crosscut
L2 Scorpion - Above All
Posts: 88
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Post by crosscut on Jan 10, 2013 0:16:18 GMT -5
Anyone have an opinion on who offers the best quality/correct thinkness base gaskets for the 2f-400 series? I've read that the original gaskets were .063, and winderosa gaskets are .020. I know that the port timing is important on these engines and I thought some of you would have some insight on this. Thanks guys,  |
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Post by scorp11 on Jan 11, 2013 23:58:29 GMT -5
The genuine Cuyuna gaskets are around .015. The winderosa ones are pretty close to that, maybe a touch thicker, but they ship two extra so you can double them up. I've done this when the piston sticks out of the cylinder a little too far.
They did have some thicker base gaskets, I have a couple, but have never measured them or run them. I don't know that they came that way, but rather were an update for sleds that had issues.
If you just stick a thicker base gasket in the piston is going to sit down below the deck a long ways. .040 below would be quite a bit.
The Stock head gaskets are thicker than the winderosa ones. That will lower the compression a little bit.
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Post by mooreperformance on Jan 12, 2013 15:32:56 GMT -5
When I attended the Scorpion Service School (back in the day) I was told that you installed the correct thickness base gasket when your finger nail couldn't feel the transition between the top of the cylinder and the top of the piston (when your nail was slid across the two).
When the edge of the piston didn't stick up past the top of the cylinder.
Not very exact I guess. But that was the spec from the engine factory!
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Post by scorp11 on Jan 13, 2013 0:44:27 GMT -5
When I attended the Scorpion Service School (back in the day) I was told that you installed the correct thickness base gasket when your finger nail couldn't feel the transition between the top of the cylinder and the top of the piston (when your nail was slid across the two). When the edge of the piston didn't stick up past the top of the cylinder. Not very exact I guess. But that was the spec from the engine factory! There is a spec for the max the piston can stick out of the cylinder. .008 or .012 measured at the wrist pin stick in my mind, but I'd have to look up the actual number. To get it flush or pretty close, .020 base gasket will be in the ballpark from what I've seen |
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crosscut
L2 Scorpion - Above All
Posts: 88
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Post by crosscut on Jan 15, 2013 9:53:16 GMT -5
That piece about the scorpion school reminds me of sitting in a class for Briggs & Stratton, to get engines donated to or school, we the instructors had to attend a Briggs factory training school. The teacher was an older fellow and although the class was only 10 years ago, he still brought up the old tip of using a matchbook to set the point gap, since matchbooks are close to .020! ;D
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jlo12to1
L1 Scorpion - The Great Snowmobile
Posts: 6
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Post by jlo12to1 on Feb 8, 2013 4:33:55 GMT -5
Friends, fyi. Page 1-9 from the 1979 Scorpion service manual: "The edge of the piston must not protrude above the top of the cylinder with the piston in the top dead center position more than .008 measured with a feeler gauge. If the piston does protrude above the cylinder, a thicker base gasket must be used. It is important that only one cylinder at a time be adjusted or the crankcase will seperate and lose its seal." Curiously, page 1-18 of the 1978 (I think it is '78, as it does not specifically have a date anywhere) Scorpion service manual discusses the same subject as follows: "The edge of the crown of the piston must not protrude above the top of the cylinder with the piston in the top dead center position. If the piston does protrude above the cylinder, a thicker base gasket must be used. See specification page for dimensions and color coding. It is important that only one cylinder at a time be adjusted or the crankcase will seperate and lose its seal." Both manuals end the subject there going on to describe cylinder head installation. Looking at the specification page in the service manual it does not mention dimensions or color anywhere for the base gasket, nor do the '78, '79, or '80 parts manuals. That is the extent of my factory manuals. It appears Scorpion raised compression in 1979, or maybe they were accounting for a difference with the hemi heads. Regardless, it is also interesting regarding compression issues to note the 1978 service manual specifies 95 octane, while the '79 manual is silent about the issue. I don't have my '79 and '80 operators manuals in front of me, but I'm pretty sure they also clearly specified 95 octane. Happy engine building, Scorpion friends.
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