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Technical Articles Copyright © Dave Propst. All rights reserved. |
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Port Flow Test Tools
Copyright © 2002 Dave Propst. All rights reserved.
Revised 4/22/2003
Introduction
This article contains pictures of a few cylinder head port flow testing tools. These are fabricated/machined items that can be built with lathe and milling machine.
The cylinder head in the photos is an Edelbrock RPM series Ford FE head. (The head in these pictures is 'as-delivered' from Edelbrock, including the rough-in 'port matching' machine work. Meaning... don't take the port machine work as anything to be pondered or critiqued.)
Cylinder Head Flow Test Adapter
This first set of photos display an adapter box which very precisely replicates the size and position of an engine's cylinder bore against the cylinder head's combustion chamber. It can be used with either flow bench or FlowQuik. Cylinder bores can be swapped out to replicate different bore sizes. This was originally designed for the purpose of investigating the effect changes in cylinder bore size has on airflow in Ford FE motors. From the 352 all the way up to the 427, these motors cover quite a wide range in bore size while potentially using the same cylinder head.
The box structure has a rubber seal in the ID of the hole in the end plate for sealing the cylinder OD. This permits rapidly swapping cylinders of differing sizes of ID's for testing.
I've so far made six different cylinder bores accurate to +/- 0.002 ID for an FE project.
Dial Indicator Fixture
The next photos are of a dial indicator fixture built for use in analyzing camshafts. It is shown next to a standard duty dial indicator and base to illustrate it's rather massive design.
The heavy duty design provides the rigidity needed for measuring camshaft lobe lift on opening and closing to 0.0001 inch or even to +/- 0.00005 inch (or at least to detect motion of such small amount when needed) with the Starrett gauge. That high degree of accuracy is extremely helpful in distinguishing closing ramp from actual cam lift when analyzing a camshaft. This precision in determining valve motion is necessary in order to come up with a real-world seat-to-seat duration figure in degrees rotation of the camshaft lobe. The combination of a standard dial indicator's 0.001 accuracy/resolution and it's less-than-stable (in terms of four decimal places) base is hard-pressed to quantify a valve event to even 10 degrees of rotation on the closing ramp of extremely gentle OEM cams like the one in the Cad motor in the picture below. One degree, or at the very most two degrees, of resolution is desirable in seat-to-seat duration data for entry in the software in question.
A visual size reference for the gauge and fixture is that the engine it is mounted to has a bore size of 4.36.
Valve Opening Fixture
The following pictures illustrate a valve opening fixture. Using a precisely machined step gauge to open the valve provides speed and repeatability. I prefer this over the typical threaded adjuster/dial indicator combination. After a dozen or so consecutive tests, cranking a threaded stop becomes very tedious. The step gauge is particularly a time-saver when the need to jump to a non-adjacent lift point arises. For example, if for whatever reason one wants to go back to 0.100 inch lift from say 0.500 inch lift, the process is immediate and instinctive. The device is also very quickly moved from one valve to the next.
This method would not be all that practical for lifting to specific computed L/D ratios since one would need to build a number of custom step gauges. For generic 0.100, 0.200, 0.300..... lift values (or 0.025, 0.050, 0.075, 0.100, 0.150, 0.200...), it is a very fast and accurate method with outstanding repeatability particularly when used with the FlowQuik.
End of Article
