Posted: Wed Nov 26, 2008 11:05 pmIt's been almost two years now since I first started by bench. And have made some silly mistakes that had me baffled at times. So this topic is to share mistakes made that affected repeatability and accuracy. Here are mine that I have learned to double check to avoid the "bench gotcha."
1. Unbelieveable high cfm readings after porting a port. Thought I was hot stuff with the grinder. Found out I had left the spark plug out.
2. Nice readings after some port work. Discovered I had not secure the head to the base mount and had a leak.
3. Really nice readings on port that I hadn't done anything too. Found out the spring under the exhaust was not holding exhaust close. I now load the exhaust valve with 90 lb spring seat when flowing the intake.
4. Manomoters not resetting to zero on drain back. Found residual overflow droplets in the tubing that needed to be purged before the reservoir levels settled properly.
5. Manometers acting funny. Found "T" coupling joint loose on the T line.
6. Changes in repeatabilty readings. Found the lift measurement setting was changing from the suction depression forces on the intake valve. Example: A setting for .400 lift would move to say .405" lift from the air flow forces. Poor keeper seating.
Who else has had "surprises"?
1. Unbelieveable high cfm readings after porting a port. Thought I was hot stuff with the grinder. Found out I had left the spark plug out.
2. Nice readings after some port work. Discovered I had not secure the head to the base mount and had a leak.
3. Really nice readings on port that I hadn't done anything too. Found out the spring under the exhaust was not holding exhaust close. I now load the exhaust valve with 90 lb spring seat when flowing the intake.
4. Manomoters not resetting to zero on drain back. Found residual overflow droplets in the tubing that needed to be purged before the reservoir levels settled properly.
5. Manometers acting funny. Found "T" coupling joint loose on the T line.
6. Changes in repeatabilty readings. Found the lift measurement setting was changing from the suction depression forces on the intake valve. Example: A setting for .400 lift would move to say .405" lift from the air flow forces. Poor keeper seating.
Who else has had "surprises"?