Mufflers and exhaust

[Steven Holekamp <holekamp@xxxxxxx>]

there is a pretty good resource on the web with pretty clear guidelines
http://www.dynomax.com/techsupport.stm

I belive their mufflers are listed for what HP they should cover but it 
does not say that directly, take a look at
http://www.dynomax.com/documents/super_turbo_specs.pdf
for each muffler there are 2 numbers like
sport - 260, 260 is the flow
"73/146" I belive these are HP ratings for single and dual exhaust

I had dynomax 2 1/2 turbos(sold by napa) in the 80's that broke like 
describe in another post, they were lifetime guarantee so i got new ones 
they broke too, my third set was a slightly different design and they were 
still good after 15 yrs

When I built a 401 las year it ran 13.10 through the 2 1/2 inch exhaust and 
uncorking the headers it ran 12.70. Based on the chart in the link above I 
went with  3 in dual exhaust all the way back and over the rear end  and 
full 3 in dynomax turbos pn 17793, i have not been to the track to see if 
it helped(I have been but had other problems) will be going next month to 
see if it helped.

I went with dynomax  because they had good info and I like info. Lots of 
good mufflers out there. These turbos are pretty quiet at hwy speed but 
have a resonant spot at about 2000rpm that is kind of annoying. I ran them 
with and without tailpipes, the tailpipes helped the resonant spot a bunch 
but did not change how the car sounded much, it did not get much quieter. I 
have heard that the straight thru designs with glass(ultraflow) don't do 
that resonate thing but have that love it or hate it glasspack sound when 
you back out of it. dynomax tech support recommended the ultraflows for my 
application for maximum performance but i am in the hate it camp for the 
glasspack sound so I went the other way

FWIW this is in  motor with 244 @0.050 cam, little cams are not as 
sensitive to backpressure and muffler choice is not as critical

I think there is some positive tradeoff on  street car with smaller pipe, 
bigger pipe increases heat transfer rate due to the surface area as well as 
the reduced velocity, so bigger pipe may lead to higher temp under hood, in 
the car and around fuel lines, tank and pump which can make you 
uncomfortable and potentially hurt performance(especially if you are 
getting all the flow you need out of the little pipe) .

Holekamp