valve types info required

[denniselbows]

evening all i wonder if some of you can give me some info or point me in the right direction on the types of metals inlet and exhast valves are made of. from what i have seen so far is you can get stainless steel ,Black nitrided stainless steel, inconnel but what is the benifits of these over stand valve type, which is sooted for higher temperatures and is wear and life of the valve shorter with fancy materials over standard original valve types. i'm no rocket scientist so this is good for this and they are for that sort of thing is all i am after. thanks in advance dennis

[rsmaku]

20v engines exhaust valves are sodium-filled. Sodium has low melting point which causes the sodium to circulate inside the valve and removing heat from the valve head. some stories i have heard that sodium filled valves are weaker and can not stand high rpms and stainless steel valves will burn due intense heat, but the last part i dont belive.

[S2central.net]

AFAIK - the sodium filled EX valves fitted in factory are well up for big boost and power levels.

[denniselbows]

the head i have is from a 7a would they have the same valve type? . another fing i had thought of the .5 mm over size valves 034 do but am not sure if they would be worth using . what i am after is what will cope with hotter exhaust gas temps just incass things run a bit hot when tuned to give the out put i want

[4WheelDrifter]

The 7A valves I have had are not sodium filled. Weigh them to find out if yours are. Weights are here.

[S2central.net]

I am very skeptical about gains from those 'oversize' valves... thats just my gut feel - have not seen any evidence either way, but its an awful lot of work... maybe worthwhile if valve seats are really bad or if the application is a full on race machine - assuming the bigger valves do have some marginal benefit at the top of the revs.

I'd prefer resilience of sodium-filled EX valves over some nth of extra bhp from oversize non filled EX valves - but thats just me.

[denniselbows]

The 7A valves I have had are not sodium filled. Weigh them to find out if yours are. Weights are here.

thanks i give it a go

[repo]

Stock turbo engine valves with a regrind are plenty enough for all of You. For any boost. And revs. Yes, I've taken them to the extreme, and beyond, and more. And some.

[S2central.net]

There you go - repo will have proven my gut feel many many times already. The case for the defense rests

[JP]

All I5 engines have same intake valves
All turbo charged I5's have sodium filled valves
Naturally aspirated I5's need there exhaust valves binning for FI use.

Sodium filled valves are one of the best valves out there for boosted application capable of withstanding tremendous temperatures well beyond what your engine will ever see.

The downfall of sodium filled valves is that the extra heat transference through the stem makes the guides wear prematurely so it is advised to change the guides every 60,000miles. Although I have seen them last as long as 100k on not so heavily tuned motors. In recent years they have been tarnished with a bad name as people where tuning up high mileage 1.8t engines which have only 6mm stems and not replacing the guides so the sideways seating of valve head to valve seat caused mechanical failure in valve heads dropping of.

Inconel has a higher melting point than stainless but can still burn just like sodium filled ones if the EGT's get too high. Got several sat about in this sort of state because the guys that ported the head believed that they would get inmproved spool up from small exhaust ports :corey:.

To go oversized valves there is various benefits that could be had depending how they are applied.

First of all oversized intake can give upto 12% more airflow than a stock valve if throat, seats and port are correctly reworked to suit. However there is no point if your intake manifold reduces the flow back to that of stock valves if it can't support the extra flow.
Oversized exhaust valves can be applied in 2 different ways depending how the seats are cut. You can either go for the 8% top end flow gain if running high lift cams. Or you can go for more area under the lift curve with no extra top end lift gains.

Realistically if a head has been reworked properly on stock valves that have been swirl polished and back cut then it will support the peak figures that the average person seeks (personally seen 650+ at the flywheel). If someone is spending the money and matching everything before and after and going high lift cams they will see benefits from oversizing the valves.

[denniselbows]

All I5 engines have same intake valves
All turbo charged I5's have sodium filled valves
Naturally aspirated I5's need there exhaust valves binning for FI use.

Sodium filled valves are one of the best valves out there for boosted application capable of withstanding tremendous temperatures well beyond what your engine will ever see.

