Could someone pass on what the acceptable manifold vacuum range would be for a 1966 L-79 engine using all stock components (carb,cam, manifold &pistons. thanks
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Re: manifold vacuum 1966 L-79
I have a 66 L-79 with no other vacuum options and mine is at 15 in. hg. Most of the Chevy small blocks that I have worked on fall in the 14-16 in. hg. range. Gary -
Re: manifold vacuum 1966 L-79
Hi Pete,
I have a '67 coupe with a stock L-79 engine. The manifold vacuum readings that I am now getting are the 18" range. These readings were lower, say in the 15" range until I performed some checks and repairs. First, I checked all of the fittings and hoses on the engine and PB booster for leaks. I also replaced the brass A/C vacuum switch and length of hose from the manifold to the heater box. In addition I checked the carb over to ensure correct float level, idle mixture, base gasket sealing and throttle shaft wear. Simply by adjusting the mixture on a good day brought it up about 1". The dwell angle and timing were also checked. Idle speed is set to 700-750. Finally, I replaced all 16 valve seals on the cyl heads with the new posi seal type as there was an oil consumption problem. The job was completed with new intake manifold gaskets. All of these checks and repairs helped bring up the vacuum a total of 3". Depending on the altitude of where you live, the readings would likely be lower at a high altitude say in Denver (alt=5000 ft), versus the southern Ontario region where I live (alt=700 ft). From my experience on nearly a dozen Chevy small block equipped cars that I have owned over the years, on a stock passenger car 350 for example, the manifold vacuum readings for engines in good mechanical condition were in the 19" range at idle (in park or neutral)...typically on a high perf engine the readings can be much lower..my '72 LT-1 for example with stock solid lifter cam produced manifold readings of only about 15" because of the high lift, long duration cam. Hope this helps...Comment
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