Need help ASAP..Changed cam..Low vacuum - Team Camaro Tech
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post #1 of 7 (permalink) Old Apr 12th, 02, 02:57 PM Thread Starter
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Guys I need some help..I have changed the cam on my 355..To a lunati([email protected] duration with a 511 lift)Since the cam change..I have had some strange idle problems...Problem #1..I only have 4-5" of vacuum...(Compression 180lbs in all cylinders)Not sure how much vacuum to expect with this cam...Problem#2..I have a edelbrock carter 750 and can't seem to get the idle circuit to function correctly(I don't believe they are working at all)..and I have gas dribbling out the primaries at idle...Runs ruff at idle but smooth up when I crack the throttle..Not sure if the cam is causing the vacuum problem or if the poorly running carb is causing the vacuum problem???or could it be the low vacuum causing my carb problems???( I have checked repeatedly for vacuum leaks..None found)NEED HELP GUYS GIVE ME YOUR THOUGHTS..Thanks

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post #2 of 7 (permalink) Old Apr 12th, 02, 04:54 PM
 
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246 @ .050=low vac.
fuel dribble=floats to high
Have someone that knows carbs dial it in for you as it will be nessary with this cam.
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post #3 of 7 (permalink) Old Apr 12th, 02, 05:05 PM Thread Starter
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Well Update..I was going to order a rebuild kit for the car when I checked the # ..It is not a 750 carb but a 600...Can the fact that it is only a 600cfm carb cause my problem??? Is 600CFM carb big enough??

Also what do you guys think about my Vacuum pressure..Is it Normal for my cam??

Thanks
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post #4 of 7 (permalink) Old Apr 12th, 02, 11:14 PM
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How much initial timing do you run? This will directly affect your idle vacuum. Something in the 16-20 range would be a good start. I wouldn't expect more than 8" with a cam of humongous duration like that.
What power piston springs do you have in the carb? You may not have enough vacuum to keep the primary rods down in the jets and need a lighter spring.
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post #5 of 7 (permalink) Old Apr 13th, 02, 04:12 AM
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Check your valve adjustment. Comp Cams warns that too much pre-load on the lifters will cause low vacuum. [email protected] is a lot of duration don't expect to get too much more out of it...

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post #6 of 7 (permalink) Old Apr 14th, 02, 12:51 AM
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Don't know much about Edelbrock carbs but to get cars with big cams and Holley's to idle, you sometimes have to drill small holes in the primary throttle plates. (less than 1/8")

The problem is, in order to get enough air for a good idle, you have to open the throttle past the idle/transfer slots in the throttle plate. By adding the small holes, you can get enough air in to allow proper idle mixture adjust.

Like DjD said, that's a pretty big cam. Don't expect to get much more vacuum out of it!
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post #7 of 7 (permalink) Old Apr 15th, 02, 04:41 AM
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<BLOCKQUOTE>quote:</font><HR>Originally posted by onovakind67:
What power piston springs do you have in the carb? You may not have enough vacuum to keep the primary rods down in the jets and need a lighter spring.<HR></BLOCKQUOTE>

I battled this SAME problem this weekend with an Edelbrock 1405 carb. Fuel was dripping from the boosters. A step down to the blue spring solved this problem for me.

I also have low vacuum at idle (10") the rods must have been in the up position the whole time at idle and not enough vacuum to work against the spring.

-Funk

[This message has been edited by CFunK (edited 04-15-2002).]

[This message has been edited by CFunK (edited 04-15-2002).]
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