pistons, forged vs cast
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Intermediate
Joined: May 2007
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pistons, forged vs cast
Im freshening up my 74, going .020 over, I ordered weisco pistons today. Im replacing cast ones, Will this mess up my ballance much, bikes just a cruiser, but Back in the racecar days, forged was the way to go. Will I be alright??
Road Warrior
Joined: Dec 2007
Posts: 1,286
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From: SoCal
RE: pistons, forged vs cast
Did Wiseco say anything about needing to rebalance the engine at their website or any of their literature you've read? If they are stock replacement pistons, you should be just fine. You could talk to a shop real quick and see if they know of a need to rebalance with the pistons you ordered. Call Wiseco themselves as soon as possible and ask. Or have the shop you ordered from check for you. I'd do it quick so you can change your order if necessary. Forged pistons have the potential of being heavier than the stock cast ones but they could easily be manufactured to weigh the same as stock.
I know you said the bike was just a cruiser but are you planning on hotrodding the bike sometime? You really only need forged pistons if you are going to run the engine hard (high rpm/load).
I know you said the bike was just a cruiser but are you planning on hotrodding the bike sometime? You really only need forged pistons if you are going to run the engine hard (high rpm/load).
Tourer
Joined: Dec 2007
Posts: 377
Likes: 3
From: Canada
RE: pistons, forged vs cast
I have forged 9.5:1 Wisecos in my shovel. When I was doing the motor, the guy who did some top end work asked me some questions about what I was doing. I told him I was doing wisecos. He said "you're going to wreck the bottom end" then proceeded to lecture me for a while and basically tell me I was an idiot - until he figured out that I was rebuilding the bottom end and balancing it for the new pistons, I just wasn't having HIM do it. Then he said "oh, never mind".
FWIW, that builder was convinced it would be a problem, and he builds a lot of nice shovelheads.
FWIW, that builder was convinced it would be a problem, and he builds a lot of nice shovelheads.
Road Master
Joined: May 2007
Posts: 953
Likes: 8
From: Central Oregon
RE: pistons, forged vs cast
I'm running the 2900 series forged pistons produced by S&S, the tolerances {piston to cylinder} are a little looser when they are set up originally making the engine much nosier when cold. I really prefer the Keith Black pistons for street use. The reason I am running the forged in my shovel are because of the shorter piston skirt due to it being a 4 3/4 stroke. When I did the top end on my 68 a few years ago with the Keith black pistons I did nothing to the bottom end. I weighed the new pistons on my paint scale to find they were with in a few 10th's of a gram, Good enough for this guy.. The engine ran fine and when I tore down the shovel to do the stroker wheels the bottom end was as tight as the day I had it built.
what type of ring are you planning on running?
BTW thats almost amazing your cylinders will clean up with only a .020 over! My old shovel was .060 over the last time I did the top end It was an 80 by then! She was growing up
what type of ring are you planning on running?
BTW thats almost amazing your cylinders will clean up with only a .020 over! My old shovel was .060 over the last time I did the top end It was an 80 by then! She was growing up
Novice
Joined: Mar 2008
Posts: 21
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RE: pistons, forged vs cast
weisco pistons may have a different skirt than your cast pistons. But as for balance issues the idea is the riciprocating weight, if you had your build sheet on the last balance you had done, you could see the weight of the front and rear piston with wrist pins and rings after rings were fit. this would give you the piston assembly weight front and back. if you could match this weight front and back, with your new assemblys this should not effect your rotational balance. Now into valve inpressions on the pistions and skirt length etc. these may present a bit of a faster wear out time on your cylinders. ? depends on how you ride the motor. Keith Black is a great piston for stock type motors but weisco is one hell of a nice product as well. just my .02 good luck
6th Gear
Joined: Feb 2008
Posts: 11
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From: Hudiksvall Sweden
RE: pistons, forged vs cast
Hello from Sweden,
Wiseco told me there is no need for balancing when changing to their 9.5:1 pistons, both pistons arepaired and your whole assembly shuld be ok, when you balance the stock engine they use balance factor 60 i belive, but you will only change the vibrations to a different R.P.M so it depends on where you usually ride (your speed)the bottom end on the shovel is a strong peace of mashinery and check your connecting-rods side play, if there is play whithin the limits. Many shovel engines are beeing rebuilt for nothing, a rebuilder of WLAa's once showed me howworn bearings shuld look like and now I know. regards Ronnie
Wiseco told me there is no need for balancing when changing to their 9.5:1 pistons, both pistons arepaired and your whole assembly shuld be ok, when you balance the stock engine they use balance factor 60 i belive, but you will only change the vibrations to a different R.P.M so it depends on where you usually ride (your speed)the bottom end on the shovel is a strong peace of mashinery and check your connecting-rods side play, if there is play whithin the limits. Many shovel engines are beeing rebuilt for nothing, a rebuilder of WLAa's once showed me howworn bearings shuld look like and now I know. regards Ronnie
Banned
Joined: Apr 2008
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From:
RE: pistons, forged vs cast
Wiseco makes the best pistons for the bucks you want to spend,in other words they arent expensive.They come balanced,ready to go with rings that seldom need to be gapped(although I'd check 'em)
They take a minute or 2 to expand into the bore of the cylinders but they'll last for thousands of miles before you have to worry about replacing them(were talkin forged here)....they're very strong and damn near bullet proof to give long life.
They take a minute or 2 to expand into the bore of the cylinders but they'll last for thousands of miles before you have to worry about replacing them(were talkin forged here)....they're very strong and damn near bullet proof to give long life.
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