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| | | | Joined: Aug 2010 Posts: 69 Wrench Fetcher | | Wrench Fetcher Joined: Aug 2010 Posts: 69 | Seems like I have done it all on this motor. It idles rough and slightly better at higher RPM but not much.
New head gasket-torqued properly
new plugs, wires, condenser, carb, manifold gaskets & alignment rings.
vacuum guage at 21 but bounces to 22 or 23 rapidly even bouncing with high rpm.
Could vacuum advance be contributing to the problem or is this a valve? How bout a lifter? any help appreciated.
Eric | | | | | Joined: Jun 2004 Posts: 8,597 Riding in the Passing Lane | | Riding in the Passing Lane Joined: Jun 2004 Posts: 8,597 | Sounds like a vacuum leak at the intake manifold. Did you check compression? You replaced the head gasket but did you check for leaking valves?I dought if the vacuum advance is causeing this.
They say money can't buy happiness. It can buy old Chevy trucks though. Same thing. 1972 Chevy c10 Cheyenne SuperIn the Gallery Forum | | | | | Joined: Aug 2010 Posts: 69 Wrench Fetcher | | Wrench Fetcher Joined: Aug 2010 Posts: 69 | I checked compression after the head gasket replace and all were pretty good and even. I just did the intake gaskets and a little gasket sealer. If its still an intake leak, what is the best way to check? | | | | | Joined: Aug 2011 Posts: 687 Shop Shark | | Shop Shark Joined: Aug 2011 Posts: 687 | Sounds like vacuum leak to me too. OLD school method is to spray a bit of carb cleaner around the suspected areas that might leak and listen for RPM changes. Make sure the gaskets and spacer are in good shape and torqued down under the carb.
Keep us posted. | | | | | Joined: Feb 2004 Posts: 29,777 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,777 | I use Propane or acetyline around the intake port/cylinder head junction. It's a lot less messy than carb cleaner. If the idle smooths out or the RPM increases, you've found your leak. Also recheck the valve adjustment. A too-tight intake valve clearance or leaky valve seat can cause the same problems. Do a cylinder leakdown check with air pressure in the cylinders to check for valve seating leakage.
Jerry
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| | | | | Joined: Aug 2010 Posts: 69 Wrench Fetcher | | Wrench Fetcher Joined: Aug 2010 Posts: 69 | ok will do this weekend. i will ask more monday. thanks guys | | | | | Joined: Jun 2004 Posts: 8,597 Riding in the Passing Lane | | Riding in the Passing Lane Joined: Jun 2004 Posts: 8,597 | With insulated pliers pull spark plug wires off one at a time with the engine idling. If 1 or more cyls. dont change that narrows it down to the particular cyl.
They say money can't buy happiness. It can buy old Chevy trucks though. Same thing. 1972 Chevy c10 Cheyenne SuperIn the Gallery Forum | | | | | Joined: Dec 2003 Posts: 2,953 'Bolter | | 'Bolter Joined: Dec 2003 Posts: 2,953 | Check that the carb hold down nuts are tight.
I had a split in the flare of my vacuum line where it entered the carb. | | | | | Joined: Aug 2010 Posts: 69 Wrench Fetcher | | Wrench Fetcher Joined: Aug 2010 Posts: 69 | sorry, u lost me on that one. By pulling off a plug wire at idle, will that isolate the cylinder with bad valve?
Eric
Last edited by edub10068; 10/26/2012 9:42 AM.
| | | | | Joined: Jun 2004 Posts: 8,597 Riding in the Passing Lane | | Riding in the Passing Lane Joined: Jun 2004 Posts: 8,597 | sorry, u lost me on that one. By pulling off a plug wire at idle, will that isolate the cylinder with bad valve?
Eric Yes. It will tell you which cyl/s is causeing the problem.
They say money can't buy happiness. It can buy old Chevy trucks though. Same thing. 1972 Chevy c10 Cheyenne SuperIn the Gallery Forum | | |
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