TOPIC:

It's getting to the point where a lot of us will be in a position of having to either replace the cylinder head or refurbish the head due to wear and I thought we should probably start a new topic based on valve seat replacement for reference for all down the road.

Frank833
You seem to be involved in the racing game and have machine shop equipment access so I would like to ask you a question please.
I have 2 cylinder heads and 6 sets of camshafts to work with. Doesn't matter what head or sets of camshafts I try to marry up, I can't get assembled with shims since I'm down to requiring 1.80 shims which are not available. My options are to grind the base circle on the cams smaller and get back some service limits or replace the valve seats and cut the seats so that I need shims up at the 2.80- 2.90 range. I do plan on grinding the cams since all of the cams I have, have an effective duration of greater than 300 degrees and that's a different story.
If you were in this position, and wanted to replace the seats, would you opt for Beryllium Copper seats or powder metal seats or .....

I have tig equipment and I can lay a bead of weld without adding material on to the old seats which will shrink the seat and let them drop out of the head (I've done this job before using this method with good results). I also have Neway cutters and can cut the new seats to my desired depth for the shims I want. Just thought that you might be in the business and could advise me here (and of course, letting everyone else know your answer is why I ask the question here and not in a PM)
Thanks,
Kawboy

Are oversized valves an option? If not, can the valve tip be ground down a bit? In the old days it was possible to buy valves that didn't have the keeper groove pre-cut - the groove was cut after the valve was 'sized'.

Can the underside of the Valve shim bucket cut down a few thou?

Bucko wrote: Are oversized valves an option? If not, can the valve tip be ground down a bit? In the old days it was possible to buy valves that didn't have the keeper groove pre-cut - the groove was cut after the valve was 'sized'.

Can the underside of the Valve shim bucket cut down a few thou?

All good questions Bucko but let's face it, if the issue is that the valve seats are too deep, then anything altered to accommodate the seats is now a compromise and will cause issues down the road. Seat replacement is a standard machine shop service more common than you may think. The technologies in valve seats has evolved dramatically in the past 20 odd years and if we are going to have this work done, I would like to gather knowledge from as many sources as possible to make a judgement and then proceed.
Oversized valves- No. The length of the valve would be measured from the valve face to the top of the stem. Shortening the stem is a possibility. You can grind a small portion off of the top of the stock valve .3mm (.012:") Then You get to the point that the valve spring keeps interfere.
Grinding the base circle of the cam- Yup, can be done and I'll be doing this eventually. An opportunity to fix what I've measured as a fault in the duration of the camshafts plus grinding the base circle also adds lift to the cam.
Grinding the tip on the bottom of the shim bucket- Maybe, however this might alter the hardness of the shim bucket.

Installing new seats and then cutting the seats so that the valve stem height is 37.20 mm would be the best move. The valve stem height can be within 37.20 - 38 mm but this spec is in the service manual as a guide for refacing valves and seats. It shouldn't be the spec when replacing the seats. If a valve height of 37.20 lets you use 2.90 or 3.00 shims then the machining or cutting of the new seats should be spec'd as leaving the valve height at the 37.20 mm spec.

Kawboy,

Thanks for the kind words. Let me say I have no experience racing 4-stroke MC engines. We do have some wild 2-strokes including a 145hp RZ350 (now 500cc). Currently we are running SBCs in our Sprint Cars, and Toyota's in our Road Race cars. Have been down the LS route and had bad luck. Switched the LS car to Toyota just because "I" needed a change. Actually the Toyota 4L V8s we have are just like a 90's era MC design.

You method for changing the seats is a good as any. I've never personally changed a seat, but yes that is one of the normal methods. I'm currently paying $695/engine for low mileage (50k) engines, so I have spare heads/blocks sitting.

On seats, I would select seats based on your valves. The various alloys that contain copper are generally meant for situations where you need to get the heat out of the valve. That would be if you have Titanium valves or you are running a Turbo. Short of that, I would run Powdered Metal. But, Powdered Metal can be just about any mix of metals so you do need to make sure you pick one that is appropriate.

Personally, I'd open the Kibblewhite catalog (www.kpmi.us), and pick from that - or call them.

On the geometry issue...

Obviously if the valve is sunk in the head, folks just need to suck it up and replace the seats.

But, on the other hand, you should not run out of adjustment until the valve is sunk so far that performance is clearly impacted. There are generally a few options:

- Grind the valve tips. This is outlined in the KZ manual - I saw the drawing, so it must be acceptable for this engine. I am sure it specifies how much you can grind off. Typically this is a very small amount, like 0.3mm. Reason is that only the tip is hardened and the hardening is not very deep. Grind through it, or almost through it, and it will hammer it'self into oblivion real quick. I personally am very nervous about this approach.

- Grind the under side of the bucket. I don't think this will get you any appreciable amount on the KZ, I don't have one in front of me but I don't think there is much that can be ground off. On the toyotas, there is a nub about 2mm high that the valve contacts, so there is lots of possible "adjustment", but grinding inside the bucket is a PITA.

- Switch buckets. Switch to Sim Under Bucket. In this scenario you replace the retainer with one that will hold a shim. The shim sits in the retainer, on top of the valve stem. The bucket contacts the shim. The cam rides straight on the bucket. This means the cams have to come out to change the shims. But you will never spit a shim. If you are going to wild cams, this is somewhere between wise and required.

- Have shorter valves made. This one is obvious, just get 0.6mm shorter valves and problem is solved.

- Grind the cam base down. In reality, removing 0.5mm from the base circle probably has no ill effect (so long as the surface is still hard). But we are always trying to get stronger cams so this seems counter productive.

Exhaust valves are quite expensive now, and I expect intakes will be too, as soon as the Vesrah stock runs out. I looked specifically at exhaust valves, and the Z900/Z1000 valves are real close except the stem length. If my head had this issue and the seats were good, I would see what it would cost to have Kibble White make me a set of valves. Might even pay to have 20 sets made and just sell the rest. I am sure they can easily accommodate making standard and 0.6mm shorter vavles.

All posts should have pictures... So here is what one of my bad engine days looks like (yes the car in the background):

Realized I did not explain how Shim Under Bucket fixes this issue. Since these shims are captive, you won't spit one and they don't have to be as strong.

So, these shims are readily available down to 1.2mm and over 3 on the other end.

This setup also lightens your valve train (the shims are much smaller OD). Buckets tend to be a bit lighter. For someone that wants to rev higher, or use a wild cam, this is a good option.

Kawboy wrote: Oversized valves- No....

Just so I'm clear: are you saying oversized valves for a 1300 are not available?