[RESOLVED] How well do stock valves handle higher boost?

[rossb]

The title really says it all. I'm about to get my head re-machined(timing belt snapped), and trying to decide whether to go ahead and upgrade to some stainless valves, or use stock valves(maybe even cheapo topline's). I remember reading something a while back about the stock valves liking to come apart(where they are pressed together) under higher than stock boost. Any information would be greatly appreciated.

p.s.: Mods feel free to delete if this another one of the beat to death topics, I tried searching

 

[Kastigir]

How much boost/HP are we talking about here?

 

[rossb]

Nothing too crazy, a good streetable car that might see a little track time.nothing too crazy. I have no real goal for the car other than that. No more than 20 psi at the max(with supporting mods of course).

 

[jjgrizz73]

Not sure if theres any difference in 1g or 2g valves but I run 22psi on a daily driver and have had no problems with them. You should be fine with a 20psi max with just the stock ones but upgrading never hurts.

 

[Kastigir]

Valves are fine up to, what the bottom end can handle. 20 psi/400 HP you're safe.

 

[T is for TURBO]

Stock valves are fine... a friend of mine is running 30 psi on a FP3065, with tons of miles on them, and the car runs just pretty well... and by well, I mean he ran an 11.28. (stock bottom end as well)

I plan on running some where between 20-30psi depending on what turbo I decide on. And I'm still on stock valves and springs. I'm not worried

 

[nkosi]

The stock valves in the 4G63 should be good up to the stock engine limit of 450hp to 500hp ...my self im running 25psi on my turbo plus a 75hp shot of nos and i have no problems ...the 4g63 is a strong motor and as long as you don't go over her limit it will live ...

 

[caged]

Yep there are better mods to spend your money on than stainless valves

 

[xioca]

OEM all the way..

 

[JusMX141]

I can't see how higher boost would destroy valves. The higher the cylinder pressure, the more it would force the valve into the seat....or so it would seem.

Poor tune is a different story. If you're too lean, you'll ruin valves and seats in a hurry.

 

[turbobluers]

I can't see how higher boost would destroy valves. The higher the cylinder pressure, the more it would force the valve into the seat....or so it would seem.

Poor tune is a different story. If you're too lean, you'll ruin valves and seats in a hurry.

Wouldn't higher boost float the valves, causing them to not seat fully? or am I bass ackwards?

 

[viperlp01]

Ya but the valves have nothing to do with that... That is the springs u use....

 

[turbobluers]

Ya but the valves have nothing to do with that... That is the springs u use....

yes, yes, i know it's the springs, im talking about geometry... just wondering if i was misunderstanding jus.

 

[JusMX141]

"Floating" refers to the valve's inability to close at higher RPM's because the valve cannot remain in contact with the camshaft. Stiffer springs would remedy this.

 

[1gcrazy]

"Floating" refers to the valve's inability to close at higher RPM's because the valve cannot remain in contact with the camshaft. Stiffer springs would remedy this.

And thus stiffer springs means more pressure on the valves.... TADA!

 

[turbobluers]

And thus stiffer springs means more pressure on the valves.... TADA!

yes, you all are correct, but all missing the original question. I know heavier springs withstand higher cylinder pressures reducing valve float. I know that. my question was in regard to jus's post about how higher cylinder pressures would force valves more into the seat... by my understanding, the exact opposite of forcing the valves into the seat is float. valves "lift" off of the seat with mechanical "permission", i.e. cam/lifter motion or with "float". correct?? therefore my question is, am i missing something as far as higher cylinder pressures forcing the valves into the seats?

Thats all i'm asking.

 

[DanaT]

With this statement, I am assuming money is no issue.

1) Go with titanium valves if you want the best. Titanium is a poor thermal conductor which means less heat transferred and is also pretty thermally stable. In addition it is about half the weight of stainless. You wont get these cheap. You can also run more RPM without valve float and softer springs due to the lighter mass.
2) Turbo applications heat exhaust valves alot due to turbos creating back pressure. These means that ti or sodium filled valves are best on the exhaust. Sodium filled draw heat away and are "Self cooling"
3) Aftermarket stainless valves will be more durable than stock valves.

All of that said, lets say you get 25000 miles out of stock valves before a rebuild. How many sets of OEM valves can you go through for the price of aftermarlet valves? How deep are your pockets? Only you can decide if it makes financial sense.

-Dana

 

[turbobluers]

How many sets of OEM valves can you go through for the price of aftermarlet valves? How deep are your pockets? Only you can decide if it makes financial sense.

-Dana

With all the knowledge, there is the wisdom. Exactly. There are alot of parts available for these cars, most of which 99.9% of this community will never actually need to fully utilize. It is true, you get what you pay for, but the most expensive is not always the best choice for YOU. Do your homework on every leg of your build and make the decisions always based on what your ACTUAL goals for the car are going to be. Well said Dana.

 

[t25fury]

yes, you all are correct, but all missing the original question. I know heavier springs withstand higher cylinder pressures reducing valve float. I know that. my question was in regard to jus's post about how higher cylinder pressures would force valves more into the seat... by my understanding, the exact opposite of forcing the valves into the seat is float. valves "lift" off of the seat with mechanical "permission", i.e. cam/lifter motion or with "float". correct?? therefore my question is, am i missing something as far as higher cylinder pressures forcing the valves into the seats?

Thats all i'm asking.

Valve springs are not for cylinder pressures but to keep the valves(rocker arms) seated to the cam lobes ,valve float means the valve is "floating" off of its seat ,usually reving past the valves spring rate,in other words the cam lobes are not in contact with the rocker arms due to the springs not being able to supply enough force,this where stiffer springs would remedy valve float,so yes you had it backwards

 

[turbobluers]

Valve springs are not for cylinder pressures but to keep the valves(rocker arms) seated to the cam lobes ,valve float means the valve is "floating" off of its seat ,usually reving past the valves spring rate,in other words the cam lobes are not in contact with the rocker arms due to the springs not being able to supply enough force,this where stiffer springs would remedy valve float,so yes you had it backwards

AHHHHH... Ok I gotcha.. we are looking at things from two sides of the same coin. Thanks fury.

 

[kris_stewart10]

so wait let me get this if i use stronger springs on my valves i could rev past what i am revving now???

what is the revving ability with stronger valve springs

 

[viperlp01]

That is why you build a nice head... To rev it up to 8k and not have any problems... Shit shep revs his to 11k??

 

[kris_stewart10]

HOLY JESUS i didnt even know Tachometers went that high aahahahahahahaha

 

[No_Skillz]

If you are revving that high, stronger springs won't do the job alone. Keep in mind the inertial energy of a mass that is moving (valves +retainers+springs+rockers) and that it needs to come to a complete stop and then travel in the reverse direction many times each second. Less mass = less inertia. If you want to rev to the moon, you need a combination of strong springs and light valves and retainers.

 

[BoredDSM]

If you are revving that high, stronger springs won't do the job alone. Keep in mind the inertial energy of a mass that is moving (valves +retainers+springs+rockers) and that it needs to come to a complete stop and then travel in the reverse direction many times each second. Less mass = less inertia. If you want to rev to the moon, you need a combination of strong springs and light valves and retainers.

Yes, and you would also need a lighter rotating assembly. Shep runs aluminum rods and most likely has some lightening on the crank.

To answer the OP question, if you can afford stainless steel valves go for it. It helps with flow and they are stronger. With stiffer springs I would get stronger valves.