EN331 (B-30) Engine Speeds Question

[dmlinton]

The Mack literature I have found for the B-30 so far gives (max?) torque rating at 1400 RPM and max horsepower at 2800 RPM. Would 1400 be on the low end of shifting RPMs and 2800 on the upper end? Disregarding speed and transmission/rear end ratio considerations, about what RPM would that EN331 be happiest at cruising down the highway?

The reason I am asking is that I have been working out ground speeds for the various combinations and permutations of transmissions, rear ends and tire sizes for the B-30P. Wish I had the truck home or had at least known enough to get the transmission and rear numbers when I looked at it.

Calculation results are fascinating - one of the first things that occurred to me is that a buyer would really need to have a had a thorough understanding of what he was going to haul and what the conditions would be as it would otherwise be easy end up with what appeared to be a gutless wonder or a speeding snail. At 2800 RPM with the standard issue 9.00x20 tires, top speed would for the TR-85 trans with highest drive axle reduction (8.68) would give a top speed of about 34 mph. Same transmission with two speed drive axle (8.28 & 6.00) would allow top speed of about 53 mph.

Interestingly, the standard TR-73 transmission with the lowest drive axle ratio (5.37) would allow for nearly 60 mph while the optional TR-730 (overdrive) transmission and lowest drive axle ratio would have allowed for nearly 70 mph. This all assuming, of course, that the truck did not either run out of horsepower or get to its destination or stop signs before it got up to those speeds.

Thing is, I don't think 2800 RPM would be the happy cruising speed for that engine. Maybe 2400 or 2500 RPM? I need some expert guidance here as I work out what my options might be in restoring my B-30 while keeping it within the realm of what a B-30 could have been upon seeing its first light of day.

[j hancock]

That is pretty much the story. Decent low end torque but not a high rpm motor. A B30 back in the day would have been a local truck. It would have been used in town or between towns. Probably most were geared to run up to 45-50 mph.

[fauthpk]

I have a B20 with an EN 291, 5 speed. I'm lucky if I hit 45mph. But I'm not in a rush when I take her out.

In your booklet it will also tell you not to lug or over rev the engine. At this point I have owned the truck for 6 years. I can shift up and down based on sound of the engine.

That is pretty much the story. Decent low end torque but not a high rpm motor. A B30 back in the day would have been a local truck. It would have been used in town or between towns. Probably most were geared to run up to 45-50 mph.

That is correct. Also the reason why the small B models don't have the rot like the larger versions. Not exposed to road salt as much.

[dmlinton]

I have a B20 with an EN 291, 5 speed. I'm lucky if I hit 45mph. But I'm not in a rush when I take her out.

In your booklet it will also tell you not to lug or over rev the engine. At this point I have owned the truck for 6 years. I can shift up and down based on sound of the engine.

That is correct. Also the reason why the small B models don't have the rot like the larger versions. Not exposed to road salt as much.

I got the ol' girl home yesterday. No brakes at all. Clutch pedal stuck down. Construction guys giving us the thumbs up on our way by.

I didn't like the spot I had parked it yesterday so was wiggling it into a better spot with my JD 420 crawler loader. Anyway got a brain storm as the old crawler found the truck a handful in neutral so figured I didn't have enough power to hurt anything. Pulled the clutch pedal up and shift trans into highest gear it would slip into easily, which turned out to be 4th. Checked the cooling fan position and jumped on the crawler and gave her a push. Wheels didn't slide and fan was in different position. Therefore, there is at least some clutch there, which I figured because the guy had been hauling a 2000 Imp. gal water tank with it, and the engine is free.

Next step, because starter has broken bendix spring, is to jack up one rear wheel, install a flat belt from tire to pulley on my 1952 John Deere MTW

(it should make a pretty good little starter), set him in motion, jump in the truck and see if she will start. There are, of course, a bunch of other checks like oil levels and coolant to check before doing any of this.

Owner said he could get over 60 mph of it going downhill loaded (up to 2000 Imp gals of milk). Calculated the speeds given TR-73 direct, lowest ratio (5.37) rear end and 10.00x20 tires and, indeed, she could hit 62 mph at 2800 RPM. The upside is that she should cruise along at 50-55 mph at a reasonably sane RPM (2250-2500 RPM).

In another development, I looked at a 1992 Navistar 4900 w/DT466 and 6 Plus transmission. Checked around and can buy this truck for less than the same motor and trans just pulled out of a truck. This could be a repower option to help insure that that Mack is going to run so well that I will feel very bad pulling the original engine out.

[Maddog13407]

exactly why your better off finding a B20, B30,B42 for the sheetmetal and a B61/B53 for the driveline if you intend to drive it far. the smaller gas jobs didn't see much over the road. they were delivery trucks and site construction trucks and didn't see the road salt.

[Maddog13407]

snap the points and stick her in 3rd gear and drag her around with a fresh can of gas in the cab and a cheap hose connected to the fuel pump. she might surprise you and take right off.

[dmlinton]

snap the points and stick her in 3rd gear and drag her around with a fresh can of gas in the cab and a cheap hose connected to the fuel pump. she might surprise you and take right off.

Yabbut, she's got absolutely zero brakes. Now, I have driven enough of these old trucks to know that it would probably rather sit still than go once the clutch is released but, although with the terrain around here, I can guarantee she'd stop with a quarter mile (and maybe change direction), but I don't really want to find out until I have brakes ... just in case. Of course, I could just turn the key off if things got spooky.

I do actually rather suspect that she will be running by Sunday evening. Would have been tomorrow evening but came across another crawler (JD 440C) that will take about 4 hours round trip to check out and that will start to make my collection JD pre-industrial series of crawlers almost complete. Don't have an MC but have a MTW and don't have a 430C but there were so few of them made that even if I could find one, I doubt I could afford the purchase price.