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Old 07-02-2007, 10:57 PM   #1
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345 questions

Just got back from a trip and have a few questions:

my 345 runs at about 3100 rpm at 65 mph with temp running about 210-215 on guage-should i run a lower temp thermostat?

the threads that i read state that installing new exhaust headers do not help(in fact a few comments about gas milage getting worse)so is the best option trying to get cleaner(colder)air flow into carb? any comments

my exhaust air fans have the crank up covers that do not seem to get up enough to get good air flow either stopped or going down the road. has anyone installed the max air vents and what did you do with the metal caps that crank up and down?

has anyone installed an indash dvd player with flip up screen that I could run a seperate feed to another wall mounted lcd panel so that both the flip up screen and wall mounted lcd tv would show the dvd? additionally the unit still has the original back up camera and dash mounted tv-has anyone replaced them with newer units and run it throught the dash mounted flip up dvd screen player(to get rid of the dash mounted tv)

i need to replace the alum skin section in the front above the windshield-is there a source for salvage alum skin sections? has a large dent around the spot light and the windshield rubber gasket has had sealant applied to stop what must have been a leak. replacing the section would allow for the windshield to be resealed etc.

i had the motor cowling(sp?) and the raised driver flooring section covered with sound damping material and then recarpeted/rubber sheet flooring installed and it works great. very happy with results
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Old 07-04-2007, 10:12 AM   #2
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mlmarch,
The motorhomes run close to that RPM at that speed. I strive for sub 3000 rmp at 55 - 60 mph. This has the added benefit of a reduction in mpg as well. The best thing you can do for operating temps and fuel efficiency is to go slightly slower. Reducing the RPM involved installing an overdrive unit like a GearVendors, etc. and chaning the rear gearing. Expensive and might not be worth the expense if you don't use the motorhome too much.

Regarding the headers, I've not seen any posts where mileage got worse. I replaced the stock manifolds and removed the AIR system and replaced with headers and a freeflow (2.5") exhaust with free flow mufflers and an H Pipe. I also replaced the ignition and rebuilt the stock carb. I get 8+ mpg consistantly towing my 71 Beetle and closer to 9 without the Beetle on the highway.

Operating temps on these engines are high. The P30 manual recommends 195 degrees for complete combustion and effeciency. Some of our motrohomes run hotter and this is typically a combination of issues but usually has to do with older cooling systems (blocked tubes in radiator, older water pump, malfunctioning fan clutch, higher temp thermostat, etc.).

I've had good luck doing a full radiator flush, replacing with a 50/50 antifreeze/distilled water mix and running something called "Watter Wetter" or "Tow Kool" wetting agent to reduce temps. I've also replaced my fan clutch (turns out it was never working when I bought it). We run about 190 - 200 on the highway now. Ultimately I'll need to replace my radiator.

The dash mounted screen sounds like a great idea. you'll have to make sure the "old school" video connections from the camera can be converted to a newer digital input. Many of these dash units can drive an external monitor so you'll have to pick one that meets your specific needs.

Replacing the front cap is a big one. Colaws Salvage in MO has units somtimes. You could also call Airstream about it.
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Old 07-05-2007, 08:33 AM   #3
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misc questions

Swebster

Sometimes it is hard to go slower-with all the traffic going by at 80mph.

I would like to get mine down to a temp range of 200 and below, when I get it in for oil change I will have the radiator flushed. I have not heard about the wetting agent and will look for it.

I did read a thread where someone put on a Banks header system and then took it back off due to milage issues. What were you referring to with the AIR system?.

I will track down Colaws-do you know what city they are in?
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Old 07-05-2007, 09:19 AM   #4
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misc 345 questions

I want to post an addtional question on the air vent covers-has anyone installed the max air vent covers and does it increase air flow thru them while driving? Do you remove the original flat covers that crank up or does the new vent cover induce a greater air draw thru them due to negative air presssure on the back side of the vents? Do they also help keep rain out when the vent is open, etc?
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Old 07-06-2007, 02:43 PM   #5
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MLM, good questions ... and so many.

My experience is that headers help. Mileage...heat dissipation and performance.

I don't have any experience with the flip ups but have a 7" double din stereo. Look for Aux. output and Video output in the specs. Also some of them now have built in reverse sensing so the camera does not have to do the mirror image work. Lots of bargains for $300 or less on eBay.

AIR was GM's attempt to blow cold air into the exhaust system at the manifolds.

Take a look at my photos for an air cleaner mod. Take the K&N filter approach forward and bring in more air to the carb.
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Old 07-10-2007, 12:02 PM   #6
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I have a dumb question about the model numbers of the Airstream classic mh's. Does the "34" in the "345" model designate the length of the mh?

