Check Valves Are Sealed

[Rob Turbo 3]

Following on from my topic in general car chat (was getting too technical for general!), I don't think my valves are bent, I think they just need re-grinding in because I only gave them a quick once over and all the inlets are leaking, some worse than others

 

The way I'd been told to test to see if they are sealing was to fill the combustion chamber with petrol and if it leaked out, the valves weren't sealing, BUT! I've tried this and the petrol goes nowhere, but I know they leal because air was getting past when I attached an air line to the cylinders

 

So, is there any way of testing they are sealing 100% after I've re ground them without wasting another head gasket?

 

Thanks

Rob

[Pug_101 0]

Following on from my topic in general car chat (was getting too technical for general!), I don't think my valves are bent, I think they just need re-grinding in because I only gave them a quick once over and all the inlets are leaking, some worse than others

 

The way I'd been told to test to see if they are sealing was to fill the combustion chamber with petrol and if it leaked out, the valves weren't sealing, BUT! I've tried this and the petrol goes nowhere, but I know they leal because air was getting past when I attached an air line to the cylinders

 

So, is there any way of testing they are sealing 100% after I've re ground them without wasting another head gasket?

 

Thanks

Rob

 

 

To check your valves roll them on a flat surface, if there bent it will be quite clear to you.

It's very hard to air seal metal to metal how did you do this as pressurising through the ports will lift the valves and air can escape through the piston rings on an engine.

Cheers

[Rob Turbo 3]

You could feel the air coming out of all the inlet ports when an air line was connected to the spark plug hole, it was a lot worse on number 2 tho, all the others seemed to hold some pressure after I stopped the air (they hissed for a second or two after I stopped the air)

 

If they are leaking like that then when the engine is on the compression stroke its going to push some of the mix back into the inlet, surely this isn't normal?

 

Thanks

Rob

[Rob Turbo 3]

Just took the valves out of number 2 cylinder, both bent as a 10 bob bit

 

Took one out of one of the other cylinders and it doesnt seem bent, but it was still leaking so I dont know if they are all bent just not very much or if its just that they need grinding in properly

 

Gutted! Thing is, I'm not sure if I've bent them by knocking them on something or if they have hit the pistons (xu10j4 head on xu10j2te bottom end)

 

I'm going to carry out further tests to see just how close the valves come to the pistons with some of that flower arranging foam (the stuff that stays dented when you press it)

 

I'm fairly sure they have enough clearence tho, before I fitted the head properly I put thick corrigated card board on top of the pistons and trial fitted the head with oil on the valves, timed it up and turned it over by hand and the card board came out with no oil, I think the foam method will be better tho, I'll use thick pieces, around 10mm so the valves will definitely touch it, but I'll see how close they get

[Guest rick03054]

Does that stuff not come apart a bit when you touch it though? Might leave crap in the bores and on the valves?

 

Maybe not an issue I just wanted to point it out because I remember it being horrible gritty stuff.

[Rob Turbo 3]

It will probably leave crap behind, but I'm trying to think of other stuff, maybe plastercine (sp? - the stuff you played with as a kid!)

 

I dunno! any suggestions?

[Guest rick03054]

Sounds better, what about blu-tack, coated with WD-40 so it wont stick to anything.

[Rob Turbo 3]

Doesn't that have some spring to it? or am I thinking of something completely different?

[Guest rick03054]

Well it leaves a pretty good imprint anyway. Would you believe I just went and dug some out a drawer and poked it with a pen to be sure!

[Rob Turbo 3]

LOL!!

 

Might have to try some then, a few layers to make sure I got plenty clearence!

[Pug_101 0]

Just took the valves out of number 2 cylinder, both bent as a 10 bob bit

 

Took one out of one of the other cylinders and it doesnt seem bent, but it was still leaking so I dont know if they are all bent just not very much or if its just that they need grinding in properly

 

Gutted! Thing is, I'm not sure if I've bent them by knocking them on something or if they have hit the pistons (xu10j4 head on xu10j2te bottom end)

 

I'm going to carry out further tests to see just how close the valves come to the pistons with some of that flower arranging foam (the stuff that stays dented when you press it)

 

I'm fairly sure they have enough clearence tho, before I fitted the head properly I put thick corrigated card board on top of the pistons and trial fitted the head with oil on the valves, timed it up and turned it over by hand and the card board came out with no oil, I think the foam method will be better tho, I'll use thick pieces, around 10mm so the valves will definitely touch it, but I'll see how close they get

 

As i said earilier if you roll them on there side it will show up if the valve is bent.

I'll explane in a bit more detail. Pick a flat, smooth and level surface (kitchen work top) and gently roll the valve it will go round and should be very smooth as it does, any jerkiness shows a bent valve. Also mark the position the valve comes to rest (ON THE VALVE ITSELF WERE IT MEETS THE SURFACE) and roll it a couple more times, a bent valve will always come to rest in the same position.

As for the blu-tack as good as anything else.

[Rob Turbo 3]

I understood what you meant, it showed 2 of them were bent but the others seem ok

[Rob_the_Sparky 10]

Well I've used the petrol trick before and it workd fine, although I did it the other way round, petrol in the inlet tract. That way you can see it seeping through much more easily. Don't see how you are meant to see it leaking the otherway round (it won't (shouldn't) pour through).

 

Rob

[PumaRacing 2]

Sorry chaps but this thread is little more than the blind leading the blind.

 

The way to see if a valve is properly straight, and that means to within a thou or so, is put it in a valve refacing machine and see if it grinds true. Rolling them around on tables is pointless dicking about which might tell you if they are bent as a banana but not that they are fit to use in an engine.

 

Paraffin and petrol in the ports is also fairly pointless. It'll show up a very bent valve but the valve spring pressure will hold a slightly bent valve straight enough to give a fair seal. That valve head is still flexing about every time it opens and shuts though until eventually it falls off into the cylinder and wrecks the engine. That's if the seat doesn't burn out first.

 

Lapping in isn't always much help either. The thickness of the paste will still give some sort of grey finish to a slightly bent valve or distorted seat.

 

It's like most things to do with engines. You can d*ck about trying to save money and end up rebuilding it again in the near future or you can use the right equipment, or go to someone who has that, and do it once properly.

[Rob_the_Sparky 10]

LOL, direct, to the point and accurate as always

[Rob Turbo 3]

Thanks for the info puma, maybe you'll have the answer to my next question (probably!) Are 1.9 Mi16 inlet valves the same as 2.0 Mi16 (s16) valves?

 

I have a 1.9 head full of straight valves!

 

Thanks

Rob

[PumaRacing 2]

Thanks for the info puma, maybe you'll have the answer to my next question (probably!) Are 1.9 Mi16 inlet valves the same as 2.0 Mi16 (s16) valves?

Thanks

Rob

 

Yes.