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· IA2
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The piston pin bore is offset a small amount to one side of the piston to help reduce noise. If the pistons are put in backward it changes the rod angle just a bit and is usually worth a few HP. As JRam said you have to watch P/V clearance if you do this, and expect to hear some piston slap. This is an old Joe Sherman trick I read about years ago.
 

· Worship me
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This only works in stock, stock replacement and TRW pistons. They all have the pin bore offset .030" to one side. If you spin the piston around you effectively move the small end of the rod .060". Now that isn't a big deal until you realize that this effectively makes the big end of the rod pass the TDC position a little early and the rod angle relative to the bore centerline is better during the whole combustion process. It just gets better leverage on the crank.

The valve reliefs are a non issue most of the time since a lot of these pistons have symmetrical reliefs so they can be put in the bore either way.
 

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Discussion Starter · #6 ·
We haven't even started putting the engine together yet, so if there is something as easy as this that we can do to get extra power, then I'd sure like to do it. We have to cut the pistons anyway, so P/V clearance shouldn't be an issue (unless we go all the way through them...). So is this a good idea or not?
 

· Worship me
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You will have more piston slap until the motor gets warm and the skirts on the pistons will wear quicker. If you want to get 50K miles out of th e motor then NO. If you plan on tearing into it again in 5000 miles then go for it. Its going to hurt long term durability is what I am saying I guess.
 

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Discussion Starter · #8 ·
What is piston slap? Is a piston skirt the thing on the side that points downwards? How will that wear? Does it contact the cylinder wall? I don't need it to go 50k, but I'd like 15-20k out of it. By that time I should have enough money to build something serious.
 

· Sign I saw on the ground:
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kinda long

The Joe Sherman article in question suggests swapping banks w/ pistons and rods, rather than pressing the pins out, spinning the piston and putting the pins back in. Swapping the pistons, ie 1 to 5, 2 to 6, etc would work even w/ only one set of reliefs in the piston crown. I'm talking about I beam rods, I have no experience w/ H beam, but that's irrelevant anywho b/c who would put a stock piston w/ the offset onto a nice H beam? The I beams are beveled and stamped, that is why the eye brows are irrelevant, b/c the bevel goes to the outside, and if you haven't taken the piston off the rod, it will naturally line up the way it was on the other bank, follow? Of the testimonials I've heard, nobody has experienced piston slap on cold start-up, where it's most prevalent.
The switch gives you in effect a longer stroke, more dwell time and faster piston speed.
This swap is said to be worth 20 hp ALONE, ceteris paribus, or everything else remaining constant.
I ran this by my machinist, as I have a stock short block sitting around, and he said that the principle was right on, but not to do it on a 100K block b/c of the potential for out of round cylinders w/ that much wear (when considering flipping banks).
After reviewing what has already been contributed, I'm just re-hashing old material. I've typed too much to just delete though. Fug it, I need to get more posts under my belt anyhow.
 

· Sign I saw on the ground:
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92 green monster

yeah, and they're called doctors:D


I'm watching Tommy Boy as we speak, or type, or something. Whatever.
 

· Darkside
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AL P said:
You will have more piston slap until the motor gets warm and the skirts on the pistons will wear quicker. If you want to get 50K miles out of th e motor then NO. If you plan on tearing into it again in 5000 miles then go for it. Its going to hurt long term durability is what I am saying I guess.

This pretty much sums it up. Why the hell would you want piston slap after you do all the work to get it together? This equates to more money than sense.:rolleyes:
 

· IA2
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BBRANJEN said:
This pretty much sums it up. Why the hell would you want piston slap after you do all the work to get it together? This equates to more money than sense.:rolleyes:
If it's a race engine that gets freshened up periodically the piston slap/wear problem is not an issue. The extra HP for essentially nothing is worth pursuing.

For a street engine - it doesn't make sense to do it.
 

· Im somebody's daddy!
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Here is how I look at it...

You've got small cubes. You aren't spinning much RPM. Anything you can do to it to increase HP with your budget is a plus. Id deck the block, flip the pistons & cut them just enough. You have a throw away motor. You can pick another one up for cheap down the road. Worse case, you bore the motor .030 and pick up some TRW's. If you get only 10 rwhp out of it, it would be worth it, IMO. Its gonna be next to impossibe to pick up any power somewhere else like that for the price. GOOD valve job and valves = $$$. GOOD port work = $$$. Custom cam = $$$. Etc... If you had the money, and I think Ive been following your posts, you could pass on this and spend cash on other stuff. But if I recall... its a budget 330+ rwhp 302 NA set-up...

Id flip em :D
 
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