Sifton Racing Cams for Street and Strip
EVO and late model Shovelhead
Including Black Widow Grinds
Our Sifton Racing Cams are of "orginal-orgin" and not to be confused with the Sifton Motorcycle Products Inc. company,
See Photo gallery.
Tom Sifton Checked all his mechanical lifter cams for over head valve engines @ .053 due too the long high ramp that he incorporated into his designs for the Aluminum cylinder head that when hot has growth. Thus allowing the valve to be slowly put on the seat with out shock or being noisy.
Due to varations in compression ratios and carbon build up, Ing timing Early Alum heads can grow as much or more
as .032"- .040" and will have more mechanical noise.
NOTE: Loss of low end power will result if you use Hyd lifter on a mechanical lifter cam do to the extra duration of the ramp zone!!
Early Flat Head cams were checked at .010"
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More on how to hop up Shovelheads coming soon From original factory race dept. notes.
Early Pan Head cam for using two front cyl heads or for F & R Swap
for Turbo and and two carbs. Turbos in the 70's I worked this engine configuration in 1974 - 1976 two years to get it right-never again?
Even though we have lost some great innovators in the motorcycle industry like my early mentor's whom I new all of my child & adult years James Kibblewhite Passed away back in February 2005 Born June 1st of "1923" I will always remember Jim telling me not to let the first failure bring you down it is the learning curve that we all must go through to be able to be better as our achievements will speak for them self-Jim's oldest son Will runs the business on a daily basis carrying out his fathers success in our home town of Pacifica California- Man like we were living right next to the Pacific Ocean! "surfs up"
Now Jerry Branch is 88 years young and to think he was developing what would be the 1984 Evo cylinder head for the Motor Company back as far of 1976!!My wife and my self will be visiting John and Jerry some time soon for their next U-tube Video on cylinder head porting-check out their first video.
More on some others we locate our earlier web site info.
How do you pick a cam?
How far should the intake valve be open at 75 degrees ATDC?
When does the intake valve close and stop the Intake flow process-and begin the squeeze well is isn't at .053" thats for sure. So when does it close ?
When the exh port is to big stuff a big tulip valve and add some real estate back into port. Tulip valves where used just for this whether or not it is the intake that is over ported or exh. But play a part in getting Torque.
Can the Int valve cause or be a restriction in the system?
How far should the Exhaust valve be open at bottom dead in relation to intake port flow ? Blow Down!
If you use wilder exh lobe on a exh port that is flowing very well what happens to your BS HP- goes out of control.look at Tq curve.
Exhaust gases will not expand more than 7 degrees
10 degrees ABDC the valve seat does recolonize piston movement So again how far should the exh valve be open at BDC
Does a lazy intake port need more over lap to initiate flow because of low velocity due to larger valve for high lift flow? The more you can see of the back of the Int valve the more power you will see.
If you can't fill the cylinder stuff it with a piston-higher compression.
So your cylinder head flow numbers make a difference It is the relation between intake air flow vs exhaust air flow @ BDC & exhaust valve lift