Flowbench Mistakes Made

[200cfm]

It'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"?

[blaktopr]

Basically the same stuff, 200. Before each test I start the bench with valves closed to 28" or higher then check the inclined, then open the valve. If it don't jive there, I know I missed something.

[larrycavan]

The spark plug left out still gets me once in a while :;):



Edited By larrycavan on 1227878601

[106-1194218389]

[larrycavan]

Here's one several of us have fallen for.......

Debating the accuracy of an orifice bench on other forums :p

[106-1194218389]

[Vicoor]

Yep, Been there.

x2 on the starting with the valves closed and checking the incline after you reach 28" static.

The springs I was using were a bit weak as well, I just doubled up on them.

It does seem like a lot to keep up with when you first get started, but once you've done a while a get a set proceedure then you can keep track of yourself and not make the annoying little mistakes.