What is the smallest and largest length classic mh made?
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Old 07-10-2007, 01:03 PM   #7
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345 = 34.5 feet long

the longest production Classic was a 370. Not many of them around

The shorest Classic was the 250. Not many of them around either
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Old 07-10-2007, 04:52 PM   #8
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Quote:
Originally Posted by David Alan
345 = 34.5 feet long

the longest production Classic was a 370. Not many of them around

The shorest Classic was the 250. Not many of them around either
When you get into the Argosy motorhomes, they made them as small as 20 feet.

WOW, a 20 foot motorhome with a Chevy 454 engine.

Almost does wheelies.

Andy
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Old 07-11-2007, 08:42 AM   #9
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Quote:
Originally Posted by mlmarch
Swebster

Sometimes it is hard to go slower-with all the traffic going by at 80mph.

I would like to get mine down to a temp range of 200 and below, when I get it in for oil change I will have the radiator flushed. I have not heard about the wetting agent and will look for it.

I did read a thread where someone put on a Banks header system and then took it back off due to milage issues. What were you referring to with the AIR system?.

I will track down Colaws-do you know what city they are in?
As Glen pointed out the AIR system is a GM emissions control which pumps fresh air into the exhaust ports (through the manifold) to re-combust exhaust gases as they exist the head.

I know what you mean about highway speeds, but we maintain 65 only through major metro areas like the NJ Turnpike or I 95 in NY/CT/MA. Everywhere else it's typically 60. It had a bigger impact on mileage than any performance improvements/tuning I've done.

Can't imagine headers would decrease mileage (Banks or otherwise) but wihtout knowing the details it's hard to imagine. Again, mine with a stock 454, stock QJet Carb, stock ignition (high temp wires), Champion plugs and headers gets pretty good mileage even when towing.

Colaws RV Salvage is located in Carthage Mo. - COLAW RV PARTS & SALVAGE | WE HAVE YOUR PART!
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Old 07-11-2007, 05:42 PM   #10
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Tune up

I have read forum topics about increasing milage and performance and it seems that most often, after all the headers , carburators, etc - etc the result is very little improvement.

I suggest that maintaning your 454 is probally the most important thing you can do to enjoy reasonalbe mileage. The ignition on these engines is very important and the routing of the plug wires is really close to the exhaust manifolds resulting in rapid deterioration. Installation of heat shields is a big +.
Cold air induction is cheap and also a big plus. Synthedic oil really is worth the expence.

These big ol engines run well at 3000 RPM but having said that, if you drive a lot, a overdrive like gear vendors might be a good investment. Slowing down to around 2800 RPM will get you close to the same (not as macho).

These older engines are prone to exhaust leaks at the exhaust manifolds and if you expereance this problem, steel gaskets ('96 - '97 J type) hold up real well. You might have to drill out the gasket bolt holes for a proper fit.

Good luck - These 454's are really great engines. If you need to do a major overhaul, consider balancing the componets
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Old 09-27-2007, 09:09 PM   #11
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Running hot, couple of suggestions.

I've had a 345 P30 454 in Texas for 15 years and have gone through several cooling fix solutions. The first approach was electric fans in front of radiator stack, not much help. Put up an air dam to stop air flow over radiator support and force air through radiator stack. Multiple thermostats, Headers, body vents ... you name it I tried it. What really hurt was coming into a city after a long hwy run (I also concur with the 3,000 rpm 60 mph comments, natural settings for these machines and I consistently achieve 9+ mpg) when the speed would slow the engine would hot-soak in the 100 deree temp. My final solution was to go to a larger diameter flex fan and remove the fan clutch all together. That worked well, temps stayed low however it sounded like a P51 mustang going down the highway and was unbearable inside. So I compromised and went back to the stock fan, but added an extreme duty Tow Truck fan clutch. The fan now runs more often, at lower temperatures and makes more noise than optimal, but I can pull a house in 100 degrees and not suffer the elevated engine temps any longer.

Hope it helps,

TXraz
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Old 09-29-2007, 10:51 AM   #12
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I tried the 160 degree thermostat trick before our last trip and was surprised to report that the engine ran at 195 the whole way. It would tip 200 on a hill but none of the 210 + on level highways.

I really can't figure out how this works...why would a lower open temp effect running temps? Perhaps just replacing the therm helps?
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Old 09-29-2007, 11:11 AM   #13
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Sometimes the thermostat is not real close to the temp sending unit.
That can make engine temp alot different than the thermo setting.

A tip if you do replace thermo...
Drill a 1/4" or less hole in the flat part of flange,
This will help you fill it up faster by letting the air out.
Plus + it keeps a little water flowing if it ever sticks, and gives you more time to get off the road.
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Old 09-29-2007, 03:05 PM   #14
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Quote:
Originally Posted by swebster
I tried the 160 degree thermostat trick before our last trip and was surprised to report that the engine ran at 195 the whole way. It would tip 200 on a hill but none of the 210 + on level highways.

I really can't figure out how this works...why would a lower open temp effect running temps? Perhaps just replacing the therm helps?

running too cool of a thermostat can sometimes make the engine run hotter. the wide open thermostat less the water go through the radiator faster than the water can dissipate the heat.
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