Adding Headers and etc.

[charles w aulgur]

Jim, What kind of exhaust system did they have on the engine that you
referred to in addition to the stock manifolds and headers? Have them
run a test on a stock 455 with stock manifolds and a stock 26' GMC
exhaust system. Then have them run the same test with Thorley headers
and the Jardine 3' exhaust system and you will see much more than a 5 %
increase. We have a 30-mile long 6% grade going east out of San Diego.
When I had the stock exhaust system on or 76 Royale I could just maintain
45 MPR in second gear going up this grade. After I put on Thorley
headers and the low resistance mufflers and 3" exhaust that I purchased
from Jardine, I now go up this same hill in high gear and never drop
below 60 MPR. I can now tow by 2400- pound Tracker up this same hill
faster then I could go not towing anything with the stock exhaust system.
That's a lot more then 5% increase, plus my gas mileage went from 9.6 to
10.6 MPG; both measured over two similar 10,000 mile trips. I have over
50,00 miles on my headers and I havn't had a single problem with gaskets,
or any other items related to headers.

I have four redundant temperature measuring switches mount to the
underside of the frame around the engine access door. They are connected
to red lights on my dash. Two are set to come on at 170 degreed F, and
two are set to come one at 190 degrees F. None of them have come on
while I have been driving in the seven years they have been on our GMC.
They have been calibrated several times so I know they are working
correctly. I have them there to give me some warring if I have a fire in
the engine compartment.

I was apprehensive before I put on the headers, as I had heard a lot of
negative comments similar to what you stated, however, I never
experienced any of them. My engine compartment did not run any hotter
and it did not make any more noise in the driving compartment. They were
the best "bang" for the "buck" as any modifications I have done to our
GMC.

Jim, don't believe all the negative things you hear about headers. I
have noticed most of it comes from people who have never had headers on
their GMCs. Try them-you will like them.

Chuck Aulgur
San Diego, CA

 

[darren paget]

Just to be argumentative here and take the other side. I wonder what the
result would have been had you changed the exhaust system but not the
headers. I think most people that have headers changed the exhaust system at
the same time. Is there any one who has changed only the headers and kept the
OEM system? Maybe the headers alone do not make much of a difference but,
rather, the entire system does. Maybe the system without the headers is not
that much different if you change to the 3" pipe and non-restrictive muffler.
Just pondering. Darren

> Jim, What kind of exhaust system did they have on the engine that you
> referred to in addition to the stock manifolds and headers? Have them
> run a test on a stock 455 with stock manifolds and a stock 26' GMC
> exhaust system. Then have them run the same test with Thorley headers
> and the Jardine 3' exhaust system and you will see much more than a 5 %
> increase. We have a 30-mile long 6% grade going east out of San Diego.
> When I had the stock exhaust system on or 76 Royale I could just maintain
> 45 MPR in second gear going up this grade. After I put on Thorley
> headers and the low resistance mufflers and 3" exhaust that I purchased
> from Jardine,

- --
Darren Paget
76 Experimental
Another Fab Day
http://www.TZEplus.com

 

[bob mclaughlin]

Darren,
I changed to headers about 4 years ago and kept the original mufflers and
2.5" tail pipe because they were in good shape. I only put them on in an
attempt to stop the recurring manifold leaks. I felt there was a little
better performance. About a month ago I put in straight through mufflers
and 3" tail pipe because the old pipes rusted away. Again, I think it
improved some. I have no before and after engineering data and without
that, my feelings may only be occurring because I spent the money and want
it to be better. Jim Anstett gives me a 5% improvement and I'll happily
settle for that. I did it more as normal maintenance than for performance
improvement.
Bob McLaughlin

- -----Original Message-----
From: owner-gmcmotorhome
[mailtowner-gmcmotorhome]On Behalf Of Darren Paget
Sent: Monday, May 29, 2000 11:20 PM
To: gmcmotorhome
Subject: Re: GMC: Adding Headers and etc.

Just to be argumentative here and take the other side. I wonder what the
result would have been had you changed the exhaust system but not the
headers. I think most people that have headers changed the exhaust system
at
the same time. Is there any one who has changed only the headers and kept
the
OEM system? Maybe the headers alone do not make much of a difference but,
rather, the entire system does. Maybe the system without the headers is not
that much different if you change to the 3" pipe and non-restrictive
muffler.
Just pondering. Darren

 

[henry davis]

>Just to be argumentative here and take the other side. I wonder what the
>result would have been had you changed the exhaust system but not the
>headers. I think most people that have headers changed the exhaust system at
>the same time. Is there any one who has changed only the headers and kept the
>OEM system? Maybe the headers alone do not make much of a difference but,
>rather, the entire system does. Maybe the system without the headers is not
>that much different if you change to the 3" pipe and non-restrictive muffler.

Darren,

I originally changed to a 3" exhaust on the Palm Beach (455) but kept the
OEM headers and muffler since the muffler was brand new and the budget was
gone by then. The improvement was noticeable but not great. I recently
replaced the muffler with a 3" performance muffler and also replaced the
cracked manifolds with Thorely headers. THe 3" exhaust gave me somewhere
around a 5MPH advantage going over hiway 17 at the summit area as compared
to the OEM configuration. The header/muffler combination means that I could
easily exceed the speed limit if I wanted to now (at least another 10MPH).

Henry