1 2
Indy "Nub" Guy
Indy "Nub" Guy PowerDork
5/3/21 10:03 a.m.

I need to prep for a 4,500 mile trip with a newly acquired Winnebago Motorhome.  It's sitting on a Chevy P30 Chassis (titled as 1995, but might be a 1994 model) with a Throttle Body Injected (TBI) 454 engine.

My plan is to change the oil and transmission fluid, and install new accessory Belts.

We'll be driving in some higher altitudes (~10,000 feet) than we have here in Indiana (500 feet).  What can I do to prep for maximum power up there?

Anything specific about these that I should pay attention to?  What else should I do in preparation? 

wae UberDork
5/3/21 10:45 a.m.

That engine sits in a bit of an inverted bucket when it's in a motorhome so the heat tends to get to things over the years.  I found that all my vacuum lines were pretty crumbly so it's worth changing them out while you're doing the belts.  There aren't that many, but a couple of them are long runs to the front.

The coolant temp sender for the dash is located on the side, right between a couple of the logs on the exhaust manifold.  Not sure why that's a good idea, but that cooked mine at one point so I replaced it - you might want to check and make sure nothing's melted and the wiring isn't likely to rest up against the manifold.

You've already found out how the exhaust likes to leak.

The one and only time that an oil filter gasket stuck to the engine for me was on my 454-equipped P30 motorhome.  While it is pretty exciting to look out the side mirror and see orange flames and black smoke, I don't really recommend it.

Yours may not be as bad as mine, but my oil fill tube is freaking impossible to get to without dumping oil everywhere.  If I have the doghouse off anyway, I pull the tube off the valve cover and fill the engine directly.  Most of the time, though, I use one of the cheap HF "fluid transfer pumps" to pump in the fresh oil.  I've tried all manner of different funnels including the ones with hoses on them and I have not found a single one that actually worked.

I have heard stories of fuel pumps failing which requires the tank to be dropped.  In an emergency, I'm told that the generator's fuel pickup can be used with an external pump.

Something chassis related:  Front camber is a function of load on the suspension.  I made the mistake of cranking my front airbags up which made the ride so much smoother, but it also created massive amounts of negative camber.  One trip to Florida and back later (or maybe it was Gulf Shores, I don't remember) I managed to completely destroy a pair of tires which upset my "buy a tire every year" refresh plan a bit.  I can't remember what I have them down to right now but I think it's just a few psi above the minimum pressure from Firestone.   And speaking of pressures, the ones listed on your VIN plate are useless.  You should find the chart from the tire manufacturer and set your pressures based on the axle weight.  Or at least take a guess at what the axle weight might be.

Also on the chassis, they made a half-dozen different versions of these stupid things so finding parts can be a pain.  So far, it seems like "gm parts giant" does a good job of matching my VIN to the actual parts and then I can use that P/N to search rock auto or FLAPS for the correct part.  So far, the only thing that I've found that is hard to find and/or expensive is a bit of my steering linkage.  Otherwise, the parts are easy to find pretty much everywhere and not tremendously expensive.  I'm putting new pads, rotors, calipers, and hoses on my front brakes for under $300 in parts.

If you're still running the 8R19.5 tires, those are getting harder to find.  I'm in the process of going to a 225/70R19.5.  I'm going to cycle them in two at a time - the first two went on the front, I'll get two more towards the end of the year and put all four of the metrics on the back, and then next year I'll do two more to replace the fronts.

I've had really good luck with Good Sam's roadside assistance in both the motorhome and in my regular cars.  The only downside is that their towing service is to the closest shop that can work on the vehicle.  If you want it to go anywhere else, you've got to pay the overage.  That said, when my Excursion blew a tire on the highway - and I discovered that my spare had a cut in it - one call to them and they found a shop that would sell me four new tires at a reasonable price and get them installed that day and then had me towed there.  The only reason I sat on the side of the road for two hours was that I didn't discover that I needed a tow truck and not a tire changing guy until the TCG showed up and I realized that I did not, in fact, have a spare tire for him.  Best roadside service I've ever had, overall.

