Valve Seats ..Unseating?

[Jccck]

Okay so i've come across this problem;

I have standard valve seats, machined to suit 2mm+ Intake and 1mm+ Exhaust Valves.
And a combination of the titanium springs, more aggressive camshaft, and booooost! Has caused a couple of seats to 'unseat' and move slightly.
Seats are being hammered into the Alloy head, mushrooming the end of the port and sitting a little crooked.
Resulting in compression loss due to valves not seating, and also slightly bent valves because they've been forced to seat on an uneven surface.

Kinda confused as to what caused this;

Steel and Alloy have different rates of expansion under heat so ofcourse the interferance between the two pieces would be ever changing.
Seats have a tolerance from factory, and it's possible i've been unlucky enough to have gotten the low end of the tolerance on both Head and Seats in multiple places.

Curious if anyone else has seen this happen, heard of a reason why it happens.. Or had it happen to them.
My Engine Builder was kinda shocked, and ofcourse we're now having custom seats installed to replace the 16 standard ones.

Just thought i'd share, i thought it was a rather interesting problem to have!

[N9netwoAccord]

Wed3k is a machinist, I'm awaiting his input. I have no idea what would cause this, maybe than defective valve guides? Unless it happened consistantly on all cylinders?

[Jccck]

Wed3k is a machinist, I'm awaiting his input. I have no idea what would cause this, maybe than defective valve guides? Unless it happened consistantly on all cylinders?

Happened on both Intake Valves in Cylinders 3 and 4.
Cylinders 1 and 2 seem alright, and all Exhaust Valves also seem fine at first inspection.

[toycar]

How much power were/are you making?

How much air/pressure are you pushing?

[Jarrett]

I'd assume that at 2mm oversize you've taken away too much mass in the seats. This greatly reduced mass no longer has the ability to absorb the impact of the valves as they crash back into them millions of times.

[wed3k]

sorry but 2mm os doesn't fit on a stock seat. either way you need new seats and proper interference fit. plus what are you running that you need to utilize a 2mm os? most of the time if the port size isn't that much bigger running that big of a valve is a waste.

[Jccck]

How much power were/are you making?

How much air/pressure are you pushing?

Not sure on the power figure.. It had a comfy 215WHP at 9PSI.
At 20PSI, we pulled it off the Dyno before we were able to get a proper read-out because we noticed it missing at low RPM.
Head will be re-assembled and hopefully in a months time i'll be back on the Dyno.

I'd assume that at 2mm oversize you've taken away too much mass in the seats. This greatly reduced mass no longer has the ability to absorb the impact of the valves as they crash back into them millions of times.

That's what we're thinking, the seat has lost so much strength it cannot take the hits.. And the interference isn't enough to keep it secure.

sorry but 2mm os doesn't fit on a stock seat. either way you need new seats and proper interference fit. plus what are you running that you need to utilize a 2mm os? most of the time if the port size isn't that much bigger running that big of a valve is a waste.

Well it did for a whole 3000KM's on 9PSI.
But the Boost increase was a bit much for it.
Yes, currently having new seats installed all round.
Bisi actually recommended the valves to me, and i trust his opinion.
He has helped with so much of my build.
Head has ofcourse been extensively ported by somone who knows what they're doing.. Not some clown with a dremel.. Don't fear =P

It's kinda funny, with all the time researching and making this Motor near bulletproof for my application.. I'd overlooked something as small as the valve seats!
Well, we've all gotta learn somehow i 'spose haha.

[choppacity]

I'm running an almost identical setup to yours, though my car is not done, but the motor is built. When i had my valves installed, the seats were replaced with larger ones to fit the valves accordingly. The machinist said that the valve surface would go beyond the seat. Hope you get it fixed and running again!

[GhostAccord]

The fact that your seats remained seated in the head for 3000km was really luck. Considering stock seats will stay seated for well over 400,000km. It was just a matter of time before they all came loose. The boost pressure had nothing to do with them falling out.

Not sure what machine shop you took your head to. However, I would avoid them in the future. Get your money back and take it else where. They should have known that the stock seats are way to thin for 2mm OS. Even the exhaust seats @ 1mm could use larger seats to maintain reliability.

[wed3k]

and performance...you want the contact as close as you can to the edge of the valve face.

[esskater892]

where could one get quality valve seats that are over sized? 2mmover intake and 1mm over exhaust

[wed3k]

sbi makes good seats then there are also martin wells which are hard as fuck to machine.

[GhostAccord]

Most engine machine shops should be able to get you what you need. From OEM and oversize replacements to more performance oriented bronzed seats.

[esskater892]

sbi makes good seats then there are also martin wells which are hard as fuck to machine.

Most engine machine shops should be able to get you what you need. From OEM and oversize replacements to more performance oriented bronzed seats.

thanks guys ill look into it.
edit: also would you be able to point me in the right direction of where to find the O.E.M valve seats size?