cycles4fun Posted January 15, 2007 Share Posted January 15, 2007 Anyone have any experiencing reboring lifter bores? Both of my intake lifter bores show excessive wear with clearances approaching .027" on one and close to .002" on the other. There was a strange rough looking wear pattern on both of the intakes like they were vibrating or something. No up and down gouging just a rough surface much like sandblasting would leave. The exhausts look fine measuring .0007" on one and .0012" on the other. The spec calls for .0009"-.00169". My service manual really does not get into the details of boring it just shows a pic of a reamer sticking down a lifter bore. I took a chunk of aluminum to practice with and bored a hole close to the size of the lifter (.8673" 1st oversize) and then used an adjustable reamer to enlarge it and test my skill at holding tight tollerances. Its pretty tricky but the outcome is very nice. I think I will have a go at it but I'm a little nervous! There is a second oversize available so if I make a mistake I can still have a way out! I imagine jigging it up on a mill would be a real pain in the butt and very expensive. The lifter bore is not on the same plane with the cylinders and since they are out of round finding center could be a challenge. I'm no machinist so I'm really just guessing here. Does anyone have any insight on the topic. Thanks in advance Mike Link to comment Share on other sites More sharing options...
mike wilson Posted January 15, 2007 Share Posted January 15, 2007 What do you mean by lifter? Cam follower? Rocker arm? Link to comment Share on other sites More sharing options...
cycles4fun Posted January 15, 2007 Author Share Posted January 15, 2007 What do you mean by lifter? Cam follower? Rocker arm? Sorry about that. I guess I'm old school. The cam follower (lifter) bore in the engine crankcase. Link to comment Share on other sites More sharing options...
pete roper Posted January 15, 2007 Share Posted January 15, 2007 To be honest it's very, very rare for the fitting of O/S tappets to be strictly neccessary. It's usually only if the bores have been comtaminated by metal particles that one needs to bore the case and yes, the way I've done it is with a hand held reamer just like in the pics in the manwell! The condition you describe sounds a bit odd. I can't remember ever having seen chatter marks in a bore? Better safe than sorry and put in an oversize. One side benefit wou will probably experience is a dimunition in top end rattling. Many people are convinced that all the rattling is valve lash noise but I've found that over-boring the tappets also hs a marked effect on how noisy the motor is, for a while anyway! Pete Link to comment Share on other sites More sharing options...
cycles4fun Posted January 15, 2007 Author Share Posted January 15, 2007 To be honest it's very, very rare for the fitting of O/S tappets to be strictly neccessary. It's usually only if the bores have been comtaminated by metal particles that one needs to bore the case and yes, the way I've done it is with a hand held reamer just like in the pics in the manwell! The condition you describe sounds a bit odd. I can't remember ever having seen chatter marks in a bore? Better safe than sorry and put in an oversize. One side benefit wou will probably experience is a dimunition in top end rattling. Many people are convinced that all the rattling is valve lash noise but I've found that over-boring the tappets also hs a marked effect on how noisy the motor is, for a while anyway! Pete Thanks Dave, Yea the wear is really odd. It cleaned it up with a bead type brake hone which visually looks fine but when measuring it the problem is obvious. I will give the reamer a shot. I'm pretty confident I can get it done. Just pokin around for input before I take the plunge! Mike Link to comment Share on other sites More sharing options...
Guest Gary Cheek Posted January 16, 2007 Share Posted January 16, 2007 Peter, What do you make of the comments regarding the bore's finish? The "sandblasted look" almost sounds like etching or corrosion at some point. (???) Does seem a bit odd for clearances on the order measured here. I think if it were my engine, I would bore- bush and then bore the bush , If you don't find yourself bushed by the boring description! It would seem an aluminum sleeve, pressed into a rebored lifter hole then bored and finished to the std lifter would be a tidy repair. Hand reaming with a non piloted ,un guided reamer is pretty shakey. While the results may be serviceable a good machine set-up would give a better chance of success. BTW , Honing of non ferrous metals can impregnate and imbed hard particles in the soft metal. They can cause a lot of damage in the long run. Link to comment Share on other sites More sharing options...
cycles4fun Posted January 17, 2007 Author Share Posted January 17, 2007 Peter, What do you make of the comments regarding the bore's finish? The "sandblasted look" almost sounds like etching or corrosion at some point. (???) Does seem a bit odd for clearances on the order measured here. I think if it were my engine, I would bore- bush and then bore the bush , If you don't find yourself bushed by the boring description! It would seem an aluminum sleeve, pressed into a rebored lifter hole then bored and finished to the std lifter would be a tidy repair. Hand reaming with a non piloted ,un guided reamer is pretty shakey. While the results may be serviceable a good machine set-up would give a better chance of success. BTW , Honing of non ferrous metals can impregnate and imbed hard particles in the soft metal. They can cause a lot of damage in the long run. Link to comment Share on other sites More sharing options...
