I have a 1989 motorhome getting miserable gas mileage. Will I improve it if I strip off all smog gear? Or will I have to change carbs. MH has no computer. Thanks group

Ken

Normally improvements from 'stripping off smog gear' are actually the result of removing altogether something that wasn't connected right in the first place. Examples are bad sensors, bad wiring and OFTEN incorrectly-routed or damaged vacuum lines. Fix it correctly-if you strip it off you're going to have to 'plug the holes' and for the most part you need to know what you're doing when you make these mods.

BTW-motorhomes of that era with gas engines often got @$#)( for milage...

-quick edit
Proper spark, good compression, properly routed vac. lines, working sensor (O2), efficient, maintained cooling systems, clean filters, new oil, clean PCV, working EGR and no leaks - something to shoot for if you don't have it already.

Thanks for the come-back. You are probably right, guess I am just lazy and looking for an easy way out

javven......forgot! Tuther thing I was thinking about was shoving a 5.9 Cummins in the MH. It is a P-30 chassis and I know GM did make a lot of P-30 vans with the Cummins engines though I do think they were 3.5 litre. Have lots of room in the engine compartment and several thousand pounds of tools that need excersize. May be a fools errand.........?

Ken (74 and still wrenchin')

my Dad has a 84 P30 motorhome with 350/T400/ 14 bolt with 410 gears. the first time he took it on a trip it got 8. it got 8 at 55 and 8 at 70, we took all the smog stuff off and I borrowed it for a 500 mile trip it still got 8, I am under the impression that if you want to improve the milage your going to have to get the RPM's down some its doing like 3000 rpm at 60.

His first plan was build up a vortec 350 and put a overdrive unit on the back of the tranny, we have done that and have been having problems with the fuel pump so haven't been able to drive it and check what it gets with that combo, I will tell you that the vortec has way more power.

He has since scrapped that idea and is putting a 4BT cummins in it, haven't started the swap yet, but it should work pretty good.

70's and 80's vehicles (carburated) all run way too lean as they come from the factory. The AIR (smog) pump system puts air into the exhaust system to cut down on emissions which in turn helps cool the exhaust manifolds which in turn helps cool the exhaust valves. Do not remove the AIR system unless you are changing to the following: aftermarketcarb and aluminum intake, rv cam and valve springs, headers and dual exhaust system. Any change to the stock equipment (without changing all of it) will only make the lean condition and resulting gas mileage worse. BTW it is less expensive to fix what you have than to change to a diesel.

Thank you for the input gentlemen. It would appear the obvious choice would be to leave things as they are or, alternatively, stuff in a little diesel (3BT). The difference in weight between the 3BT and the 5.9 seems to be considerable, and given the front suspension is independant coils it may be wiser to go lighter. The coach is 25 feet long and probably weighs 8 or 9 K. Certainly the $$$$ and humbug to go diesel would be better spent on just buying a newer better MH. However, the project does have a perverse appeal.

Thanks again for the thoughtful comments

Ken

oooops!

Had head in warm dark place.....meant 4bt.......Hey, I'm old.....


Ken