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16 hours ago, Mike Self said:

I've been replacing the 30 year old--and worn out--urethane alternator mounts on my carbureted '73 and discovered an anomaly--the pivot bolt from which the alternator hangs is the standard 8mm in diameter, with a 13mm (wrench size) nut, but the bolt head is only 12mm. 

 

I'm quite sure the bolt is original to the car, as I've never replaced it in my 43 years of ownership, and the previous owner didn't do any of his own repairs.  Is that original to y'all's cars to, or ???  I didn't remember that from the last time I messed with the alternator, which admittedly was a long time ago when I changed a fan belt.  

 

mike

The nut broke off the M8 alternator pivot bolt on my tii recently.  The last time it was off was in 2009 when I replaced the alternator.  I’ve found that by removing the (4) screws holding the radiator then sliding it as far right as you can, that upper tii pivot bolt can be extracted from the mounting bracket.

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The head is 13mm on mine.  So is the nut.  The same's true for the adjuster bolt/nut too.   I had the alternator out and in a couple of times today.  (long story) I used 13, 10, 8

The nut broke off the M8 alternator pivot bolt on my tii recently.  The last time it was off was in 2009 when I replaced the alternator.  I’ve found that by removing the (4) screws holding the radiato

Belmetric has them in zinc plated steel:  https://www.belmetric.com/jis-small-wrench-c-3_58_2280/nj8x11lylw-jis-nut-long-yellow-zinc-p-6288.html?zenid=vnett8tm3qso12vb55jdg8kk22   CIP1 has t

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6 hours ago, jimk said:

If two wrenches are needed, are there 2 separate wrenches in the tool kit?  Smart engineering, fix the car with the tools in the kit.

No 12mm wrench in the tool kit: its 8-10; 13-14 and 17-19.  But your idea certainly makes sense.  Older 8mm bolts/nuts are 14mm across the flats; my 40s Fiats and 50s Renaults all have 14mm bolts and nuts--nary a 13mm to be found.

 

mike

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5 hours ago, Son of Marty said:

Tom, that bels sure is sitting low on that pully is it bottoming?

 

Nope.  The pulley has a deep V.  There's a 1/4" of shiny depth left below the belt.  Thank you for asking though.  It's funny, it rides up high in the other two pulleys.  I wonder if I have an incorrect pulley on my alternator. 

 

Based on the numbers printed on my belt (provided by a reputable seller) the dimensions are different than the ones you suggested the other day.  "Also check your fan belt v shape 9.5x8.75".  So, I have an Alternator belt--anomaly!

IMG_9074.JPG

There's the 13mm bolt head too.  I've had that thing out three times in two days.  Glad I don't have a Tii!

 

Tom

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1 hour ago, '76mintgrün'02 said:

Based on the numbers printed on my belt (provided by a reputable seller) the dimensions are different than the ones you suggested the other day.  "Also check your fan belt v shape 9.5x8.75".  So, I have an Alternator belt--anomaly!

 

First # - width of belt outer surface (10mm), Second # - length of belt outer surface (875mm).  So you have same length but very slightly wider top of V, Tom.

 

The big IE alt. pulley bumped it to up a a 915mm length V-belt for me nowadays...

 

Tom-too

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17 hours ago, halboyles said:

The notable location for M8 bolts using 12mm heads is for the intake manifold.  I believe BMW used that configuration of fastener on all early M10 intakes.

All M8 intake or exhaust manifold nuts on M10s and M30s I've ever come across (with original fasteners) There's no room to get a socket on a 13 in that configuration.  I recently got the pleasure of removing a motronic intake manifold from an M90 and it had standard M8 nuts.  Stubby open-end wrench saved the day.  If you order M8 J.I.S. fasteners, you'll get the 12mm head.  Once you got into the M50 cars throughout the car you find a lot of 12, 16, 18 where you'd have previously seen 13, 17, 19.  It's particularly confusing on E34s since the early cars have the 13, 17, 19 fasteners, but for the same parts on later cars, you'll find 12, 16, 18.

 

Both of mine have 13mm heads on the bolt. 

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8 hours ago, wkohler said:

All M8 intake or exhaust manifold nuts on M10s and M30s I've ever come across (with original fasteners) There's no room to get a socket on a 13 in that configuration. 

And yet, as you mentioned, folks use standard 13mm nuts all the time.  They must be very patient and persistent to get them on the lower studs with an open end wrench!  We use brass nuts that are just 11mm to make the installation even easier.  Here's a pic of our new M30 linkage using the 11mm nuts.

Head Side View.jpg

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1 hour ago, halboyles said:

We use brass nuts that are just 11mm to make the installation even easier. 

What's your source for these, Hal?  Sound like the answer for some of those impossible exhaust manifold nuts that are even hard to manage with 12mm heads.

 

mike

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Belmetric has them in zinc plated steel:  https://www.belmetric.com/jis-small-wrench-c-3_58_2280/nj8x11lylw-jis-nut-long-yellow-zinc-p-6288.html?zenid=vnett8tm3qso12vb55jdg8kk22

 

CIP1 has the brass version:  https://www2.cip1.com/ProductDetails.asp?ProductCode=C13-43-6051

 

For really tight spots where the long nuts won't fit, I cut some of the length off to make it work.

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I don't have an M20 head on hand to do a mockup, but I don't see any reason why a linkage system couldn't be created for that block/head using many of the same components.  The M30 version uses a down rod (see pic) to connect to the bell crank on the side of the block.  So it might just mean creating a cable system to perform that function on the M20. 

Throttle Lever and Balancing Lever.jpg

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