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recommendations for plugging MPFI injector holes

ehall

NAXJA Member
NAXJA Member
I need some ideas. I'm planning an engine swap on another car. The highest-flowing intake manifold for this vehicle used port injection, but the car is setup for TBI. I want to plug the port injection openings on this manifold and convert it to TBI. What material should I use?

Rubber stoppers would work great for short-term use, but they may vibrate loose or crack with heat and fuel and age.

Maybe cut a brass rod into small plugs that are tapped into place? That runs a risk of cracking the aluminum or introducing corrosion from dissimilar metals. Maybe aluminum rod? Another problem is that this would leave the bottom of the opening empty, which could introduce turbulance (also a problem with the rubber stoppers).

JB Weld or some kind of epoxy would work if I can reach into the runners and make s smooth seam somehow (don't want blobs of epoxy hanging down). Maybe stick some painters tape in there before dripping it into the openings? It would be very hard to remove later if that was ever desired.

Something like seam sealer or some other kind of petroleum safe flexible adhesive may be the best bet but I don't know what. Black RTV maybe?

Ideas?
 
Assuming TIG welding the holes closed/gringing them smooth, I'd try the Aluminum rod with epoxy. Remove any excess epoxy with sanding drums or rolls and a dremel tool, or die grinder. Converting an SPFI manifold, you may want/have to do some runner work anyway.. Most SPFI setups I've seen have a slight hump upstream of the injector well, as well as a slight depression at the injector well itself. You may want to fill the depression, then smooth the runner out for smoother flow.
 
Oil galley plugs or how about just leaving the injectors in place?
 
I think I am going to drive in some small freeze plugs on top, then turn the manifold over and fill the bottom of the opening with some kind of filler material. I have found some gasoline-safe gasket maker for motorcycles and airplanes and whatnot so I assume some of that will work for the bottom of the hole with the stepped opening. That should give me a smooth surface inside and a rigid seal on the outside.
 
Isn't JB Stik fuel proof? You really just want something that isn't going to get sucked in by manifold vacuum... the gasket maker + freeze plug idea will work nicely assuming you can find properly sized freeze plugs.

Ideally you'd TIG the holes up from the inside but I'm guessing you don't have access to a TIG welder.
 
If you can't get them welded then I would thread them and put plugs in them. The last thing you want is to have a chunk of JB Weld fall out and get sucked into the engine. Though someone makes an epoxy that head porters use to reshape ports on heads.
 
I've used "splash zone" epoxy in intake ports before with good results. The head/intake needs to be 100% clean and oil free to ensure proper adhesion.
For plugging off an injector hole my first choice would be to weld, next to drill and tap and either install a pipe plug or use some aluminum threaded rod with loc-tite then grind the extra away, last choice would be epoxy. I would also cross drill the hole and install a roll pin if I used epoxy to prevent the whole chunk from falling in at once, engines can chew up and spit out small bits, the large ones cause problems.

~Alex
 
you guys are so paranoid. the holes are small and have a stepped lip, and it would take a lot more force than vacuum and vibrations to break up even a casual rubber plug

OMG DONT USE RUBBER ORINGS ON INJECTORS THEY'LL FLY APART AND GET SUCKED INTO THE MOTOR!!!111eleven
 
Well no I appreciate ideas but dial back the milspec it doesn't have to be a whole lot tougher than the cheap plastic injectors and rubber o-rings

Then just leave the cheap plastic injectors and rubber orings in place. Then no need to worry about vacum, and little vibrations. Let alone heating/cooling changing clearances, etc... keep it simple, or over do it.
 
OK then, well... I see the rational ideas are out. You are looking for creative then? OK. Wine (or champagne) corks and condoms. You are all set.

It will seal the holes, as well as show that you are well prepared in the event you meet a lady. A win, win.
 
Thats it!

YouWinThePrize.jpg
 
So I take it the cork and condoms are not a good idea then?
 
Lessee you don't want simple... you don't want perfect... you want ideas that you agree with.

I suggest bathtub caulking followed by an assortment of toothpicks, screws, bits of wire, and duct tape till the holes are full
 
Gasoila and bang in some cheap freeze plugs if you want/need the highest flowing manifold for your TBI thing.

But I still think the condoms and XXXX would be best for your needs.
 
I was looking for simple and functional ideas and I did not think I had to qualify the request as such :(

I should have explicitly said I did not want permanent modifications since the car or engine may be changed to MPFI later.
 
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