Augustus said:
As far as intenals all seem the same... Compressio, cam specs, induction...
Not quite. THe L48 had several notable changes from 69 to 80. CR DID in fact drop from 9 to 8.5 in 71. A number of heads were used over the years though the smaller valve size was used in all of them. Cat and lack of dual exhaust of course in '75. Ignition maps changed almost every year.
Augustus said:
but HP ranges from 270 to 190? Is this primarily due to the Gross to Net measurement.
Almost entirely due to change to SAE Net.
Augustus said:
I can't believe such a drastic drop on ratins. Even the 454 was at 270Hp in 72 and 73
Believe it. The SAE Net ratings are relatively accurate and rigorous. The previous Gross ratings were often grossly distorted to the delight of marketeers.
Augustus said:
My question is performance of the L48 from span 1971 to 1974 the same?
IMHO I belive yes... Maybe someone has greater insight, and I can learn a bit more. LOL
Same engine, different head castings, different ignition maps and different carb calibrations and different takes on minor emissions equip essentially.
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Tom73 said:
You are correct in that the '71 was rated at Gross HP while the '73 was rated at Net HP. Both engines were basicly the standard sedan engine but with a 4-barrel.
I think it's more accurate to say the L48 was an 'optional' sedan engine. There were more changes than 'just a carb' that included exh manifold, water pump, ignition, carb & carb calibrations, air cleaner, intake manifold, dual exhaust w/ dual mufflers...
Tom73 said:
Main difference would be that, more than likely, the '71 would have a higher compression as the '73 was designed to run on the lower octaine unleaded that was coming in a couple of years. Otherwise they were basicly the same.
Go back further to '70, for higher CR, the '71 had the same CR as later years. The 71 heads 'may' have had hardened valve seats. I think we can be relatively certain that hardened valve seats were standard by '73.
Augustus said:
That is an awesome site... A plethora of info for 73 Owners..
Those vintage artcles are great also..
Nicely done.
So main difference was CR... So it must have been 9.0 or highier...
See above... the big differences were a different head casting and different ign maps, different carb calibrations perhaps...
I don't see a website reference - can you re-post it?
