Well we finally got it done. Last week we replaced the old cracked
manifolds with new Thorley ceramic coated headers. What a difference!
When we bought the coach, the exhaust aft of the mufflers had to be
replaced. Since we expected to replace the manifolds one day, I had 3" pipe
installed from the mufflers rearward. SO, my comparison is with stock
manifolds, stock mufflers and 3" exhaust. The pickup is noticeable from
about 1500 RPM upwards. Where the coach used to accelerate with reasonable
speed before, it really gets moving now. The distance to 60MPH from a
standstill is about 20% less than the stock configuration with 3" exhaust.
I used Kroil and had no problem removing the old manifolds. Passenger side
manifold fell apart during the removal (along the middle of the manifold).
Now I need to drive it a few hundred miles and retorque.
There have been a few folks who were concerned about noise levels with
headers. Here's my tests:
Speed Before After
idle 72dB 60dB
45 MPH 85dB 63dB
60 MPH 94dB 71dB
The majority of the noise is wind noise that is coming from my front
windows. Tests were made with a Radio Shack SPL meter held at shoulder
height facing the front then sides of the cab area. Measurements are the
highest of the numbers. The before numbers are with the cracked manifold. I
think that I can get about 5dB out of the cab area just by eliminating the
wind noise - engine noise alone at 3000 RPM makes the cab sit at 64dB.
Henry
Henry Davis Consulting, Inc / new product consulting
PO Box 1270 / product readiness reviews
Soquel, Ca 95073 / IP reviews
ph: (831) 462-5199 / full service marketing
fax: (831) 462-5198
http://www.henry-davis.com
manifolds with new Thorley ceramic coated headers. What a difference!
When we bought the coach, the exhaust aft of the mufflers had to be
replaced. Since we expected to replace the manifolds one day, I had 3" pipe
installed from the mufflers rearward. SO, my comparison is with stock
manifolds, stock mufflers and 3" exhaust. The pickup is noticeable from
about 1500 RPM upwards. Where the coach used to accelerate with reasonable
speed before, it really gets moving now. The distance to 60MPH from a
standstill is about 20% less than the stock configuration with 3" exhaust.
I used Kroil and had no problem removing the old manifolds. Passenger side
manifold fell apart during the removal (along the middle of the manifold).
Now I need to drive it a few hundred miles and retorque.
There have been a few folks who were concerned about noise levels with
headers. Here's my tests:
Speed Before After
idle 72dB 60dB
45 MPH 85dB 63dB
60 MPH 94dB 71dB
The majority of the noise is wind noise that is coming from my front
windows. Tests were made with a Radio Shack SPL meter held at shoulder
height facing the front then sides of the cab area. Measurements are the
highest of the numbers. The before numbers are with the cracked manifold. I
think that I can get about 5dB out of the cab area just by eliminating the
wind noise - engine noise alone at 3000 RPM makes the cab sit at 64dB.
Henry
Henry Davis Consulting, Inc / new product consulting
PO Box 1270 / product readiness reviews
Soquel, Ca 95073 / IP reviews
ph: (831) 462-5199 / full service marketing
fax: (831) 462-5198
http://www.henry-davis.com
wner-gmcmotorhome]On Behalf Of Henry Davis
