Modified head - what valves do you run? Poll!

[x6rs]

Hope none of you guys are going for +0,5 valves without getting bigger valve seats, its totally useless, the oem seats are smaller than stock valves...
Btw im running 7a valves, 726whp, people have used stock valves for Ages, my best advice if you want to change valves, get the same size as oem but better design, on exhaust it improved flow by 30% when we tested it, more cost effektive than porting the head

[RichLV]

Is it permissible to improve them by yourself? We did something like that on ABK, wanted to follow suit on AAN, a bit of grinding at the neck of the exhaust valve as it is very thick and heavy.

[x6rs]

Oh, and i rev it to 8300rpm and i abuse it on track, so more rev limiter than idle

[Thuppu]

Just what I wanted to know. You run with e85?

[x6rs]

I wouldnt grind them myself, old valves and theyve probably been used for a while, we just changed angles on my valves.. Just put on more boost, i doubt it makes so much difference anyway, the channels in the head are bad anyway on our old 5 cyl.. Keep it simple

[x6rs]

Yes i run e85, it also helps With the exhaust temps

[RichLV]

I wouldnt grind them myself, old valves and theyve probably been used for a while, we just changed angles on my valves.. Just put on more boost, i doubt it makes so much difference anyway, the channels in the head are bad anyway on our old 5 cyl.. Keep it simple

Didn't mean grinding on old valves. I'm completely replacing all of them, and thought of giving them to a shop to lighten up and take some of that neck fat off.

[Thuppu]

I would just do backcuts on them, nothing more.

[diesel des]

To be fair how many stock 20vt motors drop valves? Never heard of a single instance. Asking a 25yr old valve that's probably done minimum 150k miles to take the heat and revs of a modified engine is what can cause a failure - fatigue. On a road car OEM valves are the still the best option IMHO.

I had a Tdi head which used sodium 2 part exhaust valves brake with less than 10k miles. 2 parts are always weaker than 1.

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[x6rs]

ok i see. I wouldnt bother, maybe the become weak instead, there are good valves to buy that dont need any grinding more than maybe angle on the seat surface. I doubt that porting and bigger valves make that much difference unless someone totallly changes the whole design of the ports and seats etc, it cost more than it gives in my opinion, based on how bad the oem design is, a little more boost is cheaper and less complicated. My head is ported properly, angles on valves recut, the combustion Chambers is ported also, but i doubt it does that big of a difference, maybe in a flow bench, but not in actual driving. Sure IF you want absolutely Max out of it on a given boost(rally w restricor) or IF youre competing in a high level and need those 100rpm sooner boost maybe. Whats most cost efficient? Gettting power is easy, you dont need more than 7a cams and a big turbo for 800+ HP

[RichLV]

I would just do backcuts on them, nothing more.

Backcuts will be done for sure. Still, that exhaust valve is heavy... Maybe I'll play it safe then.

[x6rs]

I also have another theory on the breaking valves... I think they bend before they break, they bend and hammer in the seats til they break, either bend from heat, or worn guides, then they hammer in the seat till theyve fatigued and break.. And not just that they are friktion welded 2-piece, a lot of valves is, even aftermarket. Im no expert on this at all, but i doubbt that you just can blame the valves

[popdemonic]

Good infos from Eugene about various valves (sodium vs non-sodium filled)

http://www.s2forum.com/forum/showthr...ight=sodium+7A

[popdemonic]

Some more question about the valves.what did you guy do on the valve jobs?
I have read some good ,bad between cutting vs grinding vs lapping seats.
Some said just cutting it and done.some old school said grinding and lapping is
Way better seat sealed.what is the best back cut on the valve?1,3,5 angles
For the better flow ?

[RichLV]

I did some work on my old A80 2.0 liter ABK. Valves were lightened around the neck, seats were made with a 3-angle cut and valves made to fit them.

Is it possible to use 7A non sodium filled on the AAN?