vacuum leaks......

[grande_guerre]

I need help. My 84 351W that i just put in has a vacuum leak, i think... it idles like crap but acceleration is fine. Decel is crappy too. any help would be awesome. it's carberated too. thx.

 

[Bully Bob]

Did you try spraying carb. cleaner around carb & intake..? RPM's will climb when you hit the spot/leak.

OR ...sometimes they run better with vac. advance disconnected. (cheap gas)

OR... sounds more like a timing issue.

A vac. leak sometimes runs better with choke on...this would prove it's a vac. issue.

 

[Seabronc]

Definately use some carb cleaner as Bully Bob says. You might also want to add some to your gas. Check your hose connections to make sure there are no broken or cracked connectors. If you have beden working in the area of the Ported Control Valves (AKA Vacuum Control Valves VCV on the vacuum diagram), they can get broken off fairly easily. If they all look good, based on your description, I'd guess the EGR valve is sticking or the control to it is not functioning correctly.

Goood luck,

>-

 

[grande_guerre]

The thing is, i'm terrible at vacuum and when i swapped the motor, i just hooked the carb up correctly with vacuum, but everything else, i just hoses to and went from memory of the old engine. I also stopped every port i didn't use. There are no check valves anymore, i didn't know where they went. I've sprayed wd-40 around some of the spots i think it is and it doesn't run as rough at idle anymore. so i think i've narrowed it down to a vacuum restrictor that's on the firewall, the tree on the manifold or the connections at the carb. But they all seem tight... Thanks for the help guys.

p.s. timing is good and i do not have an egr.

 

[Bully Bob]

Keep in mind, a vac. leak = burnt valve/valves over time...not a good thing.

Bob

 

[Seabronc]

The thing is, i'm terrible at vacuum and when i swapped the motor, i just hooked the carb up correctly with vacuum, but everything else, i just hoses to and went from memory of the old engine.  I also stopped every port i didn't use.  There are no check valves anymore, i didn't know where they went.  I've sprayed wd-40 around some of the spots i think it is and it doesn't run as rough at idle anymore.  so i think i've narrowed it down to a vacuum restrictor that's on the firewall, the tree on the manifold or the connections at the carb.  But they all seem tight...  Thanks for the help guys.p.s. timing is good and i do not have an egr.

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Ok then you hava a way to go. First off, you need to get a vacuum schematic for your engine. When you changed your engine, did you replace it with the same size? Was it a 302 for 302 or what? We need to get to a good starting point.

>-

 

[grande_guerre]

nope, it was a 302 to a 351W.