Greasing the front wheel bearings doesn't take a lot of time and is probably a good idea.

Double-check the inside tires in the rear for date codes and cracking.  When I was shopping I found a surprising number of instances where the outer tires were brand new and looking great while the inside ones were dangerously old.

Back to the motor.....  They also respond pretty well to new plugs, wires, distributor cap, and rotor.  All the heat that builds up under the doghouse doesn't do any of the ignition components any favors.  If you've got the Banks Power Pack installed, you'll have a K&N filter, so clean that up and give it some fresh oil.  Check the "ram-air" system, it likes to come loose.  I don't know that it really gives you all that much, but every little bit will help I suppose!

Indy "Nub" Guy
Indy "Nub" Guy PowerDork
5/3/21 11:09 a.m.

In reply to wae :

Thanks for all the tips and tricks.  I'm not sure what the "Banks Power Pack" is, but it does just have a round paper style filter element.  What brand of cap and rotor should I go with?  Should I just go ahead and throw a new coil at it too? 

Do these TBI's have a sensor that measures air density to correct for altitude changes?


gearheadE30 Dork
5/3/21 11:22 a.m.

In reply to Indy "Nub" Guy :

AC Delco parts for the ignition system. I've had a lot of problems recently with other brands, where either the cap or rotor are partially defective new and fail in some exciting way within about 1500 miles. I don't carry spare parts with me....but I do carry a spare cap and rotor now.

wae UberDork
5/3/21 11:26 a.m.

In reply to Indy "Nub" Guy :

The Banks system is a "Ram-Air" system that replaces the air cleaner housing and puts a K&N filter in along with headers.  It was the big upgrade package back in the proverbial day.  "They" claim it's good for better MPG and more power of course, but I have no idea if that can be backed up with facts.

I went with Delco parts because they were cheap on Rock Auto.  That's not a bad thought on the coil.  I know heat will generally effect those and they're probably not all that expensive or hard to replace.

Never been at altitude before, but maybe a new O2 sensor would be a good investment?  The computer "should" take care of that for you, but I think it can only do its atmospheric correction when it's at idle or at least when it's in closed-loop mode.  So if you were banging away for a couple thousand feet straight it might need some time with your foot off the gas to figure out its new surroundings.

Indy "Nub" Guy
Indy "Nub" Guy PowerDork
5/3/21 2:11 p.m.

What's a good number to set for timing ?  Factory setting is 4 degrees.  Do you guys recommend going more than that?


ShawnG UltimaDork
5/3/21 2:52 p.m.

Depending on what Banks kit you have, you may have headers, a free-flowing exhaust, tuner and transmission controller as well.

I had the full system on my old 460EFI and it made a difference in power for sure. Not sure about fuel economy, it was for towing after all.

A motorhome is pretty much the worst operating environment for any engine. Check / replace any and all rubber parts as the heat will destroy them. A new thermostat and an auxilliary trans cooler are a good idea too.

frenchyd UltimaDork
5/3/21 4:43 p.m.

In reply to wae :

I suspect your motor will do better at altitude than you will.   Whenever I crossed the Rockies or Sierra Nevada's   A few hours at altitude  10,000 feet  had me pretty light headed.   Feeling sick.  
   Whenever we flew we went on oxygen above 10,000 ft for exactly that reason. 

frenchyd UltimaDork
5/3/21 4:50 p.m.

In reply to ShawnG :

Hot air does improve fuel mileage. 

SVreX (Forum Supporter)
SVreX (Forum Supporter) MegaDork
5/3/21 5:28 p.m.

Tear it out and install a Jag V12

wae UberDork
5/3/21 5:53 p.m.

