Greetings folks,

I'm an occasional lurker on this list and need help/resources from the
community. I've been dealing with the fallout of a new engine installation
for the past year and I'm almost at my wits end. Last July 2013, the 455
motor in my GMC was making a loud 'pinging' noise on the way back from
Tahoe. Rather than drive it I got it towed back to Scotts Valley where my
mechanic at All RV in Scotts Valley determined that a crank bearing had
worn out and the piston skirt was impacting the crankshaft. It was time for
a new engine.

My first mistake was that I wanted the engine quickly for a planned trip to
Oregon at the end of August 2013. I called up Mondello Performance in Paso
Robles and Lynn Welfringer had smooth talked me into buying a really pricey
engine (Oldsmobile 455 V8) with promises of quick delivery, an easy install
and more horsepower. I'm sad to say other than the high price of the engine
Mondello didn't deliver on any of these promises. I missed that Oregon trip
and many others since then and getting this engine to run correctly has
turned into an endless sink of time and money. With every few thousand
dollars I put into it I seem to get a little closer to my goal of a smooth
running RV but it seems like a game of inches. I've done some short day
trips but I'm just so stressed at how good/bad it has been operating. I'm
at my wits end with this thing. Some days I just want to give it up but
when it runs great I genuinely love and enjoy this thing. I'm just hoping
that one day it's not going to consume so much time and money and I just
want to use it. Needless to say at this point I know a lot more about the
GMC motorhome and the internal combustion engine than I did a year ago.

I have used a number of vendors and shops in the Santa Cruz area and I know
who to trust and not to trust. Too many mechanics seem to use folklore and
address the symptoms rather than the root cause of a problem. I have been
given conflicting information from mechanics who have only a casual
understanding of mechanical problems. Once they are convinced that X is the
problem they tend to stop their observations. Also, many mechanics are
specialists and they tend to recommend products and services which are
their speciality. Many do not look at the part or problem in the context of
the entire system. Rare is the mechanic that takes a scientific or
engineering approach to a problem. Right now I'm working with a friend who
just started up his own shop in Scotts Valley and is an excellent and
detail oriented mechanic. He has an engineers mind and has been proven
correct in many cases. He also starts with the basics and takes a systemic
approach to auto mechanics. Finally, I feel I'm on a right path.

Yea, this introduction has been a little long winded but I've been holding
it in for so long. Rant over and done.

After experimenting with two different carbs (Rochester Q-jet and a Holley
4150), I finally got a Holley Terminator EFI system

installed and the engine has been running as good as it gets. The start up
(including cold start), idle and cruise from the EFI has been really,
really smooth. I'm really happy with it. My mechanic and I cleaned up a lot
of the wiring, getting rid of past mistakes, failed experiments and
rerouted the coolant lines. The engine compartment is a lot cleaner and
organized. Check it out:

http://www.gmcmhphotos.com/photos/member-galleries/p55534-holley-terminator-efi.html

My only challenge has been that there is no acceleration or power from a
stop or climbing steep grades. I've managed to hook up a laptop to the ECU
(engine control unit) and I read EFI data logs and set parameters. I've
been posting messages to the Holley forums and they have been really
helpful.

http://forums.holley.com/showthread.php?14795-Acceleration-is-sluggish-for-a-GMC-Motorhome

*My request: I'm probably looking for a Bay Area/NorCal Holley EFI tuner
who can help me tweak the fuel map. Also, looking for a recommendation of
an EFI expert who can understand the heavy loads of a GMC Motorhome.*

When these power and acceleration issues then the promise of this new
Mondello engine can be fulfilled and I'll rest a lot easier.

Thanks,

--Mark


73 'Glacier' 23' GMC Motorhome "Serenity"
Scotts Valley, CA
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