Listers:
For comparative purposes, here is a list of seated valve pressures and spring
rates taken from an old IskyCam catalog. These are their "recommendations"
for use with their milder camshaft profiles. The examples I have below are
using the same Isky replacement spring pair. I think Isky sold these springs
because they fit and not because they work well. No wonder they discontinued
them...
Car Isky Spring part # Seat Pressure Spring rate per inch
BMW 1600 # 625/626 120 lbs 300 lbs
Porsche # 625/626 110 lbs 300 lbs
Sunbeam # 625/626 70 lbs 300 lbs
Volvo 1800 # 625/626 98 lbs 300 lbs
Other English cars valve seat pressures, using other spring combinations are
listed below. The size and weights of the valve itself is a factor, and
these examples are similar sized. No other engine in the book has a lower
seated pressure than Sunbeam...or even close.
Austin Healey 100-4 105 lbs
Ford Anglia 1500 100 lbs
Jaguar 3.8-4.2 110 lbs
MGA-MGB 115 lbs
Sprite 100 lbs
Sprite Competition 115 lbs
Triumph 100 lbs
Triumph Competition 115 lbs
...and here is a BIG valve engine, for comparison.
Boss 302 Ford 135-160 lbs depending on installed height
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