Best engine/trans choice for my Silversides

[gus]

Keith,

Did you get this bus from HB Industries in El Cajon? Bob there had one for sale. I tried to find a 3751 for a long time but couldn't find a decent one, lots of junk out there. If you drove from SD to MI in three days it can't be too bad!!

Please do yourself a favor and drive this powertrain for a while before you change anything. I've driven my 4104 from VA to AR to NV and back and AR to Seattle via AZ and CA and back, a total of  14,000 miles in less than a year.

If the engine is shot you can get a good used one for a decent price. This is a very good engine and your bus is light compared to most monster buses.

Sure you go slow up hills and mountains, but that is half the fun, you see things you never see at 70mph! Nobody will ever give you a ticket in a heavy vehicle for driving slow. On multi-lane hwys just get into your lane and breeze along as best you can.

There is nothing unsafe about a slow moving large vehicle, drivers just go around you and most hills and mountains have slow-moving vehicle lanes, you just join them and sometimes you can even pass a truck uphill with the 6-71! Sometimes!

In heavy traffic give yourself plenty of space to the next vehicle-this is no hotrod-so you don't have to shift so often also put the trans in neutral and coast along when level or going downhill, this saves the clutch leg. The clutch can be adjusted to tolerable pressure if it is done properly and all the loose pins and forks are repaired or replaced. Done that.

[keithshotrodshop]

Yes, I bought bobs bus. It was (and still is) the cleanest silversides body I've ever seen. It does need a few small things to be perfect externally, such as one cab light, and at least one cargo bay door. Otherwise, the rest is very presentable and restorable. I probably already have more into this bus than it's worth, but hey, isn't that part of the game? I'm not really sure I need a complete rebuild, here is my motor 1. Leaks compression into the cooling system (and did the entire trip home from cali-but I don't think bob knew anything about this-might have happened shortly into my trip). 2. Does belch black smoke at lower speeds, but don't they all? 3. Runs pretty much smoke free when warmed up. 4. Tends to run between 190-220, this might be part compression leak, part inaccurate gauge? 5. Doesn't start if it's under 60 degrees outside without ether (I hope to purchase a water heating system soon). 6. Leaks oil, but not horribly, All together I went through 6 gallons of oil in the 2500 mile trip home, however the first 4 were all in the first 200 miles and the bus had been sitting for a long time. So, how about it guys, how does my engine sound? Also, any thoughts as to what my compression problem is? I have been told by several it probably is a cracked head, or bad cylinder 0-ring (I do have a 4 valve motor). Could this be repaired without removing the entire engine, or am I looking at a complete overhaul?

[tekebird]

if you are leaking compression into the cooling system you will have coolant in your oil...get an oil annalysis done....it will also tell you if you have other wear issues.

it should not belch black smoke at any speed, only if you are luggin it....6-71 like to be run

temp, hard to say whats going on there....220 is time to shut down

I am guessing it is just tired...and if bob couln't tell you when it was overhauled last then assume it needs it.


when they took apart the 6-71 we took out of my 04 when we put the crate new one in....they were supprised it was still running it was so worn out...LOL

just goes to show you how well the 2 strokes are built.....no series 50/60 is ever going to run when worn out

[RJ]

Keith - 

1.  Compression in the cooling system:  Most likely a cracked head. Start searching for either another head, or a shop that can repair yours.  Probably coolant in the oil, too.  Get an oil analysis kit from any local diesel dealer and send it in.  Around $25 or so.

2.  Belching black smoke:  First, check the air filter and make sure it's clean.  Second - DON'T LUG the engine!  Detroits belch a lot of black smoke if put under too much load at too low rpm.  Black smoke is too much fuel and too little air.  Gotta drive it like you just slammed your finger in a door!  Wind it up, keep it wound up!

3.  Runs pretty smoke-free when warmed up:  That's good!

4.  Temp of 190 - 220:  Put a mechanical gauge in the engine compartment to compare to dash.  Higher temp can also be related to the compression in coolant.

5.  Doesn't start under 60^o outside:  Call Luke for the correct engine block heater, 1-888-262-2434.  Also a function of lower compression from leak.

6.  Leaks oil:  Detroit two-strokes are like male dogs - they have to mark their territory everywhere they go.  Seriously, 400 miles/gallon of oil is excessive.  Should be up in the 1500 - 2000 miles/gallon range.

If you're going to pull the head to repair it, it's not that much more difficult to do what's called an "in-frame" overhaul.  Would probably solve 90% of your problems, and give you the majority of your power back, too.

Besides the fabrication issues previously noted, the major problem with stuffing a 6V92TA in the tail would be trying to cool the beast w/o cutting up the classic lines of the coach.

FWIW & HTH. . .

[gus]

Bob is a great guy. i go by and have him do some work when I go out there every Spring. I tried to buy a consigned 3751 from him two years ago but while I was haggling with the owner a guy from TX bought it sight unseen!!

