4 replies to this topic

[dantiri]

Hi everyone,

I just had a valve job done on my 12g295 including hardened inserts for the exhaust valves. 

 While the intake valve spring heights are within range at 1.33", the exhaust ones are a little too compressed, measuring  about 1.29". the springs are C-AEA525 from minispares (for standard use) which state the height of the springs at rest should be between 1.32" and 1.37". the engine is a cooper 998 with d-top pistons, CR 9:1, stock cam. Now the guy at the machine shop said he can't cut the seats any more otherwise they'll be too skinny and was almost horrified that I was worrying about the spring height. 

 

So I'm asking how big of a deal it is to have the exhaust springs height at 1.29" at rest. Is it worth to get it right and machine the spring seats?

Thanks

[OzOAP]

The spring platforms are not the problem. It's the seats. All valve heights should be the same.
Also is that right that the springs have a 0.050" (1.25mm) installed height tolerance? That is huge!

Edited by OzOAP, 19 May 2016 - 06:28 AM.

[carbon]

Dantin,

 

Are the valves you're using in the 295 head the long or short type, or mixed?

 

And do all of the valve tips sit at the same height, or are inlets higher than exhaust?

[dantiri]

Dantin,

 

Are the valves you're using in the 295 head the long or short type, or mixed?

 

And do all of the valve tips sit at the same height, or are inlets higher than exhaust?

 

All the valves have the small collet groove (12A1987). Inlet and exhaust are the same length, but the valve tips are at different heights (as much as 0.080") since the seats were cut at different depths.

[carbon]

OK, so problem lies with how the exhaust valve inserts have been fitted. If done correctly all of the valve seats (and valve stem tips) should be at same level, but sounds like this is not the case.

 

Not sure if your small collet 12A1987 exhaust valve is short or long type. If it's the short version someone on this forum may be able to say if there is an A+ version of the 998 exhaust valve with longer stem. But that might be tad too long for what you need.