What are the Pro and con of removing the Twin AIR on a 89 P30

[crd]

Greetings all,

My question is what can I expect if I remove Twin AIR system.  I have done a lot research and there some seems to be mixed opinions. I understand there maybe carb icing in cold weather. Some say the distributor will need upgrading to one that can be recurved enough. I am interested hearing from those have remove theirs.

Here is some background. I recently bought a 89 Cheiftain with a carb P30 chassis and with 71k miles. It has been parked since 08.  I am preparing it for a 10k mile plus trip next summer. (rebuild the brakes , complete tuneup.....)Saturday we took it for a 140 shake down run. For the most part all went well....except the fuel mileage. It was 5.5 mpg. I was hoping for 7 mpg.

Yesterday I started formulated a plan to improve this. I think a banks system would greatly help but at $2200 I am not sure if it will be cost effective.  So I ordered a set of Hedman elite headers, a KN filter, starter heat shield, two walker rv mufflers and a fan clutch (mine seems to be running all the time). I also plan to install a cold air intake and cross pipe in the exhaust. With all this I hope make some improvement in the fuel mileage. It seems to me that removing the air pumps may help mileage some also.

[shortbus]

How are the plugs and wires? My rig seemed to be running fine, strong, smooth, good power, but I figured I would toss some new spark plugs in and it really made a difference. I could really notice how much less I had to push the gas to hold highway speeds. I'm getting about the same mileage I did before but I've been cruising about 5-6mph faster which would really take a toll on the mileage before the plug change. I went to NGK V-powers, it is what I have always run in my Hondas and lots of the hot rod guys on some internet forums I searched around recommended them for the BBC as well.

[Rickf1985]

How did you determine your mileage with only a 140 mile run? That thing has an 80 gallon tank. (  I know, I have the same one) All of the items you bought will gain you maybe 1 1/2 MPG, not worth the expense unless you needed a complete new exhaust in my opinion. Since you put the headers on you might as well remove the air pumps since you will no longer have the A.I.R manifolds for them to supply. Removing them will not gain you any mileage, it will gain you some working room in the engine compartment. Removing the A.I.R. system will not affect the way the vehicle runs, if you disconnect the EGR valve then you will most likely need to do some distributor work. That is where you might pick up another one MPG. You are not going to make any major gains in mileage with bolt ons, just ain't gonna happen. I have gotten as high as ten on mine but most of that is driving style, start out easy, keep passing to a minimum and keep speed at or below 60. I move up to 65 MPH and mileage drops very quickly to 7MPG. The only way to know your mileage is to run though at least a half tank of gas and that is starting with a full tank and refilling to a full tank. A 140 mile shake down cruise means you are trying it out and testing the power and starting and stopping, 5.5 would be about average for that. I would bet that on a long trip of 300 miles or more that you would get your 7 MPG. One thing I can tell you is that the stock air cleaner with the snorkel out to the cool air in the front is the best cold air intake out there and you already have it.  The filter in that is massive and will flow a lot more air than that little K&N.

[crd]

How are the plugs and wires? My rig seemed to be running fine, strong, smooth, good power, but I figured I would toss some new spark plugs in and it really made a difference. I could really notice how much less I had to push the gas to hold highway speeds. I'm getting about the same mileage I did before but I've been cruising about 5-6mph faster which would really take a toll on the mileage before the plug change. I went to NGK V-powers, it is what I have always run in my Hondas and lots of the hot rod guys on some internet forums I searched around recommended them for the BBC as well.

I recently replaced the vaccum advance, plugs, wires, cap and rotor with AC brand.   I ran the rig on cruise at a steady 55 MPH. The road was had gentle rolling hills.

[crd]

How did you determine your mileage with only a 140 mile run? That thing has an 80 gallon tank. (  I know, I have the same one) All of the items you bought will gain you maybe 1 1/2 MPG, not worth the expense unless you needed a complete new exhaust in my opinion. Since you put the headers on you might as well remove the air pumps since you will no longer have the A.I.R manifolds for them to supply. Removing them will not gain you any mileage, it will gain you some working room in the engine compartment. Removing the A.I.R. system will not affect the way the vehicle runs, if you disconnect the EGR valve then you will most likely need to do some distributor work. That is where you might pick up another one MPG. You are not going to make any major gains in mileage with bolt ons, just ain't gonna happen. I have gotten as high as ten on mine but most of that is driving style, start out easy, keep passing to a minimum and keep speed at or below 60. I move up to 65 MPH and mileage drops very quickly to 7MPG. The only way to know your mileage is to run though at least a half tank of gas and that is starting with a full tank and refilling to a full tank. A 140 mile shake down cruise means you are trying it out and testing the power and starting and stopping, 5.5 would be about average for that. I would bet that on a long trip of 300 miles or more that you would get your 7 MPG. One thing I can tell you is that the stock air cleaner with the snorkel out to the cool air in the front is the best cold air intake out there and you already have it.  The filter in that is massive and will flow a lot more air than that little K&N.

