Where should a slant six with 9:1 Vacuum be at idle? i am Currently pulling 17-18 at idle, this is by hooking up a vaccum gauge to the driver side port on a edelbrock 500 cfm carb. How much vacuum at idle is normal? Running Howards 258 .473 lift camshaft.

That sounds quite good for that CR and cam combo. Adjusting valves and timing and idle mixture will have some effect on idle vacuum. Valve lash will have the biggest effect, and you can open up or close up the lash in 0.002"-0.004" increments to see how it runs. I usually end up looser than the cam manufacturer's specs.

Lou

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Hey thanks for the reply, Yes i had the dizzy recurved previous with a stock reman dizzy and the increase in compression i was not able to give a lot of Intial timing with out pinging i could only pull about 13 at vaccum, motor ran horrible alot of curb idle was needed resulting in other problems. I had the the dizzy recurved and it helped alot in power and mileage now i am pulling 17-18 vacuum, but i recently added a bit more timing just for fun and it was running bettter more power but i had light pinging under load. so i am probably going to get the dizzy slots welded up a bit more to achieve more base timing and slow down the advance if i can get 20-21 at vaccum that would be perfect, ill let you know how it goes. Also when i set the cam specs i went .003 looser got a better idle for sure, at factory specs car would idle way to high.

Sounds great. You are on the right track.

Lou

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