Engine Vacuum thru range - Team Camaro Tech
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post #1 of 3 (permalink) Old Aug 15th, 08, 03:05 PM Thread Starter
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Engine Vacuum thru range

I have a new ZZ4 Fastburn and want to dial it in. Running a vacuum off the carb I have no reading until I give it some throttle and it jumps to 10-15. Is this how it should be or should I go to direct manifold vacuum? What vacuum readings should I have at say 1000, 2000, 3000 RPM's roughly? I've never tuned this way so bare with this weekend hobbiest.

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post #2 of 3 (permalink) Old Aug 15th, 08, 04:37 PM
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Location: Oklahoma
Posts: 3,222
Re: Engine Vacuum thru range

You are on the port located above the butterfly at idle. There should be another port that has vac at all times.

As for what readings, that depends on the cam and it sounds like you have a mellow one if you see 15". Not familiar with the stock cam. Sorry

Tim Smith
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post #3 of 3 (permalink) Old Aug 16th, 08, 10:41 PM
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Question Re: Engine Vacuum thru range

I've searched this same topic on here before. Search anything "vacuum", "engine vacuum" in Engine and you'll come up with a lot of info on this topic. As for me, I had just installed a new Edelbrock performer 600 and the car runs better and starts easier. I measured both ported (passenger side)and full manifold (driver side) and was only getting 5"! I called Edelbrock and of course they asked me what cam I had... no idea, it was already in the car. Let's just say it has some long duration! Anyhow, they told me with just 5" it would mean that it was a full race cam. Who knows? When my RPM increased, my vacuum increased. I will be looking at a few things tomorrow to find out why all this is happening. It's running real rich and my mixture screws don't have any effect on RPM. Float stuck maybe? The joys of searching and learning all of these little things. Sorry for the tangent!!


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