Valve Springs

[Malcolm Parker]

I am currently putting together a new engine that will initially go in the Pytchley but could end up in the single seater.    The bottom end has a splash fed Hadley crank and rods.  The cam is an unknown quantity but came from Reg Nice.  It is a very nice piece of machining and is a standard cam that has had 0.050" ground off the base circles.  The block is the one that was on my Reliant cranked pressure fed engine.   It has Honda pistons and large inlet valves.   The cam followers are flattened to 3/4" radius and the valve springs, as far as I know are from an Austin Maxi.  I remember the engine being done by Andy Hastings and Walt Wheaton back in the late 1990's and they said that Maxi valve springs were as good as double valve springs.  To my mind the valve springs are very strong and I am wondering whether they will be suitable given that I am now using a high lift camshaft.   I am thinking about the effect on the block holding down studs and the valve heads.   Would I be better using standard valve springs?

[Charles P]

I've used Maxi in the past and yes, they're very strong. I wouldn't now.
The ambition should be to use the weakest springs that will do the job.
A few years ago I tested a bunch of springs for load across the lobe and base and came to the conclusion for my high lift cam doubles from Tony Betts gave the right loading for my use. They were actually no stronger than standard springs, but being wound from thinner wire didn't coil bind at full lift and should avoid unpleasant harmonics.
No problems to date

[Alan]

Back in the 70s and 80s I think we used Maxi valve springs because the then available Austin springs weren’t up to the job. I never use double springs now unless I’m building a race engine. Standard springs from any of our suppliers are good for up to 5000 revs or so, and the doubles I’ve been using see 8000 occasionally without noticeable valve bounce. Malcolm a .050 base circle regrind makes quite a nice cam. I used one for years until one day the crank broke and bent it.

[Ruairidh Dunford]

In the last 10 years I've had 3 engines come in with the rear foot missing off the back of the block.

All of them had these Maxi valve springs and a high lift camshaft fitted.

[Malcolm Parker]

Thank you all, I'm glad I raised the question!  My gut instinct told me that the springs seemed mighty stiff, I could hardly press the cam follower down against the spring pressure.   I will fit some standard springs.

If I see 8000rpm in the Pytchley it will probably be my final post!