A&Q about 350Z
Q:
I'm going to put some new valves in to a head this weekend.
Is the hand tool you get from Halfords/similar, complete with coarse and fine grinding paste, any good?
Or to get a proper seal, do you need to use a power tool or get a machine shop to do it properly?
Any techniques / advice appreciated. I couldn't fine much on the 'net.
The valve seats are fine BTW.
Cheers,
Chris
A:
Hey Chris. The hand grinding tool is fine but your hands will hurt for a while after. You wana keep lifting the valve while grinding. You need to grind until you get an even grey band on the valve and the seat. Its tedious on a 16v I can tell you! A power tool will make it faster but its easy to over do it. The valve face has to be clean otherwise the suction cup will keep dropping off because of lack of vacuum.
A:
yeah what he said, I've just done it on my 8v diesel head and its pretty labour intensive, a 16v is gonna be much fun!
mine were pretty good anyway and didn't take all that much work, it may be harder if they're really badly pitted.
A:
Get the attachment for your drill, your hands will thank you for it
A:
I've got one of those tools too. Hard work if it's a badly worn head. Make sure you don't get paste in the valve guides.
A:
Get the attachment for your drill, your hands will thank you for it
Where can you get this attachment?
Thanks.
A:
I wouldnt advise using a drill. You'll end up wearing out the valve seats. Just take your time and do it by hand, didnt take too long on my 8v, it will take twice as long on the valver but you'd be better doing it this way IMO.
A:
Saying that chris, places like Serdi's here in Uxbridge will recut your valve seats and valves, even multiangle them for not much money. Sort 'em out cash and you'll be o.k. Serdi actually manufacture the machinery that people use to do head & engine work so they know what they are doing.
A:
I wouldnt advise using a drill. You'll end up wearing out the valve seats. Just take your time and do it by hand, didnt take too long on my 8v, it will take twice as long on the valver but you'd be better doing it this way IMO.
When they're 'done', how can you tell?
I presume you have to keep turning the valve, since you're only doing about 90 degrees at a time?
Cheers for this.
A:
You wana keep lifting the valve while grinding. You need to grind until you get an even grey band on the valve and the seat.
Thats when you know its done.
A:
You wana keep lifting the valve while grinding. You need to grind until you get an even grey band on the valve and the seat.
Thats when you know its done.
Cheers Gurds.
Will go and buy some specs now....
A:
looks like a pencil line what it's right
A:
piece of p iss.
Hold the tool between the palms of your hands and roll it back and forth. lift and twist and continue.
minute of coarse and a minute of fine and I had an 8v head done in less than half an hour.
Doesn't take much.
you are not trying to create a wide flat spot. just a good seal.
As said above it only looks like a fat pencil line
A:
Hi Chris
You need to lap in the valve by turning the suction stick if you want to call it that in the paln of you hand lifting it up occasionaly to turn the valve.
You'll know when it's done because you'll have some engineers blue to (very lightly) dab around the seat on the valve. Place the valve into the head and then turn around 360 degrees. If theres a good blue line, you know it's a job done..
If the seats are shoddy you might have to work at them longer, usually the exhaust ones are a pain. It'll take a bit longer but doing it by hand, but it's the best way, don't want to over do it !
Edited by: madmk4
A:
Definitely by hand as you get a feel for when it is getting to a stage where it is done and I would think that using power tools would be to severe for it.
And it is a satisfying job to do IMO especially when you get to No.16
A:
And please dont forget to give it all a good wash down afterwards with parafin or simular, not good if valve paste gets left behind
A:
Are you putting new valves into an old head????? what are the valve guides like??? Do the valve seats look like they have a wide seat (aprox 4mm) or are they narrower (1-1.5mm), does the seat look even or does it look polished and slightly undulating, has the head got a single angle seat of a three angle seat with a narrow 45 degree band. Don’t lap the valves in yet until you are sure the guides are ok, the seats are ok and don’t use the course grinding paste if you can help it because it’s so course it will make a bad seat look good. A black permanent marker pen can also be used to check that the valve has seated properly
A:
just done mine... i'll mail you a suction stick thingy and some of my paste
would be dead easy to over do. just did mine til there was a nice shiny band around the valves and couldn't see any burrs or anything on surfaces...
A:
have you fitted new guides? if so be worth getting them done properly on a serdi machine
A:
You shouldn't need the drill attachment.
If the guides and seats are good it should only take a few minutes by hand on each seat and as prof says it should be a narrow line. Anything over 1-2mm and it wont last 5 minutes.
A:
The valve guides are OK.
Seats have more than one angle
You shouldn't need the drill attachment.
If the guides and seats are good it should only take a few minutes by hand on each seat and as prof says it should be a narrow line. Anything over 1-2mm and it wont last 5 minutes.
Whe you (Golden/Daz) say it shouldn't be too wide (eg 4mm) ie a narrow line, or it won't last > 5 mins, what will happen?
So will they bed in and contact across the whole seat eventually? Or is that not the way it works?
Edited by: Chris Eyre
A:
what's the best way to check the condition of valve guides?
A:
I've had good results with a leccy drill and a bit of petrol pipe. even better if the drill is reversible.
You need to push the valve in and out while it's turning, use a small amount of fine paste (not coarse) and keep it short and sweet - a few seconds in each direction on a slow speed then check and repeat if necessary. You should see a 1-2 mm band on both valve and seat.
It's a good precaution to check how proud the valve sits from the seat before you start, and then keep an eye on it as you grind. If you start to notice a difference it's time to stop.
There's probably a scientific way of checking valve stem to valve guide wear. If you can feel 'wiggle' on the valve then you probably need new guides. The tolerances are pretty tight on guides.
If the bottom ends of the guides have been cut to improve airflow they will wear much faster, and should probably be changed as a precaution.
Edited by: mikehorsb
A:
The valve guides are OK.
Seats have more than one angle
You shouldn't need the drill attachment.
If the guides and seats are good it should only take a few minutes by hand on each seat and as prof says it should be a narrow line. Anything over 1-2mm and it wont last 5 minutes.
Whe you (Golden/Daz) say it shouldn't be too wide (eg 4mm) ie a narrow line, or it won't last > 5 mins, what will happen?
So will they bed in and contact across the whole seat eventually? Or is that not the way it works?
If they are too wide they don't seal very well as the closing pressure is spread over a greater area. The narrower seal will also keep carbon deposits down due to the higher closing pressure. Also over time all valve seats "hammer down" if you start off with a very wide seat then they hammer down to being inefficient very quickly. Does that make sense I just got back for the dentist?
A:
what's the best way to check the condition of valve guides?
Place the valve in the guide but put your finger at the other end of the valve guide so as not to allow the valve head to reach it’s seat, then move the valve head from one side to another (in the same direction as the cam lobe moves ie: front of car to rear of car is a transverse FWD engine) the maximum limit according to VW is 1mm of movement in the head. The exhaust guides ware faster than the inlet. VW guides are crap and I would always recommend there replacement is you are rebuilding the head and it’s done more than 90k