Joe,
The numbers you have from Aaron (also in one of the older comp
manuals) are suspect, as they don't add up.
42 + 180 + 76 = 198 duration.
The actual measured duration on my A7 was 191.
This was my valve timing
before rebuilding my engine. I can't find my 'after rebuild' notes. Checking
clearance is .013
Inlet opens 44 Inlet Closes 67
Exhaust opens 74 Exhaust
close 37
I had Elgin regrind my A7. Before you go for a new cam, have your
old one checked by a cam guy.
If your cam is one of the original factory
billet, a tell-tale sign is that the fuel pump lobe was never ground, it's
probably worth checking to see if it is useable as is or needs to be reground.
Regards,
Tim
From: Joe Guinan <joeg@neb.rr.com>
To:
fot@autox.team.net
Sent: Friday, October 4, 2013 12:05 PM
Subject: [Fot]
Kastner A7 in 1147 Spitfire Questions
Friends,
I've finally installed the
used Kastner A7 cam in my 1147 race engine and am
having trouble getting it
timed correctly. When I set the #2 valve (intake
on #1 Cylinder) to open at 42
degrees, I cannot get the closing number
anywhere close. It's at 60 something
on closing. Haven't even checked where
the #1 valve starts to open, as this
seems so wrong.
Specs I received from FOT Aaron Johnson are below.
- Inlet
opens 42 Inlet Closes 76
- Exhaust opens 76 Exhaust close 42
- Duration 293
Lift at valve .410
- Checking clearance at the camshaft is .013
- Rocker arm
clearance is .020
Information I received from Kas himself is close to the
above;
"That cam was done early on but it will work fine. The timing is Inlet
42-71
and the exhaust is 71-42. The cam has 293 degree duration and .410 lift
at
the valve. As I remember the checking clearance is .013" and the running
clearance is .020"."
Kas also added, "Just for your information I believe
that cam is done on a
factory billet meaning that the base circle is very
close to the stock
diameter. Check to see if it is. If so, you can get a
dynamite cam profile
put on that cam at Moon Equipment. You cannot E-mail them
but phone and ask
for Bill Jenks and then tell him you want the A-10-A. This
will go onto that
cam fine if it is the factory billet I used for lots of the
camshafts. That
was the latest grind (54 - 90 and the gross lift is .517" )and
it was
terrific but you do need high compression to deal with it."
Note the
difference in closing measurements in the two sets of specs?
I know I have
TDC on the crank set correctly. I'm seeing 42 degrees on the
degree wheel when
the dial indicator on the top of the pushrod shows the
valve has opened .013
inch. The valve stays open like it should for most of
a rotation but is only
at 60 something on the degree wheel when it has
closed to only being open .013
inch.
What am I missing / not understanding?
I already have the head
installed, but I'm about ready to pull the cam out
and get a new one, or
follow Kas's suggestion to send it out for a regrind.
I am running high
compression with "pop-up" pistons. Something about this
cam just doesn't seem
right, and adds to my suspicions about running a used
cam in this newly
rebuilt engine. Hate to spend the money and time, but if I
have to do it, I
might as well do it now.
Thoughts and opinions welcome...
Thanks,
"Jedi"
Joe Guinan
Fremont, NE
_______________________________________________
fot@autox.team.net
http://www.fot-racing.com
Donate:
Archive: http://www.team.net/archive
Forums:
http://www.team.net/forums
http://autox.team.net/mailman/options/fot/1964spitfire@pacbell.net
_______________________________________________
fot@autox.team.net
http://www.fot-racing.com
Archive: http://www.team.net/archive
|