Valve tolerance - advice needed

[Mgrene]

Evening forum.

so, I’m doing my first maintenance check on my Supra and this evening I decided to check the valve clearence.

my spec is briefly:

- HKS 264 cams

- Brian Crower valve springs and retainers

- Brian Crower valves

According to the manual, the tollerance must be:

Intake: 0,15mm-0,25mm

Exhaust: 0,25mm-0,35mm

So far all is within spec except for one intake valve. The lowest feeler gauge I have is 0,05mm and that won’t even go between the cam and the shim

Here are my questions:

1) the one valve with the low clearance will of course get a new shim, but what does it mean in practice when it is so low? Is there a change that the piston will hit the valve ?

2) The manual is of course based on stock motor. In my case I’m running with different cams, springs and valves. Can I still follow the tollerances in the manual? What are you guys running with?

I have not meassured all yet, simply to tired. Will meassure the rest tomorrow.

 

Edited March 8, 2021 by Mgrene (see edit history)

[Mike2JZ]

HKS cams typically use similar valve clearance specs to stock. A quick bit of googling shows that they should be 0.2mm intake & 0.3mm exhaust +/- 0.03. So going to stock specs will be fine. 

In the case of the valve that is to tight you won't run the risk of the valve touching the piston with these cams, however once they engine gets warm and everything expands you might find that you lose performance on cylinder one as the valve runs the risk of not being able to seat itself properly back into the valve seat. Over time this could lead to issues with burning out a valve for instance. You could confirm if this is the case by getting the engine warm then doing a combo of compression & leak down test, if valve isnt closing fully then you will have a leak from intake valve. 

I assume this is a stock engine, or has it been built before previously? It would be useful to know, but very hard to see with the head still on, if the valve clearance issue has been caused due to a movement in the valve seat or if something else has worn out over time. I'd start with changing the shim on that valve to bring it back into spec and see how it goes. 

[Mgrene]

19 minutes ago, Mike2JZ said:

HKS cams typically use similar valve clearance specs to stock. A quick bit of googling shows that they should be 0.2mm intake & 0.3mm exhaust +/- 0.03. So going to stock specs will be fine. 

In the case of the valve that is to tight you won't run the risk of the valve touching the piston with these cams, however once they engine gets warm and everything expands you might find that you lose performance on cylinder one as the valve runs the risk of not being able to seat itself properly back into the valve seat. Over time this could lead to issues with burning out a valve for instance. You could confirm if this is the case by getting the engine warm then doing a combo of compression & leak down test, if valve isnt closing fully then you will have a leak from intake valve. 

I assume this is a stock engine, or has it been built before previously? It would be useful to know, but very hard to see with the head still on, if the valve clearance issue has been caused due to a movement in the valve seat or if something else has worn out over time. I'd start with changing the shim on that valve to bring it back into spec and see how it goes. 

The engine is fully built with aftermarket parts. Producing 700-900 whp.

After the re-shimming I am actually planning to do a compression and leakdown test.

Now that I’m going to re-shim, would it be a good idea to replace the stem seals as well? Is this at all possible with the head still installed. I have read about a toyo-tool that can be used but now sure if the one I looked up is the right one?

 

[Mike2JZ]

The reshimming procedure will not require you to remove valve springs or change valve stem seals as you are only changing the shim that sits on the bucket. 

I don't know how long you have been running with that kind of power, but typically valve stem's dont need replacing unless you have issues with burning oil and you suspect one is damaged or worn from age and has gone brittle from many heat cycles. There are many different valve stem tools out there, I haven't used the one you linked, but have used similar products and they work fine. 

Given that you have a fully built engine, its possible that this valve clearance issue was a mistake from when it was first assembled, or perhaps the valve seat is damaged/moved in some way from running under high stress. 

[Mgrene]

8 hours ago, Mike2JZ said:

The reshimming procedure will not require you to remove valve springs or change valve stem seals as you are only changing the shim that sits on the bucket. 

I don't know how long you have been running with that kind of power, but typically valve stem's dont need replacing unless you have issues with burning oil and you suspect one is damaged or worn from age and has gone brittle from many heat cycles. There are many different valve stem tools out there, I haven't used the one you linked, but have used similar products and they work fine. 

Given that you have a fully built engine, its possible that this valve clearance issue was a mistake from when it was first assembled, or perhaps the valve seat is damaged/moved in some way from running under high stress. 

Thanks Mike.

I'm aware that it is not necessary to replace the stem seals when re-shimming. However, given the fact that the engine was built approx. 10 years ago and hasn't (to my knowledge) been open since, I think it wouldn't hurt to replace the stem seals now that I do have the valve covers and camshafts off anyway.
The engine has not done many miles (primarily used as showcar) but I imagine that parts such as stem seals wear out over time.

I would really love to check the valves also but since the head is still installed, that will not be possible. I have to settle with the leak down test to tell me if any valves are bent or not seating properly.

Since it's so many years since the engine was built I think it will be difficult to tell the reason why the intake valve is so way off tolerance. If it is because of a lazy builder who didn't measure this when building the engine, well, it is just another great example why I want to do stuff myself. 

 

Edited March 8, 2021 by Mgrene (see edit history)

[rider]

I would have thought that the degradation of the valve seals is both time and temperature dependent. With, temperature being a major factor. You only have to look at how the rubbers and plastics 'on' the engine age relative to those around the engine. So if the engine has been little used then I'd expect that the stem seals will be virtually as new. 

If you do want to go ahead and looking for a good tool I have a Lisle collet tool ready for when I finally get around to changing my stem seals. I bought it on the strength of reviews and there are a couple of tube videos showing people using it, one on a 2JZ. It costs around £30.

https://www.amazon.co.uk/Lisle-36200-Keeper-Remover-Installer/dp/B000P0ZJIS

Edited March 8, 2021 by rider (see edit history)

[Mgrene]

1 hour ago, rider said:

I would have thought that the degradation of the valve seals is both time and temperature dependent. With, temperature being a major factor. You only have to look at how the rubbers and plastics 'on' the engine age relative to those around the engine. So if the engine has been little used then I'd expect that the stem seals will be virtually as new. 

If you do want to go ahead and looking for a good tool I have a Lisle collet tool ready for when I finally get around to changing my stem seals. I bought it on the strength of reviews and there are a couple of tube videos showing people using it, one on a 2JZ. It costs around £30.

https://www.amazon.co.uk/Lisle-36200-Keeper-Remover-Installer/dp/B000P0ZJIS

Thanks for the link but I have actually already ordered this from toyotool.com