Series IIA "Bitsa" Dormie

[Stayalert]

9-9-2014

Had my '67 Dormobile for about 17 years and it has been dormant for several years….I am considering renovating it to be a contender for highway, mild off road, 4 season camping. emphasis on Winter camping and pipe dream of chasing snow on the Powder Highway…

As is:

70's era Chevy Straight six <> rover non-synchro gearbox/T-case with fairey OD <> salisbury rear axle/Stock (I think) front axle. Drum brakes on all four corners with a vac. assist hydro boost thing, painless wiring harness….3 fuel tanks….interior wardrobe, kitchen, etc. currently removed….

Thinking:

- diff gearing change to slow drivetrain down at highway speeds, Axle change to facilitate this??, maybe power steering, maybe increased engine performance or engine swap, Diesel? Maybe more robust tranny (5 Spd lose OD? disc brakes? Propane/diesel furnace? Lots of questions….Just starting to brainstorm and formulate scope/budget/schedule/resources/vendors/etc….Most of the work would be farmed out….The rig is a "Bitsa" and I'm no purist so I'm not glued to british parts…..


Whaddaya think????

Rob M
Norwich, VT

[superstator]

Be interested to hear what you do for winterizing. I've had visions of using mine to dirtbag in ski area parking lots, but it's a ways off yet. Adding a webasto or similar aux heater is high on my list, plus maybe some amount of insulation. I think they do make petrol parking heaters, but the diesel versions are much more common and simpler to install.

[ignotus]

If you are not doing the work get ready to spend big. I'd start with pulling the Chevy and getting it rebuilt unless you want to go diesel. disc brakes are from various suppliers when you can find em, the Timm Cooper conversion is being made by; http://forbynbros.com/
Check out TeriAnn's website for tons of good info on conversions both engine and tranny. http://www.expeditionlandrover.info/
Other than that Gooooooooooooooooooooooooooooooooogle is your friend. HTH

[Stayalert]

yeah insulating a dormobile will be tough for sure….I was thinking diesel webasto for heat...

[TeriAnn]

Golly, where to start ...

Drivetrain: I suggest 292 Chevy six if yours isn't the 292. Put a 1960's cylinder head on it. Most of the '70s heads are more restrictive and have small coolant passages so the engine runs hotter. I would couple it to a Chevy top loader 4 speed gearbox (http://www.expeditionlandrover.info/gearboxSwap.htm) just because all the parts to connect it to the engine are off the shelf without modification. The five speed gearbox is longer and the shift lever is right up against the seat box. I've been in a 109 with 292 six and it had plenty of power.

Go to Advance Adapter (http://www.expeditionlandrover.info/advance_Adapter.htm) for a gearbox to transfercase adapter. Use either a Ashcroft high ratio modified Series transfercase or a stock Series transfercase with an overdrive. Heystee (http://www.heystee-automotive.com/) (Santana clone) or Romerdrive. Keep the stock R&P ratio. Going to a 3.54 R&P will do good things for your high range but would destroy your low range for driving off road.

You can insulate as much as you want but as soon as you pop that top you only have that thin plastic tarp between you and the cold. The Dormie stove warms up the interior quickly. The cheap way to let it be cold at night and move around in your sleeping bag in the morning to fire up the stove. With both burners and the broiler going it will warm up the interior in just a few minutes. You can buy a propane heater but they do take up space and they are loud. At least the Esper exhaust is loud.

As one bitsa owner to another ask away

[yorker]

[VIDEO]https://www.youtube.com/watch?v=8UC-jqHDsLk[/VIDEO Lump port it & get Leo Santucci's book.

http://www.12bolt.com/lump_head_information

http://www.12bolt.com/292_dyno_testing


Any of the Chevy 6's would be good and have plenty of power for you. Swap to a US truck 4 speed and you can change ring and pinion ratios to get better highway cruising, if you aren't a purist consider TOyota Landcruiser axles, they are strong and come in 4.10 ratio stock(FJ40/45/55/62 US spec 60's used 3.70's), brake upgrades are simple and cheap, differentials are passenger side and adapting them to a 109 Land Rover chassis and drive shafts is pretty simple... With the truck 4 speed you'll have plenty of low range and with a properly tuned I6 you'll have torque at the low end right where you need it too. They make excellent truck engines.

