I just checked the vacuum on my rebuilt 261 and fiddled with the timing, and got only a mas of 15 inches. I thought it was due to the 3/4 cam or dual carbs, or leaky gaskets or bad valves.
However, after checking all that I talked to a friend and he said that engines produce less vacuum at altitude. Where I live is about 5,500 feet above sea level. My friend said its about 1 inch per 1,000 feet. He said 15 inches is good here and it would be 20-21 at sea level.
Has anyone else heard this?
'51 Chevy 1/2 ton w/'62 261, HEI, offy, fentons, dual carter/webbers, t-5 & 12 bolt posi
| 
