Valve grinding

[RobLN]

I'm refurbishing a 16V cylinder head and was wondering if anyone has any tips on the details of fitting / grinding the valves.
I've been advised that the optiomal sealing 'line' width (valve to seat) should be around 1.5mm - 2mm after having ground to fit.

Any tips much appreciated.

Solid Edge; I-Deas 7 to 12; NX4 & currently NX5.

 

[patprimmer]

Have you searched under multi angle valve job

Regards
Pat
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[MiketheEngineer]

This needs to be done correctly. Seek out an old engine manual for this type or find an old machanic that knows what he is doing.

While I suggest that - I have done the same as you explain - but on very cheap engines - lawnmowers, etc. and if I screwed it up - at least it ran a few more hours before totally shot. But a 16 cylinder engine is probably worth a few bucks.

 

[evelrod]

This is THE tip, Rob....

Seek out a competent shop with a good reputation for servicing your particular engine. Finding the shop that the fast cars are using, if you are racing, is a start.

The best way to learn is to watch an expert. It is not rocket science but it does require a level of experience and a very conscientious machinist if you are looking for perfection.

Over the last 50 years, I did all my own valves. At my age, I don't have the steadiness or eyesight to do the delicate work any longer ;o( Now I farm out the head work. Our two race cars are now running "pro" built heads. Surprisingly, they were not all that expensive, considering the performance.

Rod

 

[Peter7307]

One extra point ...expect to pay for this.
It does take a level of experience as Evelrod pointed out as well as time and constant checking ; all of which costs money.

Good luck with the rebuild and running.

Pete.

 

[RobLN]

Thanks for all your responses. I'm not building a race engine so I'm not too concerned about absolute perfection. However I do need a certain amount of reliability from the fixed engine.

My local mechanic advised to just swap out the valves as is wih no prep./grinding. Its a modern VW golf head and he said that the accuracy of the modern engines / valves and given the relatively good condition of my current head, it would not warrant the need to lap in the new valves.

As an engineer I think that's a little optimistic but he claims to have had decent results from just swapping in the past and that the engines have subsequently been running OK without issues.

This engine suffered from water pump failure which took out the timing belt and bent some of the valves. (hey VW what a great idea - lets mount the water pump on the main timing belt!)- hence the valve work now required.

Anyway, I'll probably go and get a book on the subject or speak to the VW dealer.

Solid Edge; I-Deas 7 to 12; NX4 & currently NX5.

 

[evelrod]

For a "modern" street engine that has a "few bent valves" from a broken timing belt....Yeah. I see no real problem with just dropping in a new set of valves. Just be sure that there is NO damage to the seat inserts. Several ways to check for seating....stick a vacuum cleaner in the port and listen with a stethoscope (a piece of fuel hose will suffice). I prefer to lap the valves a bit. Easy to do with a batt powered drill motor on the valve stem and a little "up and down" action. Nothing major, just to see if the valve seats. Like you said, NOT a race engine.

Rod

 

[chammyman]

having done ohh about a billion snapped nelts in my time don't just chuck the valves in and reassemble, lap them in, use only fine paste and not much of it. do it by hand.

If worried about reliability some of the ones I have done have gone on another 200k or so miles and been happy enough.

very, very rarely will a cut seat and a valve actually seal right, even with decent equipment (topline serdi etc). I get the occasional joker wantign hand radiused seats and they don't care if the seals away in a few hundred miles.

Also 16 valves aren't much to do, try doing 3 or 4 16v heads a day though!

was it the usual plastic impellar slipped/broke thus allowing the pump to pull out and mangle the valves?

 

[RobLN]

Thanks for the advice Evelrod, Chammyman. I've got the kit for lapping the valves in so I'm going to give it a go. I've got some time so I'll try and do it well. The rest of the car is in really nice condition so I'd like to keep it a while longer.
Yes it was the plastic impeller. It disintegrated and left bits of plastic all over the place. The new OEM one has a die cast impeller. VW live & learn. Now they just need to mount the pump on an aux belt (like they used to) and we'll be all set!


Solid Edge; I-Deas 7 to 12; NX4 & currently NX5.

 

[patprimmer]

My Honda just bent the valves after the distributor seized up. It seems to have overheated and burned some plastic and created some corrosion inside. It is driven off the inlet cam.

It also drives the water pump of the timing belt. It seems they built in a double jeopardy.

Regards
Pat
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[chammyman]

Theres loads of cars out there with water pumps driven by the cambelt, european cars especially.

They changed the impellar to metal a while back, common issue with them. Working on heavies you see the same thing, Volvo FH12's are notorious for the impellar spinning on the shaft but not so much dropping off funnily enough. Gear driven off the cam gear on them.

 

[vagman2]

If you talk about 5-valve cyl head, the VW's recomendation is "Do not rework, only lapping-in is permitted"

 

[RobLN]

Thanks for all your advice.
I did the work over the weekend and refitted 16 new valves, seals, new head bolts/gasket, timing & cam belts & water pump. Started first time after the work. Car now runs better than it ever did. I think a saved myself about £800 compared to getting a garage to do it.

Solid Edge; I-Deas 7 to 12; NX4 & currently NX5.

 

[evelrod]

And, Rob, you have started down that long, dark path that can easily lead you to a single life and near poverty...<grins>
Good job. I'm glad to see some engineers are not afraid to try something new. Watch the slippery slope, though...LOL

Rod

 

[Thecardoc]

Word of caution. I know you already have this done but depending on the model and year the front engine mount may use TTY bolts. If it does they must be replaced every time they are removed. Attempting to re-use them works for a brief period of time, but they continue to stretch, then loosen, and then fail completely and allow the mount to move contact the belt and cause it to fail again.

 

[RobLN]

Hi thanks for the warning. I saw that the mounting bolts on the die cast engine mount (LHS) were either 16mm or 18mm hex head head drive. They looked pretty stock to me and I torqed them to FT. Didn't look like stretch type bolts. The engine has been out a couple of times before and the bolts look original. I will keep an eye on them though.

Solid Edge; I-Deas 7 to 12; NX4 & currently NX5.