71 vs 92 Series

[TomC]

All this talk about the two 2 stroke series used in buses (there was a 51 and 53 series-noisy with not enough power, 110 series-not used on highway, and the 149 series-way to big and heavy) and that some think that they might have a 92 series, or maybe a 71 series.  Here are the distinguishing differences.
71 series-  It was made in 1, 2, 3, 4, 6 cylinders in-line; 6, 8, 12, 16, 24 cylinders in a V.  The 4-71, 6-71, 6V-71, 8V-71 were the popular bus engines (MC6 originally had the 12V-71, but were all replaced with 8V-71T's).  The 6V-71 and the 6V-92 both look identical if both were either turbo or not turbo.  The main way to tell if you have a 71 series is to open one of the valve covers and look at the 4 valve configuration (if you have a 2 valve engine it is definitely a 71).  On the 71 the valves are positioned in a square, whereas the 92 series has the two bottom valves further apart then the top valves. 
The 92 series was made in V's at 6, 8, 12, 16, 20  (8 cylinder in the middle with a 6 cylinder on each side).  The 8V-92 has a vibration dampener on the front of the engine (looks like a small flywheel).  The blocks are also stamped 92 behind the thermostat housing (can't remember if it is on the right or left side).
All 2 strokes could be rotated either direction with a cam and oil pump change.  The 6-71 was used layed down under the floor in Crown and Gillig school buses.  I've even seen generators on off shore oil rigs with a 12V-71 stood up vertically with the generator at the bottom and the engine on top.  Good Luck, TomC
                                               
                                               

[DrivingMissLazy]

Tom, quick question. Roger Penske had a very nice yacht that I installed a ShorPower converter on. He had three 24V propulsion engines. Could they have been 92 series instead of 71 series. Cost at that time was of course of no consequence. I think they were installed in the early 90's.
Richard

[TomC]

Those were 24V-71TA with 4 turbos and 4 blowers per engine rated at 1800hp at 2300rpm.  They were two 12V-71's put together (if it had been 92's it would have been 3 8V's put together-which I don't believe was made by Detroit).  It was the last big 71 engine made.  The fishermen loved them since they were low profile engines and with 24 cylinders, were turbine smoooooth, but not real fuel efficient.  Now, Roger Penske I believe has his yacht powered by a pair of 16V-2000 MTU's that put out around the same 1800hp.  Good Luck, TomC

[RJ]

All -

Another quick way to determine if it's a 71 or 92 series is to look in the center of the camshaft idler pulley, on the opposite end of the block from the transmission.  Cast in the center will be what engine it's installed on (6V71, 8V71, 6V92, 8V92).

8V92s are extremely easy to determine - the crankshaft pulley/vibration damper is HUGE.

FWIW & HTH. . .

[NJT5047]

Another way to tell a 71 from a 92 series is the shape of the inspection port covers.  92s have large square covers. 
Regarding the 2/53 engines being noisy...you got that right.  I had a John Deere tractor (D435) that was noisy as #ell, but that thing ran and worked until I got tired of steering it after 20 years..  A shot of either in weather below freezing and it would always fire right up.  Ran on fumes.   That was really the only redeeming quality of the tractor.   The DD 2/53 was a short, unloved JD experiment that farmers didn't buy into.   Unlike the marine industry, farmers didn't care for small diesels.  It wasn't considered a real JD unless it was a "Johnny Popper".   
JR

[luvrbus]

you may not believe this but Richards x  bus DML has a 8 v92 in it without a damper on it