Valve guide advice

P

PeterZRH

Well-Known Member
I've got a set of early 1990s Range rover heads to replace my standard P6 heads and I'd like some advice and to fill some gaps in my knowledge. This head has the single valve springs and the large valves and know unleaded compatibility (as do all V8s most probably anyway).

I'd like to fit the later style of valve stem seal which fits both inlet and exhaust valves as these actually work unlike the washer style guides in the head currently. Now in order to do this I can either replace the valve guides with those with a step in the side or the existing ones which are in good order can be machined.

Now the guides and seals are cheap enough and it's a guarantee that I'm unlikely to need it done again probably in my Rover motoring lifetime. However Am I correct in saying the valve seats must be recut and possibly replaced to match any newly fitted guides?

Is the alternative that the guides are machined in situ (is that possible?) and the valve seats left alone, merely needing a light grinding in of the valves on refitting to ensure a good seal? If so, how much (length and width) needs to be machined from each guide?

Advice please.
 
Peter,

I replaced valve guides on 4 heads and none of the valve seats had to be recut but you won't be sure. On all 4 heads i got after grinding in i got a nice even line on the valve and valve seat.
I am not a machining specialist but i believe that machining the valve guides still fitted to heads is possible but will not be cheap.
If you decide to replaced the guides, i advise you to get a tool made for removing the old and fitting the new guides. This avoids that the hole in the guides will become smaller when the guides are fitted. You still may need to ream the holes in the guides a little but adjustable reamers can be bought cheaply. (chinese quality but these will do perfectly)

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Whatever you decide to do, i advise you to check the preload as described beneath
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Preload can be set with shims under the rocker shaft mountings. All 4 heads i did needed shims to get the right preload on the lifters

Regards
Peter
 
Thanks, exactly the info I was looking for. I'll give it a go and if I can't get a good fit with the valve or two, I know a local shop which can sort me out for not much money, it's barely a few minutes work for them anyway. Not everyone I've read about was quite as fortunate as you with this regard.

It's also handy for me to simply understand the implications of such work even if I were to hand it over to a shop. I don't like going into these situations unarmed shall we say...

The seals I've got are genuine as they are cheap. The guides I plan to get are not as there is a huge difference between genuine and aftermarket price-wise. Any view on this?
 
PeterZRH said:
The seals I've got are genuine as they are cheap. The guides I plan to get are not as there is a huge difference between genuine and aftermarket price-wise. Any view on this?
Click to expand...

Unfortunately i cannot enlighten you on the quality of the aftermarket guides, but bear in mind that if they turn up to be cr@p and wear out in no time at all, your work and expenses to fit the new seals will be totaly wasted, probably ending up with heads in a worse state than you started with. Also if they cause sticky valves, you know that you will have to remove the heads to rectify the problem.
Fancy stuff is not strictly necessary, but there is no point building an engine with cheap parts.
 
PeterZRH wrote,...
I'd like to fit the later style of valve stem seal which fits both inlet and exhaust valves as these actually work unlike the washer style guides in the head currently.
Click to expand...

Hi Peter,

Land Rover obviously took a different view as they stopped fitting them to the 10 bolt heads as the seals had a propensity for coming off. Brand new cylinder heads would leave the factory without the oil seals fitted.

Might I suggest that a better option would be to have your existing valve guides "K Lined".

Ron.
 
Peter,

I got my valve guides from JRV8. You cannot use original guides as these guides are shorter then the guides in your heads.I don't think using non original guides is a problem as these are relatively simple parts. I agree with Demitris that the valves should move absolutely freely in their guides. I bought a adjustable reamer for around 20 Euro's.
Having opened a few RV8 engines i have seen that valve guides without seals last longer then valve guides with seals fitted. I assume this is caused by the fact that valve guides without seals are better lubricated by the engine oil. This however didn't stop me from fitting guides with seals.

Ron,

I have never seen a 10 bolt head without these seals being fitted. All later Range Rover V8 engines like the 3,9 i have seen were supplied with these seals. The seals have a tight fit to the valve guides and i have never seen an engine where the seal has come off. The seals get a little brittle after high mileage
Peter states his valve guides are not worn and he only wants to fit seals so K-lining is not a solution. K lining is used when the clearance between valve stem and guide is too much but it doesn't help when no seal is fitted.

Regards

Peter
 
Hi sorry to drag this thread back up , I’ve fitted the valve guides with the modern style stem seals a kit supplied by v8 tuner , I have done around 100 miles since my rebuild and while searching for a noise took the nearside rocker cover off to find just over half the seals have split or torn , is there a better quality seal? Or is it due to the cam having to much lift? It hasn’t effected all the valve seals ?
Any help will be greatly appreciated thanks
 
When fitting those guides I make up a solid lifter and check for seal / spring cap clearance at full lift on one valve, and then set the rest of the guides to the same height. Sounds like the seals have taken a pounding from the spring top cap.
Without consulting a reference book I cannot recall the spec.
 
Some seem to have made it unscathed and other not , I suppose it would be back to machine shop , my original heads never had seals but I’ve fitted the later sd1 heads , didn’t these have some flimsy rubber washer on the inlet valve only? Should I be worried about the lack of a stem seal?
 
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I suppose it all depends on how tight your valve to guide clearances are as to how much oil is going to get down them. It looks like you are going to have to pull heads to sort the problem, unless you can cut the remaining seals off in situ, or use the cunning string through the plug hole trick to hold the valves up whilst removing the springs.
However looking at this :- How to Set Up a Cylinder Head
You need 0.050" clearance over the top of the guides, seal fitted.
You can use an old rocker spacer spring as a test valve spring and assembling a head using an old pre crushed head gasket and an old lifter made solid work out the clearance you need. If it is tight and you want the guide to go down put the head in your oven at 200c for half an hour and then using a drift that goes down in the guide as well tap the guide down to get the clearance you need when using a seal on top. Measure the amount of guide sticking up when that one is set and then repeat for all.
 
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I have got on well with Real Steel modified guides PN DW125 and DW 135. They are stepped for a seal. These have a good taper when they come through into the port and when I have used them with a higher lift cam than stock and set the height, the taper has appeared in a good place in the port. I have always done the change at home by putting the guides in the freezer overnight and the head in the oven at 200c. I take the guides out of the cold one at a time and quickly fit them, returning the head to the oven periodically.

I remember going on a factory visit to Lotus many years ago and watching a guy working on a head fitting guides. Lotus spec was to heat the head as described above and chill the guides - not so in the real world. It was clear watching for a while, the heads and guides were room temp and the guides were bashed in within seconds and then on to the next etc. A lot of the guys on the tour noticed and commented.
 
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