[greenmeanie]

The early heads vs later heads is rather moot. The one you want to avoid is the version with the integral manifolds. If you want power then stump up the cash for the lump ported heads as stated by Matt above- its a night and day difference in the breathing and you can choose from several different valve sizes up all of which are bigger than stock. Also look carefully at sumps and swap for one that provides clearance over the front axle. Keep in mind that it is quite a long engine which can present some challenges if you wish to keep an earlier recessed radiator look. The water pump sits quite low compared to the Rover radiator so you'll probably end up with an electric fan. Now, if you get interested in the Chevy sixes the bible for building one is the Chevrolet Inline Six-Cylinder written by Leo Santucci. If you want more info go over to Inliners.org and you'll find more experts than you can shake a stick at. There is so much info on how to build for different applications that it is a waste for me to try and summarize here.


The person to talk to on these engines is Tom Langdon of Langdon's Stovebolt fame. He does some very nice cast exhaust manifolds plus a host of other goodies. He worked on the design of these engines for GM and he's forgotten more than most will ever learn about them. The big take away from talking to him for several hours is that gearing is critical. The 292 is a torque mill with the peak way down the RPM range compared to a V8. As such you want to gear it for somewhere between 2200-2400rpm at 65mph. This means the 4.70 diffs will make you spin too fast and don't really buy you anything. If you want a higher revving engine go for the 250 as its geometry allows it to rev harder and it still has plenty of grunt. Look at the standard ratios used by GM on their vehicles with this engine to help design your drivetrain.


The big six is an awesome engine. I'm running a '74 292, lump ported head, .060 overbore, 9;1 compression pistons, Cloyes timing gears, Clifford intake, Langdon exhaust manifolds, HEI, Megasquirt, Delco CS144 alternator, GM Spam can PS Pump and an AC compressor.

10171
10172

[TeriAnn]

Any of the Chevy 6's would be good and have plenty of power for you. Swap to a US truck 4 speed and you can change ring and pinion ratios to get better highway cruising, if you aren't a purist consider TOyota Landcruiser axles, they are strong and come in 4.10 ratio stock(FJ40/45/55/62 US spec 60's used 3.70's), brake upgrades are simple and cheap, differentials are passenger side and adapting them to a 109 Land Rover chassis and drive shafts is pretty simple... With the truck 4 speed you'll have plenty of low range and with a properly tuned I6 you'll have torque at the low end right where you need it too. They make excellent truck engines.

4.10:1 is an aftermarket option made for Defenders that do some rock crawling. Use a coiler carrier off a RR classic or Disco I. I think that the ratio is the worst of both worlds. The highways revs would still be too high for good fuel mileage on the highway and you would loose gearing for slow off road travel. I'm still a fan of keeping the 4.75 R&P for off road travel and either an overdrive or Ashcroft high ratio modified transfercase for highway travel. Either will give you the range for both highway and technical off road.

If you are only going to do mild off road work on maintained trails and don't need the low gearing you can just go to the coiler 3.54:1 ratio. The 3.54, Ashcroft transfercase and 4th overdrive all have a very similar ratio at the axle. A 292 will provide the power needed to push the 3.54:1.




The big take away from talking to him for several hours is that gearing is critical. The 292 is a torque mill with the peak way down the RPM range compared to a V8. As such you want to gear it for somewhere between 2200-2400rpm at 65mph. This means the 4.70 diffs will make you spin too fast and don't really buy you anything. If you want a higher revving engine go for the 250 as its geometry allows it to rev harder and it still has plenty of grunt. Look at the standard ratios used by GM on their vehicles with this engine to help design your drivetrain.

10172

Lots of good engine advice in this post. It is important that you decide how you will use the truck. If you are doing any sort of technical off road travel you will want low gearing to slowly take a big heavy Dormobile over the rough stuff and down hills. If you make your gearing changes at the diffs to get acceptable highway RPMs you will loose the versatility off road. That's why I keep suggesting making your gearing modifications in the middle with either an overdrive or high ratio transfercase. They allow you to have your cake and eat it too.

