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Old 6th November 2019
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Default Summaries from Slack Tube Testing

I'll update this post as I go to keep all this info in one place.


A. Before changing to new umbrellas;
1. The rear umbrella was more stiff than the front one which was 'like new'.
2. I pulled the oil cap off at hot idle and the engine stumbled or died.
There was oil frothing in the oil tank when I pulled the cap off.
The frothing got less when the cap was 'slightly' off.
It didn't have any affect pulling the cap at cold idle.
3. There are app. 1/4" fluctuations in the pressure readings at 1000 and 2000 RPM.
The fluctuations are relative quick changing.

B. After changing to new umbrellas;
1. The engine loped a little better.
2. There was no noticable change in RPM with the oil cap removed.
3. There was no frothing of oil in the tank with the cap removed.
4. Engine sounds / lopes better with new umbrellas.
5. Residual vacuum was decreased with new umbrellas across the RPM range.
6. The engine flipped over to positive pressure at a lower RPM.
7. There was less gap between the pressure changes from 1000 and 2000 RPM.
8. Fluctuations of pressure at 1000-2000 RPM are much slower.

C. After restricting both breather bolts to 1/8" openings;
1. The smaller bolt holes actually reduced vacuum.
2. They also offer more control of CC pressure throughout the RPM range by creating lower pressure swings.

Other testing:
1. The air/fuel mixture did not have an affect on CC pressure.
2. There was no difference in pressure with the air cleaner on or off during testing.
3. Timing changes did not have an affect on CC pressure.

Other Notes:
There was no oil spewing / puking out the A/C before or after changing the umbrellas.
There was no extra drag on the motor before or after changing the umbrellas.
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Last edited by Hippysmack; 7th November 2019 at 20:10..
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