Jeff M., I had to delay your road test, an issue was uncovered on another coach that we had to work and the rest of you guy, take this to heart. If you have not addressed this, YOU are in harms way!
So a couple came in with a real problem with their coach.
The owner is doing his best to being a good steward…..has updated key features to include a FiTech fuel injection system, aluminum fuel tank, brakes, bearings, etc.
The FI system was installed by a non GMC shop who while a quality shop had no knowledge of this so please follow me:
GM was please to announce in 1973 the GMC Motorhome was engineered for a 15 year life span…….what is it now 45 years? Everything has this viable lifespan and we are wayyyyyyy past our design parameters.
After 45 years of extreme heat cycles pulling 12,000 pounds, because of the concave intake manifold design to accommodate a flat floor, the intake is overheated across the middle of the intake. This differential heat across the middle of the intake causes this crack to form in the secondary port….it looks like this if you pull up your carb and look.
and a view from the other side
lliterally every carb we pull up we see this. What the motor heats up and the metal expands, this crack will allow exhaust gasses to contaminate your fuel ports…..the motor will have very low vacuum, the motor may start and idle but will quickly fall on its face going into gear or accelerating.
This intake is damaged and will leave you on the road! The FiTech fuel injection system was not performing well. Mileage went from 8 to 4mpg! A carb would have simple shuT down but the active FI system adjusted its ass off and made the motor keep running……bad mileage but it drove to the Keys and back getting horrible mileage.
EVERY 455 and 403 intake has this after 45 years and brother you MUST pay attention on this.
The owner had thought the FiTech system was Crap, had gone thru them shooting problems….O2 sensor……etc. Truly the problem was this crack!
What should you do? Don’t run out and buy a new intake, any aftermarket intake will need a doghouse ( your flat floor will be gone. Pull up your intake NOW! Take it to a machine shop, have it cleaned and magnafluxed. If this is the only crack on the original cast iron intake, reinstall it with a Mr.Gasket fiber intake gasket set, remove the “turkey tray” and install stainless steel block off plates to stop the exhaust from entering the intake from the heads. Your problem will be repaired and this problem will be fixed. We have 100% success doing this. You really must do this.
We had to postpone the road test to dig in fast and fix this coach, the folks were on the road traveling. We needed to stop and get them back out. There is no option to this condition. Fix this on your time….not like this on vacation! You will be much safer! Don’t do this and like I said, you are risking your trip. Nuff Said?
Guys seriously, if you have now read this and choose to do nothing, you have just wasted 30 minutes of my time……don’t call me if your motor starts running crappy and all your mechanic friends are scratching their collective heads…….. Please help them and yourself. Ok, I’ve done what I can for you. Its not illegal to be stupid but don’t waste my time with your stupidity! Sound rude hey? I’m serious as the heart attack I had this year….listen to me!
Outs time, see ya tomorrow…..
all fixed now………
