(The rod ratio is as you've correctly guessed, something like 1.7 and
above
is desirable. The std. P76 motor has a stroke of 3.5" and a rod length of
6.25" this gives a ratio of 1.78. The higher the ratio number, the longer
the piston 'pauses' at TDC and BDC. This has benefits for the combustion
process, but I can't remember the details.)
Reply:
A rod/stroke ratio below 1.5 is not ideal and a rod/stroke ratio is very
good, however, many successful engines have a rod/stroke ratio between
1.5 and 1.7. I read an article once that ran a Chev 383 strocker on a
dyno with 2 kits using different rod lengths. The engine produced around
400bhp, and the difference was 15hp max (started on come in above 4000
rpm). There was a correponding small increase in torque (but still in the
2% to 3% range). Worth considerating but not of overwhelming importance.
A P76 crank in a Rover/BOP block has the following rod/stroke ratio:
Rover 5.66 rod 1.62
Chev 5.70 rod 1.63
Chrysler 5.78 rod 1.65
I have an Excel spreadsheet that allows modelling of different pistons
(compression height, bowl volume etc) for Rover/P76/BOP standard and
stroker engines (including compression calculation). If me know if you
would like me to email you a copy.
(Does anyone know what the factory specification for deck height
(crank centerline to top surface of block) is for Rover 3.5, Rover 3.9, or
BOP 215?)
Reply: The block height on the only Rover 3.5 I have measured was 8.9565"
The Prostroke P76/Rover block 272ci kit looks like it will retail for
approx. AU$1800 (US$1134).
Regards,
Peter Kent
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