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I don't think (but don't know) the amps are grounded by the thru bolts that fasten the amps to the plate, the plate which is then fastened to the rad cross/cover plate. The screws, sheet metal screws really, tie into a type of U clips that slide over a cut out/slot in the radiator cover. Considering what these things do and the amount of charge, voltage, power they deal with it seems that this would be a VERY poor ground design if much or any of the grounding depended on a U clip screw down for the heat sink with the amp bolted into that, but who knows...?
I believe, and will take a close close look, where the mounting screw for the amp itself comes into contact with the amp is plastic casing as well. It's not a metal sleeve or metal cap in the amp that receives the underside of the phillips screw/bolt that threads into the heat sink underneath for grounding.
The bottom face of the amp is metal of some sort and would come flush up against the HSink plate but still, the contact (I think) would be impeded and not helped by the thermal paste... I would guess that the paste might not be as conductive as metal to metal, but don't KNOW that either. Could fill an ocean with what I don't know, smh...
Even precision surfaces like computer processors and their heatsinks use thermal paste. Every surface has imperfections, and a good thermal paste helps fill any gaps or imperfections to transfer heat better. The paste isn't an insulator, it is a heat conductor. I tend to use a high quality paste like Artic Silver which transfers heat even better. If the surfaces were perfectly flat with a mirror finish and free of imperfections (impossible), and perfectly clamped together (also impossible), metal to metal would be better. We don't live in a perfect world.
Even precision surfaces like computer processors and their heatsinks use thermal paste. Every surface has imperfections, and a good thermal paste helps fill any gaps or imperfections to transfer heat better. The paste isn't an insulator, it is a heat conductor. I tend to use a high quality paste like Artic Silver which transfers heat even better. If the surfaces were perfectly flat with a mirror finish and free of imperfections (impossible), and perfectly clamped together (also impossible), metal to metal would be better. We don't live in a perfect world.
Understood... Does the paste conduct heat AND electricity or,,,, ?
No - heat only - some of the metalised ones do have a degree of conductivity but nothing you could use as a circuit unless you got into the real exotics and they are stupid expensive.
No - heat only - some of the metalised ones do have a degree of conductivity but nothing you could use as a circuit unless you got into the real exotics and they are stupid expensive.
The amps generate a fair bit of heat, which is why they were probably mounted to the cross support- it's a big surface area to dissipate heat.
The earlier cars with Lucas ignition mounted the module to the intake manifold, so that a: it is a big lump of metal to conduct heat, and b: the air going through the manifold to the engine cools the manifold.
Surprising as it may seem, on top of the intake manifold is the coolest spot in the engine bay.
The amps generate a fair bit of heat, which is why they were probably mounted to the cross support- it's a big surface area to dissipate heat.
The earlier cars with Lucas ignition mounted the module to the intake manifold, so that a: it is a big lump of metal to conduct heat, and b: the air going through the manifold to the engine cools the manifold.
Surprising as it may seem, on top of the intake manifold is the coolest spot in the engine bay.
Oh, understood... But I think Jaguar in and over time must have even been a bit surprised themselves at how much damage the heat of these engines was doing to some/many of the individual components and wire looms etc in these cars.
To me, both choices for placement were not good ones and from what I've read here and there folks have made adjustments to try and alleviate... Heat is essentially vibration at the atomic level,,, and conduction is a transfer of energy and atomic monkey business between atoms in contact with one another. In this case there HAD to be a better choice for placement...or a better way.
In the case of heat conductivity (and I ain't no physicist) there has to be some inverse relationship between the relative heat of two materials and the rate at which heat will be transferred from one to the other as the heat energy in both materials rise. Placing a thing that needs to be able to shed heat on something that's HOT, in my eyes, is bone headed. That's jus me
If I wasn't such a chicken I would like to get the amps and the resistor pack out of the engine bay all together.
And most of your assertions are fundamentally correct - they went with a compromise location not a common sense one.
Unfortunately the trigger technology of the day isn't what we would expect today, it is a lot more sensitive to noise and heat so if you're moving away from the distributor much farther than standard then the use of a higher grade wire is wise. To be fair to Jaguar everyone was on a learning curve with fuel injection and such.
If you consider also the PVC used in the wiring as one such case - it isn't rated for the temperatures it see's under a V12 hood especially in the traffic we see today, this accelerates the depletion of plasticisers in the insulation and so it goes hard and cracks - but if you want to see bad get a real old classic that uses rubber inside a cloth braid - that stuff crumbles on contact.
On the heat rejection thig I can recall driving our motorways (freeways to the islanders off the coast) and you rarely if ever dropped below the legal speed limit - these days you are lucky if you can even reach that limit especially around cities - in the UK at least.
Aluminium is not a good conductor of heat but it is used for cost reasons, for what it is worth I am moving mine off the inlet manifold (my system is Lucas / Bosch)), which I don't think is so cool after sitting in traffic even with air passing through it, I'll likely find a spot ahead of the radiators but not decided where yet. Electronics hate heat, sure it will function but the anticipated lifespan decreases as temperatures rise.
The heat sink you showed is a CPU or GPU cooler and is designed for a vertical downward airflow so unless you put a fan on top it will not be that effective. You need copper, you need fins in line with the vehicle airflow - I don't know if this chokes the accountant but these are what I'd be looking at - I'm considering one similar to mount my Lucas amp.
Good, good good words... Thank you both...
I had no no no intention on using that heat sink in the photo. I just think it's nice looking.
A bit of an update. I hate to do this to y'all.
