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Livin' Free Indeed
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Discussion Starter #1
Is it normal for a 103" SE or a 107" S&S stroker motor to burn a quart of oil in a 1000 miles on a fresh build? My 95" doesn't hardly burn any. A friends 103" SE doesn't burn any, but his 107" S&S does. Just trying to find out what's normal.

Thanks
 

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IronButt
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6,364 Posts
If you are talking about Charlies bike I thought he said it was a 106?? Some combos are not of the best design. Long rod small bore can creat problems as the piston is very short in a 106 you have to install the wrist pin before putting on the oil rings. As the piston is so short that the pin is up so far for the long stroke. Hence you can run into problems with piston stability. This type of piston is commonly known as a " slipper piston" . Also the long rod small bore are not high revving types. Building a stroker motor is fun and can offer great gains if done properly. Take my 124 for example, 4.375 stroke with a 4.250 bore, a engine that large that is only .125 from being a square motor allows plenty of leeway as my pistons are not very short the rod length is a 103 type crank. Some designs like the 114 are a over square type beign that the bore is larger than stroke, 4 inch stroke with a 4.250 bore, = quick revs and good tq. 107 is bore only with stoke stroke.

The oil usage is common on the 106 kit from my experiance, myself am not a fan of the kit ,one reason is design, the other is cost. You have to buy a crank, split the case, and you end up with a rather poor design and have spent much more than say a 107 or a 114.

But that is off the oil topic, Dave did he state to you the amount of oil per oil change that was being used?? , also with stroker motors you can end up puking it out the over flow due to lack of case volume. With removal of balancers on a B motor you have ample volume. If the oil pump is not scavagiung correctly he may be loosing oil there as well. But most time that is noticed . A/C head breather is that is going into the a/c can use plenty of oil and not show as a leak or puddle on the ground.

By the way what are you doing for thanksgiving??
 

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As mentioned above, my experience with the 106's also is that while there were no oil consumption issues when new, they seem to develop oil consumption around 25-30K miles, and I agree that it likely can be traced back to the design and material of the pistons.

Also more care has to be exercised during assembly and it wouldn't be the first time a ring wasn't marked properly, or?
 

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Livin' Free Indeed
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Discussion Starter #5
You're right it is the 106". :duh?: The builder told him they all burn oil & he couldn't explain why his 103" didn't burn oil. The 106" is this builder's preferred set-up, guess he likes building oil burning engines.
 

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Highly Seasoned Rider!
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I'm not the expert here, just a qualified observer. That said, having the piston so short that the wrist pin is partly shrouded by the oil ring is not a good design for low oil consumption.

Slipper pistons are a race-bred design. Some excess oil consumption is to be expected.
 

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The short skirt design was developed by Cosworth Racing. It has many great features and oil usage has never a problem. The practice of pulling the oil ring down over the wrist pin hole has been around for decades. It has 2 reasons behind it, ring stability and accommodating longer strokes. HDWRENCH stated most of the reasons for oil usage in that particular motor. Piston rock is ALWAYS evident in long stroke, small bore setups, especially if the wrong alloy is used. Expanding the ring pack will eliminate the problem.
 

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Highly Seasoned Rider!
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Dron54 said:
The short skirt design was developed by Cosworth Racing. It has many great features and oil usage has never a problem. The practice of pulling the oil ring down over the wrist pin hole has been around for decades. It has 2 reasons behind it, ring stability and accommodating longer strokes. HDWRENCH stated most of the reasons for oil usage in that particular motor. Piston rock is ALWAYS evident in long stroke, small bore setups, especially if the wrong alloy is used. Expanding the ring pack will eliminate the problem.
I personally don't think that 1,000 miles to the quart is a problem in such a motor. Short skirt slipper pistons have been around for a very long time. They come up whenever an engine has an extremely long stroke. The shorter the piston, the more likely that it will rock. Not exactly sure what you mean by expandng the ring pack. Sounds good to me, though if it works. :)
 

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Expanding the ring pack means to just widden it by increasing the distance between the rings. A ring pack (3 conventional rings) is rendered ineffective at around .870" for .063" sets and on the other end it can't be expanded to more than 1.75 before the flutter from detonated gasses becomes devastating.
 
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