High comp 472 vs. low comp 500
- Thanks to Richard for this post:
My '70 Fleetwood with the 10:1 472 runs like a Swiss watch on 89
octane when it's lightly loaded and the ambient temperature is no
more than 85 or so (engine temp 180-190). When it's heavily loaded
and the temperature goes above 95 (engine temp 210-230) not even
straight 93 octane will keep it from rattling.
My '69 LeMans with an 8.5:1 500 never knocks on 87 octane with the
factory spark timing. The weight difference between the LeMans with
me in it and the Cad with a full load is easily over 1000 pounds,
which makes a big difference too. If you're thinking about which
engine to put in a 7000 (I hear) pound hearse, the 8.5:1 engine would
definitely be the way to go.