Reply to "New engine/low HP"

> But what about PI?

Ahh, you meant Pi :-) I forgot about that post and totally missed your
meaning. I saw PI and thought Pantera International and drew a deer in
the headlights blank stare :-)

> David's engine builder dyno'd the motor with both intakes, I don't have
> the figures before me, but the Yates intake made something like 40 bhp
> more above 5000 rpm. David did indeed elect to run the Yates intake.
> For every extra bhp the Yates intake made above 5000 rpm, the motor lost
> an equal amount below 5000 rpm.

Do you recall which Yates intake he used? Some don't work well out of
the box and need plenum work. I suspect they are designed that way to
permit custom work to allow them to be used on restrictor plate engines.
Also, a carb optimized for the Yates intake with annular boosters might
have been able to close the gap on the low end. Some of these tuner carbs
are pretty good these days but they have to be matched to the combo.
Sometimes the annular boosters help a bunch sometimes they hurt. It's a
completely differen type of carb but just to show the influence a carb can
have, I loaned a Strip Dominator to a buddy once to test a Predator (a.k.a.
Kendig) variable venturi carb once. With the variable venturi carb, the
big port Strip Dominator was better from idle on up than a much worked on
Offy Dual Port with spreadbore carb combo optimized for low and mid-range.
The Predator was able to meter fuel and low vacuum signals and overcame
the big open plenum of the Strip Dominator.

> I would have selected the Performer personally. You probably know that
> about me by now.

and I would have picked C302B heads with an IR intake :-)

> Good point Dan, I glossed right over the carb last night. I have witnessed
> the 750 Holley take motors into the 500 bhp range, and the HP series, which
> weren't around 20 years ago, will do even better. But I can't argue that you
> can probably bolt 40 bhp on by going to an 850 HP carb, especially on a 377
> stroker motor.

> On the street I would advise Art to run the smaller carb.

I'd rather him run a carb that flows 830+ CFM but meters as well or better
than a standard Holley 750. Proper attention to airflow can yield a carb
that flows more but atomizes better. A friend with a 372C, very similar
cam to the one Art is running (same specs but with XE lobes), and stuffed
4V heads with Parker Funnelweb just borrowed a Demon 750HP (I think he said
it flowed 815 or 830 CFM) and was amazed at how much better it was than his
750 Holley across the board. It was tuned on the dyno and I should be able
to get jets and power valve info should Art choose to go that route.

> Isn't Dennis A runnng a 750?

Dennis is running a tuner carb. I forget the exact specs but it flows quite
a more than 750. I don't have the numbers handy but it was in the range
where it needed to be.

> At this point, could I possibly gain 40 horses by switching to an 850?

I loaned my spare Blue Thunder to a Pantera owner in Kentucky (Jack Butler)
for a dyno test against an Offy 360and an Edelbrock Performer. The engine
was a 377 cube 351C stroker (0.600" solid lifter cam, 108 lobes, 6" rods,
offset ground crank, 10.5:1 compression, Willy's modified 950 HP carb, also
tested his old 650 Holley). Unfortunately, he ran all the tests with MPG
intake port plates, so I think that biases the intake manifold results but
not the carb results. The Offy 360 did very poorly, down 50 HP to the
Edelbrock. While the Offy isn't much of an intake, I think the port plates
hurt the Offy but helped the Performer which has smaller ports that match
more closely to the port plates. The Blue Thunder did best but the margin
between it and the Performer wasn't as large as expected, probably due
to the port plates. I loaned out my binders with the dyno sheets and Jack's
write-up but I believe the combo made a bit under 475 HP. Jack said the
Willy's modified 950 HP carb made a huge difference over the admittedly
undersized Holley 650 DP. IIRC, the carb change was equal to the difference
between the best and worst intakes (over 50 HP). You're starting with a
larger carb so I would think your results wouldn't be as dramatic but there's
power to be had.

> Here is one more little bit of info regarding my car: I think one of my four
> glass packs is bad based on the sound. I can see most of the way thru all the
> glass packs and I see no obvious obstructions. It seems like a long shot, but
> could this be the problem or part of it?

You need to get a look at Vizard's muffler tests. Even though you could
see straight through them, some of the glass packs were terrible when it
came to flow.

> Can any of you folks recommend some new mufflers that will flow well?

Walker flow rates their mufflers now using the Vizard suggested standard
pressure drop. Other manufacturers will tell you the pressure drop if
you call the tech line and ask. Look for Vizard's no loss exhaust article.
I'll see what I can dig up plus I'll ask a co-worker on his muffler dyno
test results. Due to competition, mufflers have come a long way in recent
years and the best ones can rival no muffler at all.

> Are there any to stay away from?

Quite a few, unfortunately. The other thing big cork in the exhaust is
likely your collectors. Most of the off-the-shelf Pantera headers lack
a meaningful collector and headers are much more sensitive to collectors
than primary pipe lengths. I bought my headers uncoated so I could
hack off the collector and put a proper one on.

Dan Jones