5 replies to this topic

[Angus 850]

I have a 12G295 head which I will be fitting to my 1989 standard 998 with a stage 1 kit, no cam change.
The head has been skimmed (80 thou), new valve guides fitted. The head currently has single springs fitted. Considering that I have another 12g295 for spares, should I fit the double springs from the spare head or keep the single springs?

[nicklouse]

I would fit these

http://www.minispare...h/classic/valve spring.aspx|Back to search

[Angus 850]

Thanks Nick. I am not sure if valve stem oil seals where fitted to the early heads. Can I use the A+ type or do I need to use the small o-ring rubber type?
Cheers

[toppers3933]

use the Viton ones. just push them on and you're golden. on all 8.

[absx2]

The most important thing is to identify what springs you have, then make sure the fitted length is within tolerance or you will have valve float issues.

If you have a 12G295 with 1275 length valves ( quite common and roughly 3 mm longer ) you will need to shim the springs to achieve the correct fitted length.

Likewise if the head has had the valve seats seriously cut ( again common on a 12g295 ) you will not get the required poundage without shimming.

I`m with nicklouse and fit 12G1015 but make sure the fitted length is correct 1.320", 33.5 mm The springs come with all the information you need and that way you know exactly what you have.

ADU4905 or the better LJQ101160 if you feeling rich for the valve seals, all 8 

 

Double springs are over the top and A+ single springs are great for high revs so no problems there.

Edited by absx2, 25 October 2018 - 05:10 PM.

[Angus 850]

The most important thing is to identify what springs you have, then make sure the fitted length is within tolerance or you will have valve float issues.
If you have a 12G295 with 1275 length valves ( quite common and roughly 3 mm longer ) you will need to shim the springs to achieve the correct fitted length.
Likewise if the head has had the valve seats seriously cut ( again common on a 12g295 ) you will not get the required poundage without shimming.
I`m with nicklouse and fit 12G1015 but make sure the fitted length is correct 1.320", 33.5 mm The springs come with all the information you need and that way you know exactly what you have.
ADU4905 or the better LJQ101160 if you feeling rich for the valve seals, all 8 
 
Double springs are over the top and A+ single springs are great for high revs so no problems there.

Thanks for that, I will check very carefully. The head is very good condition, skimmed, new valve guides, valves and springs fitted in the last few years by the previous owner. The valves are not the standard long groove collets type but the small cotter type.
All the work has been done professionally and I have no reason to doubt the quality of the work. I had concerns when I saw the different type valves and the single springs instead of the double but no longer concerned after reading your post.
I will measure the springs, Just to be on the safe side.
Cheers