Carb Way

what is the best way to tune a carb, that has a loby cam?

i no how to tune a carb on a engine that idles smooth, either with a vacuum gauge or a rpm meter! you look for the highest vacuum or rpm for each side of the carb at idle!

but with a loby cam, the idle is very erratic! so is there any other way to tune it other than just doing it by ear?

You use the same means, just do it alittle diff.

The engine will smooth out as the RPM comes up, set idle RPM higher than norm so its somewhat smooth (1000-1300 rpm), then use a vac gauge to tune mixture screws to highest vac reading.. Then lower your rpm back down to norm idle rpm.

Now a few other tips.. Engines with big cams likes more timing at idle. Set timing at idle to 16-18* BTDC with vac advance un hooked, then limit the mech. advance in the dizzy to give you a total of 36*, and use a recurve kits springs to get total timing all in at 3,000 rpm

Use an adjustable vac advance can on dizzy to dail in as much timing as the engine can take with out pinging. The amount depends on compression, head type, cam size, etc. Most performance engines will be limited to 8-12* of vac advance though. Use full manifold vac for the advance, not ported/timed

Big cams make less vac at idle and that can cause all types of probs with carb dail in.

Check your highest vac reading at idle with transmission in drive.. Half that number.. Now install a power valve or step up spring in your carb that matchs that halfed number of your vac reading.

Like if you have 10" HG at idle, install a 5" power valve if holley, or 5" step up spring if carter/edelbrock

Take out the std PCV valve and throw it away. Buy a PCV valve for a 1969 camaro z28 DZ302, parts stores norm stocks these (why I don't know), and install a true valve cover breather on the other cover