Someone is bound to suggest 3.54:1 R&P and a gearbox with a granny first. Having lived with a granny first in a LR I suggest NOT going this route. Yes it gives you good highway gearing and a good low range first but there is this HUGE gear ratio gap between first and second gears. And most off road driving calls for a gear ratio within that gap. Also a granny first in high range is too low for starting off from a stop on pavement. You end up with 3 usable street gears. I suggest a close ratio gearbox.

About engine modifications. Typically anything that adds HP adds it to the high RPM range by sacrificing low RPM power. Unless you are taking your Dormobile to the drag strip, when looking at any power modification be sure to ask what happens to power below 3000 RPM. Your best bet will be to look for mods that increase engine torque. Those will not hurt low end HP.

About the picture: Greenmeanie that is about the cleanest conversion I remember seeing. Really nice job!!! I see you are in Phoenix. What are you using for a radiator to handle the summer heat on the trail? What dimensions? and what kind of electric fan are you using? Power steering and air conditioner too. Nice. You will have to do a writeup on your air conditioner for the web. if you don't have a site I would be happy to host a writeup for you.

[eagle597]

I too would be highly interested in an article or post about the AC modification. Particularly the firewall/ heater core modifications and interior.

[rwollschlager]

Was this door mobile in CT recently? A guy approached me in Saybrook and told me about a dormie with a chevy 6 that was for sale, but he never got back to my with contact info until the truck was already gone.

Instead of propane/diesel furnace, look into a Webasto/Eberspacher/Espar heater. They run off diesel fuel and are commonly used in boats, semi's, and other applications where a vehicle will need a lot of serious heat.

[yorker]

The 292 is a torque mill with the peak way down the RPM range compared to a V8. As such you want to gear it for somewhere between 2200-2400rpm at 65mph.


exactly:
1966 GM truck repair manual,power ratings: 292 inline 6 has 170 hp at 4000 rpm and 275 fbs of torque at 1600 rpm.283 V-8,175 hp at 4000 rpm,275 ft lbs of torque at 2400 rpm. Your gearing philosophy has to consider that difference. Highway performance expectations are different too so period gearing (On GM/Chevy P/Us may or may not work- OTOH With an overdrive it probably will.

[edit] Most of you know this but it is probably worth mentioning for those less accustomed to Land Rovers. In a LR high range ratio is something of a underdrive*- so comparison with other trucks ring and pinion ratios should take that into account. A 199Range Rover with 3.54 diffs also has a 1.22 High Range ratio and is like driving around with 4.3 diffs in an American car. A Series Land Rover with 4.7 diffs has a 1.15 high range ratio so they are like 5.4 diffs in a US vehicle.

* Some people like Teriann, Greenmeanie, and Mercedes Jim have the Ashcroft High Ratio Transfer Case (HRTC) that does the exact opposite- it is effectively an overdrive. http://www.ashcroft-transmissions.co.uk/the-series-vehicle/high-ratio-transfer-case-kit.html

[Stayalert]

still brainstorming….Nope hasn't been in CT…..Webasto/espar was my initial thought for heat as well….

[meatblanket]

If you go with an SM465 4 speed then you should use the 3.54 coiler diff in front and re-gear your Sals to 3.54. Off road performance will still be improved versus stock. That transmission has such a ridiculously low first gear that it more than makes up for the ratio change from 4.7 to 3.54.

SM465 1st is 6.56 to 1
Series 1st is 3 to 1

[TeriAnn]

If you go with an SM465 4 speed then you should use the 3.54 coiler diff in front and re-gear your Sals to 3.54. Off road performance will still be improved versus stock. That transmission has such a ridiculously low first gear that it more than makes up for the ratio change from 4.7 to 3.54.
SM465 1st is 6.56 to 1
Series 1st is 3 to 1

I have always been a fan of Data so here goes

You end up with that really huge gap between first & second gears in high range making it a 3 speed gearbox on the street. But otherwise this looks to be an attractive combination.

