Dusterbd13 Reader
11/25/11 6:41 p.m.

ok, so im looking harder and harder at injecting my small block mopar.

i already have a victor jr manifold that has cast in bungs on each runner, intended for either injectors or nitrous nozzles. doing some looking around last night, i came across this. http://www.rossmachineracing.com/injectortool.html

seems like this would be my answer. i have a pretty good drill press, and a full woodshop to make wooden jigs with.

is this a process i could do with normal shop equipment? or is there any other diy way to machine a manifold for injection?

or am i looking to find someone with the equipment and pay him?


familytruckster Reader
11/25/11 7:14 p.m.

The other way I've seen intakes done is to weld on injector bungs. like these http://www.compperformancegroupstores.com/store/merchant.mvc?Screen=PROD&Store_Code=FS&Product_Code=307017

Those, as most look like just a piece of pipe, not a nice stepped bung, like that bit could do,especially with the pre cast bungs in the intake.

OrangeAlpine New Reader
11/25/11 7:39 p.m.

In reply to Dusterbd13:

Don't exactly understand what you what to do.

If you are thinking about drilling holes in the manifold and fuel rails to accept the injectors, you do not need the fancy, stepped drill. I drilled a fuel rail using two drills instead of the stepped drill. Almost 8,000 miles and all is well.


Dusterbd13 Reader
11/25/11 9:25 p.m.

what im trying to do is take a carb only single plane manifold, cand convert it to port injection. this will necessitate injector mounting holes in the manifold, as well as making fuel rails. care to enlighten me on the process you used to make yours?


turboswede SuperDork
11/25/11 9:33 p.m.

Drill small hole to fit the nose of the injector, then drill a bigger hole for the O-ring.

Finish the holes and chamfer them to get the O-rings to seal properly and not tear.

They don't have to be exact, just very close. The O-rings allow for some misalignment.

OrangeAlpine New Reader
11/25/11 10:41 p.m.
turboswede wrote: Drill small hole to fit the nose of the injector, then drill a bigger hole for the O-ring. Finish the holes and chamfer them to get the O-rings to seal properly and not tear. They don't have to be exact, just very close. The O-rings allow for some misalignment.



Curmudgeon SuperDork
11/26/11 6:52 a.m.

It's going to be pretty important to get the injectors pointed at the rear of the intake valves. I'd suggest taking advantage of the factory's engineering and go check out some factory small block Mopar manifolds to see what angle they uesd, then duplicate that on yours. Angle accuracy with a drill press is very possible, as you mentioned you'd want to make a jig to hold everything steady and of course take your time.

Since your manifold already has the cast in bungs it should only require drilling in two steps, as mentioned. That site shows the 'D' extrusions for making your own rails, if that's not the way you want to go there are plenty of OE FI setups out there that use steel rails with the 'cups' brazed to them and it should be no real problem to adapt that type for your setup. This one is from a Miata.

Dusterbd13 Reader
11/26/11 8:41 a.m.

so i guess the next question is what kind of tolerances do i need to have for the injector placement? within 1/64? 1/32? also, im wonderding now if my manifold is thick enough to drill properly. what kind of thickness do i need to have?

and i like the idea of using OE rails. thats on my list for the next pull-a-part trip.


Curmudgeon SuperDork
11/26/11 9:28 a.m.

1/64 or 1/32 off center should not be a big deal. Having them all at the same angle will be very important for the rail to fit and seal properly.The thickness you need will depend on the injector dimensions. I don't have any sort of manifold around to look at so take this as coming from my memory, which is like a stainless steel sieve: the injector hole is done in such a way that the injector tip does not stick out into the port. That keeps it from creating turbulence. So if the manifold is not thick enough there to allow that, then I'd look at using some of those weld in injector bungs to get them up and out of the port.

novaderrik Dork
11/26/11 12:23 p.m.

hit teh craigslists and teh ebays and find a manifold that's already set up for the injectors.

Curmudgeon SuperDork
11/26/11 5:46 p.m.

Now where, pray tell, is the fun in that?

Dusterbd13 Reader
11/26/11 7:40 p.m.

and the problem with that is that there are no readily availible MPFI manifolds for the LA style small block mopar. edelbrock makes two. the super victor efi (4000-10000 rpm, $500+) and their pro-flo 2 full efi setup (3000+, proprietary parts). the magnums are completely diffferent animals.

if it were a pissibility, id be all over it like a fat kid on a twinkie. but its not for my combination and budget. hence making my own.

i also realize running a TBI derived setup is a possibility. but were still talking ~2k to get it up and running, and its still TBI (reason i cant do junkyard TBI is hp level . im laying 425 at the wheels off the bottle. no GM TBI, even the big block, will support that. so im in aftermarket, 4 valve, 4 injctor territory. used holley commander 950 TBI units occasionally come around, but then were back to proprietary parts and a lot of reinventing the wheel. if im going to reinvent the wheel, its gonna be a damn good wheel to start with)

anyway, i think im going to start making a fixture and taking measurements of wall thicknesses this week. ill post up the wall thicknesses to see if y'all think i can get away with just drilling, or if im going to have to find a guy to TIG bungs iin my runners.


erohslc Reader
11/27/11 6:35 p.m.

I'd seriously look at using bungs, but use epoxy/JBWeld to place them in the manifold instead of welding. The O-ring seal to the bungs only has to handle manifold pressure/vac, and the same is true for the adhesive. Industrial filled epoxy or real JB Weld is fully up to this task.
The real accuracy needs to be in the fuel rail(s), as they handle high pressure fuel. The fuel rail machining has to be accurate, and the finish has to be smooth, so that the O-rings will seal correctly. Using adhesive for the bungs allows you to assemble the rail, injectors, and bungs into an assembly, and then dry fit that assembly to the manifold. Holes too tight? Open them up. Injectors binding or cocked because the hole in the manifold needs work? Fix it as needed. The machining for the holes in the manifold is not critical, because the adhesive will fill gaps, and adhere to a rough finish. Fit the assembly in place, and figure out the fuel rail mounting hardware and bracketry. Once that is built and fitted OK, you have everything needed to hold the injectors in perfect alignment while the adhesive cures, no jig or fixture required. Once it all fits OK, use a small piece of Saran Wrap over the injector tips to prevent fouling from the adhesive. Apply the adhesive, place the assembly, tighten the fuel rail mountings, and touch up the adhesive as needed to eliminate any voids or excess. After it's fully cured, inspect, and fix anything that needs attention. Trim away excess adhesive.
Repeat as needed.

Worse case, it's a total blowout, you chip/grind away the adhesive, and do it over.


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