Sale ends todayGet 30% off any course (excluding packages)

Ends in --- --- ---

progressive double spring race valve springs

General Engine Building Discussion

Forum Posts



Tech Articles

Talk about engine building here. New products, tricky questions or showcase your work - If it's engine building related it's welcome here.

= Resolved threads


I have been trying to research progressive springs and how they work and whether they are a possible solution for my application. I am running a race cam that the manufacture recommends race springs with a minimum seat pressure of 200 --higher would be better. availability of such is really limited, in the US and UK.

my cam is a very low lash cam (5-6 thou) with consequences for it moving our of that spec of shattered followers. I've been adviced that above 7200 rpm the risk of valve float increases if the spring isn't up to the demands and that reverbs right back down to the followers. so I was thinking that progressive spings might be a solution, not really knowing how they work.

on my second engine due to follower failure

so hive-mind, light me up...

builld: BMC A series bored to 73.5MM or 1380

APT scatter pattern cam SPVP5

MED race push rods

MED 1.5 roller rockers

MED Full race double springs

Forged Steel 6' conrods

Omega 73.5 mm short skirt piston

stock EN16t crank balanced

aluminium head

200 lbs seat pressure? That HAS to be a typo - are you sure that isn't nose pressure (yeah, it's actually force, but convention...)?

Main advantage of them seems to be their resistance to harmonics, same reason as "behive" designs, because the rate is different at each point along the camshaft. Vizard, widely recognised as an "A" series guru goes into them in some depth - https://www.youtube.com/watch?v=uHw3mWYgO6M

As for the follower failure, that seems to be either a follower issue and/or a bad camshaft design with badly designed clearance/quietening ramps.

Thanks for the reply Gord- yes my mistake--seat is at least 100# according to my notes from David Anton of APT and nose pressure of 200#. I have Vizards book but traveling--thanks for youtube link.

We usually reply within 12hrs (often sooner)

Need Help?

Need help choosing a course?

Experiencing website difficulties?

Or need to contact us for any other reason?