In reply to SVreX (Forum Supporter) :

On more than one occasion I have fantasized about buying a 2500 and swapping a Duramax in to mine to make a FrED.....

gearheadmb SuperDork
5/3/21 5:57 p.m.
Indy "Nub" Guy said:

In reply to wae :

Do these TBI's have a sensor that measures air density to correct for altitude changes?


The map sensor is used by the computer as the baro sensor when you first key it on. It uses that as its reference until the next time you shut it off. So if you start the engine at the bottom then drive up a mountain it probably wont run great when you get to the top. So once you get up there do like the computer guys say, turn it off and on again.

Gearheadotaku (Forum Supporter)
Gearheadotaku (Forum Supporter) UltimaDork
5/3/21 8:49 p.m.

Put a fresh fuel filter on. A partially clogged filter will strain the pump.

If you refresh the ignition system, carry a spare module and make sure you  have the right tools to change it. I think the bolts are 5.5mm

There is a very long version of the oil filter for heavy duty trucks (Wix 51794) for a bit more capacity and less restriction. If you can fit it, go for it.

Check you rear diff fluid and look for leaks at the axle seals.

APEowner Dork
5/4/21 2:17 a.m.

In my experience the Banks stuff is well engineered and does what Gale Banks says it'll do.

The speed density system doesn't need to know.ambient  atmospheric pressure.  It only needs to know absolute  manifold pressure which the MAP sensor provides.  It'll make less power at altitude due to the lack of air but it'll have the proper air fuel ratio all the way up the mountain.

dean1484 MegaDork
5/4/21 6:18 a.m.

What about radiator hoses?  Bring spares?  

Indy "Nub" Guy
Indy "Nub" Guy PowerDork
5/14/21 6:10 a.m.

I've been checking these items off my list one at a time.  Last night I started it, after dark, with the engine cover off and the "new" plug wires the previous owner installed were making a pretty significant lightning show out of several of the them, especially the coil to top of distributor wire.


What's a really good, high quality brand wire set that I can install ?  I would really prefer pre-made wires.


Thanks in advance.

ShawnG UltimaDork
5/14/21 8:58 a.m.

In reply to Indy "Nub" Guy :

Check your spark plug gap too.

GM spec'd 0.060 for a while and it can cause arcing through the wires. If the P/O just installed plugs without gapping them, that may be what's happening.

Bring the gap down to 0.040 or 0.035 and you'll be fine.

0.060 works ok until the plugs get a little dirty or worn and then you get ignition problems.

Wires are the least "bang for your buck" upgrade. Any name brand set will be fine.

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) MegaDork
5/14/21 10:49 a.m.

The 454 TBI wasn't a powerhouse at 215 hp (235hp in some), but it will get the job done.

Normal maintenance should be done as has been mentioned, but I wouldn't worry about power adders and here's why.  The TBIs (both small and big block) are fantastically well-matched assemblies.  The heads, cam, intake, TBI, exhaust, and compression are all fantastically matched to the 215 hp.  It's not like an LS that has amazing heads and high compression just begging for a cam swap for a magic 80 hp.  It's all engineered for 215hp, so headers, cold air intake, and a bigger exhaust will likely mean you gain 5-10 hp.  I would just run it as-is and skip the power-adders.

The speed/density EFI is fine at altitude.  The MAP sensor and TPS do a fine job of compensating.  

Check the wear items, hit the road, don't stress.

frenchyd UltimaDork
5/14/21 11:10 a.m.

In reply to Curtis73 (Forum Supporter) :

Save your old parts and take them with you. If you have a failure of the new replacement. ( not totally unknown to happen ) The old one will at least get you to someplace where you can get a replacement. 
  Besides my lifetime has proven that anything you have spares for will never fail. The failure will always be what you don't have a spare for. 

volvoclearinghouse PowerDork
5/14/21 11:37 a.m.

