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View Full Version : Ironhead 900 H Cam questions--Patrick? Dr. Dick?


Moon Wolf
14th November 2011, 23:48
Took apart a 67 XLH engine last night. The two middle cams, 2 and 3, are Marked H. I and 2 have no marks.

The cams have similar wear--all in good condition. I've seen the P cam and unmarked cams in the same motor before, but I don't know anything about these. Any insights will be appreciated.

http://i229.photobucket.com/albums/ee256/mtroytaylor/IMG_2897.jpg

Monte03
15th November 2011, 00:20
Moon, these appear to be real early Sifton Cams when Tom Sifton was at the helm in San Carlos, CA, the H Cams as you can see have a real sharp corner drop off 'ala' Minus Minus cams, if these are the real H they have a lift of .435 the
intakes open@ 33 deg close @ 45 deg, these were for a Hot Street or Strip XL back in the day,
Book States for 55" Road and Drag
So My Question is, How did they Run on the Bike???
I have a set of full Sifton H cams that I never used..
Monte

DR DICK
16th November 2011, 08:21
if the timing #'s on that #4 are 20 & 42 that makes it a h grind.

if 20 and 47 it a +h grind

way back when, there was an offering of h intakes with -/+ exhausts.
one step down from the +h int with -/- exh.

all of these were single h grinds were 'supposed to be' .436 lift. but iv never seen any. all i ever had my hands on were .390 or .375. that makes em bolt in after the interfear got squared away.

appears that those are manufactured pre 72 and after 66.

around 70 was some messing around with having to alter some profiles to reduce valve to valve interfear cause of the new -70 big intake. that may be why 1+4 are unmarked.

lets see the other end.

Monte03
16th November 2011, 12:31
When I get back to work I will scan my Sifton cut sheet, this sheet is way before my 1981 Sifton Anniversary Book, the sheet looks early - mid seventies
the sheet states:
XL Cams
2H 3H Inlets Opens 33 deg Close 45 deg .435 for 55" Road&Track
1H 4H Exh Opens 42 deg Closes 20 deg .435 for 55 - 65" R & T

ultimately at the bottom of the cut sheet the famous - / - cams are noted as the XL stroker cams, many Old Timers I talk to that raced still say that due to the wide duration, minus/minus cams are the perfect fit for a stroked XL regardless of the .436 lift

Moon- you may have some real classic pieces there.....
*this was the seat of the pants era when grind and test at the track ruled.

brassy63
17th November 2011, 10:04
So what valves would you use if you were running them in a 900 with a S&S stroker bottom end I got a set of minus minus cams set up for a magneto camcase

mrmom9r
17th November 2011, 12:31
R length 1 15/16" intakes with 1 3/4" exhausts.