Flow Job and Spring Testing
Friday, October 9, 2009
The head is getting flow tested. This will calculate the airflow through the head at various stages of valve opening (or cam lift). One cylinder is done at a time. The head is clamped to the flow bench. The air source and vacuum come from underneath (the cylinder opening). When testing intake flow, a vacuum sucks the air through the intake port. When testing exhaust flow, air is pushed out through the exhaust ports.
The head is setup for intake flow testing. There is an bell mouth shaped plate attached to the intake port being tested. This helps smooth air flow into the head for a more accurate reading. The four black knobs poking out of the top of the head are used to open and close the valves a specific amount. Readings are taken at various amounts of lift (usually 0.050” increments and logged into Flow Pro software. The software is used to generate a graph showing the flow of the head.
When the head is delivered, Dana will provide me with the flow data reports & graphs, as well as a bunch of other details about the head.
Dana’s flow bench is custom made and a very high quality piece. There are not many in existence and since the creator/manufacturer passed away, there aren’t likely to be any new models anytime soon. The best part of this particular flow bench? The operator! Dana has been great to work with and I’ve been very impressed with his knowledge and attention to detail.
I also asked to take a few pictures of the spring tester in use. Just as Dana said before, the stock 94-97 Miata valve springs rate at about 10.5mm of travel with 156 pounds of pressure at 10mm (the amount of lift of my cams).
We’re still awaiting the exhaust cam, which was out of stock at Maruha and had to be ground. It shipped from Japan this week and should be here soon!