To get the mpg I filled up then got on the Interstate. Drove 70 miles then return to the same station and filled up again.  I ran the rig on cruise at a steady 55 MPH. The interstate had gentle rolling hills. The added work area under the hood would be an added bonus

[Rickf1985]

Cruise control can sometimes cost you mileage because it tends to accelerate at a faster rate than you would when it comes to a hill. We will tend to let it accelerate a little above the 55 on the downhill slope to get a running start up the other side and this saves gas. Cruise control cuts the gas as soon as it hits the set speed so when you hit the bottom of the hill with cruise you are immediately back in the gas again accelerating up the hill. this also costs gas mileage. One thing you need to check is all of the vacuum lines since they are mostly all tied into the TVS at the front of the engine on the thermostat housing. If any are leaking and I will bet they are then the vacuum advance is probably not working correctly. Believe it or not, disconnecting all of the emissions stuff will not gain you any mileage at all. It will help the engine run smoother with the exception of the EGR. If you disconnect that just plug the line but leave it in place in case you have pinging issues, then you can just plug it back in again until you can get around to backing up the timing.

[beaverman]

2 things that may help, if your installing the new headers and a cross over and mufflers Hopefully flow through), if you don't have at least  3 inch exhaust pipes ( 4" would be better, your not going to help the mileage much, big block chevys need mass amount of cool air in and mass amount of exhaust going out to help increase both mileage and horse power, and for every turning pulley that you eliminate on the drive belts you should see a 10 to 15 horse increase per pully, more horsepower, engine lugs less, small increase in mileage, where you can gain even more mileage is to get a gear vendor over/ under drive and change that turbo 400 3 speed to a six speed , now are you going to travel enough over the next 10 years to see a return on the investment? that is the bottom line!

[crd]

2 things that may help, if your installing the new headers and a cross over and mufflers Hopefully flow through), if you don't have at least  3 inch exhaust pipes ( 4" would be better, your not going to help the mileage much, big block chevys need mass amount of cool air in and mass amount of exhaust going out to help increase both mileage and horse power, and for every turning pulley that you eliminate on the drive belts you should see a 10 to 15 horse increase per pully, more horsepower, engine lugs less, small increase in mileage, where you can gain even more mileage is to get a gear vendor over/ under drive and change that turbo 400 3 speed to a six speed , now are you going to travel enough over the next 10 years to see a return on the investment? that is the bottom line!

Beaverman
Thanks for your reply,
My rig currently has three inch duals with what appears to be restrictive mufflers (they are huge and very quiet) I have ordered two 3 1/2 free flowing RV mufflers and plan to install a 3 inch cross pipe when I install the headers and K & N filter.

I agree that eliminating the two air pumps will only increase the horsepower a little. But every little helps. I realize that these MH aren't going to get great mileage. But if I can get close to 8 MPG I will be happy.

I have looked into the gear vendor. While their product would help however I don't think I will travel enough to recover the $3200 investment. That is also why I didn't go with the banks system($2200). Both are great products.

I am hoping I will be able to recover my $700 investment(Hedman elite headers, a KN filter, starter heat shield, two walker rv mufflers and a fan clutch ) over our 10k mile trip next year.

[crd]

Cruise control can sometimes cost you mileage because it tends to accelerate at a faster rate than you would when it comes to a hill. We will tend to let it accelerate a little above the 55 on the downhill slope to get a running start up the other side and this saves gas. Cruise control cuts the gas as soon as it hits the set speed so when you hit the bottom of the hill with cruise you are immediately back in the gas again accelerating up the hill. this also costs gas mileage. One thing you need to check is all of the vacuum lines since they are mostly all tied into the TVS at the front of the engine on the thermostat housing. If any are leaking and I will bet they are then the vacuum advance is probably not working correctly. Believe it or not, disconnecting all of the emissions stuff will not gain you any mileage at all. It will help the engine run smoother with the exception of the EGR. If you disconnect that just plug the line but leave it in place in case you have pinging issues, then you can just plug it back in again until you can get around to backing up the timing.

Rick Thanks for your reply. Great advice. What is a TVS?

