Mick, Generally the 55A Bosch alternator is just about bullet proof, and when they fail it's either the brushes or the reg that give up the ghost. As you've indicated rear bearing failure is almost always something to do with the tensioning system, mainly over tightening or misalignment causing variations in belt tension in the course of a crank revolution. The only check that I'd do with this one is to rotate the engine through 4 lots of 90 degrees and check that the belt tension is even in each quadrant of the crank rotation. The lower mounting bolts tend to break on the L series bracket if not kept fairly tight after belt tensioner adjustment. Have you had a history of breaking the tensioning bracket or the lower mounting bolts on any of your alternators? Sustained rpm with the stock pulley ratio will not hurt an alternator till you go well over 6000 rpm and sustained for long periods which is around 22K rpm at the alternator in the normal scheme of things. I've seen a Bosch or Hitachi take 6K+ rpm in competition for hours on end without any signs of distress to the bearings. If you change the pulley gear to reduce the alternator rpm in relation to the crank you increase the diameter of the alternator pulley or reduce the size of the crank pulley, however the latter will also slow down the water pump which is in some cases a desirable thing (i.e. for a dedicated race engine.) Very small changes in diameter at the alternator end have a rather dramatic impact on the output of the alternator at low rpm but the crank pulley is not so sensitive to change. The standard L4 series Datto alternator to crank pulley ratio is in the vicinity of 3.7:1.
regards Terry -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of mick ralph Sent: Friday, 21 March 2003 12:00 PM To: [EMAIL PROTECTED] Subject: Re: Alternators for L series Thanks Terry I just grabbed an 85 bluebird one from the wreckers for $30. Thats the second one I've done in not many miles and each time its been the same with the back bearing being shot to bits. I checked the alignment and it seems ok, and i usually run the belt on the loose side. I'm wondering whether because the engine seems to run at higher than normal revs, usually always above 4000rpm, that maybe this is not good for the alternator??? Does it need to be geared up/down? Any thoughts? Cheers Mick ----- Original Message ----- From: "Terry Rudd" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Thursday, March 20, 2003 10:55 PM Subject: RE: Alternators for L series > Mick, > > The only Nissan that comes to mind as a possible donor off the RB30 engine > (R31 Skyline has either Bosch, Mitsui or Hitachi) and the Bosch item is a > big bugga physically but only rated at 70 Amps. I've got one here but > haven't gotten around to checking it out as far as L or FJ suitability goes. > The bottom bracket spacing will be the main problem from no more than just a > preliminary visual check. > > regards > Terry > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of mick ralph > Sent: Tuesday, 18 March 2003 11:36 AM > To: [EMAIL PROTECTED] > Subject: Alternators for L series > > > Hi > Having just blown up another alternator yesterday, and having to leave the > Datto all on its own at a friends farm, I gotta put something decent on it. > I blame Toby for this BTW cos he rang me on the w/e and told me he had blown > his. > What Model cars have alternators (with built in regs) that will fit str8 > into my L20B and have better than the 55amp bosch ones i have been using. Is > there a 85amp available? What should I be looking for at the wreckers? > Cheers > Mick > > > > > --membersozdat------------------------------------------------------- OZDAT Mailing List Please Note:- Send (un)subscribe requests to [EMAIL PROTECTED] Send submissions to [EMAIL PROTECTED] No unauthorised redistribution of this email http://www.ozdat.com/ozdatonline/index.htm http://www.ozdat.com/ozdatonline/listindex.html http://www.mail-archive.com/[EMAIL PROTECTED]/ ---------------------------------------------------------------------