cycles4fun Posted January 17, 2007 Author Share Posted January 17, 2007 The reamer I was practicing with was a bit too small so as I previously stated I bored a hole in a chunk of aluminum (6061 I believe) the same depth as the lifter bore. I was able to step it up in very small increments just a couple of tenths or so each pass of the reamer and the finish was beautiful, dead smooth with nearly a polished finish AND perfectly round. The only issue was the last 1/4 inch where the reamer pass's through the end of the hole. Without the aid of a pilot it is prone to chatter as it is largly unsupported as its exiting through and chatters a bit. If I stopped it from going all the way through the hole and backed it out while still rotating it clockwise the chatter would not occur and the size was not affected leaving a perfectly round hole with no taper. Beaming with cofidence I purchased a new reamer within the correct range and gave it a go on the chunk of aluminum before I attacked the lifter bore. What an absolute piece of shit! The thing would not even remotely begin to clean up a freshly drilled hole and chattered uncontrollably. Against my better judgment I purchased a reamer made in India and it is a total piece of crap! They did not have any other choices so I figured it should at least last a couple of holes or so. The P O S won"t even work!!!I'll take it back tomorrow and bitch! The slightly smaller reamer I was practicing with previously was a joy to operate and obviously was much higher quality. So now I'm back to square one. I know with a high quality reamer it should work fine, but I do agree without the aid of any pilot its tricky business at best. I might go down to boys at San Jose BMW and have a chat with them as they have a very reputable machine shop and may have some ideas. I'll also hunt around on the Internet for some precision American made reamers. Word to the wise, if you are buying machine tools buy the best you can afford or don't bother. Mike Link to comment Share on other sites More sharing options...
mike wilson Posted January 17, 2007 Share Posted January 17, 2007 BTW , Honing of non ferrous metals can impregnate and imbed hard particles in the soft metal. They can cause a lot of damage in the long run. From the description of the wear/damage, I suspect that something like this has been the original problem. It's odd that only two bores out of four were affected, though. Link to comment Share on other sites More sharing options...
Guest Gary Cheek Posted January 17, 2007 Share Posted January 17, 2007 The reamer I was practicing with was a bit too small so as I previously stated I bored a hole in a chunk of aluminum (6061 I believe) the same depth as the lifter bore. I was able to step it up in very small increments just a couple of tenths or so each pass of the reamer and the finish was beautiful, dead smooth with nearly a polished finish AND perfectly round. The only issue was the last 1/4 inch where the reamer pass's through the end of the hole. Without the aid of a pilot it is prone to chatter as it is largly unsupported as its exiting through and chatters a bit. If I stopped it from going all the way through the hole and backed it out while still rotating it clockwise the chatter would not occur and the size was not affected leaving a perfectly round hole with no taper. Beaming with cofidence I purchased a new reamer within the correct range and gave it a go on the chunk of aluminum before I attacked the lifter bore. What an absolute piece of shit! The thing would not even remotely begin to clean up a freshly drilled hole and chattered uncontrollably. Against my better judgment I purchased a reamer made in India and it is a total piece of crap! They did not have any other choices so I figured it should at least last a couple of holes or so. The P O S won"t even work!!!I'll take it back tomorrow and bitch! The slightly smaller reamer I was practicing with previously was a joy to operate and obviously was much higher quality. So now I'm back to square one. I know with a high quality reamer it should work fine, but I do agree without the aid of any pilot its tricky business at best. I might go down to boys at San Jose BMW and have a chat with them as they have a very reputable machine shop and may have some ideas. I'll also hunt around on the Internet for some precision American made reamers. Word to the wise, if you are buying machine tools buy the best you can afford or don't bother. Mike There are cutter sharpening services in most large cities. A good cutter sharpener can take a reamer that is ground to the proper size and grind a pilot that is a good fit in the existing hole. I am still concerned about the original cause of your problem. It seems Mike Wilson is thinking in that direction too. Link to comment Share on other sites More sharing options...
mike wilson Posted January 17, 2007 Share Posted January 17, 2007 There are cutter sharpening services in most large cities. A good cutter sharpener can take a reamer that is ground to the proper size and grind a pilot that is a good fit in the existing hole. I am still concerned about the original cause of your problem. It seems Mike Wilson is thinking in that direction too. Probably something as simple as the assembler having a dirty finger when they wiped installation lube on the bore. "Excuse me a moment please, my ear is full of milk" Oliver Hardy Link to comment Share on other sites More sharing options...
cycles4fun Posted January 18, 2007 Author Share Posted January 18, 2007 I believe I am the only one to have disassembled this engine so I can assure you a hone has never touched the lifter bores. I also am very clean and meticulous when assembling my engines and always use good assembly lube so I really do not believe I created this. I had the heads off a couple of times, the most recent (15k miles ago) for the installation of a 94mm big bore kit. The reason I took it apart this time was to have all the rotational assembly expertly balanced as I have been chasing a vibration and want the engine to run as smooth as possible. I have discussed this with Mike Rich and he recommended a shop for the balancing. When carfully inspecting all the components I discovered the intake valve lifter bore wear. I am very anal retentive regarding oil maintenance and I can assure you the lifter bores have never seen a hone up to this point. The lifters are original with 52000 miles on them. I"m pretty anal retentive regarding oil maintenance and use a very high quality synthetic blend. The cam was perfect so It should not be creating any issues. Honestly in reality it would likely live happily as it is but since I'm there I figured I would try and make it perfect. I dropped the crankcase off at a trusted auto machine shop tonight and we discussed the possibilties. He agreed I could run it and it would likely work fine but also agreed it is out of spec by around .001" or so and not perfectly round. He asked that I leave the crankcase there and he would get back to me. After dropping it off off there I went to another friends general machine shop and borrowed the correct reamer and it worked flawlessly on my test piece leaving beautiful holes. I really think this is the way to go but will wait for the other opinion to come back before making a final decision. This is likely putting everyone to sleep so I'll shut up now. Mike Link to comment Share on other sites More sharing options...
mike wilson Posted January 18, 2007 Share Posted January 18, 2007 I meant the original assembler, in the factory. Not at all bored. Link to comment Share on other sites More sharing options...
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