Actually, I think you are exactly right. Last night at about 1:00 PM I
finally got it all fairly clear, though I set it at nearly zero advance.
Right now I'm set at:
intake: 36.5 btdc open 76.5 close duration 293 centerline 110
exhust: 80 open 39 close duration 299 centerline 110.5
overlap is 75 all measured at .020 check clearance at the follower.
And by the way, thanks to Alan Taylor for his recommendation of the isky
book--it's on the site and I'm printing it right now--ten really good pages.
Also thanks to Kas for putting me on the right path, Tony for specs that got
me in the ballpark, and all the rest of you for ideas and encouragement.
Sure is nice to be able to yell HELP!! And get it, day or night.
As always, I'm learning more about this than I really wanted to know, but
maybe it will stick for a few weeks. My brain is getting pretty FIFO and the
turnover time is getting short.
-----Original Message-----
From: Jack W. Drews [mailto:vinttr4@geneseo.net]
Sent: Sunday, February 27, 2005 9:32 AM
To: Bill Babcock; 'Tony Drews '; 'owner-fot@autox.team.net ';
''fot@autox.team.net ' '
Subject: RE: Yikes and cam problem:: HELP!!!
Some comments that may or may not help.
I've charted the specs on three old Isky cams and eight currently available
cams, seven from Erson (BFE) and one from Solow.
All the cams but one have symmetrical lobe centers - that is, intake and
exhaust centerlines the same distance from TDC, except when the cam is
advanced or retarded of course.
The old standby for years was the Isky TR666. At .050, it had Intake open
15 close 55 exh open 55 close 15, typical of older cams. (I must admit that
this is what is in my engine, probably the reason that I'm so slow. No
advantage to winding it over 6000. But that's another debate)
The Erson (Long) cam #149 is quite different. At .050, it has intake open
13 close 45, exhaust open 53 close 5. That puts the lobe separation at 120,
but the spec is to set it at intake 114 before TDC and exhaust 106 after
TDC. This cam is a very nice cam for a warmed-over street engine. I suspect
that is a quite old grind.
The one I find that seems closest to what you have is the Erson #23, a very
recent Erson (BFE) cam used in most of the fast cars (they have a newer,
wilder one). it has .050 events at intake open 27 BTDC close 59 ATDC,
exhaust open 67 BTDC, close 19 ATDC. Centerlines are intake 106 and exhaust
114., which means it has separation of 110 and is advanced 4.
All that may be confusing, but here's a pattern that I see: Lobe centerlines
are generally equal, and are between 105 and 110 each side of TDC. Most
recent cams I've compared have lobe centers at 108. In all cases of
symmetrical cams, the manufacturer recommends advancing the cam three or
four degrees. That is the case with the Greg Solow cam that Tony is running
in his engine.
if I was faced with your dilemma, I'd set the cam with intake and exhaust
lobes equidistant from TDC, and then advance it three or four degrees.
But then, there must be someone out there who knows more about it than I do.
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