on valences and vapor lock, a downside to originality Options

[1970 Neun vierzehn]

For thirty-one years I had run my 70/4 w/o a rear valence panel of any kind (see 3rd photo). After prolonged driving in hot weather or hard driving in warm weather (ie autocross), the car was afflicted with vapor lock (fuel pump in original location).
Keeping the gas tank mostly full helped alleviate the problem.

Now, since the OEM "deep" valence is in place (see 1st and 2nd photos), just a moderate run of 12 miles in warm temps causes vapor lock problems with an almost full tank of fresh gas. We all know that the factory installed a shorter valence later in the 914s' model run. One reason typically cited is the panels' tendency to collect debris and snow(!), but another less emphasized reason was no doubt the increase in engine compartment/rear trunk/under car temperatures.
The shortened rear valence and repositioned fuel pump no doubt greatly reduced the vapor lock problems but early 914/4s are still seriously afflicted if configured as originally built.