Valve cleaning
- Thread starter Biohazard
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A wire wheel mounted on a bench grinder or electric drill is the most effective tool for decarbonising valves IME.
Cam Lube is the stuff you want for coating the cam lobes during asembly. This is really only needed with new cams and followers though, and usually comes with a cam 'kit'.
Cam Lube is the stuff you want for coating the cam lobes during asembly. This is really only needed with new cams and followers though, and usually comes with a cam 'kit'.
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right thanks, no I want to use it anyway.. even with the original cams you can still encounter bother iirc. I won't need anything else for rebuilding will I?
right I can jam my mains drill into my work bench... I'll just use that. I was only concerned the wire brush may be a touch too abbrasive for the valves but I'll trust you on that!
right I can jam my mains drill into my work bench... I'll just use that. I was only concerned the wire brush may be a touch too abbrasive for the valves but I'll trust you on that!
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I normally use a blunt chisel because I find the wire wheel doesn't get through the hard deposits. Worth a try first though, especially since you have a lot of them. Blunt chisel because a sharp one scratches the valve up.
I'd just use engine oil for re-assembly. As said, you only really need cam lube for new cams and followers. Hope you kept all your followers in order
I'd just use engine oil for re-assembly. As said, you only really need cam lube for new cams and followers. Hope you kept all your followers in order
Valve heads are made from very hard steel alloy, a wire wheel works fine without damage. I have cleaned literally hundreds of valves this way with no problems apart from some carbon deposits that even the wire wheel wouldn't shift. To get them really spotless you can mount the valve in a drill and use some emery strip, though watch the fingers and stay away from the valve seat area and valve stem with emery.
Any deposits on the valve stem area can be removed with a solvent such as brake cleaner or (my favourite)cellulose thinners.
I'm sure you know this but the most important point with re-using a cam and followers is to keep each follower matched to it's original lobe.
Any deposits on the valve stem area can be removed with a solvent such as brake cleaner or (my favourite)cellulose thinners.
I'm sure you know this but the most important point with re-using a cam and followers is to keep each follower matched to it's original lobe.
what's the benefit in cleaning them? when i did mine i just lapped them and bunged them straight in
also, all the workshop manuals i've used state just to oil the cams if theyre being reinstalled - it's my understanding that special compounds (like graphogen) are needed only if the cams or bearings are brand new
also, all the workshop manuals i've used state just to oil the cams if theyre being reinstalled - it's my understanding that special compounds (like graphogen) are needed only if the cams or bearings are brand new
I normally use a blunt chisel because I find the wire wheel doesn't get through the hard deposits. Worth a try first though, especially since you have a lot of them. Blunt chisel because a sharp one scratches the valve up.
I'd just use engine oil for re-assembly. As said, you only really need cam lube for new cams and followers. Hope you kept all your followers in order
nope I just pulled them out willy nilly. I found what I expected, buggered hydraulic tappets.
picking up my new set tomorrow from the post office, so I'd guess they'd just go back into any hole since they didn't originate from my head. no major scoring or anything, anywhere considering. cam lobes look beautiful, like they day they were made!
ok will just use oil then.
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Mine aren't. Mine are just stainless steel, nothing exotic and a wire wheel damages them.
Depends on the engine, older engines foul their valves up quite a lot and the stem and head get coated in hard scale. Get too much on there and it starts disturbing the flow.
Ok, they say you should use new tappets with a new cam and vice versa or you get accelerated wear just to warn you. I've re-used a cam and used new tappets and the only thing that happened was they went out of adjustment very quickly that first time. You probably won't see that because they are hydraulic but it will knock a few thou off the cam. Probably won't even notice it, but if your budget stretches that far think about putting a new cam in.nope I just pulled them out willy nilly. I found what I expected, buggered hydraulic tappets.
picking up my new set tomorrow from the post office, so I'd guess they'd just go back into any hole since they didn't originate from my head. no major scoring or anything, anywhere considering. cam lobes look beautiful, like they day they were made!
ok will just use oil then.
