BMW N62 valve guide replacement

[BCjohnny]

Well ….. while sharing some misgivings rather than tell you not to do it maybe a little advice on how to do it might help if you're determined enough, have the time and patience

Why are the valve tips important? Is that specifically for this engine because of Valvetronic? I was thinking that valve height could be an issue because of that Valvetronic but then again the hydraulic lifters should even things out if the valve height is within the spec

Most engines have a valve stem protrusion height tolerance, usually gauged off the spring seat and increasingly important if you have a non-adjustable hydraulic valvetrain

On older V8s this can be up to 40 thou,or so, but in your case I’m guessing it’s not so generous

Ideally you need to obtain this tolerance ….. maybe an AERA member can help ….. but if you can’t the one way would be to adopt an empirical approach to it

If so assemble your least worn valve / seat combo, assess the ‘wear’ as best you can, measure the stem protrusion and deduct this, minus about another ten thou or so

This you’d consider your minimum stem protrusion height, and your tolerance above this in length would what would seem reasonable ….. 10 thou or so would not seem unreasonable

You should have a 20 thou or so tolerance over what previously ran

The big problem you’ll now have is correcting all 32 valve heights …… although with your new exhausts you will probably be able to juggle a few to get them in spec …… most machinists just won’t want to know, as the last person to touch it is always the first to blame when something goes wrong

So you need to ‘jerryrig’ something to tip the stems to something approaching perpendicular ….. it’s not as difficult as it sounds in all honesty

To help set the heights turn up a tube that equates your maximum stem protrusion tolerance as your metric, and use a vernier to measure and adjust

Just be wary of taking too much off any one valve tip and run into retainer clearance problems

Valve spring tester, no I dont have that neither

For what you’re doing, you don’t really need one, just compress a pair of springs in series and gauge each, selecting one as a control to check the rest ….. any duds will be obvious


As regards the rest of it, it’s a shame you bought the Neways, you’d have been better off with any reasonable ball bearing stoneholder stone set up, but you have what you have

IIRC the Neways run interference angles, 46deg etc

I’d put all you angles in with the cutters, and either get the guy who skims ‘em to kiss just the seats with a stone or look online for a cheap used set up …… or even just a couple of pilots and stones, stoneholder & dresser

Lap everything in with 600 grit or finer

Also check the valve guide bores in the head casting when you knock them out, shine a light in there and you’ll soon see if you’ve a problem ….. likewise assess each individual fit when they go back in

I’m sure some might drive a coach and horses through all this, but it will get you close if you’re sharp and have an aptitude for it …… and if it all goes pear shaped as you say pick up another pair of heads

[MotionMachine]

The reason these alusil engines are burning oil is because they are alusil engines. I sleeve the V8's, the V10's and the V12's for performance builds and have bored/honed S62's for street builds. Alusil is a great concept but doesn't last forever, especially if the engine is overheated. All their motors do show exhaust guide wear. It's not unusual to replace all exhaust but intakes are still good. I use liners exclusively, rarely do I replace a guide.

The only bronze reamer that works is the AVV carbide. I never ream anything, I rigid hone with flood oil bath but I bought an AVV reamer to do a 60V V12 Ferrari for a dealer that insisted on replacing the guides with OE. Turns out that was the right call, the guides were too worn out for liners, at just 15K miles. That reamer worked awesome, it went through the guides like butter. Straight round smooth bores right to size, no honing required. I've tried all the other brands of "bronze" reamers over the years, none of them worked.

[MotionMachine]

The reason these alusil engines are burning oil is because they are alusil engines. I sleeve the V8's, the V10's and the V12's for performance builds and have bored/honed S62's for street builds. Alusil is a great concept but doesn't last forever, especially if the engine is overheated. All their motors do show exhaust guide wear. It's not unusual to replace all exhaust but intakes are still good. I use liners exclusively, rarely do I replace a guide.

The only bronze reamer that works is the AVV carbide. I never ream anything, I rigid hone with flood oil bath but I bought an AVV reamer to do a 60V V12 Ferrari for a dealer that insisted on replacing the guides with OE. Turns out that was the right call, the guides were too worn out for liners, at just 15K miles. That reamer worked awesome, it went through the guides like butter. Straight round smooth bores right to size, no honing required. I've tried all the other brands of "bronze" reamers over the years, none of them worked.

[HDBD]

I have used AV&V and the Clortec tools.
https://www.clortech.com/en/
Both are made in Canada and either provide great results. If honing is needed I use a P180 sunnen. Bronze manganese material is very tough.

[flashcoder]

The reason these alusil engines are burning oil is because they are alusil engines. I sleeve the V8's, the V10's and the V12's for performance builds and have bored/honed S62's for street builds. Alusil is a great concept but doesn't last forever, especially if the engine is overheated. All their motors do show exhaust guide wear. It's not unusual to replace all exhaust but intakes are still good. I use liners exclusively, rarely do I replace a guide.

The only bronze reamer that works is the AVV carbide. I never ream anything, I rigid hone with flood oil bath but I bought an AVV reamer to do a 60V V12 Ferrari for a dealer that insisted on replacing the guides with OE. Turns out that was the right call, the guides were too worn out for liners, at just 15K miles. That reamer worked awesome, it went through the guides like butter. Straight round smooth bores right to size, no honing required. I've tried all the other brands of "bronze" reamers over the years, none of them worked.

How do you get the liners installed without reaming? I was thinking you need to get the old crooked worn out guide straight and centered before you can install the liners.. I was thinking about liners initially but then I really could not put the whole picture together, what thickness, which material, the required tolerances and the whole inches vs mm math, where to buy them and how I am going to get it done w/o machine shop. I believe liners need more experience than just punching out the old guides and installing pre-machined ones and all what is left is reaming to the specified final ID.

Youre correct the exhaust valves have more wear and the valves themselves are significantly worse than intakes. But the intake guides are the ones causing oil burning. I was surprised to find out that BMW repair manual specifies the allowed valve to guide tolerance (measured as pictured below, valve stem flush with guide at the bottom) is 0.5mm and the ISTA+ dealer software manual says even.. wait for it.. 0.8mm! It seems like they did that to avoid customer complaints and warranty repairs because - look its within the spec we dont need to do anything. Just imagine almost 1mm side travel is allowed in valve to guide tolerance. Amazing. No wonder exhaust valves look burned to hell..

I disagree on alusil, these engines do not burn oil because of alusil. Sure they will burn oil if the cylinders are scored as a result of overheating or oil starvation - any engine will for that matter but this is not because alusil. Maybe you are thinking about the older engines that had nikasil plating which was reacting with sulphurs in gasoline that eroded the surface and eventually all of these engines burned oil and needed sleeves to continue to operate. Alusil is tough, it is very hard, provides better wear resistance and better heat transfer than cast iron. Wet sleeves could be superior for high performance as you said but thats big $$$.

I dont know where you guys buy those AV&V reamers. Could not find where to buy them..

[MotionMachine]

OK, you got me, I don't know squat about allyousell or this nikulseel stuff you're talking about.

https://www.youtube.com/watch?v=J43RkJTHdCE&t=157s

https://www.youtube.com/watch?v=IH54cPqoB1o

https://www.youtube.com/watch?v=aX5c6rlrYcw