Author Topic: diy cam regrinding  (Read 9927 times)

318is91turbo

  • Newbie
  • *
  • Thank You
  • -Receive: 1
  • Posts: 48
    • View Profile
diy cam regrinding
« on: October 07, 2013, 05:20:41 PM »
has anyone ever tried it? thinking about picking up some used cams for cheap and a micrometer. using a table grinder. and seeing what happens.

bigskyis

  • Newbie
  • *
  • Thank You
  • -Receive: 0
  • Posts: 39
    • View Profile
Re: diy cam regrinding
« Reply #1 on: October 08, 2013, 05:15:46 AM »
What is going happen is you will have wasted a lot of time and energy. You want cams, buy them. Or at least let a professional grind them to your specs. 

wazzu70

  • Nasty Nick
  • Hero Member
  • *****
  • Thank You
  • -Receive: 18
  • Posts: 671
    • View Profile
Re: diy cam regrinding
« Reply #2 on: October 08, 2013, 11:46:47 AM »
Are you serious? You need to have the shape of each lobe be the same. There is no way you are going to be able to replicate that. Also, the shape of the profile matters A LOT. An improper shape will cause your valvetrain to self destruct. It takes a lot of math to get a correct lobe shape!
-Nick
91 E30 M42 with VEMS

bmwman91

  • Administrator
  • Legendary
  • *****
  • Thank You
  • -Receive: 33
  • Posts: 2798
    • View Profile
    • http://www.e30tuner.com/
Re: diy cam regrinding
« Reply #3 on: October 08, 2013, 01:05:44 PM »
As stated above, don't do it. Cams cost what they do because of the insane cost of the specialized equipment that cam houses must invest in, as well as the sheer number of hours that it takes to do a precision grind on a cam even with machinery developed specifically for it. Then factor in all the engineering time put into the design of the cam profile. Many times there will also need to be a tempering / hardening operation performed on them if the lobes don't meet Rockwell hardness requirements after welding. Then there is the importance of the surface finish of the slip surfaces (lobes, bearings). And of course, if you want to increase lift you will need to weld on additional material before the precision grind, which is a whole process in itself. Just getting remnant oil out of the porous cast iron prior to welding is basically out of reach for a DIY'er. If you do a DIY job, assuming that the car even really runs, chances are that you will end up destroying your lifters and maybe even breaking valve springs.

So yeah, it isn't a DIY activity by any stretch of the imagination. Leave it to the experts that have invested $millions into equipment and know-how. I spent many hours on the phone with Metric Mechanic when I was having issues with cam wear in my custom engine, and even they contract cam jobs out to the experts.
« Last Edit: October 10, 2013, 11:46:50 PM by bmwman91 »

06/05/2011 - 212,354 miles
Visit HERE for a plethora of 318iS stuff and some other randomness.  Would you say I have a, plethora, of pinatas?

318is91turbo

  • Newbie
  • *
  • Thank You
  • -Receive: 1
  • Posts: 48
    • View Profile
Re: diy cam regrinding
« Reply #4 on: October 08, 2013, 06:02:12 PM »
you make it out to be some godly knowledge or seomthing. its not all that difficult if you simply understand it. measure twice grind once. i understand it. and actually might have access to a cnc lobe grinder soon. :)
and its just a extra set of cams im about to buy im trying it on. if it doesnt turn out proper i wont put them on. simple as that.

DesktopDave

  • Administrator
  • Legendary
  • *****
  • Thank You
  • -Receive: 60
  • Posts: 5076
  • Lives in the 80s
    • View Profile
    • The Iconic BMW
Re: diy cam regrinding
« Reply #5 on: October 08, 2013, 08:43:44 PM »
you make it out to be some godly knowledge or seomthing. its not all that difficult if you simply understand it. measure twice grind once. i understand it. and actually might have access to a cnc lobe grinder soon. :)
and its just a extra set of cams im about to buy im trying it on. if it doesnt turn out proper i wont put them on. simple as that.

If you figure out how to do it, I have a great opportunity for you!  Not in a BMW though. 

The Honda 80's V4 motorcycles had really bad problems with cam wear.  If you could figure out how to resurface those cams, you'd have a nice little side job regrinding scored cams & followers.
'08 Karmesinrot 128i 6MT
'86 Zinnoberrot 635CSi (M30B32/G265/3.46 torsen LSD)

Sold: '97 Montrealblau 318iS, '91 Brilliantrot 318i, '91 Brilliantrot 318iS

bmwman91

  • Administrator
  • Legendary
  • *****
  • Thank You
  • -Receive: 33
  • Posts: 2798
    • View Profile
    • http://www.e30tuner.com/
Re: diy cam regrinding
« Reply #6 on: October 09, 2013, 01:20:47 AM »
you make it out to be some godly knowledge or seomthing. its not all that difficult if you simply understand it. measure twice grind once. i understand it. and actually might have access to a cnc lobe grinder soon. :)
and its just a extra set of cams im about to buy im trying it on. if it doesnt turn out proper i wont put them on. simple as that.

