I just read the article. Unfortunately the author is a tad misinformed about the SBB. He made a few false statements. Pick them out for yourself. "The very mild factory cam used in the 1970 GS350 is the same one used in the 280 HP 350 Skylark of that year. Both engines were rated at 10 to 1 compression. The 1970 GS350 was given a rating of 315HP because of the ram air effect of the GS hood..." Regardless, my question was answered. I would feel better if a leak down test and a cam measurement was performed on the engine prior to the test. They did a compression test where all cylinders were between 157 and 163 which is better than nothing. I find it surprising and disappointing that the factory overrated the engine.
The GS hood creates almost no ram air effect because it is too short to get out of the boundary layer. Plus the ram air effect, as opposed to cold air, starts to be significant above 100 mph.
Misinformed or, inaccurate would be correct while the term "false statements" implies the author made statements knowing they were incorrect. He certainly didn't do that. To wit, only two of the statements were inaccurate. "The very mild factory cam.........is the same......." -- True statement. The cam was identical on all 350 motors '68-'72. "Both engines were rated at 10 to 1......." -- 2 bbl & std. 4 bbl motors were 9.0 to 1. 315 HP motor was 10.25 to 1. "1970 GS350 was given a rating of 315 Hp because of the ram air......." -- arguably partially true. The rest was compression and distributor and carburetor calibrations. Here are the three Buick 350 engine codes available in 1970: Code SO - 2 bbl carb, 230 HP, 9.0 to 1 compression Code SB - 4 bbl carb, 285 HP, 9.0 to 1 compression Code SP - 4 bbl carb, 315 HP, 10.25 to 1 compression As for the factory over-rating the engines, it was common back in the "high performance" days for the factories (all of them) to overrate the motors that gave the cars more than 10 pounds per HP. On super high performance motors that would be under that, they often lied so as not to be penalized by the insurance companies. (or, perhaps by the NHRA?)
I remember in the late 60 and early 70s that so often you had to finance both your car and your auto insurance premium payments. For some their monthly insurance payment was more than the monthly car payment. All the factory compression ratings seemed to be 1 point or so above the real compression ratios. There were NHRA factoring considerations for drag racing and GM policy limitations for a 10 to 1 maximum power to weight ratio. There were rival company ratings considerations that sometimes made one manufacturer put their thumb on the rating scale to make it look like they were competitive. You drive with torque while you sell cars based on the maximum horsepower ratings. It is the area defined by the area under the torque/horsepower curves over an rpm range that really counts and not the maximum horsepower ratings.
I did not imply a Buick brother was lying. I stated he was misinformed. according to the 9/69 Buick parts book there were at least two 350 cams in 1970. Evidence is here http://www.v8buick.com/showthread.php?59353-What-to-do& the NHRA specs show 3 1970 350 cams and their specs. It's possible that there was a unique SP cam that was never in the Buick parts book. It would be interesting to know where the NHRA got their info. NHRA specs below H.P. Disp. Cl Dish/Dome Ht/Vol Valves Cam Lift Springs Notes 260 350 .010 Dished .235" 1880/1505 382/389 Outer Only 285 350 .010 Dished .235" 1880/1505 377/384 Outer Only 315 350 .010 Dished .075" 17.3 cc's 1880/1505 382/398 Outer Only A
Yes, there were two cams listed in 1970 but, one of them was for the 350 2 bbl motor. (your link provided states this in post #14 & 16) We've been talking about the 285 HP and the 315 HP 350 motors. They both used the same cam. As for the NHRA listing 3 cams, that is easily explained by looking at the 1st cam on the list. It is for the 260 HP motor. That motor is the 1971 and up 350 4 bbl motor (with 8.5 compression) and was not available for the 68-70 motors. (see the link post #18) It's possible that the NHRA was using a later Buick parts book which listed the "260" cam as a replacement for 350 motors. At any rate, the 4 bbl 350 motors all used the same cam from 68-70.
Ray, I hope I haven't offended you. I'm not here to ruffle feathers or prove I'm right. I find this stuff very interesting and would love to get to the truth or as close as we can to the truth 46 years after the fact. There are inconsistencies in the specs so naturally I want to find the truth. I should've posted the complete 1970 NHRA specs. link to NHRA specs http://www.nhra.com/tech_specs/engine/blueprints/BUI-70.rtf or click below Another thought was what if you built a blueprinted '70 SP 350 and milled the block to get the true 10.25:1 compression? If the '77 SBB in the article made 302/408, a 70 SP with a true 10.25:1 just might make 315/410 with a stock cam. It might be a challenge to run it on pump gas though.
No offense taken in the least. I also enjoy uncovering correct info after all these years. Looks like the NHRA specs on the 260 HP motor actually didn't refer to the '71 and up 350 but referred instead to the '70 350 2 bbl motor. I've seen different HP ratings for the 2 bbl. motor, 230 HP and 260 HP. Either way, the NHRA spec shows a unique part number for the 2 bbl motor and again, the two 4 bbl motors used the same cam. Yes, it would be fun to be able to test a fully blueprinted '70 350 motor. Perhaps someone on the forum has done one with a stock cam or maybe Jim @ TSP has done one in the past.
Old thread but interesting. Stock intake, mild cam, and stock manifolds I'm assuming? 302 HP is pretty impressive.
