Metal grinding paste to bring trash nozzles back to life

[tjts1]

Anybody tried bringing old junk nozzles back to life using grinding paste? I have these old injectors that came with my #17 head which installed 3 years ago. The injectors were caked in waste vegetable oil goo. Nozzles were seized solid so I dumped the whole lot in a jar full of acetone and forgot about them for the last few years. Fast forward to today and some of them actually came apart. Disassembled everything threw them in a tumbler for a few minutes with fresh acetone. But of course the pintles got separated from their nozzles. When I tried one and the pop tester it was just pissing all over the place starting at 400psi. So I used a bit of metal grinding paste on the tip of the pintle and a drill like this:
https://youtu.be/W-bazrdH1HM
FF to 6:20

And the result...
https://youtube.com/shorts/WRqYJelHkZg?feature=share

The pop pressure is a bit high but no pissing, leaking dribbling etc. This is a bosch india 265 nozzle. Not exactly known for its high quality. I'm tempted to try these in the car just for shlts and giggles. Bad idea or terrible idea?


https://imgur.com/a/C5Xwwsx

[dieselbenz1]

I have done similar with valve lap compond but by hand. It has always improved the spray pattern. I would instal them after a cleaning everything up again.

[Felching]

By doing that, you have destroyed the nozzles. They are machined to less than 0.000xx" tolerances. Adding a ten-thousandth to that by wearing them with that paste they are junk.
Pintles and holders are matched sets, if they are separated and lost track of their match they are worthless.

[tjts1]

Originally Posted by Felching

By doing that, you have destroyed the nozzles. They are machined to less than 0.000xx" tolerances. Adding a ten-thousandth to that by wearing them with that paste they are junk.
Pintles and holders are matched sets, if they are separated and lost track of their match they are worthless.

Yeah, I'm not so sure about that. These were garbage nozzles ready for the bin, why not experiment on them? They're working a lot better now than when I got them.

[sgnimj96]

These days, unless you are stepping up to more expensive nozzles, those super-tight precision and matched tolerances of (made-in-x) bosch nozzles are a crap shoot with a high leak rate NEW. It's like they don't care anymore and expect people to fix them.

[BillGrissom]

Originally Posted by Felching

... Adding a ten-thousandth to that by wearing them with that paste they are junk.

You truly think one can remove 10 mil w/ a little paste. Maybe if you spun it for a year. For reference, the spark plug gap in an old 1960's engine is 35 mil. The pop-tests looked good, so what is the risk? Just need to swap in a thinner washer on the spring or sand down the existing one. To adjust the other way, I bought a few bags of thin washers from McMaster-Carr (posted PN's in past).

Re pop-pressure, I suspect people exaggerate the importance. I say this because as-found my 1985 300D had 3 non-turbo injectors installed, which popped at 1500 psig (recall). Replacing them and adjusting all to the correct 1950 psig didn't noticeably affect how the engine runs. My home-made pop-tester has both a mechanical gage and an electronic pressure transducer so I can electronically record the pressure trace and better pick the peak where the poppet first opens, but really over-kill re above experience.

[Shern]

Correct me if I’m wrong, but I believe the number to the left of the decimal is one mm -unless there’s a reason people need to measure tolerances in meters. Think he’s talking about removing one ten thousandths of a mm.

Originally Posted by BillGrissom

You truly think one can remove 10 mil w/ a little paste. Maybe if you spun it for a year. For reference, the spark plug gap in an old 1960's engine is 35 mil. The pop-tests looked good, so what is the risk? Just need to swap in a thinner washer on the spring or sand down the existing one. To adjust the other way, I bought a few bags of thin washers from McMaster-Carr (posted PN's in past).

Re pop-pressure, I suspect people exaggerate the importance. I say this because as-found my 1985 300D had 3 non-turbo injectors installed, which popped at 1500 psig (recall). Replacing them and adjusting all to the correct 1950 psig didn't noticeably affect how the engine runs. My home-made pop-tester has both a mechanical gage and an electronic pressure transducer so I can electronically record the pressure trace and better pick the peak where the poppet first opens, but really over-kill re above experience.