Off road in low range:

Overall gear ratio at the axle = gear selected in gearbox X selected transfercase ratio X ring and pinion ratio

SIII: first = 3.68:1, second = 2.22:1, stock transfercase = 2.35:1, stock R&P 4.7:1

low range ratio at axle: 40.65:1 first low, 24.52:1 second low


SM465: first 6.55:1, second 3.58:1, stock transfercase = 2.35:1 low, 1,15:1 high range, coiler R&P = 3.54:1

Low range first = 54.49:1, low range second = 29.78:1

For the kind of off road driving I do I consider 55:1 to be a near ideal low first. When you convoy with other series vehicles a lot of the time you are in low second. The 29.78 ratio may be close enough if you have good low end torque to handle your lower RPMs but you need to be careful about outrunning stock Series rigs on the trail.



1:1 high range fourth

Stock SIII gear ratios:
high range fourth = 5.41:1 which with 32 in. dia. tyres gives you 3692 RPM at 65 mph.


Stock transfercase with 3.54 R&P:
high range fourth = 4.07:1 which with 32 in. dia. tyres gives you 2778 RPM at 65 mph.

Ashcroft high range transfercase with 4.7:1 R&P
high range fourth = 4.01:1 which with 32 in. dia. tyres gives you 2737 RPM at 65 mph.

The overall ratios of the two combinations are similar and both would work well. The only real difference is that with a NP435 you have a 4 speed gearbox on the street and with the SM465 with its granny gear you have a 3 speed gearbox on the street.

[yorker]

I have always been a fan of Data so here goes

You end up with that really huge gap between first & second gears in high range making it a 3 speed gearbox on the street.

The overall ratios of the two combinations are similar and both would work well. The only real difference is that with a NP435 you have a 4 speed gearbox on the street and with the SM465 with its granny gear you have a 3 speed gearbox on the street.

If you find a close ratio NP435 that is true, most I've run across are wide ratio. (I suppose you could use a close ratio T19 toowhich is more common) Those wide ratiotransmissions were designed largely when work trucks were 2wd or even 4wd with a 1:1 transfer case so the first gear was meant to be something of a low range in and of itself. Sometimes you'll even see them marked L-1-2-3 instead of 1-2-3-4. A vast majority of vehicles back then had 3 speed transmissions so using the truck 4 speeds as a 3 speed around town generally wasn't seen as a problem- nowadays it seems odd and to some- annoying.

[greenmeanie]

I have always been a fan of Data so here goes



Ashcroft high range transfercase with 4.7:1 R&P
high range fourth = 4.01:1 which with 32 in. dia. tyres gives you 2737 RPM at 65 mph.



Way to much rpm for a 292 and even a 250 if he is still thinking Chevy 6.

[yorker]

Way to much rpm for a 292 and even a 250 if he is still thinking Chevy 6.

I wonder if a Roverdrive/roamer drive could survive with the torque?

http://www.solemnwarning.net/transmission/newgraph.cgi?max=80&unit=m&gears=First%3D16190.4709684814%3BFirst%20OD%3D1165 7.1390973066%3BSecond%3D7915.91064756447%3BSecond% 20OD%3D5699.45566624642%3BThird%3D4329.41391404011 %3BThird%20OD%3D3117.17801810888%3BFourth%3D2561.7 8338108883%3BFourth%20OD%3D1844.48403438395&redline=4500 (t18/series T case/roverdrive/3.54)

Gear Speed (MPH)
10 20 30 40 50 60 70 80

Fourth 426 853 1280 1707 2134 2561 2988 3415
Fourth OD 307 614 922 1229 1537 1844 2151 2459

http://www.solemnwarning.net/transmission/?

[TeriAnn]

If you find a close ratio NP435 that is true, most I've run across are wide ratio.

Most all Ford NP435s have a granny first and most of the Chevy NP435s are close ratio. Gears on the later NP435s are interchangable.

I'm running a NP435 with Ford case and Chevy close ration gears inside. It mans a Chevy clutch disc and a Ford pressure plate but it works just fine. With the Ashcroft high ration transfercase & 4.7:1 R&P it gives me real close to 55:1 low first, a low second close to a stock Series low second (which make traveling with others easier) and decent highway gearing.

[Stayalert]

Yeeesh....I thought my Dormie was dormant....turns out I have been also.....I still have the dormie. boughtb a van a few years ago and chased snow for a couple of monthes the first Winter we had the van. LOVED it.....I need to think about selling the dormie.....Rob Norwich, VT