Hi I,m new to the site but have been lurking and researching. Here is my question. So most re-builders say machining the top plate or shimming the armature is a band aid at best hack job at worst and that the preferred method is to machine the poppet and seat. Now from what I can find new poppets and valve bodies are not available to us mere mortals, the re-builders may have a source but that is their lunch money we'd be messing with if they released their sources. No offence to the re-builders, everybody need to put food on their table. Here is what I don't understand how is taking material away from the poppet and seat any different than adding shims or machining the top plate? I seems to me it is almost like saying 2+2=4 but 1+3 does not equal 4. I'm not sure I get it, taking material from the poppet and seat should reduce armature clearance not increase it.

 

There are no new Poppet valves available to anyone. The Poppet and injector body are a matched set, you can't just replace something like a worn part. The Poppet goes up and down millions of times in one position and beats a unique seat in the injector body based on how each happens to be wearing during this. So Machining the actual Poppet and Poppet seat is the 'correct' way to 'restore' the tolerances. The problem is this costs $75 per injector with a 50% success rate (been there, tried that), and the affordable rebuild gets out of hand very quickly. So, the practical way to achieve the same thing is to machine the injector body to restore tolerances. The wear is still there on the Poppet and the Seat, but the relationship between the Armature Plate and Solenoid is what needs to be restored for proper injector function, and machining the injector body does this. Machining the Poppet seat eliminates the wear (like doing a valve job in a cylinder head), but it's just not practical at all. You would be buying brand new injectors if this was the case because it'd be cheaper.
But lucky for us these injectors were designed to be machined in this manner over and over to rebuild them over and over.

Also in rebuilding the injectors, there are things you want to machine, and things you don't. There are shims you want to change, and some shims you don't. Lots of assembly, measure, take apart, adjust, repeat. Then there's the flow testing, take apart, adjust, repeat. There's a lot to it actually, more than people realize.
Sure you can buy shims for $.50 on eBay and "Fix" your injectors. But you aren't fixing anything, you're only making them run better than before.
There's a big difference.