That's a fair point, but I was assuming the OP was working on an engine made within the last 50 years..
Very true, worn followers means the cam lobes have worn to match them. New followers with a worn cam will be dead in quick order. My brother fitted a set of new followers to his XR2 many years back, and within 200 miles they were as bad as the original ones, despite the cam lobes not looking visibly worn.
I fail to see how. 
The cams are perfect, as were the hydraulic tappets that came out.. no scoring at all. the head is actually in incredible condition considering. The only thing wrong with them was the spring inside the tappets had collapsed meaning it would not generate full valve lift - the car had been ragged stupid or overheated, a mixture of both probably given the orange fluid spray marks I wiped from the underneath of the bonnet.
I've never heard of replacement hydraulic tappets buggering up a cam before. As I said before, the cam is as clean as any of the F7P engines i've had apart. It looks brand new, I've pulled scored/chipped cams before etc. They use double valve springs, so it should be in a state of constant zero lash. So wheres the thou of mills coming off from then?
Although I would like to be proved wrong, although I've never heard this on any of the car forums I frequent.
The cams are perfect, as were the hydraulic tappets that came out.. no scoring at all. the head is actually in incredible condition considering. The only thing wrong with them was the spring inside the tappets had collapsed meaning it would not generate full valve lift - the car had been ragged stupid or overheated, a mixture of both probably given the orange fluid spray marks I wiped from the underneath of the bonnet.
I've never heard of replacement hydraulic tappets buggering up a cam before. As I said before, the cam is as clean as any of the F7P engines i've had apart. It looks brand new, I've pulled scored/chipped cams before etc. They use double valve springs, so it should be in a state of constant zero lash. So wheres the thou of mills coming off from then?
Although I would like to be proved wrong, although I've never heard this on any of the car forums I frequent.
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If the original followers are in good condition, then you should have no problems replacing them with new ones. If the surface of the old followers is starting to get even slightly concave however, new ones will get chewed up very quickly because the cam profile is no longer flat, even if it looks ok. A new, flat follower and a worn cam lobe cause such high point loads that the oil film quickly breaks down and you get metal-metal contact.
What engine is is out of interest?
What engine is is out of interest?
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The cam lobe surfaces and the lifter surface will not wear completely flat. It'll be slightly curved, can almost guarantee it, and the two surfaces wear into the same shape and mate together. This is why you shouldn't mix up your lifters when you take them out because you'll mismatch the surfaces and they will have to wear themselves in again and you'll get lots of wear. So when you put a new lifter in it will have a flat surface on a curved surface, they will bed in and something gets worn down prematurely. If it's the lifter then no problem but if it's the cam you'll lose lift.
Like I said, I've done it and had no problems but it's a high lift cam in a 50 year old engine so I won't notice the wear very much. Not telling you you have to do it, just letting you know the implications
Like I said, I've done it and had no problems but it's a high lift cam in a 50 year old engine so I won't notice the wear very much. Not telling you you have to do it, just letting you know the implications
Surely either way (cam or tappet) loss of material will result in loss of lift? if it goes cam/lifter/valve, shouldn't matter where the material is lost you'll still lose lift/power anyway no?
Yes I do realise how stressed the valve timing components are. its a renault 16v 1764cc F7P lump fyi.
I'll take the feeler/ruler to the lobes tonight to see if I can identify any pitting/concaveness, but I really couldn't see any. Why would two flat surfaces wear down into non flat surfaces if the pressures applied are not at funky angles?
I don't think I'll encounter any problems, i'd guess that my cams are relatively wild.
Cheers for the help guys!
Yes I do realise how stressed the valve timing components are. its a renault 16v 1764cc F7P lump fyi.
I'll take the feeler/ruler to the lobes tonight to see if I can identify any pitting/concaveness, but I really couldn't see any. Why would two flat surfaces wear down into non flat surfaces if the pressures applied are not at funky angles?
I don't think I'll encounter any problems, i'd guess that my cams are relatively wild.
Cheers for the help guys!