The downfall of sodium filled valves is that the extra heat transference through the stem makes the guides wear prematurely so it is advised to change the guides every 60,000miles. Although I have seen them last as long as 100k on not so heavily tuned motors. In recent years they have been tarnished with a bad name as people where tuning up high mileage 1.8t engines which have only 6mm stems and not replacing the guides so the sideways seating of valve head to valve seat caused mechanical failure in valve heads dropping of.

Inconel has a higher melting point than stainless but can still burn just like sodium filled ones if the EGT's get too high. Got several sat about in this sort of state because the guys that ported the head believed that they would get inmproved spool up from small exhaust ports :corey:.

To go oversized valves there is various benefits that could be had depending how they are applied.

First of all oversized intake can give upto 12% more airflow than a stock valve if throat, seats and port are correctly reworked to suit. However there is no point if your intake manifold reduces the flow back to that of stock valves if it can't support the extra flow.
Oversized exhaust valves can be applied in 2 different ways depending how the seats are cut. You can either go for the 8% top end flow gain if running high lift cams. Or you can go for more area under the lift curve with no extra top end lift gains.

Realistically if a head has been reworked properly on stock valves that have been swirl polished and back cut then it will support the peak figures that the average person seeks (personally seen 650+ at the flywheel). If someone is spending the money and matching everything before and after and going high lift cams they will see benefits from oversizing the valves.

thanks that has been a great help

[S2central.net]

How much of that 12% gain on a flowbench is attributed to well matched ports, throats and seats done nicely - and is that keeping the same valve lift in before/after measurements ?

I'm no head guru but I just cannot visualise a 12% gain from oversize valves alone... Methinks there are multiple factors in play here.

Lets also remember that any flowbench gain might only be useful to extract more peak power on full blown race engine - it doesn't necessarily give more performance across the rev range. This is the problem about quoting numbers for various tweaks as there is great potential to confuse people and such information can be misleading when used by the wrong hands. NOT wanting to start an argument here - just pointing out that one measured parameter does not tell us everything.

[JP]

You're right figures are only a small interpretation of the grand scheme. As a general rule of thumb if I quote percentage gains it is based on an average gain of area under the curve of what is considered to be a useable lift range (upto 450thou). It will not include the potential restrictions imposed by intake and exhaust mani's.

As reference;

Just fitting an oversized valve to an existing port will pick up a little bit of lift in the very low to mid lift range. An area where the cam spends very little of it's time so no real power gains or benefits will be seen from this.

Open the throat up to the correct size respective to the valve and you will see midrange lift gains where most roadgoing cams operate.
The problem now being that the port velocities will become too great at high lift ranges for aftermarket cams. So to benefit with those you then need to open the port up to slow the airspeed down again.

At which point you hit the next stumbling block as the minute you bolt the stock intake on you loose a very high percentage of what has just been gained.
This is why it becomes a careful balancing act to ensure everything in the equation is correct for the application in question.

As for the usefulness of a flowbench in extracting power figures not very if all you are relying on is flow gains as it is not the be all end all of the equation like you say. More than anything it is only ever there to point someone in the right direction, real life experience from trial and error is where the figures can be properly interpreted and incorporated.

Here's one for you, to show what can be achieved when everything is matched correctly.
A dyno pull from earlier today running a low boost running in map on a 1.8t with all the ignition timing knocked out of it (10 degrees as a reference point).
It's running the lariest cam that catcams supply on 1200cc injectors and drives extremely civilized on the road with an incredibly smooth power delivery, albeit the 1400rpm idle.
When you compare the power curve to a 1.8t with a fully mapped gt3071 .82 a/r on a stock head and cams. It has like for like power delivery until 5000rpm after which it just carries on going till redline. As reference the turbo on the plot is a gt4094 with 1.06 a/r. So port work up with everything else before and after perfectly matched has allowed the out and out race spec configuration on low boost to spool up and drive like a mid powered street/strip setup pushed to it's limit.