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#1 Alternator heat shield

Posted: Mon Apr 03, 2023 5:39 pm
by DWW
Is there any point installing one on an S1 3.8 with an alternator conversion as they never were supplied from factory?

#2 Re: Alternator heat shield

Posted: Mon Apr 03, 2023 5:50 pm
by mtnjag
I put in the simple stainless shield that goes between the manifold and rear if the Alternator.
Note that the REAR of the alternator is the INTAKE and the front fan pulls air from the rear through the alternator and out the front. So the rear shield at least breaks the direct radiation.

If your talking about the larger nacelle type shield over the top I think that's more of a safety protection shield for the belt and pulley.

#3 Re: Alternator heat shield

Posted: Mon Apr 03, 2023 6:21 pm
by DWW

#4 Re: Alternator heat shield

Posted: Mon Apr 03, 2023 9:58 pm
by mtnjag
That's like the one I used.

#5 Re: Alternator heat shield

Posted: Tue Apr 04, 2023 12:52 pm
by Series1 Stu
I made one for my 3.8 using 0.7mm stainless steel sheet and rivetted some fibreglass thermal matting to the back.

It was more for preventing radiant heat transfer when stationary but allowing airflow when on the move. I remember thinking that the factory 4.2 item appeared pretty ineffectual for radiant heat.

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Regards

#6 Re: Alternator heat shield

Posted: Tue Apr 04, 2023 1:37 pm
by DWW
Good idea.

#7 Re: Alternator heat shield

Posted: Tue Apr 04, 2023 1:43 pm
by mtnjag
Good idea. Ugly but likely effective. Functionality wins, may put it on the projects list.

#8 Re: Alternator heat shield

Posted: Tue Apr 04, 2023 4:27 pm
by DWW
Ordered from Martin Rubey.

#9 Re: Alternator heat shield

Posted: Mon Apr 10, 2023 1:47 pm
by DWW
Installed today looks like it means business😀forgot to take a photo🙁

#10 Re: Alternator heat shield

Posted: Mon Apr 10, 2023 4:20 pm
by caveman
Did you opt for S1;
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Or S2;
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Or both. :shrug:

#11 Re: Alternator heat shield

Posted: Mon Apr 10, 2023 4:47 pm
by DWW
S2, a slightly tidier appearance....more pleasing to the eye.

#12 Re: Alternator heat shield

Posted: Mon Apr 10, 2023 5:30 pm
by mtnjag
The larger shield doesn't really do anything for heat as far as I can see. More of a "safety" shield I think. The simple stainless one shields the rear air intake of the Alternator from the exhaust manifold heat, somewhat anyway. The added shielding added by Series1 Stu does an even better job.

#13 Re: Alternator heat shield

Posted: Mon Apr 10, 2023 6:51 pm
by caveman
mtnjag wrote:
Mon Apr 10, 2023 5:30 pm
The larger shield doesn't really do anything for heat as far as I can see. More of a "safety" shield I think.
DWW wrote:
Mon Apr 10, 2023 4:47 pm
S2, a slightly tidier appearance....more pleasing to the eye.
:yeahthat:
S2 half the price too!

#14 Re: Alternator heat shield

Posted: Mon Apr 10, 2023 7:10 pm
by Geoff Allam
I recall that at one time there was a thread where it was suggested that the s1 shield was there to improve air flow through the alternator. Is that no longer considered correct?

#15 Re: Alternator heat shield

Posted: Mon Apr 10, 2023 7:17 pm
by caveman
Strangely, just read about it on JagLovers, not convinced tbh;
https://forums.jag-lovers.com/t/series- ... d/383259/3

#16 Re: Alternator heat shield

Posted: Mon Apr 10, 2023 7:53 pm
by Series1 Stu
mtnjag wrote:
Tue Apr 04, 2023 1:43 pm
Ugly but likely effective.
Non taken!

Actually, I agree it is rather ugly. You've shamed me into thinking about designing and making a new version.

Regards

#17 Re: Alternator heat shield

Posted: Mon Apr 10, 2023 9:14 pm
by Geoff Allam
Steve, that just shows how bad my memory is getting. I recalled the thread and the variety of theories but completely forgot that I had started the thread. Anyways, since then I have acquired an original series 1 shield and will install both it and the little series 2 one just for good measure.

#18 Re: Alternator heat shield

Posted: Mon Apr 10, 2023 10:03 pm
by mtnjag
Geoff, It never was correct. On these and most alternators air flow is back to front. The fan in front PULLs air from the rear of the alternator, through and out the front. Seems counter intuitive I know but that's the way they work. Common misconception.
That's why the shield between the exhaust manifold and the rear of the alternator makes sense and the top shield is a cosmetic or safety shield that leaves the rear completely exposed to the exhaust manifold heat. Might even make the alternator hotter when at a stop by enclosing it and not letting heat radiate off, don't know.

#19 Re: Alternator heat shield

Posted: Sun Nov 09, 2025 4:11 pm
by rfs1957
Not truly an Alternator Heat Shield ............. but might inspire someone.

Mine is a Dynalite alternator, hidden within a plausibly-credible dynamo body - it would be even more convincing if the rear casting espoused the true diameter of the central body, but it passes muster from a few yards away.

I've always hated the way - even on the original - that the exhaust manifold bakes the wiring, which gets horribly brittle over time ; and on the Dynalite, with its extra electronics, I can't believe that dropping the temperature considerably won't improve its life - even if it does come with a Lifetime Guarantee.

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So here you have a Period Accessory called the Cool-O-Matic, which - once powder coated (a process I generally hate, but accept on stuff like this) - looks pretty acceptable and appropriate in the context.

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Don't form a queue, once was enough :waiting:

#20 Re: Alternator heat shield

Posted: Mon Dec 22, 2025 10:06 pm
by mtnjag
Why the holes blocked by the case and heat insulation.
I would think better solid with an air apace between shield and case.