[tiinytina]

Make sure that the Hedman headers have the exhaust to carb return ducting to the snorkle, and use the original snorkel with a KN filter in it RAM air intake from nose behind grill.   Running in cold temps without the exhaust return will get you carb ice quickly without... yea Been there did that 3.2 MPG.  I put the BANKS on when the price tag was only $1200 a few years ago... it has the hot air return port. Both AIR systems are removed.  Heavy Duty fan clutch.  2.5" dual exhaust with Magnaflow mufflers. Complete tune up, using high "Race" quality wire set, delco plugs.  All that said.. yup there is power under the gas pedal when I need it and she sounds like a pack of Harley's... because you have it doesn't mean you have to use it nor should use it at every opportunity, that got me the 5.5 when first had it all.  I have logged every single drop of gas for the 10 yrs we have had Gone AVG about 3k a year miles.  3.2 MPG was the bottom, 9ish the top (flat and most likely a tail wind LOL)...  Average is about 7.4.   I don't haul with full water/waste water.  I may have 10 gallons of fresh on board for on road bathroom use, I use the dump station before hauling homeward. Her GVW is about 13,800lb (tiffins have an aluminum tube frame vs wood of many Winnies)   I keep her 55/60 MPH and don't tow anything.  I have cruise on her never use it. no dash AC.  All the investment has gotten Gone an engine which purrs, runs smooth and does have power when you need it.  Can't say any of the above greatly improved mileage.  Southern MD to Breezewood PA which is up and over the Appalachians, in the slow lane... 6.3mpg is my average.   The only thing I have not done is add the airtabs on her trailing edges which Frank said got him 1or so MPG gain from drag reduction.  I am still looking for red silicone vacuum lines to replace all though all the rubber ones are good last check.  I just like red... :-) 
Tina

[bluebird]

A carburated 454/400 never got very good mpg, even in pick up trucks. If you get 8 mpg you will be very lucky. My 80 26 ft. Itasca would only do 5 to 7 mpg and it was tuned very good, with a very well preped quadrajet. If you plan on driving the speed limit, plan on 5 to 6 mpg. Those coachs were designed for the 55 mph mandated speed limit. My coach will do 9 mpg but it is MFI and has an over drive trans. It runs about 2000 rpms at 65 mph and is much more aerodynamic than the older coachs. Personally I wouldn't spend a lot of money on it trying to get the fuel mileage up. Motor homes just don't get good fuel mileage, even the newer ones. You can spend 3 4 5 thousand or more, but you are only going to improve the mpg only sightly. If you get it running real good, drive it and have fun, and don't worry about the mpg. Just put gas in when it needs it. I normally don't even check my mpg anymore. Only reason I even checked mine is I just purchased this coach last Nov. and checked it on the trip home. 

[Rickf1985]

2 things that may help, if your installing the new headers and a cross over and mufflers Hopefully flow through), if you don't have at least  3 inch exhaust pipes ( 4" would be better, your not going to help the mileage much, big block chevys need mass amount of cool air in and mass amount of exhaust going out to help increase both mileage and horse power, and for every turning pulley that you eliminate on the drive belts you should see a 10 to 15 horse increase per pully, more horsepower, engine lugs less, small increase in mileage, where you can gain even more mileage is to get a gear vendor over/ under drive and change that turbo 400 3 speed to a six speed , now are you going to travel enough over the next 10 years to see a return on the investment? that is the bottom line!

Beaverman, Where are you getting your dyno information? 10-15 horse per pulley on air pumps! Those pumps are almost zero restriction and have no draw to them at all, you will gain less than 1/2 horse power from taking both off. as far as the exhaust goes bigger is not always batter, Once you get so big as to lose scavenging then you are actually hurting your power. Dual 2 1/2 is more than enough for a stock 454. And one 3" flows almost as much as dual 2 1/2" It actually flows the same as dual 2 1/4". Diesel engines will benefit from super large exhaust but not gas engines, you have to balance things out or you lose power, torque and mileage. Not to mention you also move your power band way up the RPM scale.

And just to give a reference for the air pumps............ The average large shop air compressor in a tire shop uses a 10 horsepower motor.

[tmsnyder]

Maybe not costing 10-15 hp each, but they sure aren't ADDING any 

I looked at it as one less thing to break and leave me stranded on the side of the road b/c one of them was on the same belt as the fan w/p, alternator. 

