The Triumph Dolomite Club - Discussion Forum

GrahamFountain wrote: ↑Mon Jul 24, 2023 9:14 pm Is there a difference between alternators for cars from 76 on and before?

Further to what has been mentioned in the replies,
the early 1850s had a Lucas 15ACR alternator from new, the wiring to these is different to an 17ACR
but the actual mounting is the same.



Ian

xvivalve wrote: The A127 (as fitted to the Montego, Maestro etc) is a direct replacement requiring no modifications; even the multi plug fits straight into the back of it.

Well it would have been a direct replacement, if I'd remembered that with new alternators, the hole in the front for the adjustment bracket is threaded, where my old reconn'ed one had been stripped and drilled M8 clearance - with a bolt through it and a nylok nut on that.

So there was a bit of digging in the junk box for a set screw to fit. I assume it was 5/16 UNC, though I did expect an alternator from a more modern car would be metric. But what I think must be an M8 bolt don't fit, and neither does what I think is 5/16 UNF.

I did put a nut on the back, so the alternator bracket is at least partly in compression, not the threads in it being entirely in shear, which I assume is why the reconn'ed one was stripped. Might swap that for a nylok nut if I can find an odd one.

As to the engine end of the adjustment bracket. I'm thinking about 3 inch of 5/16 UNF studding, locktite'ed in the block, with a thin/half nut against the chain cover plate to hold it, and two nuts locked together on the other side of the adjustment bracket. I might then need a few washers between the bracket and the alternator to make up for the thin nut - or take out some of the offset in the bracket. But then there's no chance that adjusting the alternator will loosen the bolt through the chain cover. I know it hadn't vibrated out, even though loose. But it would be a pain if it did.

Graham

GrahamFountain wrote: ↑Thu Jul 27, 2023 5:05 pm

xvivalve wrote: The A127 (as fitted to the Montego, Maestro etc) is a direct replacement requiring no modifications; even the multi plug fits straight into the back of it.

I assume it was 5/16 UNC, though I did expect an alternator from a more modern car would be metric. But what I think must be an M8 bolt don't fit, and neither does what I think is 5/16 UNF.

OFF Topic: but as an aside, as an ex Classic Citroen owner, M7 were very common around the engine bay (I still have an M7 Helicoil kit!), M9 were also used (50's < 70's DS front wing lower bolts, weirdly) so one should never assume on any classic that you know the thread size

It's even more complicated with the TR7, as the body and interior is all metric threads, but the engine is all imperial threads. So it's interesting when it comes to the bolts attaching the engine to the front subframe.

Graham

It doesn't help that metric threads also have varying pitch sizes, so you can have several M10 bolts but with different TPI!

xvivalve wrote: ↑Thu Jul 27, 2023 8:13 pm It doesn't help that metric threads also have varying pitch sizes, so you can have several M10 bolts but with different TPI!

It's all part of the 'joy' of running classic cars, keeps the brain cells functioning whilst trying to ignore the arthritic joints

xvivalve wrote: ↑Thu Jul 27, 2023 8:13 pm It doesn't help that metric threads also have varying pitch sizes, so you can have several M10 bolts but with different TPI!

Rather like UNC and UNF!

cliftyhanger wrote: ↑Fri Jul 28, 2023 8:30 am

xvivalve wrote: ↑Thu Jul 27, 2023 8:13 pm It doesn't help that metric threads also have varying pitch sizes, so you can have several M10 bolts but with different TPI!

Rather like UNC and UNF!

Nah, you can tell by sight which you have/need with UNF and UNC; M10 1.5 and M10 1.25 are too close for comfort

xvivalve wrote: ↑Fri Jul 28, 2023 9:39 am

cliftyhanger wrote: ↑Fri Jul 28, 2023 8:30 am

xvivalve wrote: ↑Thu Jul 27, 2023 8:13 pm It doesn't help that metric threads also have varying pitch sizes, so you can have several M10 bolts but with different TPI!

Rather like UNC and UNF!

