Hello, The steps I would take to diagnose are as fallows: warm engine to operating temp, with a known good tach attached, kill each cylinder one at a time by unplugging or shorting plug wire and record rpm drop, the cylinder(s) with the least drop will indicate the problem area. If more than one cylinder is indicated look for a common cause: such as being on same idle circuit (restricted idle jet,disruption in carb itself), or intake runners connected. A valve will seat at cranking speeds when it won't sometimes at idle but won't be noticeable off idle. Connect a vacuum gauge and look for oscillating needle. Back off fast idle screw and restrict incoming air with choke blade to see if rpm raises (just a quick way to check for too lean). A leaking intake gasket sometimes is hard to find if it is on the underside of the manifold. A pyrometer can be used to help with exhaust gas temps by taking a reading close to the heads (higher temps = leaner cylinders). Of course reading the plugs if engine condition allows is a must.
On Thursday, August 7, 2014 10:02:03 PM UTC-5, gto64gto wrote:
Some comments-- starter fluid is a liquid where propane is a gas and will find smaller or any leak easier. I still think the problem is on the left bank because of a vaccum .leak between head or intake. Compression is measured in the cylinder- it wouldn't have anything to do with a leak unless a blown head gasket or warped head which would be to check.
Back to the Home of the Forward Look Network