I have a pair of 243 heads with valves from a 06 Grand Prix GXP that I had cleaned up and a Serdi vavle job performed on. I measured the installed height with BTR seats and retainers for their dual platinum springs and they came out to 1.772. I tested 4 different valves and all came out to that. I used telescoping gauges between the outer most section of the retainer and the spring seat along with a micrometer to read the telescoping gauges. Does this seem right for a pair of 243 heads that have had a valve job? I thought for sure i'd be over 1.8 and have to shim since factory is around 1.8. I didn't keep any of the old seat integrated seals to measure the differences in the seat height unfortunately. If it seems too far off i'll suck it up and track down one of the on stem valve spring height mics.

Now, assuming the 1.772 is right, am I still OK with not shimming? Spring specs are 155 lbs @ 1.780", 380 lbs @ 1.180", 400 lbs @ 1.130. If my math is right, the BTR .660 lift dual platinum springs coil bind at 1.070 leaving me with .090 from coil bind on the intake side at my cams max lift of .612. On the exhaust side i'd be .107 from coil bind at the max lift of .595.

 

It seems like you should have a little more installed height, however the closer you run to coil bind the happier your valve train will be at higher rpm's, so I would run them as they are. Coil bind should be 1.050"

 

There you have it, right from the horses mouth.

 

None of the stock heads I have worked on set up at 1.8". Would need to check my notes but from memory I believe they were around 1.76" so to me your numbers seem plausible. The other good thing is that they were the same. A number of guys have had the valve seats done and gotten large variations in valve stem height.

 

Thanks a bunch Brian. I'll leave it alone then. Saves me the trouble of having to redo my valve stem seals since I forgot to check the spring height before pressing them on. Once I get my pushrod measurements I'll be bugging you for a set of 3/8 pushrods.

That does makes sense then. I checked the valve drop before and after having the heads shaved 0.010 and it remained the same which makes me believe about that much was taken out of the seats which would put it near 1.77. I specifically used this particular machine shop for the valve job because he guaranteed me every valve would be same height. I expressed my concerns about that upfront after reading some horror stories on here.

 

If I can remember right my stock 799s were 1.79 installed height.