Re: [AMC-List] Continuing Saga of Doc the Jeep, Part II.5

[Nick Lenarz <n9viw@xxxxxxxxx>]

> Here's a little something to put in your pipe: Altering the cam
> advanced also mods the power band (as in where it starts/stops in the

> RPM band) I used the 3 key set in my '66 Fairlane's 289 and couldn't 
> get any top end RPM. It had brutal power to 1700 RPM then fell
flat...
> It also pinged like a banshee! Retarded the cam and voilà! no more 
> probs!

That's what I'm hoping to experience with mine. I pulled the front end
of the Jeep last night, and got the timing set out. Sure enough, it was
set to the advanced position, and a review of the documentation that
came with the timing set showed me that it imparted an extra FOUR
degrees of advance, not three! Oy.
When I reset the crank gear and reinstalled the set, it didn't seem to
move either crank or cam in the least, so I wondered if I did it wrong.
I spent half an hour looking at the timing set in relation to the cam,
trying to figure out how such a small change could make such a huge
difference in running. I finally figured it's just that 4* is minuscule
in physical reality, but valve timing is so precise it doesn't take
much to throw it off.

> btw this cam is pretty radical compared to older amc six cams.  the
> '76-80 2bbl and '81-'90 cams are in the upper 250s, 257 and 259 deg
> iirc.  my '66 cam is 244 and i have a book that lists that as stock
> replacement for all '64-'79 except the late '70s 2bbl.  when i went
> to build a hot 232 up in the early '80s, the most radical hydraulic 
> cam i could find was 278 deg.
> the '87-'98 4.0 cam is 280.  in '99 they reduced exhaust duration to
> the 260s.

Andrew, I would be interested in seeing this book, or at least an
excerpt thereof. The Comp Cams cam I have lists its duration as 252
deg. If the stock cam had MORE duration, why would they advertise this
cam as having increased torque and power from the stock unit? It also
makes me wonder what the profile of the stock 4.2 cam used in '82 was,
and whether I would have been better off to have kept it and simply
degreed it myself rather than buying a new cam when I rebuilt the
engine?

I should be able to get back to the engine on Wednesday night, and if
all goes well, I will have it started before too long... I will post my
results afterward.



 
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