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recommendations for plugging MPFI injector holes

Of course I have used it. I would not have suggested it if I had not.

NOW, that does NOT mean I have used cork and condoms on an intake manifold. You were being silly, so was I.

Gasoila does work... and quite well.

I haven't heard of gasoila before, have you used it in the past?

Dorman makes small freeze plugs in a bunch of different sizes, so some kind of stable gas-safe filler to block up the inside of the hole would be great..
 
No, plugging the hole would not be a good use. But sealing in a plug is right up its alley... and not a problem with gasoline.
 
Isn't JB Stik fuel proof?
I looked into this. Yes the stik is more fuel resistant than regular JB Weld but it's half the strength and has a smaller temperature range. The advantage of the stik is that you can form and apply it underwater. The intake wouldn't be usable if it was ever fully immersed in anything so I don't think that's a factor.

I've used "splash zone" epoxy in intake ports before with good results.
That came up in some searches but mostly about shaping intakes, and it's also really expensive.

Most of the search results are in praise of regular JB Weld. People seem to do a lot with it, for example http://forums.bimmerforums.com/forum/showthread.php?t=96007
 
Just a footnote. The injector holes measured at almost precisely 14mm. Dorman has small freeze plugs in various sizes, and we decided to use the 9/16th inch (14.3mm) cup-style brass plugs (565-008 for a box of 10).

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Unfortunately they deformed too much on installation (like, one of the side walls would stretch way out and there was no way to return it to shape) so we had to abandon the idea. After thinking about the problem more and researching various options we decided to use Permatex Right Stuff since it had all the properties we wanted:

This elastomeric rubber technology is blowout resistant and [...] also protects against leaks caused by vibration and thermal expansion. [...] Resistant to ATF, coolant, oil and other shop fluids, it is sensor-safe and operates in environments with temperature ranges from -75°F to 450°F (-59°C to 232°C) continuous, 500°F (260°C) intermittent.

The injector openings are cone-shaped and then a cylinder at the bottom for the o-ring, so something like Right Stuff is perfect--stays flexible, resists petroleum, resists vibrations, and stands up to high temperature.

In the end we bought a TBI manifold so didn't get a chance to try it, but I have no doubt it is the right material
 
Being a machinist and fabricator, if it were mine, I would get some alumarod and get out the torch and fill the holes with the high zinc contact welding rod. You can do this with a propane torch. This is the stuff you see the guy using at the fair where he welds a pop can back together. It melts just under the temp of the aluminum and if you are careful, you can fill the holes permanently. When done, you can sand/mill the surface down and not be even able to see the weld. I have welded alternator cases and tcases many times. I have used it several times to add a mounting tab or lengthen one on an alternator. Done properly, the result is actually stronger than the original. You can pick it up at your local welding supply.

To add tabs, I make a plaster mold of the item, then remove the plaster where I want to add the tab. Then I heat the part up and start building up the part, filling the area I removed. It is like a poor man's casting process.
 
If you don't want permanent then good luck. Any type of glue or sealant is going to be a royal pain to remove. Your best luck might be to use tape on the inside and puddle "The Right Stuff" in the hole and let it cure for a couple of days. You stand a fair chance of getting it out later with the least likelyhood of it leaking.
 
If anyone is interested I manufactured a custom adapter plate to put a 4.6 stroker into a 4.2 intake system with tbi conversion. There is other work as well but the plate has been xad designed minus port matching. I do all of my porting by hand so did not have the machine shop do that part.[email protected]
 
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