit from one company..i highly recommend scat.

 

[347HO]

I would only recommend Scat or Probe if the rotating assembly is to be balanced to 28oz.
There are other manufacturers such as Eagle which allow neutral balance or zero imbalance for considerable less cash in machining and mallory.
There is a definite advantage to neutral balancing... but is not for everyone and every application.

 

[5spd GT]

I would only recommend Scat or Probe if the rotating assembly is to be balanced to 28oz.
There are other manufacturers such as Eagle which allow neutral balance or zero imbalance for considerable less cash in machining and mallory.
There is a definite advantage to neutral balancing... but is not for everyone and every application.

Those LS1 and 4.6 utilize it from the factory.

From my understanding, Scat is a good budget brand with a bit better finish over Eagle, but when you get the forged set-ups they both are nice

 

[347HO]

Those LS1 and 4.6 utilize it from the factory.

From my understanding, Scat is a good budget brand with a bit better finish over Eagle, but when you get the forged set-ups they both are nice

I also agree... Scat is a good budget brand crank, and the few I've seen definitely have better finish everywhere over Eagle... don't know if that makes one better than the other though.

 

[AnthonyR23]

This to some will sound crazy.. that I'm even considering this.. we have an air compresser but don't have really good machining equipment.. I know that this would be much harder and would take alot longer.. but is it possible to do this yourself... with certain tools.. has anyone rebuilt their engine without a machine shop... just wondering... and be honest... It is an experience I would like to have... but would want to take care that everything is done right.. any thoughts??

 

[vristang]

This to some will sound crazy.. that I'm even considering this.. we have an air compresser but don't have really good machining equipment.. I know that this would be much harder and would take alot longer.. but is it possible to do this yourself... with certain tools.. has anyone rebuilt their engine without a machine shop... just wondering... and be honest... It is an experience I would like to have... but would want to take care that everything is done right.. any thoughts??

If you want it done right, then take it to a shop...

How will you...
1. align hone the mains
2. deck the block
3. ACCURATELY hone the bores

I'm sure there are other things that I'm not thinking of now, but that should be sufficient...


I agree, it would be fun to try, just to see if it is possible...
But there is MUCH more risk involved

jason