| Author | Message | ||
     Carl Jones Experienced User Username: carl888 Post Number: 12 Registered: 4-2013 |
Assuming the same transmission, what differences if any would one associate with either engine? Is there any preference? I have never been in a 6 1/4 litre equipped Silver Shadow. I suppose one would assume the 6 1/4 engine is slightly smoother with less low down torque, is this correct? I notice that both variants feature the 3.08:1 final drive so the rpm/km/h remains the same. | ||
| Bob UK Unregistered guest Posted From: 94.197.122.76 |
UK cars with 6250cc came with a 4 speed and fluid flywheel So it's difficult to judge. But I suspect that both engines produce about the same power. And use about the same amount of petrol. I think one wouldn't notice s difference, with a three speed box and covertor fitted to a 6250. (Message approved by david_gore) | ||
| Carl Jones Experienced User Username: carl888 Post Number: 13 Registered: 4-2013 |
Thanks for the reply Bob. I've incorrectly assumed that Australia at least in 1969/70 would have received the same specification cars as the UK. Here we have a few what I suppose you'd term, an "Intermediate" Silver Shadows. That is from about #4483 the transmission changed to the turbo 400 sometime in 1968. Then at #8742 in late 1969 the 6 3/4 engine arrived. Not sure how many cars in total but I've seen maybe half a dozen over the years. Never been in a 6 1/4 Silver Shadow but I recall my friends folks had a Silver Cloud II and I particularly remember the refined engine. | ||
| Jan Forrest Grand Master Username: got_one Post Number: 755 Registered: 1-2008 |
I may be wrong, but my understanding of the increase from 6 1/4 to 6 3/4 litre swept volume was in response the the fledgeling California anti smog laws (first in the world). In order to keep within the specifications all new cars were fitted with exhaust systems that effectively strangled the engine through excessive back pressure. Crewe decided the easiest way to combat the reduction in HP at the wheels was to bore/stroke the engine block for a little more volume/power. | ||
| Bob UK Unregistered guest Posted From: 94.197.122.83 |
The California smog laws did prompt the increase also a 7250 engine was made but not used. Fortunately in the UK we don't bother with smog and old cars. So one can tune the engine, as long as there's no smoke. I think a restrictive exhaust makes for unhappy engines. (Message approved by david_gore) | ||
| Jan Forrest Grand Master Username: got_one Post Number: 756 Registered: 1-2008 |
The UK 'no smoke' rule only applies to the earliest Shadows and previous models. Later models ('64 on?) have to pass the same pollution levels for CO and other hydrocarbons as 21st century cars. |
