Does Hi-flo Cat Help Or Hinder Stock Valve Springs?

[MercuryXr6Turbo]

Hey all...

Soon to get my custom tune. Only mods will be injectors, PWR trans cooler, F6 cooler, F6 lower intake and K&N panel. Only chasing between 260 - 270rwkw...

I know that (most) BA's have valve spring issues... my question is as above, does fitting a high-flo cat relieve pressure on the valve springs? ie. reduce valve float? Getting mixed opinions on this one...

If anyone can explain the theory behind the yes/no answer it would be appreciated.

Cheers

[Ralph Wiggum]

Yes a high flow cat will help reduce the pressure on the exhaust valve springs, however a high flow cat can also result in over boosting so you will then run into drama's with intake valve springs.

Luke

[galapogos01]

makes sense. more exhaust backpressure would make it harder for the spring to close the valve - so less would have to be better. would have thought it to be pretty marginal though.

[MercuryXr6Turbo]

Cheers guys, so reduced back pressure = reduced pressure on springs therefore more scope before valve float correct? Makes sense to me. Kinda got me concerned thou, one of the tuners I had spoken to said more back pressure would keep pressure up on the springs which sounds right, BUT said would also reduce valve float due to more pressure on springs?!?!?! Hmmm.... comments???

[Ralph Wiggum]

The increased back pressure acts on the face of the valve and effectivly makes the springs weaker. As the valves are held open slightly the lifters pump up to take up the valve lash and the valves remain open slightly. This is why many cars with stock springs and high boost run rough after a wot full boost run.

Uprated valve springs will make the engine feel stronger through the whole rev range.