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 7/9/2010 5:23 PM
 

My wife and Kids moved from Ft. Lauderdale to Park City UT using a 1985 Executive RV 35' with a chevy 454 engine with 49K miles. We had the cam replaced in Florida with an RV cam, Edelbrock 750cfm 4bb carb, new 6 core radiator, new fan clutch, and replaced all the vacuum lines. From Florida to TX we were running around 210 at speed of 60, but then as we entered the hill country the RV started to jump up to 220 to 230, and really bog down on the run up the hills. We also started to hear "popping"from the carb as the altitude increased. We had to drop the RV in Denver at a reputable shop, they tried to get the RV to run well but it is still running very hot and has trouble going up hills. We never would have made it here. Has anyone had such a problem with theirs? We are running out of ideas and the wallet is getting empty fast.

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 7/9/2010 10:26 PM
 

I'll take a stab at this. The back firing through the carburetor is more than likely bad plug wires. Those old motorhomes were notorious for burning up plug wires. When they short out across each other it creates a premature fire in one or more of the cylinders, if that cylinders intake valve happens to be on the intake stroke and the plug fires it backfires back through the carb. As for the lack of hill climbing power, you're driving a big block which wasn't designed for all the weight a motor home weighs plus more than likely all your belongings stuffed in there. If you're climbing steep inclines at anything over 20 mph you're doing great, and I'm not kidding. Fuel mileage will follow suit, you'll be getting about 4 mpg while climbing and probably about 7 on a relatively level road. The overheating quite possibly is either the thermostat or the water pump trying to go out, more than likely the thermostat. You can always put a lower temperature thermostat in that older asperated system, I'm thinking we used a 185 degree or lower, it's been several years since I had to deal with your current problems.

Good Luck


Neil
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 7/10/2010 2:22 AM
 
 Modified By RVA  on 7/10/2010 1:23:08 AM

I'll echo Neil's comments regarding the spark plug wires. If they aren't new, change them. They're notorious for causing a lot of grief to a lot of 454 RVers. Good luck. - Dave

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 7/11/2010 11:20 AM
 

I feel your pain! Our '91 Allegro Bay had the same engine. We spent hundreds of dollars trying to fix, to no avail. New spark plug wires were a big help, but even after adjustments to the manifold, etc. (over 10 thousand in repairs the first year), it always heated up in the Hill Country, Davis Mtns. or even on a high overpass in town. Glad to be rid of it. Now pull a 5ver with diesel truck - much improved was to go. Good luck!!!!

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 7/12/2010 6:17 PM
 

As previously stated, spark plug wires will most likely help. Another thing to check is timing. Considering the symptoms the ignition timing sounds a bit too advanced. Did you have the distributor re-curved when you did the new cam? When going to a higher performance camshaft it is best to re-curve the advance on the distributor to match the newer cam. Another possibility is the need to change jets in the carburetor. It could be running a bit lean. Exhaust may me a little too constrictive causing the engine to get too warm too.

I have to disagree a bit with Neil in that a 454 should be able to achieve something substantially better than 20 mph on a steep uphill grade. While mine is a Ford 460, they are both big blocks and not that much different and I can easily maintain over 40 mph and if the road permits and usually 50-55 mph up a 6% grade. That's with my pickup towing my 32' fifth wheel. I'm not saying I can compete with a modern diesel but I will say they can be made into competent tow engines, though it requires some alterations.

Just my $.02. Good luck!

Ron

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 8/6/2010 9:44 PM
 

I can sympathize with you. I also have a chevy 454 1994 Fourwinds class A with just under 50,000 miles. Three weeks ago I drove it to NJ, took 10 to 65 to 85 to 95 so that I didn't hit any steep mountains. Just north of Atlanta we ran in to some low mountains and the engine temp rose a bit and the engine seemed to struggle but I slowed down knowing this was going to happen. Coming back we got off 95 too soon and ended up going through the carolina mountains. Granted the hills weren't overly steep, but I also had the popping sound a few times and my engine service light came on. After the engine cooled down it never came on again and when we hit fewer inclines things went back to normal. I rarely take such a long trip and don't usually encounter many hills in my part of Texas so I am not looking to upgrade in the near future, but I will say if in the future I decide to do more traveling long distances I will have to upgrad to a diesel and newer model.

Gotta love those old RV's though

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 8/8/2010 5:09 PM
 

I pulled a 37 foot fiver with a 460 and had no problem maintaining 50 -55mph. When iI hit the bottom of a steep grade I just downshift into 2nd to keep the rpm's up. If you let the transmission shift on it's own it will bog down. Most of the time if the temp goes up it is because the tranny is overheating, by downshifting you run more fluid thru and it runs cooler.


Gary; garyjanc@hughes.net
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 8/8/2010 8:32 PM
 
 Modified By RVA  on 8/8/2010 7:36:15 PM

Gary - I think one reason Ford owners may have less problems with overheating is because the Ford F53 (460) chassis includes a tachometer and I don't think the Chevy P30 (454) does. I learned to drive my Ford chassis using the tach instead of the speedo, and quickly learned to keep the RPMs above 3000 on hills. This not only helps the tranny, but also enables the engine to run cooler. As you point out, when it comes to hills, manual shifting is preferable to depending on the tranny to make the right decision. There are after-market tachs available for the Chevy, which would probably be a good investment. Good luck. - Dave

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 8/9/2010 10:23 AM
 

Dave,

Even with Diesel's RPM's are important. They have a lot more torc but they have to be in the right RPM range to be effective. If you lug a diesel meaning the RPM's are too low for the grade you can watch the temperature rise.

The only time I have heated the motor after I had experience was climbing a couple of grades in Death Valley. It was 10:00 in the morning and 130 degrees. Everytime I would try the climb I would only get two miles and the temperature would rise to 200 degrees. I would just pull off to the side, put the rig in neutral and rev the motor. The temperature went down immediately.

We pulled the entire Teton Pass, out of Jackson Hole, 12 miles at 12% grade and never did heat. I was pulling at 2200 RPM's which is right for our 300 cummins.


Big Bad John & Runaround Sue & Paris *Hammock,Florida* *97 Dutch Star Diesel* *76 VW Bay Window Bus* *91 Classic Harley Davidson* *1949 Ford Lead Sled* *2012 HD LSV
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 10/28/2010 10:09 PM
 

Check out the fan clutch. I had a 1988 Travelmaster that was driving me nuts overheating on hills until I pulled the engine cover and discovered the fan was barely running. The fans disengage when running on flat ground but are suppose to reengage when under load. It will look great when idling cold.

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