I have a crane 168731 with stock springs and hydraulic roller lifters in a gen6 502 . I know the open spring pressure is 120lbs. lighter than what crane recommends and believe I having valve float. The question is with a set of eddie marine manifolds with long risers would the valve float cause reversion. The cam size is not causing this to happen and I don't believe the exhaust is causing it either. But something is causing the water to come back. I have fresh water cooling and had the exhaust pressure test all is fine. I'm upgrading the lifters and springs with higher open pressures to cranes specs. Any suggestions.

Absolutely possible.

No way your open pressure is that weak.

With that cam you need to be 140-150 closed 4-500 open is a great range.

Will the engine even rev past 3500 rpm's? If your valves have been floating with those springs, you might have bent one all ready. If one of them is bent, then that can cause your reversion since the valves are not closing.

I would say that you aren't closing anyway with that little spring pressure.

You need to pull the heads and start over and have somebody set them up the right way. Also remember that your spring pressures need to match. If you have had a valve job done then your valves are not sitting in the hole at exactly the same depth and that changes your spring pressure.

Good luck

If in fact you are off that much in presuure you beating the hell out of the cam, won't cause the revision but can destroy the engine if something breaks, also pay attention to the installed height...

Another problem with too low spring pressure is you are stressing the lifter tie bars in a big way. The spring pressure is not enought to keep the lifter on the cam, they fly off the ramp and stretch the tie bar/rivet assembly. That's usually why roller lifters fail and spin because of too low spring pressures. Been there and cost me over 10k!!!!

Exhaust valves not sealing well will cause reversion. It's possible you damaged some with the light spring pressure. I would be very worried about the lifters if you ran it long like this. Floating the valves really pounds the needle bearings in the rollers. Having a roller fail will put little bits of metal all through the engine. They will embed themselves in the piston skirts and ruin the bores. Run 150lbs seat min. 160-170 won't hurt either.