Tweet
I,m thinking about replacing my 79 year old cams and I see Andrews has a fairly stock cam, but I want a little bit more. I think the Andrews has a little more duration, but I,m thinking it could use some more lift also. I,m running the linkert m-51 carb so I don't have a lot going on there. Any thoughts, places other than Andrews? Thanks! 1939 UL
-
-
More lift may need more room in the relief pocket, sometimes only the corners need touching up.
More intake duration helps, more exhaust not so much, but the usual regrinds use the original lobe centers which are too wide. Maximum intake valve closing should be at 65° ABDC, the remainder of the intake duration added should be on the opening side (BTDC). Raed my article on re-timing the cams here: http://www.victorylibrary.com/tech/degree.htm
The M-51 is a restriction, try the 1-1/8" M-51L etc. venturi (reproduced, quality unknown). If you want to keep "traditional" appearance, an M-74 will help even with your manifold (needs a bolt pattern adapter), use your M-51 float bowl. -
The only Andrews UL cams that I have been around had a .003" bigger outer journal than the inner one making it impossible to line ream the bushings. We had to make a special fixture and do each separately. Jerry
Originally posted by Ward View PostComment
-
I was told by one cam builder that at .390 lift with high compression heads is about when you have to start checking head clearance. Seems like you would lose a bunch of compression fast clearancing for valves. Maybe you could make some up by angle milling the head. I wonder if Andrews has made any changes to the journal mis-sizing? Has anyone talked to them about it?Comment
-
Intake lift clearance is a combination of how high the seat is (how many valve jobs), what valve head diameter, and what seat angle (30° is better for flow, but it's not OEM). The actual relief pocket isn't accurately machined but roughly cast with an irregular roof and corner radius, not difficult to clean it up with a mill at the proper angle or even a Dremel. The volume added to the chamber I would guess at 1/10 of a point of compression (since the chamber is very large)
Some cam manufacturers (Leineweber, Argetsinger) can supply lobes larger than any regrind, which should be on the list for a high performance engine.
IMHO exhaust lift isn't critical.
I haven't spoken to John Andrews in decades, but he was, shall we say, not an easy person to discuss things with: he's right and you're not.Comment
Comment