I'm trying to treat the source of the noise at the moment (but haven't had time due to moving house)
I reckon some tweaks to the exhaust system might fix it.

_________________
1972 Datsun 1600, S14 SR20DET Engineered (204rwkW @ 17psi.)
viewtopic.php?t=6579
#SR20Datsun @SR20Datsun

Some reading:

http://www.sounddeadenershowdown.com/cgi-bin/index.cgi

_________________
My project: Datsun 510 w/ FJ20ET
100% Certified Datnut

Yeah the datsport stuff is realy good, wouldn't bother with anything else its not worth it, got to remember your in an old DATO, noise is half the fun!

_________________
DVSDAT VIC PLATES FOR SALE IF ANYONE'S INTERESTED

street machine mag feb 2011 issue. good article in there. it sold me, im getting sum.

_________________
1600 with FJ20 & Simmons. something different.

I've been through all this before and home made speaker building / audio is another hobby of mine.

Its all about creating 'dead' panels or 'non-resonant' panels.

The Dynamat type products are a complete rip off. They are all just a bituminous based (like tar) type of material with adhesive backing. If you want to save HEAPS of $ then go to an automotive paint supplier and buy their car deadening sheets (fraction of the price of dynamat).
The sound deadening principle here is adding weight to the panels, changing their resonances. The down side of this is extra weight.

Baz can explain a good method of applying his stuff (which i've used extensively in a 1600 before (inside roof, doors...etc and can recommend). The main advantage is that it is very very light weight and easy to shape/cut. Ideal for those tricky areas such as inside doors.

It is important to make sure any sound deadening materials are glued to a clean panel and then all edges are sealed to the panel to prevent any water from entering, sitting and causing rust.

Further noise reduction may be achieved my checking your rubber seals are doing their job and or adding extra seals. To go even further, dacron/acoustic foam/convoluted type foam mattress pillow tops/offcuts from clark rubber may be used as 'bass traps' to absorb lower sound frequencies.

http://www.carbuilders.com.au/

I've had a few mates use this stuff and found it awesome!!! They deliver all over OZ too!