Net HP Figures ????????????

[HI WINDING MONZA]

Basicly, what I've read is that the difference of gross HP ratings and Net ratings is 90. ( add 90 to the net to get gross) Now on big blocks, I've read its 120? My "new 425 cid " motor is rated at 180 Hp - 260 Tq net and with a .030 overbore, I'm thinking 190 Hp net- 270 Tq net. This is with A/C, PS, Alt, waterpump and mechanical fuel pump . I eliminated the fuel pump , PS , and A/C. Any Input? This is a completly stock rebuild including the cam with only the overbore . Doug in AZ

[res0o7eb]

A percentage would be better. I think in 1973 the HP values for new cars were SAE Net values. In 1972 they were gross values. So, a percentage factor could be calculated using the two HP numbers for the same engine. Granted there were a few differences and emission requirements were rearing its ugly head.

[Sirshredalot]

I am not sure but I also believe they where rating horsepower numbers at 3500 rpms too.

I have a feeling that it would be difficult to get only 260lb ft. of torque out of 425CI.
My brothers buick 455 4bbl from 1973 made 300hp and 500lb ft. of torque bone stock thorugh the exhaust manifolds.

God bless
-Shred