Like Alex said, play dough was needed, kinda. I looked and dug and looked and asked around and finally found someone with a band saw that could take about 7mm off the finned heat sinks. This worked.
I drilled my holes, applied some paste, used self tapping screws with a tight thread and bolted the amps down to the sinks. Then bolted the heat sinks to the rad cover using the OE U clips and screws, just a longer set.... Plugged in the amps... Turned the key, she fired right up. But something may be wrong.
I didn't bolt in a supplemental ground cable from the heat sinks and amps to the rad cover just yet, but will. Anyways,,,
Forever, at start up, the volts on a little digital volt meter I have in the lighter hole on the ski slope ALWAYS reads 14.0, 14.1 or even 14.2 volts. Always! Granted I hadn't started the car for a about 6days, maybe longer, but I don't think it's that.
Today it never made the 14v. Was at like 13.7 from the outset, then went down and hovered at 13.5... I went for a short drive and the volts stayed there. 13.4, 13.5... I NEVER get down to 13.4V even with the blowers on, lights on with brake lights (all at the same time) it never goes down that low. Today I had no appliances or lights on in the car. 13.4?
Now 13.4v might not sound like a big deal. The readings (and I don't know how dead on the meter is) from this digital meter does and has always served as a nice guideline... I've had it for years now and it does let me know and has always been consistent. I ALWAYS see the 14.1 volt at start. Then, around 13.8 13.9. Always. I trust it...
Could it be a voltage pile up, poor ground, something with the ignition amps I just made changes to, causing this?
Last edited by JayJagJay; Jul 20, 2022 at 06:45 PM.
Some time ago one of our members reported the Wires from the Ignition Amplifiers were getting Crushed against the Closing Panel when the Bonnet/Hood was Closed
Because there is almost Zero Space between the Wires from the Ignition Amplifiers and the Bonnet/Hood Insulation on the Top of the Radiator Closing Panel
Just a bit of a Wild Guess but that could be your problem?
So if you've got any 'Play Dough' left over ..........................
Last edited by orangeblossom; Jul 21, 2022 at 02:53 AM.
I am FRESH out of the play dough you sent, Alex, 😆
I got to playing with it,,, then left it out, now it's all dried up! Thanks for the shipment!
I drove the car into work this morning. Sorry for the long post and false alarm. Things are back to "normal"... Thank you.
Today, after work, even though it's supposed to be 10000and4 degrees, I will add the additional grounds and call it done. Hopefully slap up a couple of photos. It's not such a messy job, as I'm known for.
The only difference between today and YESTERDAY, is a WORKING. Speedometer... I'll tell ya of my stroke of GENIUS!!! I actually SEARCHED and waited til I found a speedo dial - WITH THE CORRECT PART NUMBERS! What do ya KNOW about that! Part numbers,,,, matter?
WELL I'LL BE DIPPED! 🤣
A fine line between HOBBY, and mental illness
Some time ago one of our members reported the Wires from the Ignition Amplifiers were getting Crushed against the Closing Panel when the Bonnet/Hood was Closed
Because there is almost Zero Space between the Wires from the Ignition Amplifiers and the Bonnet/Hood Insulation on the Top of the Radiator Closing Panel
Just a bit of a Wild Guess but that could be your problem?
So if you've got any 'Play Dough' left over ..........................
Did I miss this post? Strange.
There is a WARNING included in this, read on...
Yeah Alex! I was/am amazed at how tight it gets in there with what seems like a gentle slope of the hood. I am happy to say (considering underhoid temps) that my car has ZERO insulation on the hood side of things. It came that way. Just a metal hood face underside. What that will do to paint over time, I guess I'll see.
So,,, things in place. The WARNING is there is very little if ANY room between the top face of the rad support/cover and the radiator itself, underneath. I used self tappers for the ground cables, the smallest ones I had, and after going thru the rad cover/support they immediately ran into the radiator... YIKES... There is NOT a lot of wiggle room. With smallest zip inz at the very very front of the plate, there was enough room to zip in the self tappers for ground cables. But if you do this, definitely LOOK to see what kind of clearance you have.
After messing with all this stuff a while I really started to get the feeling that the amps are not grounded by the sleeves at bolt down points but I could be wrong. Jury is still out. As it is now, I have the amps well fastened to the finned sinks with fine thread self tapping bolts thru the (thin-ish) top plate of the sink,,, and the finned sinks, as OE, are then fastened to the top rad support by U-Clips and an OE slot in the top of rad cover/support. If it was and is grounded this way as OEM,,, I don't think (considering all the electricity folks have taught me are handled by the amps) it was a good design. So bad I settled on the idea that the amps CANT be grounded by their fasteners and the rad plate...? But, who knows...?
Anyways. I direct grounded the plates to the rad cover support. See pics.
note the 2 blank holes... Zero clearance between top rad plate and rad core for self tapping screws...
Last edited by JayJagJay; Jul 28, 2022 at 06:28 AM.
Did you bed the Ignition Amplifiers down on Top of the Aluminium Heat Sink Strips with Thermal Heat Sink Paste (like you would use for a Computer CPU) something like Arctic Silver ?
Please don't tell me No! even if you didn't or I will need a Bottle of JD just to kill the pain
Did you bed the Ignition Amplifiers down on Top of the Aluminium Heat Sink Strips with Thermal Heat Sink Paste (like you would use for a Computer CPU) something like Arctic Silver ?
Please don't tell me No! even if you didn't or I will need a Bottle of JD just to kill the pain
Alex
Hahaha...
I did. Thanks. That paste is some funky stuff. Gets everywhere... Tip O nose, included
