Bombraz:

I do not have the software you need, but I can recap what I have learned from messages above. There are at least three (3) H.P. rating schemes:

1. Bare engine, no generator just water pump. This is probably what you are used to and what I read in the early article about the Isky-280H cam.

2. Engine with generator and transmission, H.P. measured at the tail shaft. This is apparently what GM changed to in about 1972 or so as explained above by Gary. This is about 50 H.P. less that in 1.

3. Rear wheel H.P. measured by a chassis dynamometer with the car on rollers; this is the "real" H.P. of the car but may be only about a hundred or so.

I was also fooled by the change in the way H.P. is/was reported in the early 1970s, but I think something else was going on. I bought the cheaper two-bolt 350 that came in the '76 Corvette and it was rated at only 190 H.P., presumably at the tailshaft, BUT (!) the heads are the 883 castings, definitely NOT the high flow heads. Thus you may be one of the lucky owners of the earlier 350s with better heads. Check the last three digits of the casting number in the middle of your heads between the rockers and compare to:

http://www.angelfire.com/tx5/randysr...Headguide.html

You probably have better flowing heads on the '71 than on my '76 350. I am going to trade in my two-bolt for a four-bolt block but keep the low compression heads and only use a torque cam from:

http://www.kendrick-auto.com/chevrol...y_cam_spec.htm

GM part # 12353915 developed by Crane with/for GM looks like what I want with duration (194) less than 200 degrees for economy and slightly more lift than the stock cam. With only three speeds on my TH350 I have to use a 2.79:1 8" Maverick rear to get some economy so I need torque in the low rpm range. I guess I just want a mild street rod and I do not intend to race at my age (66) so I am hoping for 18 mpg with maybe only 250 (tailshaft) H.P. in a light roadster body. By the way if you check the weight of Corvettes in the '70s they are not as light as you might expect and are usually over 3000 pounds, so I hope a 2200 pound roadster will move OK with only 250 H.P. and I can use 89 octane gas and get 18 mpg and still have fun. I really like the Essex 350/350 installation on this thread as something one can do without much help from a shop and still get a neat installation.

Best Wishes,
Don Shillady
Retired Scientist/teen rodder