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MikeF
02-01-2002, 02:51 PM
What are your thoughts on offsetting the piston pins? What kind of performance gain can come of this modification on an engine? Seems like it could benefit the Torque and HP output!
Also....What are your thoughts on Aluminum connecting rods in a jet boat application? Do you think they would hold up (and for how long)? Thanx!

058
02-01-2002, 03:11 PM
Its already done on stock engines. Pins are offset app. .060" to the outside of the engine. This is done to keep the piston quiet when the engine is cold and clearance is at maximum. Performance pistons usually are not offset because noise isn't an issue.

LakesOnly
02-01-2002, 09:50 PM
Here is an interesting anecdote that is somewhat related to your question:
Someone I know was awarded a patent several years ago for what he calls "cylinder tilt-angle." His theory was that while the piston is travelling downward on it's power stroke, the big end of the connecting rod is essentially moving sideways (perpendicular) to the piston's motion, and so useful power is lost. But by tilting the cylinder several degrees toward the downward-rotation side of the crank's throw, that downward force of the piston is more positively transmitted (linear) to the crank throw and turned into useful power. This basically uncovers a major engineering flaw in the basic design of the piston engine. (Number of degrees of tilt is confidential.)
Others before him submitted similar claims but were denied an award by the patent office due to lack of proof. This machine shop owner, however, painstakingly modified/re-sleeved a Formula Ford engine block and then raced the car. (The Formula Ford class is an extremely restricted spec-racing class where all spec's--cam, pistons, carb, suspension tuning, tires, etc. are identical on every car in the field.) He beat second place by almost two minutes. Last I heard, he was negotiating with Ford Motor Co. on the liscensing of his patent.
Now, here is how this story relates to your question: Similar power increases can be created by offsetting the piston pin, because if the piston pin at the small end of the conecting rod is moved over toward the downward-rotation side of the crank's throw, a similar, linear transmission of power (from piston to crankshaft) is created.
I have not researched this any further to find out which custom piston manufacturers are producing pistons like this (or offer it on a special-order basis), but I've heard it's been done. And I have no idea how much offset is used. If you find any intersting technical information on this (or even a manufaturer that offers it), please drop me a line and let me know. http://free.***boat.net/ubb/wink.gif
L.O.
[This message has been edited by LakesOnly (edited February 01, 2002).]

spectras only
02-01-2002, 11:24 PM
Lakes Only, interesting topic! I'm sure if someone dwelved into this subject ,could find more info.There are a lot of good ideas that never materialized due to problem funding ,or been shelved for "political" reasons.As you probably aware of the "new" technology of fractured connecting rods versus conventional rods ,to improve perfect mating .My friend's 1938 Rudge Ulster {500cc motorcycle]came with that technology way back then! The BMW motorcycle came with this method a few years ago with much fanfare as if they reinvented the wheel.The Belgian FN had driveshafts on it's 1904 model. A friend of mine has one in his livingroom amongst other old oddities http://free.***boat.net/ubb/biggrin.gif . Cadillac's 8-6-4 found it's technology in the new 12 cyl 750 HP Northstar engine [much improved of course http://free.***boat.net/ubb/wink.gif],and Mercedes's CL model copied that idea as well hm,hm .Good hunting for new info

superdave013
02-02-2002, 06:10 AM
Mike, Stay away from the Aluminum connecting rods. They are drag race only. The life span is measured in the # of passes. I see them for sale at the long beach swap meet all the time. I asked a guy what he paid for a set once. He says "Only 100 bucks, I got a great deal!" Uh, sorry buddy, I thought. He just bought a set of used up rods!
Get a set of Olivers or Carrillos and you will have them for years and years.

Flat Screwd
02-03-2002, 08:53 PM
Some thing about offset wrist pins that has not been talked about is the ellimination of dead lock at TDC and BDC. So if the crank is on TDC the con rod is not in a straight line with the crank but rather tilted slightly.
As far as alun rods go I would have to dissagree with Superdave. There is two things that kill alum rods first is rapid decelleration AKA "tension", and the second is heat soak. Alum rod got a bad rap from drag racers and circle track racers.
Circle track is on the gas off the gas and so on, maybe 1/4 of the race is high RPM decellaration therefore creating tension in the rod.
Alum rod failer from drag racers is mostly cauced by heat soak, they run filled blocks with no water and create a lot of heat by way of blower and high compresion. They start the car, stand on the gas ,and at the finnish they shut down. Basically what this does is cook every thing in side.
I know people who have run alum rods with grate sucess and some for as much as 8 years and only replaced them because it was time for a new motor. If this a jet your building than its even better, low RPM and the motors under a constant load. Even in a v drive the same goes.
Just my thoughts

MikeF
02-04-2002, 09:09 PM
Lots of good reply's! L.O......Sounds like your friend has done his homework and going to benefit from his hard work! Good to hear! Thanx for the responses! Mike