RE: 10548 cams

[Robert_A_Brady@xxxxxxxxxxxx (Robert A Brady)]

Dana wrote:

"My experience has been that the "48" cams do provide a subjectively
substantial increase in performance, with the greatest gains occurring
between 3000 and 5000 RPM.  To get the maximum benefit from the cams,
however, it is not only necessary to time them correctly, but to  increase
fuel flow at higher RPM to take advantage of the improvements in breathing.
 Changing the idle mixture won't necessarily do the job.  On early SPICA
cars, moving the ambient temperature-adjusting lever on the FI pump from N
to F helps some and doesn't cost a penny.  The best solution, however, is a
high-performance SPICA pump calibrated to your cams."

I will certainly admit that I haven't gotten everything dialed in yet.  The 
cams are now at 99.5 degrees (or as close to that as I could get them with 
the AR Ricambi cam timing kit).  There's no question that the car is now 
faster from 3k - 5k rpms in 4th gear (one of my benchmarks used in lieu of a 
dyno at home :)).  However, since installing the cams and benchmarking them, 
I also: installed a "new" engine (used but I replaced rings and seals), 
installed a new front exhaust (stock style, replacing the previous stock 
style one... so I don't expect any changes from that), and replaced the 
wheels/tires with 195-65-14s (I had 185-60-14s) which are a bit larger in 
diameter than the other ones.  So, with all those confounding changes, I 
still managed a couple of tenths off the 3-5k/4th gear time (typically in the 
7 sec. range).  I'm sure there's more room for improvement.  I just need 
tinker time.  So, I'm convinced that they add performance, I just expected 
more.

That said, after my first true romp with it yesterday, I can say that it 
seems to enjoy the 5-6.5k rpm range more than in the past.  The 10520 cams 
seemed to peak around 5.5k.  These pull hardest from 5-7k. Again, an 
improvement.

I've tried fiddling with the temperature compensation settings.  In the past, 
I've found little measureable difference in them.  I'll try again with these 
cams.

The SPICA pump is stock.  One of these days I'll get around to getting an 
Ingram pump, but there are other priorities right now.

Ignition is marelliplex.  I agree with Dana, electronic ignition is a great 
improvement over points.

I'll have to swap the wheels/tires again to eliminate that variable from the 
mix.  I'll also have to do a compression check on the "new" engine to compare 
it with the previous one.  

I'll continue to tinker.....

Bob Brady, DVAROC
Yardley, PA

PS.  One noteworthy source suggested I time the cams at 102 degrees.  Can 
anyone offer their experiences with optimum timing for these cams?

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