Gents, I have been attempting to find a problem in what I believe is a leak in the intake manifold causing fouled plugs for approaching 3 years and am at wits end. The motor has been heavily modified and the heads and block have been cut a couple of times each which required the intake manifold to be cut as well.
However the plugs are fouling and the intake is definately very damp with oil upon inspection. After a couple of years of tryinng on and off to diagnose the problem, I finally gave up and took the motor to a very reluctant Kroyer's Racing at the Las vegas Speedway. They are an award winning Nascar engine builder. They mocked the motor and said that the intake manifold was binding on the bolts slightly which required them to bore the intake bolt holes. After which, they concluded that the intake manifold was cut well and fits the head valley well. They also confirmed that the heads and block were cut straight. Unfortunately, upon reassembly and start up - same problem. Now, they are not interested in an easter egg hunt and have asked that I go elsewhere for solution.
The PVC system has been modified to simply loop the passenger crankase through a filter and back into the plenum and the driver side vents to atmosphere. The filter in the loop is not wet so we are fairly confident that it is not coming from the crancase. Additionally, the lower end of the motor is new so blow by is fairly assumed to be negligible, if any. The other symptom seems to be that under boost the plugs seem to clear a bit and then after lengthy idle (i.e. vacuum) the plugs foul again. This would seem to also support galley oil being pulled into the intake.
Intake has been assembled 4-5X so assembly error is highly unlikely. Heads are new and have been tested for leaks and nothing. Don't see it being the valve stem seals as it should pull the oil into that cylinder and not through the entire intake.
QUESTION: we feel the next step is to either put a vaccuum or charge on the intake and attempt to diagnose leak that way. Motor is currently on stand. Anybody done this?
QUESTION; how else would oil get into the intake if we assume it is not coming from crankcase ventilation????
I don't want to give up here as the motor has been heavily upgraded with h beam rods, diamond pistons, stud girdle, tons of aligning and balancing work at Kroyers, valves, porting, etc, etc, etc,. Nonetheless, this has been one of the most frustrating experiences of my 42 year existence.
Any help, please.
Larry
However the plugs are fouling and the intake is definately very damp with oil upon inspection. After a couple of years of tryinng on and off to diagnose the problem, I finally gave up and took the motor to a very reluctant Kroyer's Racing at the Las vegas Speedway. They are an award winning Nascar engine builder. They mocked the motor and said that the intake manifold was binding on the bolts slightly which required them to bore the intake bolt holes. After which, they concluded that the intake manifold was cut well and fits the head valley well. They also confirmed that the heads and block were cut straight. Unfortunately, upon reassembly and start up - same problem. Now, they are not interested in an easter egg hunt and have asked that I go elsewhere for solution.
The PVC system has been modified to simply loop the passenger crankase through a filter and back into the plenum and the driver side vents to atmosphere. The filter in the loop is not wet so we are fairly confident that it is not coming from the crancase. Additionally, the lower end of the motor is new so blow by is fairly assumed to be negligible, if any. The other symptom seems to be that under boost the plugs seem to clear a bit and then after lengthy idle (i.e. vacuum) the plugs foul again. This would seem to also support galley oil being pulled into the intake.
Intake has been assembled 4-5X so assembly error is highly unlikely. Heads are new and have been tested for leaks and nothing. Don't see it being the valve stem seals as it should pull the oil into that cylinder and not through the entire intake.
QUESTION: we feel the next step is to either put a vaccuum or charge on the intake and attempt to diagnose leak that way. Motor is currently on stand. Anybody done this?
QUESTION; how else would oil get into the intake if we assume it is not coming from crankcase ventilation????
I don't want to give up here as the motor has been heavily upgraded with h beam rods, diamond pistons, stud girdle, tons of aligning and balancing work at Kroyers, valves, porting, etc, etc, etc,. Nonetheless, this has been one of the most frustrating experiences of my 42 year existence.
Any help, please.
Larry
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