455 BBO Mods needed for auto transmission.
August 9th, 2011, 03:54 PM
#1
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Join Date: Jun 2011
Location: PHOENIX, AZ
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455 BBO Mods needed for auto transmission.
I'm looking at a big block 1972 455 BBO that's in a Ford truck with a manual transmission. What mods are needed to put this motor in my car with auto transmission. I have a 72 cutlass S ,stock 72 3 speed trans. Also why are the HP & Torque ratings different from 70 to 72. Is there really a noticable difference when driving or is it that way they had to rate motors because of the laws back then? It's confusing..Any help will be appreciated.
August 10th, 2011, 09:19 AM
#2
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Join Date: Mar 2007
Location: Northern VA
Posts: 47,259
I have a 72 cutlass S ,stock 72 3 speed trans. Also why are the HP & Torque ratings different from 70 to 72. Is there really a noticable difference when driving or is it that way they had to rate motors because of the laws back then? It's confusing..Any help will be appreciated.
August 10th, 2011, 09:26 AM
#3
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Location: PHOENIX, AZ
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72 455
Unbolt the bellhousing, remove the flywheel, bolt on a flexplate, bolt on the AT.
There were two issues with the HP drop. The biggest effect was the change from a gross HP rating to a net HP rating. Gross was the bare engine with an optimized air inlet and exhaust. Net was as installed in the car with real air cleaner, exhaust, and accessories. There is an SAE spec for this test configuration. The other issue was the federal requirement to use low-lead fuel starting with the 1971 model year, which lead to lowered compression and milder cam profiles. In 1971 GM published both numbers (gross and net). As an example, the gross number for the W-30 dropped from 370 to 350 HP. The net was like 320 HP, so you can see that the largest part of the drop was simply the test method, not the emissions changes.
There were two issues with the HP drop. The biggest effect was the change from a gross HP rating to a net HP rating. Gross was the bare engine with an optimized air inlet and exhaust. Net was as installed in the car with real air cleaner, exhaust, and accessories. There is an SAE spec for this test configuration. The other issue was the federal requirement to use low-lead fuel starting with the 1971 model year, which lead to lowered compression and milder cam profiles. In 1971 GM published both numbers (gross and net). As an example, the gross number for the W-30 dropped from 370 to 350 HP. The net was like 320 HP, so you can see that the largest part of the drop was simply the test method, not the emissions changes.
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