Nah, you can tell by sight which you have/need with UNF and UNC; M10 1.5 and M10 1.25 are too close for comfort

What is tricky, or handy, depending on circumstances, is m8 fine and 5/16unf are almost interchangeable. After a caliper bolt fell out of my spit rear (MGF brakes) I assumed it would be a std M8 bolt. Nope. And I didn't have any M8 fine bolts (why would I?) with me in teh wilds of the Scottish borders. As it happens, a 5/16 setscrew will go in about 6-8 turns before locking up. That, plus a nyloc wouond on the setscrew got me home.
Yes, teh bolts had be torqued up fully when assembled. But the roads were SO awful all sorts of things were happening to cars.

When home I found some genuine bolts, and assembled with some loctite (medium grade, the strongest stuff is too darn strong)

I expect other sizes will be very similar too.

Well, that Lucas A127 alternator is in and running. Only a slight issue with the old connector bending the bottom 6.5mm spade instead of connecting to it, but that bent straight with no damage. Seems to run smooth, confirming the random knocking was the old one, and once the bent spade was sorted, the ignition light went straight out on starting.

So, as it was no more expensive than a 17ACR lookalike one, I'm as happy as can be expected of a Yorkshireman - damned near smiled at one point.

On the issue of M8 vs 5/16 UNF, I have noticed that sometimes an M8 bolt will get some grip in a 5/16 UNF hole where a 5/16th bolt won't tighten at all. But I guess it will have to be Helicoiled at some point.

Graham

xvivalve wrote: ↑Thu Jul 27, 2023 8:13 pm It doesn't help that metric threads also have varying pitch sizes, so you can have several M10 bolts but with different TPI!

The bolts on my servo, that hold the servo to the body are M8, but imperial 3/8 unf that hold the brake master cylinder to the servo

Dave/

new to this wrote: ↑Fri Jul 28, 2023 8:20 pm

xvivalve wrote: ↑Thu Jul 27, 2023 8:13 pm It doesn't help that metric threads also have varying pitch sizes, so you can have several M10 bolts but with different TPI!

The bolts on my servo, that hold the servo to the body are M8, but imperial 5/16 unf that hold the brake master cylinder to the servo

Dave

Unless your servo is some b'stard hybrid from China or somewhere, or the studs on the m/cyl side have been died down for some unfathomable reason, then they aren't!

Early servos, up to around 78 were imperial with 5/16" UNF studs into the body and 3/8" UNF studs for the master cylinder. Later cars had all metric studs with M8 x1 to the body and M10x1 to the master cylinder. The same master cylinders, single or dual circuit, will fit to either imperial or metric servos.

Steve

Carledo wrote: ↑Fri Jul 28, 2023 8:56 pm

new to this wrote: ↑Fri Jul 28, 2023 8:20 pm

xvivalve wrote: ↑Thu Jul 27, 2023 8:13 pm It doesn't help that metric threads also have varying pitch sizes, so you can have several M10 bolts but with different TPI!

The bolts on my servo, that hold the servo to the body are M8, but imperial 5/16 unf that hold the brake master cylinder to the servo

Dave

Unless your servo is some b'stard hybrid from China or somewhere, or the studs on the m/cyl side have been died down for some unfathomable reason, then they aren't!

Early servos, up to around 78 were imperial with 5/16" UNF studs into the body and 3/8" UNF studs for the master cylinder. Later cars had all metric studs with M8 x1 to the body and M10x1 to the master cylinder. The same master cylinders, single or dual circuit, will fit to either imperial or metric servos.

Steve

My mistake should have said 3/8 unf

Dave

Your servo has had its rear case replaced with a later one, probably because the original rotted out as it is quite common for the rear case to corrode. A few that we've had reconditioned have had to have this done.

Well, the thread in the alternator lower (on the Sprint) front bracket isn't 5/16 UNC and is M8, like I thought it should be on a later car like the Maestro.

So, when I thought the M8 bolt I had didn't fit, either it wasn't M8, possible given the above, or it did fit and I just got it wrong.

Now I'm over the problems caused by trying to fit a UNC nyloc nut on the back of the bolt through the bracket under the alternator, I have to get an M8 nyloc and fit that.

Worse than that, now I have to buy a 5/16th UNC bolt to have a use for the nyloc nut I didn't need.

Graham