If you get it all figured out, be sure to let us know. You'd probably be able to make good money if you have those sorts of skills.

06/05/2011 - 212,354 miles
Visit HERE for a plethora of 318iS stuff and some other randomness.  Would you say I have a, plethora, of pinatas?

wazzu70

  • Nasty Nick
  • Hero Member
  • *****
  • Thank You
  • -Receive: 18
  • Posts: 671
    • View Profile
Re: diy cam regrinding
« Reply #7 on: October 09, 2013, 10:00:28 PM »
you make it out to be some godly knowledge or seomthing. its not all that difficult if you simply understand it. measure twice grind once. i understand it. and actually might have access to a cnc lobe grinder soon. :)
and its just a extra set of cams im about to buy im trying it on. if it doesnt turn out proper i wont put them on. simple as that.

Lol. You have absolutely no idea what you are talking about.
-Nick
91 E30 M42 with VEMS

318is91turbo

  • Newbie
  • *
  • Thank You
  • -Receive: 1
  • Posts: 48
    • View Profile
Re: diy cam regrinding
« Reply #8 on: October 09, 2013, 10:06:39 PM »
wazzu, you just wait good sir. you will see. and i shall charge you double if you come to me.

bmwman91

  • Administrator
  • Legendary
  • *****
  • Thank You
  • -Receive: 33
  • Posts: 2798
    • View Profile
    • http://www.e30tuner.com/
Re: diy cam regrinding
« Reply #9 on: October 09, 2013, 11:10:25 PM »
Whatever ends up happening, just make sure to post some pictures. It's going to be a pretty good learning experience for you.

Folks in here aren't trying to give you a hard time. It's friendly advice. Many of us have been DIY'ing and fabbing stuff for well over a decade and, well, the reasons why we don't grind our own cams have already been plainly stated. If it was feasible to DIY it and save $1k, people would be doing it already. Anyway, if you have an extra set laying around and it didn't cost you anything then I say go for it since it won't cost you anything when you have to toss them into the scrap heap.

Anyway, what are you going for exactly in terms of the grind? What sorts of lift and duration are you targeting? What ramp rates will you be dialing in, and will those profiles be tappet-friendly? Cams for rocker arms, rollers and lifter buckets all have different profile requirements. If I knew what those were exactly, I'd tell you, but I don't.

06/05/2011 - 212,354 miles
Visit HERE for a plethora of 318iS stuff and some other randomness.  Would you say I have a, plethora, of pinatas?

bmwman91

  • Administrator
  • Legendary
  • *****
  • Thank You
  • -Receive: 33
  • Posts: 2798
    • View Profile
    • http://www.e30tuner.com/
Re: diy cam regrinding
« Reply #10 on: October 09, 2013, 11:16:56 PM »
you make it out to be some godly knowledge or seomthing. its not all that difficult if you simply understand it. measure twice grind once. i understand it. and actually might have access to a cnc lobe grinder soon. :)
and its just a extra set of cams im about to buy im trying it on. if it doesnt turn out proper i wont put them on. simple as that.

Lol. You have absolutely no idea what you are talking about.

Shhhh. I want to see pics of the DIY process lol.

We were all at this stage at one point. "Anything's possible, there's no reason to pay some jerks that claim to have special knowledge for something I can just DIY after thinking about it for a week!" I remember back when I was ~20 and was posting about designing and DIY'ing my own wheel hubs for a 5-lug conversion. Jordan told me I was a f***ing moron and "damning others with my stupidity" haha. And he was right, it was a dumb idea! But that didn't stop me from spending a bunch of time researching the idea and coming to my own conclusion that turning my own wheel hubs was a quick way to end up dead!

As far as cams, I really had no idea how involved those were until the last year or so when I was in constant contact with Metric Mechanic about my top-end issues. Jim over at MM really hooked me up with the knowledge dump. For one, I never knew that the lobes have a slight angle on them so that they don't run perfectly parallel to the lifter, but instead cause it to rotate and distribute wear across the slip surface, without cocking it in the tray of course.
« Last Edit: October 09, 2013, 11:20:33 PM by bmwman91 »

06/05/2011 - 212,354 miles
Visit HERE for a plethora of 318iS stuff and some other randomness.  Would you say I have a, plethora, of pinatas?

