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I'm possibly looking at buying 1 of 3 crowns right now. One is a 1975 35' with a Cummins 855 or NHH-250, The other is a 1966 35' with a Cummins 743T or NHH-262, the third one is a 1976 but I don't know anymore, I'm going to see it tomorrow. Any advice between the 2 Cummins?
Andy
Every Crown built was a custom built bus. There was no "standard" Crown. So every Crown is just a little bit different.
I have seen just about every combination of engine and transmission. The most common power package combination in the last twenty years of production was the 6-71 with an Allison. I personally have seen more DD's with the RR's than I have the Cummins. Most of the Cummins powered Crowns I have seen came with the Allison.
Standard transmissions became the exception rather than the rule. Road Rangers became extrememly rare due in large part to the fact they are much more difficult (read that expensive) to train drivers to drive them properly compared to automatics. Add to that fact the RR's became a more expensive option than the automatic and you can understand why so few buses were built with RR's.
All things being equal, the small cam NHH220/262 is not as good of an engine as the big cam NHH250. For one thing, the head design was changed making the newer engine less prone to head gasket leaks. In addition, the big cam engine can be hot rodded to much greater HP than the small cam. For the small cam, 262 HP is about the top of the charts. For the big cam, 300-350 HP is possible.
The majority of Crowns left the factory in the later years with the DD 6-71T which was rated at about 250 HP. The odds are pretty good the third bus has the DD.
The DD is a very good engine but the 2-cycle engines just don't put out the HP as well as the 4-cycle engines do. The 6-71T can be hot rodded but about the most you will get out of one is 275-300 HP. You will also start to have problems with overheating.
Thanks for all that info Mark. I just looked at the 3rd bus. It didn't have the Crown ID plate so I'm not too sure about it. The engine didn't look like the Cummins motors that I've seen so I think you're right it's a Detroit 671. Also the first two buses have the Roadranger 10 speed and this one has a 5 speed so I think I'm leaning towards the first two. I've never seen a 671/10 speed combo. Did the ever offer that or did all the 10 speeds go with the Cummins?
Get the 10 speed!! I have a Gillig with a 10 speed Roadranger '64. Also,I have a 70' Crown tandem with 671 Detroit turbo with a Allison 6 speed auto. Glen, Mojave ca.