Cams timing and all that

[Bernie Jacobsen]

Fredric,

Are you a "rock crawler"?   I am VERY interested in low RPM performance.   I
am considering a low stall speed converter. What sources have you found?

Reply off list since this is pretty far off topic,

^Bernie

-----Original Message-----
From: Fitzgearld, Fredric <fredric.fitzgearld at intel.com>
To: 'Fuel Injection List' <diy_efi at efi332.eng.ohio-state.edu>; Robert
Humphris <r.humphris at indigo-avs.com>
Date: Friday, March 27, 1998 1:19 PM
Subject: RE: Cams timing and all that


>WOW, I think I can actually contribute something, here.
>
>It is true that advancing the cam will give you more "Grunt".  It's a
>common thing to do for those of us that are "Rock Crawlers".  The whole
>power/torque band of the engine moves down the RPM range.  And that's
>fine for us because we rarely see anything over 4500-5000 RPM.
>
>Now, we get to the argument: how much is too much?  I personally have
>run some cams as much as 8 deg advanced.  Generally, 4 deg is the agreed
>maximum.  But then again, it depends on the cam, and the application.
>
>I haven't had that much experience with boosting, but I suspect that you
>will have a big problem getting any usable torque from off idle to about
>1500-2000 rpm.  Then again, you may not care about that range.  If you
>have a torque converter with a stall for 2K you'll never see that range,
>anyway.
>
>But then again, What do you want to do with the vehicle???  If it will
>see a lot of street use, you may want to reconsider building the engine
>for the 5K-7K RPM range.  If your hiway RPM is about 2700-3200 RPM, and
>you have a 2000-2500 stall, the tranny will be slipping the whole time
>you're on the hiway.
>
>One other thing, Some of ht after-market, stockish, timing sets have
>built it cam timing that has been retarded for emissions.  To really set
>the cam timing you will need to find TRUE TDC and use an index wheel.
>But then you probably knew that.
>
>With what I know about boosting, which is not too much, I would get the
>engine set up to run in the RPM I want, then try to add more boost to
>the lower RPM range to cover the "void".  Then again, it all depends on
>what the engine is used for.
>
>Then again, Maybe I can't help at all.   :)
>
>FEF
>___________________ Reply Separator _________________________________
>Subject: Cams timing and all that
>Author:  Robert Humphris [SMTP:r.humphris at indigo-avs.com]  at MSXGATE
>Date:    3/27/98 6:37 AM
>
>
>Some while back someone wrote that advancing cam timing improved low end
>response.
>
>Now I know that this will result in loss at high end, probably peak
>torque will move down the rev range please could someone confirm this?
>
>The crux of the matter is this:  I am gonna run my engine at 7.5:1 as I
>want to run silly ammounts of boost.  To help eliminate lag, I was
>thinking of running a whole load of ignition advance, and advancing the
>cam to give me a tractable ammount of low end off boost.  No I know that
>a gain in one area comes with a fall in another... so what pit fall am I
>going to get here?
>Is the engine going to get upset with the cam timing and refuse to rev
>above a certain level? or is there something I just cannot see yet?
>
>
>Rob Humphris
>