Reply to "New engine/low HP"

quote:

Originally posted by Daniel_Jones:
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