In the 454 in my BST, It's reknowned for cooking the spark plug wires. A buddy of mine gave me some "asbestos" (not really, but some sort of heat insulating sock-like material) booties to put over the boots where they attach to the plugs.  I bought a set of new plug wires, I think they were Standard brand or something, about $50, they seem decent quality.  Make sure your exhaust is good and sealed up.  Bring a spare starter- the starter lives underneath the hot exhaust manifold.  Keep the oil full.  Consider running about 40% coolant, and some water wetter + distilled water.  Water conducts heat better than coolant. 

Uncle David (Forum Supporter)
Uncle David (Forum Supporter) Reader
5/14/21 9:03 p.m.

Besides all the above good advice, new rubber fuel lines, new soft brake lines, inspect the brake hard lines (GM brake lines from that era really like to rust), inspect wheel cylinder seals, and fresh brake fluid. Porterfield R4S pads and shoes.   And replace all the vacuum lines. 

Indy "Nub" Guy
Indy "Nub" Guy PowerDork
5/14/21 9:15 p.m.

Thanks for the additional tips guys.  I crawled under the rig and put a timing light on it (after disconnecting the magic wire) and the timing was REALLY advanced. off the scale BTDC.  Probably 20 degrees. 

I pulled it back to the factory setting of 4 degrees.

Edit: this is not my pic, I found it while doing a search.

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) MegaDork
5/14/21 9:38 p.m.

Edit... nevermid.  Reading is important

Did you pull the wire (brown I think) before checking?  TBIs have a special procedure where you set it to X degrees after pulling that wire off.  Then the computer sets timing from there.  20 degrees BTDC is not unheard of for a low-compression engine... especially a BBC with its big, wide chambers.

wae UberDork
5/14/21 11:32 p.m.

One other thing to mention: don't forget about your generator!  You probably have an Onan Emerald 4000 which is a good setup, but they wind up sitting too much.  If you're going to be plugged in all the time you won't need it, but if you need to do an overnight boondock-style, if your campers get a little too toasty and you need to run the AC, or if you're just pulling over to serve lunch and want to run the microwave, it's good to have it ready.  Mine is about the same vintage as yours and I just discovered that the rubber line that connects the hardline from the tank to the fuel pump was completely rotted and leaking.  It's probably 1/4".  If it's been sitting and won't start, they're a little stupid with their fuel pump.  Pull the connector that should be hanging under the oil fill area and touch it to the positive terminal and you should hear the pump fire up.  After giving it a prime, put the connector back and it should fire up.

I was able to take the plugs and wires to AutoZone for replacement.  They sold me two generic plug wires for about a buck each.  I probably should do the points as well, but I hate points.

udidwht New Reader
3/13/23 8:22 a.m.

Great info for these P-30 chassis set ups. They are very reliable and the most common issue/s seem to be...

1. Spark plug wire/s burnt (easily fixed by purchasing heat socks or Hi-temp sleeve material you cut to size)

2. Electrical gremlin/s that are often tied to dirty ground wire/s and or the engine-frame braid cable.

3. Keeping them running cool. An often overlooked one is ensuring the radiator fins are clean. Difficult due to the large AC condenser w/integral oil cooler that sits smack dab in front of the radiator. I highly recommend taking the time and remove it and clean the radiator fins out. Then once clean every year use a 'Radiator genie' and wash it out from behind by lifting the lower shroud off the clips. I replaced my condenser/oil cooler just this past year after finding that the oil cooler was leaking. It wasn't until I removed it that I found the radiator fins full of who knows what. Even after I made a couple of attempts to clean it out from behind previously before the work I did. I did a write up on the work I did (lots of pics) and you can read over it here: https://www.gmt400.com/threads/condenser-oil-cooler.59140/

Use only distilled water with an appropriate amount of coolant in them. No tap water. Bought it in Sept 2014 and since then I put roughly 30K miles on her and she's been great. Averages on the flats with no winds 9.XXmpg @ 60mph.

1 2

You'll need to log in to post.

Our Preferred Partners