Here is the deal with building a piston/rod combination where there will be little to no oil consumption issues. It depends on the builder. 99% of the engine builders (namely, local and some "professional") do not use proper piston to wall clearance, oil support ring land type and position, appropriately.
First, I want to here why a 5.4" rod is preferred
QUOTE]
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.
- There is NO oil ring intersecting into the ringland. This allows heat to penetrate into the oil ringland area. Heat chases away oil. You want oil in the piston pin boss.
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.
- A shorter rod is also good for boosted and nitrous applications.
Explain this... because boosted and bottled applications don't require much but a nicely matched camshaft.
- There is more piston material on the 1.175" pistons.
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.
You cannot possibly say that you will have no problems with the 347 with the oil ring intersecting the wrist pin area.
Mark O'Neal from Coash High (Probe) and Barry R from Survival Motorsports are extremely knowledgeable and are in this very field being discussed. You want to know what they recommend for the street?
That is right, the 1.175"/5.315" combination
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.
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.
While some may not agree nowadays it is not a bad idea to simply buy a stroker shortblock from somewhere like Fordstrokers.com or CHP. They are less than 2000. You do the math, 1000 dollars of machining/cleaning and assembling, plus you need to buy a decent kit. My next motor will be this way, and I'll sell off my old stuff to get a little money back.
my 2 cents
By the way there was a ton of just plain wrong info earlier, do not build your motor based on what strangers on the internet tell you. Call a shop with a good rep like the ones I mentioned earlier that builds these motors everyday and listen to what they say. If you are in a stock block you do not need a forged crank.
Matt
There is some bad information in this topic. Even some coming from those saying there is bad information
Listen here...
First, I want to here why a 5.4" rod is preferred
Do the 5.315"/1.175" combination.
- There is NO oil ring intersecting into the ringland. This allows heat to penetrate into the oil ringland area. Heat chases away oil. You want oil in the piston pin boss.
- A shorter rod is also good for boosted and nitrous applications.
- There is more piston material on the 1.175" pistons.
- The only positive I see on the 5.4" rod is that it is a very slight difference in grams of weight.
Here is the deal with building a piston/rod combination where there will be little to no oil consumption issues. It depends on the builder. 99% of the engine builders (namely, local and some "professional") do not use proper piston to wall clearance, oil support ring land type and position, appropriately.
You cannot possibly say that you will have no problems with the 347 with the oil ring intersecting the wrist pin area.
Mark O'Neal from Coash High (Probe) and Barry R from Survival Motorsports are extremely knowledgeable and are in this very field being discussed. You want to know what they recommend for the street?
That is right, the 1.175"/5.315" combination
A Ford Lightning utilizes a completely different bore and stroke combination:
3.55 (bore) x 4.16 (stroke).
A SBF 302 uses a 4.00"/3.25" combination.
There is a big REASON why 99% of rods and pistons do not intersect in the automotive industry.
Now, for the rod ratio not being a factor. Sure, I agree with that. 99% of us do not need to worry about it for our purposes. However, Nascar uses a 1.93:1 rod ratio for a reason.
Some claim it is simply the by-product of the stroke and rod used. Nascar did testing and shortened the piston as much as possible to lighten it and utilize a longer rod. This gives a better rod ratio, aka, less frictional losses. Someone needs to pick up a book from John Heywood
In a world of extracting every last HP and engine longevity at 9-9500 RPM for 500 miles, they think of EVERYTHING. Thinking of everything is what determines the difference between #1 and #2. 2 HP can make or break a race over 500 miles. 2 HP just happened to be what the GM engines (358 CI) noticed from switching from a 5.250" rod to a 6.1" rod. Extreme example? Maybe, but there is truth. The Pro Stock guys are using 1.71:1 ratios.
Do not take this to an extreme. Rod ratio is typically highly exaggerated to most people. However, a good solid idea that I see in the professional world is a higher rod ratio as the RPMs increase.
Some may argue, well look at some of the foreign vehicles like Honda. Running 1.5:1 (similar) rod ratios, but look at their bore size. Very small.
The rings take the brunt of the wear. I actually have a formula to figure out the differences in side-thrust.
I often wonder why many credited engine builders want a thicker outside wall, than inside
You will see, per capita, higher rod ratios last longer than short rod ratios.
But, this is not something that any of us guys in here need to worry about.
If you want to read more about strokers, check out the link in my signature.
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?