You ought to like this... I just got off the phone with a specialty brazing ring mfg and they said the sloppiest tolerance you can have between the hole and shaft is 0.006". Interference fits work best.

I've only got 1/8" to press in there and don't want to risk deformation of the caps. I'd think it would be a real PITA to press a flat shaft into a curved surface w/ a hole in it w/o a fixture of some sort.

 

That's why liquid nitrogen came up -- the insertion force would be much less. Like I said before, I don't really have the experience to have an opinion if they would shake apart, but it kinda makes sense that if the wall thickness of the barbs was too small, they might deform... As for thermal expansion issues, they can't get that hot since the plastic ones don't melt (much).

One thought -- why copy the plastic caps exactly? Why not make them a little bigger and square or rectangular? The holes for the injectors could be machined out as usual, and the barbs could be standard NPT threaded fittings coated with the proper teflon tape and screwed in.

 

Cuz I want 'em to be purdy.

 

But, you could mill slots on the tops and anodize them so they look like hot-rot valve covers or monogram Dad's signature on the sides...

Personally, I think that the ones you never have to look at are the purdiest ones of all.

 

You will need a fixture, especially if you dry (no heat/freeze) press them and that I would not do.

The proper method would be to under size the Injector bore until after barb installation, ream the bore true and polish.

You might want to think about growing the cap OD some.

I assume the barb is made out of 5/16" round stock, turned to 1/4" leaving about a 5/16" barb on the end, thus the neck going into the cap is 1/4" Dia.??

It really should be in at least 3/16" into the cap, preferably beyond 1/4" (or the barb neck dia.)

Don't heat them higher then about 400-450F, 6061 starts to soften at about 500-550F, anneals at about 750-800F, melts at about 1050-1100F.

Personally I like them pretty much like you did them, though I probably would add more fins ... But I'm a radial engine nut and I like round finned cylinders...

-Enjoy
fh : )_~

 

Yeah these IDI's sound sweet but nothin' compared to a big 'ol radial Some day I'll own a radial haha Them small Rotec's just don't sound the part though so I'll have to go big... lol

 

Not sure why some of you are concerned with "heat" & "vibration" for these caps. The caps are floating on rubber o-rings, isolated from both of your concerns. Heat and vibration is not a factor. Some people should lighten up and don't be such a knitpick. After all we're not going to the moon with these things.

 

I measured the temps of hot injectors. They're hot, the caps get hot and the lines start to get pretty warm. The tops of the caps touch or come extremely close to touching the injectors.

 

Well ... half the fun is debating the "finer points". I've certainly learned a few things from other people's nitpicking in this thread, including how to spell nitpick (sorry, I just couldn't resist that one). Besides, we're talking about one of the most problematic aspects of the entire truck. Any improvements would be welcome and Ford/International doesn't seem interested in working on the problem.

Eagerly awaiting the next attempt!

 

I had well over 200K miles on my original return caps and hoses, and never had any leakage problems at the caps. And I have yet to have issues with any of the replacements I've ever used. I believe that the failures are mostly due to improper installation of the caps/o-rings and using low quality parts (and constant fiddling with them). With the last IDI being built over 16 years ago, I would hardly expect any OE support for an issue that really wasn't back then.

I do like how these are turning out, just for the bling factor alone. Very nice work

Jason

 

You know how it goes. You can build a great widget and someone will say, why the hell didn't you do this!? Then you'll sit there and think, why the hell DIDN'T I do that!?! 100 minds > 2 minds.

 

I re-use my caps, I simply buy o-rings and line to redo my return side. I might break down and buy a complete set shortly, but suspect that I'll likely just round up some spares off my parts motors and not bother.

It's really not the caps that are a problem, it's the o-rings. Once they hit a certain amount of heat and age, they won't seal properly. The last toolroom I worked in we bought o-rings by the thousands, we would use likely 4-500 a week. (Our tooling was all watercooled, and every time anything was taken apart, the o-rings were replaced with new) I saw o-rings get literally baked when there was a problem with the water supply, and last only a few minutes.

The reason the viton o-rings are better is they hold their elasticity better at higher heat, allowing them to maintain a seal for longer.

One of the bigger issues with this design is the fact that it is radial loading on the o-rings, meaning that they are sealing on the diameter, rather than a linear loading, where they are sealing on the face so to speak. When possible, we designed out tooling in such a way that we were sealing linear, and that would cause the o-ring to expand in diameter against metal, creating a seal on top, bottom, and inner/outer diameter of the o-ring. With the return lines, they are only sealing on the inner and outer diameter, which makes them more likely to leak in the first place.

 

can someone please tell me how to turn the pump up on my truck its a 1988 f350 with a 7.3L non turbo thank you

 

Maybe I should retract that part of my previous post. Problems with return lines/caps/o-rings do seem to come up a lot, though.

Last night I woke up with the idea of using ridgid (steel?) lines with flare fittings instead of the barbs and rubber lines. That way, the caps would be less likely to be moved after installation. However, I'm guessing that thermal expansion of the lines would likely move the caps relative to the injectors and cause the o-rings to fail quickly. Oh-well...

 

Often these issues are simply maintenance. These o-rings are in contact with fuel, which in itself tends to dry out rubber, in a high heat area, with high vibrations present, and so forth. Expecting them to last 20-30 years without replacing them is basically a dream at best, and unrealistic. The 7.3 I pulled out of the livestock truck (superduty) a few weeks ago still has grey paint on the return lines.....think that it may have had an air intrusion issue?

I know my '89 dually, when I did it 6 years or so ago, I recall the lines having paint on them too, so they were likely 15 years old when they got replaced. It needs to have the engine pulled, heads pulled, and injectors, gp's, pump, and a few other things done though. There's at least one gp broke off in a head, that was broken off when I got the truck, so it will be a major PITA to replace some day.