Alternative valve springs

[promotor]

I'm currently trying to sort out an issue with a T/C head regarding valve springs.
The current valve springs are QED standard valve springs. In my opinion they are way too stiff for the engine to be used in (1700, sprint cams, 6500rpm). So, I want to change to some lighter springs.

Also the exhaust valve seats haven't been cut to the right height to allow a decent installed spring height (using standard length valves) - they are installed around (minimum) 1.1240" but need to be 1.170" installed height. This means the springs are effectively stiffer than specced, and also don't have enough clearance between coils at full lift.

Standard OE Lotus springs don't work out either as they are even worse regarding how to close to coil bound they will be at full lift.

I don't want to change to longer valves and thinner buckets or cut the ex seats out by a ridiculous amount so my option is to find some other springs that allow fitment into the space available.

Q55 look to be almost perfect except for the cost (at approx ?165!) - can anyone point me in the direction of some suitable thinner light duty springs? Unlikely I know but I'd prefer to try and find a set first before the pull of the Q55's takes over.

I thought about using just the Q55 retainers and collets as they allow the springs to sit higher therefore lowering the spring loads and giving more room, however the Q55 retainers don't fit inside the springs I currently have fitted!

Any tips/tricks/insider info as to where my ideal valve springs are hiding?

Cheers

[rgh0]

If the exhaust seat has not been cut correctly and the valve is sitting to low in the head then I would have thought the easiest approach would be to recut the valve seat to get the correct valve location. You can then use standard springs and buckets and shims.

cheers
Rohan

[promotor]

Yes I would prefer to do that however to get the required space back the seats would have to be cut by approx 0.040" and if I'm honest I don't trust many (if any) people around here to do it accurately and within a similar tolerance to each other. However it would get me to be able to use approx 0.080" shims if done correctly.

The seats that were in the head were done by a well known company in the UK and were cut to approx 44 degrees so that the valves had absolutely no chance of sealing. I have managed to rectify them with a stone valve seat tool but there is no way I can take 0.040" out with that tool.

If the seats were successfully recut there is still the issue of obtaining new standard valve springs to original Lotus spec - as the springs mentioned earlier are not near to original spec in terms of strength or free length etc I'm not confident about finding any that are similar.

I did mention the spring issue to QED (as I ordered some standard ones to replace the too hard ones and found them to be exactly the same part!!) and they didn't suggest they had any close to the originals.

Maybe this is all in vain but I've got to try first!

[rgh0]

The original standard twin cam springs I have measured have specs as follows based on outer spring length

60 lbs at 28.5 mm / 1.124 inch
160 lbs at 19.5 mm / .77 inch

This gives you the 0.35 inch valve lift in a .36 inch lift sprint cam and acceptable installed and cam nose loads
Coil bind occurs at 18 mm so you have 1.5 mm / 0.060 inch clearance to coil bind which is the minimum I would accept.

So your 1.124 inch install height should just work with original standard springs if you can still get them to the standard specification these days. I have not tried to buy any standard springs for a long time so i am not sure what they actually supply these days.

Amazed to hear you cant find anyone to reliably cut seats to a specified valve install height. I could not build engines without that from my local machine shop.

cheers
Rohan

[RichardHawkins]

Promotor,

I had similar trouble finding a good machine shop, and finally went to Serdi UK who are in Uxbridge just west of London. They seem to do good work. I know it's a long way from home for you but you might like to consider them. John Dormer is the man I spoke to.

Richard Hawkins

[promotor]

Rohan - thanks for those figures. I've just measured some standard springs and got :

57lbs @ 28.55mm
152lbs @ 19.55mm

so it seems we're around about the same figures - possibly my gauge reads slightly different to yours (although I "calibrated" it by weighing myself on digital scales and weighing myself on the gauge and it was pretty much exact to a pound!!) and maybe the springs have suffered over time and aren't as strong as they used to be.

I can't believe it either regarding machining work particularly coming from Sheffield which is still famous for steel and machine shops in days gone by. I'm sure there'll be some around but finding them is one thing and trusting them another!

Richard - cheers for the heads up. Serdi make good machines so it sounds like they would be good guys. I don't want to take or send a head anywhere where I can't just call in and check on progress though.

Still got making enquiries into valve springs at the moment.

[holywood3645]

I have a set of QED55 springs and platforms i didn't use.
Make offer
In US
James