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View Full Version : DIY KA24DE Top Feed Fuel Rail Conversion


DMSHIRCLIFF
08-19-2019, 07:48 PM
Alright, to start off with I'm not sure that this is in the right sub, so I apologize in advance if it isn't.
After lots and lots and lots and lots (did I mention lots?) of issues with my side feed injectors I decided I wanted to do the top feed conversion. I did not, however, like the price of the top feed conversions. So me, being me, decided to save some money and build a top feed conversion system myself

First lets go over the required tools for the job:
Drill press (a hand held drill will work, but a press makes it so much easier)
Tap Handle
3/4-16 tap (borrowed from work)
13.5mm Drill bit (borrowed from work)(a 14mm would work as well, the 13.5 was kinda tight)
10mm Drill bit (actually owned this one)
3/8-16x20 Stud
3/8-16 tap
Center punch
Center drill bit
Hacksaw Blade
Calipers
40-2000 grit sandpaper (in whatever increments you deem necessary)
Tap Magic or cutting fluid
1"x1" aluminum angle

Next we will go over the parts list:
Fast Fuel Rail Extrusion (FST-30700218B)
6AN-8AN O-ring Fitting (FST-54023B-1)
6AN-6AN 90* Elbow (SUM-260687B)
Wear Resistant Delrin (McMaster part #8576K23 - 1 ft)
(2) M4-0.7x10 SHCS
(2) M8-1.25x20? Hex Head Screw
2 Part Epoxy
Part of your old fuel rail or similar
O-rings

Before we get started note that this is a rather tedious process and this guide is written under the assumption that most of you all have some basic machine knowledge. Your holes have to be perfectly lined up, square and not botched for the orings to actually seal properly.

Time to get started! First you have to make the "adapter pucks" for the intake manifold itself. I took the piece of delrin, found the center of it, drilled and tapped a hole for the 3/8 bolt. This served as a way to chuck the rod into my drill press. WARNING - THIS IS INCREDIBLY DANGEROUS AND QUITE FOOLISH ON MY PART. DO THIS WITH EXTREME CAUTION
Now, that that's out of the way you'll want to turn your drill press to the slowest speed setting, get your sandpaper and go to town on a 5-6" section of delrin. You'll want to sand this down until it fits in the manifold holes. It takes some time, so patience is required. Once you get done with the 40, you can work your way up through the grits and get a close to original finish on the delrin.
After you get the section of delrin to size it's time to start cutting. I cut my pucks tall enough so that the injector seated flush with the bottom and on the shoulder of the injector. I did this by setting the table on the drill press to cut off the bottom 13mm, used the hacksaw blade and table as a guide to cut the pucks perpendicular.
Side note, this actually ended up being a little too tall, but you can use your judgement on that one. Or you can bypass this step all together and buy the adapters for $50.
Lastly for this part you need to drill your centers, find them, pop a 13.5mm hole in each of them and voila! You are done with the first step.

Next we will move on to the actual fuel rail. The first and easiest step is to tap the end of the rail to accept your AN fitting (the 3/4-16 tap). There is no need to drill or sand this hole, it is pre-drilled perfectly for a 3/4 tap.
Next you're going to want to cut your rail to the proper length. I cut mine at 13.875", you have some leeway on this dimension. After cutting you length, you can polish the aluminum with your progressive sandpaper grits to get a nice shiny finish.
Now comes the fun and tedious part, drilling the holes for your injectors. You're going to want to be extra careful, marking and drilling these holes as it could mean the difference between a leaky fuel rail and a solid one. Mark your first center, this mark can be made anywhere close to your AN fitting end. Just be sure that your hole will not end up drilling through the threads.
Again, I cannot stress the importance of getting these holes dead on, so double, triple, and quadruple check my dimensions!!! But the hole spacings I came up with are, 96.20mm, 97.9mm, 95.95mm. Mark them, center punch them, and I personally like to use a center drill bit to be extra sure the bit doesn't wander.
Now a little side note here. I do not have a vise for my drill press, being the cheapo I am. So, I found 2 2x4's, some angle iron and vise grips. This allowed me to hold onto the fuel rail and keep it perpendicular to the bit. (see pics for a better understanding)
Drill your first set of holes with the 10mm drill bit, these holes will go all the way into the main bore that runs the length of the rail. Next you will want to counterbore these holes with your 13.5 (or 14mm) bit. You want to counterbore them to around 7mm deep.
Lastly, you need a way to mount your fuel pressure regulator. This is where your old fuel rail comes in handy. You are going to want to cut off the section of pipe that the regulator actually bolts to. Around 10mm, enough to shove up in the fuel rail, but not too much that it covers up the hole you just drilled. After you have this piece cut, give it a good sanding. You want to get all of the paint and plating off of both the inside of the fuel rail and the outside of your pipe.
Once this is done, smear it with a healthy dose of 2 part epoxy and let it set up over night.

Now you're almost done!! All you have left to do is cut your mounting brackets, bolt it into place and check for leaks!

edit, when you assemble this, you are going to want to place o-rings or use rtv between the plastic pucks and the intake manifold to prevent vacuum leaks

https://imgur.com/a/XxnbCo7

tuzzio
08-20-2019, 08:00 AM
Honestly, fairly well done. Props to you.

da_crew10
08-20-2019, 09:40 AM
Very cool. Was this to save some doe? Or just a better end product than that of other brands?

DMSHIRCLIFF
08-20-2019, 11:16 AM
Very cool. Was this to save some doe? Or just a better end product than that of other brands?

It was purely a money save on my part. Besides the time it took, I only ended up being out about $85, not including the cost of the injectors of course.

duhafnusa4
08-22-2019, 11:09 AM
Where can I buy those injector plug adapters? They look nice, like they can fit on lots of stuff

S14rebuild
08-25-2019, 07:07 PM
Feel like im missing out on pics here...

feito
08-25-2019, 10:42 PM
Many years ago I was planning on using a fuel rail from an old ford probe, ones with the 2.2l engines, same as the mx6. The holes lign up, just need to figure out how to mount it.

andisan
08-26-2019, 07:50 AM
Don’t know if it matters or not, I went in to get new fuel line from an auto store and didn’t notice that on the fuel line is says “ not for fuel injection”, I noticed it on one of you’re pictures and remind it me of my situation, I had to redo it with the right fuel lines


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