Does this 243 installed height seem right?
Does this 243 installed height seem right? 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.
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.
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.
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.
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.
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.
