5 replies to this topic

[stormduck]

Hi peeps, I need some info about valve springs. Firstly, how long do they last? Are they items that where out, or virtually indestructable? I have no idea.

Secondly, is there a table about that matches required max rpm with required valve spring lbs?

My reason for asking is that i'm fitting a 12G295 head to my 998, along with possibly an mg metro cam and 1.5:1 rockers - based on the des hammill book i have - tuning the 998, with this set-up i'll have 9.8mm of valve lift, which seeing the max on the 998 is 10mm this seems ideal. But i need to choose the best springs for the job.

i'm trying to find out the details of the double valve springs I have that came with the 12G295 head i have. They are standard fitted springs but don't know where to turn to get info that i understand. I have a Des Hammill book for tuning the 998, and the info for the valve springs in there makes sense - like lbs for fitted spring, lbs for spring compressed by 10mm of valve lift, coil bind height. But the book only lists for double springs fitted to the Cooper S, which i assume is a 1275. The David Vizard book i have lists the springs fitted to the 12G295, but not in figures that i understand - Should i be even thinking about fitting these as i don't know their age (although i could get them tested when the engine goes in to get machined), if not, where would be some good places to source them or get good info about the varying types???

Cheers!

[Jammy]

The 12G295 heads that were only fitted to Mini Coopers. So I assume the figures you have in you 'Tuning the 998' book you have are correct.

[stormduck]

i understand what you're getting at, but the 'Cooper' was a 998cc, but wasn't the 'Cooper S' a 1275 fitted with a 12G940?

[Wil_h]

Firstly, what is the max lift figure you have actually mean? As in waht will happen if you wexceed this figure?

I reckon that iif the springs fitted ti the 295 you have are original, then the chances are that the'll bind with 10mm of lift.

Mini spares sell some nice springs made from thinner section steel to allow more lift. fitting these would be the safe option.

But a dry build with an ols head gasket will let you see if the springs bind before you put the engine totally together.

I have a similar spec mini, only differance is I don't run 1.5s

Wil

[stormduck]

the max figure is again taken from the book - i assume the valves will wallop the pistons!

Yeah there is a chance the old springs will bind at 10mm....and looking on minisport website a set is only £25, but they have NO details about them whatsoever! I think that's real bad myself, i'll have to contact them or find somewhere that does give good details to buy them. I think i'll be looking at a set that reaches 150lb pressure or so when compressed to 10mm to have an engine capable of revving to 6k - 6.5k rpm.

what's an ols head gasket fella - just for use when doing a test build? Sounds a good plan.

what cam do you have and what's your thoughts on the performance of it?

cheers. dave.

[Wil_h]

sorry sausage fingers ols = old.

try these springs http://www.minispare....aspx?pid=33655

I use an MG metro cam and run 10.5:1 CR. I'm not overly impressed with the cam to be honest, but the engine gives around 60 BHP and returns 45MPG, which is fine as I mainly use the car for commuting.

For a real screamer of a 998 my fave cam is the kent 276, but don't expect 45MPG with it.

Wil