michael whiteman
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- Mar 2, 2021
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I have spent three days and five phone calls compiling information regarding valve springs in the 79cc Predator engine. Unfortunately this information is not found in any one place, and sometime it is inaccurate. My measurements were made with a dial micrometer and some pretty accurate spring loaded bathroom scales. Even if the numbers are not exact, the comparison between them is right on. As I have stated before, most of these performance parts along with the information is intended to be used on the 212cc engines. There's not much interest in its "little brother". Although some pieces will interchange, you need to be careful.
First off, forget about using the 18 lb springs. With the stock cam's 0.310" lift and the stock 1.5 ratio rockers producing 0.456" total valve lift these springs will become stacked or coil bound. This is totally unacceptable because it will bend the push rods and prematurely were off the cam lobes.
The stock valve spring is said to be good to 5200rpm maybe 5500? rpm when it begins to float.
This reads 7lbs spring pressure at the installed heigth of 0.850" and 20 lbs at 0.394" compressed, at full lift.
The 10.8 valve spring is taller than the stock spring but the wire diameter is smaller. Not sure the 10.8 means lbs.
This one reads 10lbs @ 0.850" and 22lbs @ 0.394"
If you add a 0.060" shim It reads 12lbs @ 0.850" and 24lbs @ 0.394"
The UNUSABLE 18lbs spring reads 14lbs @ 0.850" No reading @ 0.394" due to coil binding
On the 212cc engine this 18lbs spring is good to 5600rpm
The 22lbs valve spring is good to 7000rpm
This one reads 17lbs @ 0.850" and 42lbs @ 0.394"
Conclusion:
If you are considering any of this you have already removed your governor and hopefully installed a billet aluminum flywheel.
Ask yourself: How often am I going to be at 7000rpm? Because the rest of the time you are putting a lot of pressure and premature wear on all your valve train. I choose something a little better than stock with the 10.8 valve springs and a 0.060" shim.
At ACE Hardware I found a stainless steel washer that measured 7/8" O.D. and 1/2" I.D. With a little filing I opened it up so it would drop over the boss machined in the head. Then I slipped the oil seal over the intake valve along with the spring.
I'm thinking this should be good to aproximently 5700rpm, which is plenty fast for me. I hope this lessens your confusion like it did for me. BTW: The 0.060" shim used with the stock valve spring will cause it to coil bind. NR Racing has the best selection of valve springs and the best prices along with very fast shipping.
First off, forget about using the 18 lb springs. With the stock cam's 0.310" lift and the stock 1.5 ratio rockers producing 0.456" total valve lift these springs will become stacked or coil bound. This is totally unacceptable because it will bend the push rods and prematurely were off the cam lobes.
The stock valve spring is said to be good to 5200rpm maybe 5500? rpm when it begins to float.
This reads 7lbs spring pressure at the installed heigth of 0.850" and 20 lbs at 0.394" compressed, at full lift.
The 10.8 valve spring is taller than the stock spring but the wire diameter is smaller. Not sure the 10.8 means lbs.
This one reads 10lbs @ 0.850" and 22lbs @ 0.394"
If you add a 0.060" shim It reads 12lbs @ 0.850" and 24lbs @ 0.394"
The UNUSABLE 18lbs spring reads 14lbs @ 0.850" No reading @ 0.394" due to coil binding
On the 212cc engine this 18lbs spring is good to 5600rpm
The 22lbs valve spring is good to 7000rpm
This one reads 17lbs @ 0.850" and 42lbs @ 0.394"
Conclusion:
If you are considering any of this you have already removed your governor and hopefully installed a billet aluminum flywheel.
Ask yourself: How often am I going to be at 7000rpm? Because the rest of the time you are putting a lot of pressure and premature wear on all your valve train. I choose something a little better than stock with the 10.8 valve springs and a 0.060" shim.
At ACE Hardware I found a stainless steel washer that measured 7/8" O.D. and 1/2" I.D. With a little filing I opened it up so it would drop over the boss machined in the head. Then I slipped the oil seal over the intake valve along with the spring.
I'm thinking this should be good to aproximently 5700rpm, which is plenty fast for me. I hope this lessens your confusion like it did for me. BTW: The 0.060" shim used with the stock valve spring will cause it to coil bind. NR Racing has the best selection of valve springs and the best prices along with very fast shipping.
