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Motorhome giddyup

 
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phydeaux
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Joined: 05 Mar 2007
Posts: 84

3114.12 points


1997 Oldsmobile Aurora

PostPosted: Mon Feb 10, 2014 12:16 am    Post subject: Motorhome giddyup Reply with quote

I have a '93 Fleetwood Bounder 34' motorhome on the Chevy chassis. Power comes from a 454 tbi backed by a 4l80e. It developed a nasty exhaust manifold leak on the trip home from nw Kansas. Not to mention the severe overall lack of power lugging the weight around, it was a long ride home back to Houston Tx. What kind of bolt on options do I have for a budget of around 2k? I don't want to whoolie the beast, but I'd like to upgrade the hitch and pull mommas Exploder at roughly 65mph. Not looking for a hotrod, just a reasonable amount of power to do what I want. Turning a few heads in a motorhome would be nifty as well.
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Big Dave
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Joined: 04 Dec 2005
Posts: 2644
Location: Tampa Florida
119910.22 points



PostPosted: Mon Feb 10, 2014 8:47 am    Post subject: Reply with quote

Do you have the tubular stainless steel manifolds or the cast iron versions? If you have an exhaust leak with cast iron manifolds that is a sign your beloved big block has gotten very hot indeed.

I say beloved because your TBI induction system is next to useless, yet no one will change it to something better, implying that they must like it. To my knowledge they do not run motor homes through the sniffer or visual inspection.

If it were mine I would yank the motor and rebuild it with higher compression pistons (install flat tops in place of the dished ones), replacing your peanut port heads with older oval port cast iron heads off of a 1967-'73 car. Add a hydraulic roller RV cam and a square bore Holley 750 carb (vacuum secondary or mechanical won't matter as it will be wide open all the time anyway) on top of an aluminum high rise dual plane manifold.

As good as the 4L80e is, the 6L90e tranny is that much better. I would replace the tranny if you can afford it after the rebuild with a used one out of a wrecked Silverado pick-up or van.

If that doesn't generate more grunt to drag an extra vehicle along behind you, you will need to consider a turbo charger or a diesel motor conversion.

Big Dave
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journeyman
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Joined: 12 Jul 2007
Posts: 107
Location: Moscow
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PostPosted: Mon Feb 17, 2014 6:27 am    Post subject: Reply with quote

I feel your pain.
Mine is a 92, same situation a number of years ago.

The 454 is NOTORIOUS for cracking the stock exh. manifolds in a motorhome. When mine cracked, it was my chance to look at it as an incentive to buy the Banks SST headers. They have thicker tubing and a full 5/8" thick flange. I wrapped mine to keep things a little cooler under the doghouse. Also, the wrap ever so slightly increases efficiency.

Like Dave said, the TBI is a bit of a, well OK, it actually is a worthless piece of fecal material.
One of the problems with the TBI system is equal distribution to all cylinders at various throttle positions. Not going to happen.

I also bought a set of Aluminum "Jim Feuling" heads that are more efficient and have tiny chambers. Nice bonus too: the spark plugs are moved from the finger-burning position (next to the exh. manifold), up top where it is easy to change... a bit like a hemi. I also installed a Snow water injection system. I am pretty happy with it.

All things considered, the improvements I have seen have not been that significant from the feel of the driver's seat. I did increase MPG's from 5.5 - 5.8 to nearly 7 (towing heavy, GCW over 28,000) running over passes, so that was quite encouraging. I have not checked it solo, but it used to get between 9.3 and 9.8 depending on driving conditions. I am looking forward to testing it again.

If your exh. manifolds are cracked, take this opportunity to invest in the Banks long primary headers. They are pricey, but head and shoulders above other branks in terms of quality. You will see immediate torque and efficiency gains.
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Big Dave
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PostPosted: Mon Feb 17, 2014 10:36 am    Post subject: Reply with quote

Chevy had so many problems with cracking exhaust manifolds that they developed a set of stainless steel shorty manifolds to replace the cast iron manifolds.





Unfortunately since GM no longer makes the big block any more they no longer make these manifolds so you have to find them used.

Because the big block isn't big enough (a 502 short block would be a good start towards your upgrade, but this 540 that includes heads is the same price that Chevy charges for their short block)

http://www.ebay.com/itm/BBC-502-OR-540-SHORT-BLOCK-W-ASSEMBLED-ALUM-HEADS-INCLUDED-DART-BIG-M-BLOCK-/290710627778

You need to consider a longer stroked motor for more displacement.

You can actually save on gas by going to a bigger motor because the smaller displacement motor is constantly running wide open which not only wastes gas but creates a lot of heat as your TBI runs lean at WOT.

I have never used one but Chevy created the 8.2L (496) EFI motor to compete with the power of small diesel engines found in light pick-up trucks (mostly in competition with Ford's Power Stroke diesel, as they have already ceded that they can not beat the performance of the Cummings diesel used in Dodge pick-ups). You an find these 8200 Vortec motors in bone yards for peanuts (they still retain the peanut port head which is one reason no one wants them). If you got one complete with everything including wiring and computer it might make an improvement over what you have now as the engine used sequential fire port injection instead of TBI. With a turbo charger added to this engine using passenger heads (preferably using bigger valves) as is it will answer all of your problems.

Big Dave


Last edited by Big Dave on Wed Feb 26, 2014 12:01 am; edited 1 time in total
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journeyman
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Joined: 12 Jul 2007
Posts: 107
Location: Moscow
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PostPosted: Mon Feb 17, 2014 5:19 pm    Post subject: Reply with quote

Again... what is your budget?

Think through this carefully before starting. There are a lot of options (stroke is my favorite... but expensive), but your final goal will determine what is the most practical for you.

Wife and family-budget are key in this. Is there a 'hard limit'? if so, be doubly careful.

The Banks headers might make the most sense for you, but remember that after the header install you will most likely have to re-tune/re-chip to make it run right.
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10sec.et
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Joined: 29 Mar 2006
Posts: 3472
Location: Houston,Texas
346624.78 points


1969 Oldsmobile Cutlass

PostPosted: Fri Feb 21, 2014 12:06 am    Post subject: Reply with quote

glad you posted that here. i dont really know what to tell you on a motor home. i dont do stuff that big.

you need to pm me your info since you keep changing phone numbers.

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journeyman
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Posts: 107
Location: Moscow
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PostPosted: Tue Feb 25, 2014 11:26 am    Post subject: Reply with quote

Do post what you decide. I am curious which direction you will take.
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