on 9/16/01 6:48 PM, Andrew B. Lundgren at email@example.com wrote:
> How many horses were lost when they went to the low compression
> Andrew Lundgren
Good question. There are other changes that make it not quite clear cut (for
example, smaller inlet valves starting in 1975), but one way of looking at
it gives a 17hp net loss between 1972 and 1975. This may not sound like
much, but is a greater than 20% loss, which would have to be significant in
performance terms. The last RB cars (I think 77-80) picked up another 5 or
6hp somewhere (I think chiefly by going to electric fans), so let's regard
these as optimal for the single carb configuration. In that case, it almost
looks like you'd be right back with the 1972 cars if you converted one to
dual carbs. It's a little hard to compare the pre-smog cars with the 72 and
later models because all the sources switched from Gross to Net horsepower
ratings in that time period. So the difference between 98hp (gross) in 66
and 79hp (net) in 72 sounds a lot bigger than it is. The real difference is
probably less than 10hp net, basically attributable to detuning for smog
control (plus air pump parasitic losses).
Back to your question, my guess is that the change from 8.8:1 to 8.0:1
compression in itself cost maybe 5 to 8hp net, at most. One could answer
precisely by comparing the figures for the HC and LC engines for a given
year, but I can't recall ever seeing those figures in print.
BTW the above applies to NA models only.
'66 MGB GHN3L76149
If you're near Mountain View, CA,
it's the red one with the silver bootlid.
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