S&S Cycles V-Twin "X-Wedge"

5

5 Horse Fan

New Member
#4
#4
Well, the purpose of three cams was to straighten out the exhaust tappets against the cam lobes. The exhaust pushrods travel over the tappets at very near 90 degrees.

Three cams also gives you more adjustability.:thumbsup:
 
Last edited:
J

~JM~

Banned
#5
#5
Sorry... It doesn't make sense to me to have 3 camshafts in a 2 cylinder, pushrod engine.

Might as well go with an overhead cam design, with one cam per cylinder.

Of course... I can't see spending $20+k on a Harley either, so maybe its just me.
 
Oldsalt

Oldsalt

Well-Known Member
#6
#6
All 45 cubic inch and 80 cubic inch Flathead V-twin Harleys, dateing from well before WW II had 4 cams, one for each valve. Flatheads, however, have some problems but the push rod big twin doesn't. However there are a number of reasons to keep the push rods on an air cooled motocycle engine and forget about overhead cams. One is total engine weight. Two might be the heigth of the engine is increased. Three the CG of the bike is raised. Four, added expense. Five is the fact that head cooling [by air] on an overhead valve engine is infinitely better than the same engine with the cams on top. Water cooling might then become a necessity [more added weight and cost and negative CG change and maintence and a lot more things to break], or at least require a greatly enhanced oiling system so copious amounts can be used to cool the head [ala early Ducatis 250 and etc.]. Six is the fact the some method must be used to drive the OHC. This usually involves masking a vertical portion of the cylinder barrels with the resultent loss of cooling and also results in a highly non-symetrical barrel which can cause cylinder distortion. I'm not impressed by S&S's belief that they can improve the large displacement V-Twin with some cam gear changes.
 
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