318is91turbo

  • Newbie
  • *
  • Thank You
  • -Receive: 1
  • Posts: 48
    • View Profile
Re: diy cam regrinding
« Reply #11 on: October 10, 2013, 07:20:14 PM »
i mean its not even that. ill make sure i post some pics. it could be a few weeks, maybe a month or two before i start this. making my grinding bench should be fun. :) theres a difference in diy'ers who think about how to do things. and then theres diy'ers who do the things they think of. im a do'er idk about you guys.

bmwman91

  • Administrator
  • Legendary
  • *****
  • Thank You
  • -Receive: 33
  • Posts: 2798
    • View Profile
    • http://www.e30tuner.com/
Re: diy cam regrinding
« Reply #12 on: October 10, 2013, 10:42:39 PM »
i mean its not even that. ill make sure i post some pics. it could be a few weeks, maybe a month or two before i start this. making my grinding bench should be fun. :) theres a difference in diy'ers who think about how to do things. and then theres diy'ers who do the things they think of. im a do'er idk about you guys.
Nothing wrong with that. Just saying, the reason that people don't DIY everything isn't because they are lazy. As long as you are going into it with the intent of learning and having some fun, all's well.

Again, what are your design goals for these? Lift vs duration? How do you plan to increase those items? It's going to involve welding on the lobes, no way around it. Draw out the cam timing maps to get a good picture of your overlap targets. ANYONE can grind a cam. FEW can set the right design targets and actually execute the cleaning/welding/quenching/grinding operations. The issue here is how much power you will end up losing as a result, and whether or not the lifters will be salvageable afterward. Remember, you want to put a VERY slight angle on the running surfaces, like a few mils across the lobe width, so that they spin the lifters in place and distribute the wear. A straight grind would be a disaster. The cams may be free, but a new or rebuilt head and lifters probably isn't.

More power to you though. It's all just words of caution based on decades+ of personal experience.

PS
If you are going to weld on the cam, and I can't see any way to avoid that, you need to bathe the cams in a solvent that evaporates cleanly (acetone, MEK, xylene...NOT paint thinner) for a good few days to extract the oil out of the porous casting and then stick it in an oven for a day or two to fully evaporate the solvent. Trying to weld porous cast metal that was soaking in oil for decades is an exercise in futility. You are going to want to TIG it as well. MIG is likely to warp the cam since it heats a lot more than the work area.
« Last Edit: October 10, 2013, 11:45:44 PM by bmwman91 »

06/05/2011 - 212,354 miles
Visit HERE for a plethora of 318iS stuff and some other randomness.  Would you say I have a, plethora, of pinatas?

wazzu70

  • Nasty Nick
  • Hero Member
  • *****
  • Thank You
  • -Receive: 18
  • Posts: 671
    • View Profile
Re: diy cam regrinding
« Reply #13 on: October 11, 2013, 10:52:54 AM »
Ill just drop this on here to help explain. Grinding the lobes is the easier part. The shape of the lobes is very complex.

http://lotusproactive.files.wordpress.com/2013/08/lcvt_insert.pdf

Lots of people DIY and get significantly worse results after the "upgrade" because they have no idea what they are doing. This is one of those times :)
-Nick
91 E30 M42 with VEMS

wazzu70

  • Nasty Nick
  • Hero Member
  • *****
  • Thank You
  • -Receive: 18
  • Posts: 671
    • View Profile
Re: diy cam regrinding
« Reply #14 on: October 11, 2013, 11:08:36 AM »
Quote from: bmwman91
We were all at this stage at one point. "Anything's possible, there's no reason to pay some jerks that claim to have special knowledge for something I can just DIY after thinking about it for a week!" I remember back when I was ~20 and was posting about designing and DIY'ing my own wheel hubs for a 5-lug conversion. Jordan told me I was a f***ing moron and "damning others with my stupidity" haha. And he was right, it was a dumb idea! But that didn't stop me from spending a bunch of time researching the idea and coming to my own conclusion that turning my own wheel hubs was a quick way to end up dead!

Interestingly enough I designed a 5 lug hub that would fit directly on the 4 lug spindle (smaller spindle diameter). I analysed the design in FEA and also had some guys in dimensional management verify my tolerances were correct for that application.

The killer is the cost of billet in that diameter! The cost to have them machined to proper specs for flatness, perpendicularity, runout, ect. Would have been too high to justify. An order of 20 sets was not enough volume to bring the cost down to something I felt had a chance of selling so the project was abandoned. I would have to have the hub shape cast and machined instead of using billet, but no way I was fronting the money for a proper mold!

A hub is not impossible to DIY, but its definitely not for the random guy on the street to attempt :)

I will be working on another attempt at a 4-5lug front hub conversion in the future though trying to get the cost reasonable!
-Nick
91 E30 M42 with VEMS