Where should I look for a vacuum leak?

[priderocks]

Pretty sure I have a vacuum leak. The engine is a pretty stock rebuilt 383, power brakes, stock distributor with vacuum advance. What sources of leaking should I be looking for? I said stock but I actually have an extremely mild Racer Brown camshaft, but still have only 12 inches of vacuum. According to the folks at RB, it should be more. Plus, the car acts like it has a leak. Where are leaks most likely to occur and be substantial enough to adversely affect performance? I intend to reseal the intake as the last resort. Could a crack in a power break hose or vacuum advance hose be enough to make a car run crummy? Hoses are new.

[Bullitt-]

spray some carb cleaner around everything to do with the intake, carb & vacuum hoses while the engine is idling.    When you hear the idle change your zeroing in on it....don't forget the brake booster

[Moparal]

   pcv valve check ball, and I hope you degreed the cam in place. How is the timing?

[NorthWestcuda]

You might also disconnect your boster and plug the hose.  If this increases your vacuum your booster probably has a leak.  As Bullitt said though, spraying  carb cleaner around it will do the same.  Be very careful,

[Chryco Psycho]

power brake booster is often a problm , it i seasy to check just plug the port on th eintake & see if it runs differently
 where is the timing set , you may not have enough advance

[MEK-Dangerfield]

Under the carb, or around the intake manifold are common places for leaks. Can I ask what makes you think you have a vacuum leak?


  Mike

[priderocks]

MEK, my carb is an Edelbrock 1406 (new), which is a 650 cfm. The car comes off choke properly, idles well, but off idle to about 2000 rpm the car boggs badly, occassionally backfiring.  But the giveaway to me is the car seems to surge at steady throttle. What does that sound like to you?

[Chryco Psycho]

well timing , low float level , not enough fuel being squirted in as the throttle opens ,weak fuel pump , wrong springs under the metering rods could all cause soem of the problems

[hooD]

MEK, my carb is an Edelbrock 1406 (new), which is a 650 cfm. The car comes off choke properly, idles well, but off idle to about 2000 rpm the car boggs badly, occassionally backfiring.  But the giveaway to me is the car seems to surge at steady throttle. What does that sound like to you?

well timing , low float level , not enough fuel being squirted in as the throttle opens ,weak fuel pump , wrong springs under the metering rods could all cause soem of the problems

   Sounds like a lean fuel mixture with the occasional backfiring.  I'm assuming that its spitting up (backfiring) through the carb....right?
Have you tried adjusting the air/ fuel mixture screws?