Beaverman, Where are you getting your dyno information? 10-15 horse per pulley on air pumps! Those pumps are almost zero restriction and have no draw to them at all, you will gain less than 1/2 horse power from taking both off. as far as the exhaust goes bigger is not always batter, Once you get so big as to lose scavenging then you are actually hurting your power. Dual 2 1/2 is more than enough for a stock 454. And one 3" flows almost as much as dual 2 1/2" It actually flows the same as dual 2 1/4". Diesel engines will benefit from super large exhaust but not gas engines, you have to balance things out or you lose power, torque and mileage. Not to mention you also move your power band way up the RPM scale.

And just to give a reference for the air pumps............ The average large shop air compressor in a tire shop uses a 10 horsepower motor.

[Rickf1985]

Maybe not costing 10-15 hp each, but they sure aren't ADDING any 


I looked at it as one less thing to break and leave me stranded on the side of the road b/c one of them was on the same belt as the fan w/p, alternator.

Much better way of looking at it, that is why I took mine off, the upper one had a bad bearing and the bottom one is almost impossible to get to. My Pace Arrow has a seized bottom pump and I need to get it off just so I can move the rig. luckily the AC belt will power the water pump so I will just take the belt off for now but as you say, if it goes on the road you are in trouble. And those AIR pumps do fail regularly.

[Froggy1936]

Just for comparison sake My rebuilt  1977 Mini Winnie W 1995 Chev  5.7  TBI & 4L80E Trans W OD & lock up TQ . Weighing in @ 12000 & Air Tabs  Latest Average MPG is 9 @ approx. 65 MPH  Which is approx. the same as the Quadrajet was $2000.00 ago !  Frank

[Rickf1985]

Frank, What gear ratio is in the rear? With the overdrive transmission you may be running fourth gear in a lot of places where the engine is running far below the power band. Pulling 12,000lbs. you should be running 4:10 gears if you are running 16 inch tires. 4:56 gears would probably be better.

[crd]

Greetings All
I just wanted to update this post. I have installed the Hedman elite headers, a KN filter,  flow master mufflers, crossover pipe and a fan clutch . I removed both AIR pumps.  We are currently on our first road trip since making the upgrades. These changes have really woke up our rig. It is really responsive with more enough power. I will post our fuel mileage once we get back home.

[crd]

We just completed our first road trip since making the upgrades. Our fuel mileage has gone from 5.5 mpg to 8.4 mpg.

[Rickf1985]

That is great tpo hear, If it stays that way over several tanks of gas and differing driving conditions then you have spent wisely.

[tiinytina]

With the exception of the cross over on the exhaust Gone has same set up except Banks vs hedmans... AVG is about 7.4... got 7 last tank but did have the genny running for several hours, roads mostly flat.. she likes about 50-55mph... no toad. 13,800 lb with about 60 gal of fuel and empty water tanks.  Tiffin has tubular aluminum coach frame so a bit heavier than the wood framing. 

[tmsnyder]

Wow you're fast!  Can you come over and work on mine?

Did you do anything for the timing now that you're not reburning the intentionally enriched exhaust with air injection?

Greetings All
I just wanted to update this post. I have installed the Hedman elite headers, a KN filter,  flow master mufflers, crossover pipe and a fan clutch . I removed both AIR pumps.  We are currently on our first road trip since making the upgrades. These changes have really woke up our rig. It is really responsive with more enough power. I will post our fuel mileage once we get back home.

[crd]

THANKS it seemed like it took for ever. no i havent  adjust the timing yet . I wanted to run it at the stock setting. Do you think i should? if so what should I set it at?

Wow you're fast!  Can you come over and work on mine?

Did you do anything for the timing now that you're not reburning the intentionally enriched exhaust with air injection?

[crd]

With the exception of the cross over on the exhaust Gone has same set up except Banks vs hedmans... AVG is about 7.4... got 7 last tank but did have the genny running for several hours, roads mostly flat.. she likes about 50-55mph... no toad. 13,800 lb with about 60 gal of fuel and empty water tanks.  Tiffin has tubular aluminum coach frame so a bit heavier than the wood framing.

This mpg was without the gen running however we had about 30 miles of the famous Nashville rush hour traffic. We water tanks were full on the while going to the camp grounds but empty on the way home. The route is gently rolling hills. The speed was 55-58 mph. I didnt use the cruise as RICKF1985 suggested.

[tmsnyder]

What mpg?

[crd]

That is great tpo hear, If it stays that way over several tanks of gas and differing driving conditions then you have spent wisely.

Thanks. I am sure this is the best mpg I will see.  its going to change with load and road conditions. I did have about 30 miles of heavy traffic in Nashville. I was really easy on the throttle trying not to open the secondaries. I maintain between 55-58 without the cruise as you suggested.