1 This is your biggest problem as I see it Checking the head bolts torque might help but I doubt it.
2.Normal, keep it revved, no lugging. Also smokes on hard pulls if you use too much throttle. Black smoke is the signal to back off or down shift.
3.Yes
4.Should run around 175-180 except on long pulls in hot weather. 220 is probably too high.
5.Normal. I use ether in cool weather. There should be a small cup on the right upper side of the air box intake for inserting ether. Just spray a small amount into the cup, close the lid, walk around to the front and hit the starter. Works every time.
6.Normal. Don't fill it to the top, I run one-half to one gallon below full. You probably are throwing most of it out, probably around the rear main seal-mine does this.  However, there are many places for oil to leak. Check around the vent line from the crankcase to the governor. This is a common leak spot.

Your rings were probably stuck. That bus had been there a long time. I didn't buy it because I wanted one mostly converted. I'm too old to start a complete conversion. You were extremely lucky to drive that bus that far with no major problems.

I'm no DD mechanic go I won't give you any technical advice, I'm going by my experience with mine in the past year and a half.

Heads can usually be repaired on any engine without removing the engine. I think pistons, rings and liners can also-not certain of that. Find a good DD old timer-Repeat that!
7.

[DrivingMissLazy]

One thing that the guru's did not ask was what motor oil are you using? If it is anything other than DElO 100 40 wt or its equivalent, then that could be the cause of excessive oil consumption. When I finally found out that I was using the wrong oil (15/40), and changed to the correct oil  my consumption dropped 50%.
Richard

[keithshotrodshop]

Well, thank you all for the help. Let me touch on a few things. Yes, I orignally was running 15/40 (at bob's reccomendation) but was told by several to go to a straight weight oil. I have not done a complete oil change yet, but since I started using straight 40, oil consumption has decreased greatly. The bus does not leak alot. A few drips here and there, but no real puddles. The oil analysis is a good idea. I just assumed that if there was coolant in the oil, I would see the typical "mayonasse" that you see in a gas engine. I see none of this, however my coolant has turned black with diesel smoke.

I think you guys have sold me on keeping the engine, and eventually turboing it, so I'll ask more questions in the future about that. I probably will overhaul my own unit, however what should I excpect to pay for a crate 6-71 on exhange?

[gg04]

The easiest swap is a 671ta ddec from a 89 to 96 transit...same left hand engine with a control box from a ford or gmc with the same motor adjustable from 220 to 350 hp.....Have over 50,000 on mine with really no problems...drives like a late model... Best other engine swap I have ever looked at was RW's with a series 50 and a auto....really clean swap into a Silversides....all doable at home..gg04

[tekebird]

you might want to check barnhart Bus in PA, they have some nice pics of a repower on a 37/4151

as for your cold starting......it should start on it's own well below 60 without heat or either.

if it is not it's because it can't produce enough compression (heat) to ignite fuel

you should easily be able to start down to around freezing without heat or either with batteries that are in good shape.

[tekebird]

http://www.bernhardbus.com/1947_silverside.htm

[keithshotrodshop]

The easiest swap is a 671ta ddec from a 89 to 96 transit...same left hand engine with a control box from a ford or gmc with the same motor adjustable from 220 to 350 hp.....Have over 50,000 on mine with really no problems...drives like a late model... Best other engine swap I have ever looked at was RW's with a series 50 and a auto....really clean swap into a Silversides....all doable at home..gg04

Do you have any pics of this swap? Where are you located, is there any chance I could see it in person. That kind of horsepower should handle an auto fine, if there is one that will bolt up.

[keithshotrodshop]

I googled that engine and came up with nothing. What brand of bus did it come in?

[gg04]

671ta ddec's are from flex metros and redone gmc rts's ....series 50 and cummins from the same models with reversers and 730's or voith transmissions....the 671ta ddec is a direct bolt in replacement..you can keep your original trans...or use the auto...enough power for either...same power and torque as a 6v92 but in alot tougher package...everyone told me when I started this conversion it would destroy the trans and driveline if I turned up the HP and torque...didn't happen..best To buy a complete donner bus ..that way you have all the parts to do auto trans if you want to..plus upgrade brakes and steering if wanted...gg04

[TomC]

Keith- in my opinion-it is time for a overhaul.  2 stroke engines should start unaided down to the high 30's.  I was in Grand Canyon for two days in late April.  Down to 38 at night. I started the bus on the second morning from the rear in case of needing starting fluid.  It rotated about to revolutions and fired up a bit rough with white smoke, but within a minute was smoke free running smooth-and this at over 6,000ft elevation.  Also, I get about 2,500 miles on a gallon of oil (8V-71N).
If I were you, I'd overhaul the engine to turbo specs, install an air to air intercooler on the right transmission door, install the turbocharger above the transmission, and run 7G75 injectors.  This will give a comfortable 300hp @ 2,300rpm, with 840lb/ft of torque-or about the power output of the 8V-71N.  Because of the air to air intercooler on the other side of the bus from the radiator with electric fans, you probably won't have to increase the size of the radiator, althgough it would be a good idea to have a row or two of tubes added.  I have seen this setup on a 4104.  The 4104 owner said made for a hot rod, and with the turbocharging, will not smoke at high altitude.  Would be neat to see a turbo on the 3751.  Good Luck, TomC

[keithshotrodshop]

Thanks, that is along the lines of what I was thinking. My radiator is brand new, so I'll probably try using it first, but if the temp rises, make it bigger. I've also thought of adding an additional radiator where the factory a/c used to be.