Heatshields; single use or multi use? Here is the power to choose!

[Mark(The Miser)UK]

Here is almost all I know about heatshields. 
I'm an advocate for multiuse, but others are not.
Users can determine their own safety factor, knowing what I've discovered.
Here in the UK they can run to nearly $10 each if you go to the wrong stealership. I hear that they are becoming a traded commodity in the USA recently. Money is important to me, but not the sole criteria.
Knowing how to reform a shield can become important if you are experimenting, and changing those injectors regularly, several times a day in some instances.
These shields are a form of mild steel, and are designed to deform under injector tightening to form a seal between injector and shield, and also between shield and the head. The head side of the seal is a little ledge which actually becomes furrowed by the concentric ridges that are on each shield.These ridges help to seal, the first pic actually shows a shield with high points on the edge which has allowed carbon to fill the gap.
This is not neccessarily a bad thing as the bare metal perimeter bands show this shield is sealing.



Each shield is pretty well different on the surface due to the machining, which means each change of shield makes new  cuts into the soft ledge, and wears the head out a little more.


It is for the above reason, that I reuse the same shield in the same injector seat. It is my conclusion that reusing the same shield reduces this inherent wear.
I can't remember how many years I reused a single set in my car. If I say 5 years, then I won't be far off. I do remember though that I reused the set of 4 for 14 times before one failed. It failed catastrophically on it's 15th reformation. The other three survived, so I don't know how much life they had left in them. Here is it's pic, alongside one of it's surviving sisters  and another one of their underneath:EDIT At this point, I changed all shields for peace of mind, and ease of accounting ]

For a short time I went into panic mode when the shield failed, and felt like those 'Doom and Gloomer's'  "What if the bits had fallen into the engine"
However, studying the dead shield made me realise that the fracture was always going to happen during the 'resetting'  process, because the bearing I use pushes the inner area and tries to rip the hole bigger. If it doesn't happen, then the injector actually recompresses the inner wall together in a non fracturing direction. There only needs to be a resetting of a little over 0.5mm or 20 thou, and I use my thumb nail to check the gap between the shield and the injector by resting it on an injector see pic

I have found the 'magic of the 'Mole' grips is that they can deliver a metered pressure that can be repeated. I know previous advocates have hammered, punched, or used a drill press, but this method is convenient and accurate. As grips are not graduated, initially, under distorting and checking is the way to go.

To the pessimists who aren't members of the extreme, imminent damage clan, but don't believe that the shields can seal correctly, I say that of the 56 resettings on these 4 shields, only about 4 or less times has the shield needed a little extra tweeking to stop a leak. That equates to 1 shield in 15. I am sure that that is a better record than some single use advocates. Part of the reason is that the final tightening that distorts the shield actually creates a polished wring fit contact between shield and injector

Sometime ago I posted a little puzzle for fun when these shields had a mere 8 times reuse. They were placed alongside 4 single use and asked people to identify which are which. Only one dared humiiation, here it is again
 
I hope that this little essay explains the rationale of my position, and justifies it Especially as I have saved 10 x the purchase price of my car by doing this

Mark
EDIT:
 Re the ball bearing, I've found that about 3/8th to1/2 inch 'ball park' works well, because you don't want the clamping force to be acting too much radially from the centre of the hole, but more nearer perpendicular to the hole's circumference.

Before finding a spacer, I used an M12 19mm AF nut quite successfully...

[wdkingery]

Thanks for the writeup man I'm sure I'll be using this soon. I love low dollar ingenuity!

[rodpaslow]

Ditto

[ORCoaster]

I had a 50/50 chance at getting it correct but I did actually deduce the correct set by really studying the wear on them and using your hint at the time about dropping them and getting them dirty.  At least that might be what the hint was.

[8v-of-fury]

Thanks for the writeup man I'm sure I'll be using this soon. I love low dollar ingenuity!

Yessir.

[ToddA1]

^^^^ what the hell is that in your sig?  I was mesmerized by the sheer oddness of it.^^^^

On topic.  Personally, I've never reused a HS, because I get them for about $1 each, but I guess I'd consider it.

When a HS leaks, would I just see fuel weeping from the injector threads?  I'm not too sure I'd feel comfortable just tightening them if they leaked.... I'd hate to crack an injector boss just to save $1.

-Todd

[ORCoaster]

What did I tell you 8V,  those kids need less sugar and more time outdoors.  Odd indeed.

[maxfax]

Great writeup one this!!   I'll give my testimonial, it works..  Usually I end up reusing them for the sake that I always forget to have an extra set around when I need them...   

[Baron VonZeppelin]

There aren't many places left selling them for $1 range.
Ones that have old stock - some are still doing $1 +/-
Get them while you can.

New stock is $3 - $4 each for Bosch Heat Shields.

Thanks for the hepful info Mark.

[rs899]

Thanks Mark

I'm in.  I have been reusing them but resetting them in a far less certain way (hammer).  I need to find a proper ball and seat fot your mole grips ( we call the vice grips) method.

[R.O.R-2.0]

Thanks Mark

I'm in.  I have been reusing them but resetting them in a far less certain way (hammer).  I need to find a proper ball and seat fot your mole grips ( we call the vice grips) method.

the little SLEEVE that comes in compression tester kits is the same size as heat shields..

[ORCoaster]

You mean this sleeve?  What is it for anyway?  Comes with two copper washers in the same hole in the tray.  Where does it go?  I only need the injector mimic and the take off to the gauge mechanism from the kit.

Just curious, thanks for the tip.  Going to put my ball bearing in the kit instead of the tool box and maybe I won't loose it all the time.

[R.O.R-2.0]

yup, you got it buddy..

[ORCoaster]

I know I "got it"  the ladies tell me that all the time. 

But what is the sleeve used for in that compression testing kit?

[Mark(The Miser)UK]

Re the ball bearing, I've found that about 3/8th inch 'ball park' works well, because you don't want the clamping force to be acting too much radially from the centre of the hole, but more nearer perpendicular to the hole's circumference.

Before finding a spacer, I used an M12 19mm AF nut quite successfully...