[ykobayashi]

This is an interesting thread. All my old nozzles are in a box. I’m going to be keeping them after reading this. Never know…the way my cars keep going I’m going to look and nozzles may be NLA at some point.

[Mike D]

"A mil is a thousandth of an inch — .001 inch. It is a typical manufacturing dimension."

https://www.deeproot.com/blog/blog-entries/mil-thickness-what-does-it-mean-and-how-do-i-measure-it

[Clemson88]

Originally Posted by BillGrissom

You truly think one can remove 10 mil w/ a little paste. Maybe if you spun it for a year. For reference, the spark plug gap in an old 1960's engine is 35 mil. The pop-tests looked good, so what is the risk? Just need to swap in a thinner washer on the spring or sand down the existing one. To adjust the other way, I bought a few bags of thin washers from McMaster-Carr (posted PN's in past).

Re pop-pressure, I suspect people exaggerate the importance. I say this because as-found my 1985 300D had 3 non-turbo injectors installed, which popped at 1500 psig (recall). Replacing them and adjusting all to the correct 1950 psig didn't noticeably affect how the engine runs. My home-made pop-tester has both a mechanical gage and an electronic pressure transducer so I can electronically record the pressure trace and better pick the peak where the poppet first opens, but really over-kill re above experience.

Points and plugs gaps were in inches. I set plugs at 32 (probably thousants) and don't remember point gap, 28 maybe. Seem like I bought a dwell meter when I got the dual point distributor.

"...never remember..." What a redneck!

[BillGrissom]

Originally Posted by Shern

... Think he’s talking about removing one ten thousandths of a mm.

Sorry, I was thinking like a 'merican. Probably did mean mm. If true, then 1/1000 of a mm is 1 um (micrometer or "micron"), which is slightly more than a wavelength of visible light (400 to 700 nm). That level of material removal is termed "polishing" since the surface can then reflect light without much scattering. I think that polishing is what the OP intended to achieve and don't see how it could make an injector pintle worthless.

[Frank Reiner]

Originally Posted by Felching

By doing that, you have destroyed the nozzles. They are machined to less than 0.000xx" tolerances. Adding a ten-thousandth to that by wearing them with that paste they are junk.
Pintles and holders are matched sets, if they are separated and lost track of their match they are worthless.

Originally Posted by BillGrissom

Sorry, I was thinking like a 'merican. Probably did mean mm. I think that polishing is what the OP intended to achieve and don't see how it could make an injector pintle worthless.

Note that Felching was indeed speaking in inches [ " ]. One one-hundredth (.00001") or one one-tenth(.0001") of one one-thousandth of an inch(.001") is, for the purposes of this discussion, polishing.

[Felching]

Originally Posted by Mike D

"A mil is a thousandth of an inch — .001 inch. It is a typical manufacturing dimension."

Correct. Injection parts are matched to the 0.000x inch tolerance, modern ones can be even tighter.

[tjts1]

Originally Posted by Felching

Correct. Injection parts are matched to the 0.000x inch tolerance, modern ones can be even tighter.

Well now they're matched even closer.

.00000000000000000000x inch tolerance

[BillGrissom]

Originally Posted by Felching

Correct. Injection parts are matched to the 0.000x inch tolerance, modern ones can be even tighter.

So you meant the OP might have removed 0.1 mil (0.0001") with grinding paste. When you said "10 thousandth", I interpreted as 10 x 1/1000 of an inch, or 10 mil. What you meant was "one ten-thousandth".

That seems reasonable since grinding paste is a bit coarser than polishing compound, which removes on the order of 0.5 micron = 0.02 mil. 2000 grit sandpaper is in that ballpark since it can polish a metal surface mirror smooth. But, I doubt it would be a problem. The main criteria in the pintle surface is that it be very conical to give a tight seal and uniform opening around the circumference as it opens. If one removes enough metal that the pintle sits lower in the hole, that will just result in a lower pop pressure, which can be adjusted by adding thin washers behind the spring. As long as he spun the pintle in the paste, it should be uniform.