RobbMc fuel filters and fittings: which size works for us?

[robroy]

Good morning,

I like the looks of RobbMc fuel filters and fittings. It looks like the fuel filter bodies have NPT threads on them, and the fittings have NPT on one side (to go in the filter body) and AN on the other (to go on your fuel hose).

Here are the filter bodies; RobbMc has a large and small model--I'd get the small one (about 3" long):



And here's one of the fittings:



I'm new to AN fittings, so I looked in Wikipedia and see that a -6 AN connection fits 3/8" OD tubing. And a -8 AN connections fits 1/2" OD tubing. Here's the article I read: http://en.wikipedia.org/wiki/AN_thread

Five questions come to mind:

1. Which fitting size would work for our trucks (AN -6 [3/8" OD tubing] or AN -8 [1/8" OD tubing])?

2. Would the fitting be an exact fit, or would it need to be adapted to the stock fuel hose size (5/16" or 3/8", I'm not certain which)?

3. How does the fuel hose actually attach to the AN connection? Does it just press over the end and get a hose clamp to seal?

4. What material would be appropriate on the NPT threads to ensure a good seal? Teflon tape, grease, or nothing at all?

5. Perhaps this should have been question #1: Do you guys think these fuel filters are top notch, and a sensible choice considering the alternatives?

Thanks very much for all the great advice!
-Robroy

[Dragon]

1. Which fitting size would work for our trucks (AN -6 [3/8" OD tubing] or AN -8 [1/8" OD tubing])?

2. Would the fitting be an exact fit, or would it need to be adapted to the stock fuel hose size (5/16" or 3/8", I'm not certain which)?

3. How does the fuel hose actually attach to the AN connection? Does it just press over the end and get a hose clamp to seal?

4. What material would be appropriate on the NPT threads to ensure a good seal? Teflon tape, grease, or nothing at all?

5. Perhaps this should have been question #1: Do you guys think these fuel filters are top notch, and a sensible choice considering the alternatives?
-Robroy

Stock mechanical fuel pump use 3/8th or #6. The Military designation AN (Army Navy) specifies something very unique the flare is not available from any place but AN supply houses. The flare is at a different angle than regular plumbing and HVAC fittings.

You can from some Hot Rod sites by AN to SLIP (hose slip on) adapters.
Check this out! http://store.summitracing.com/egnsearch ... 4294906726

I don't use anything on my fittings anymore except liquid Teflon. The tape has little strings that get into jets. needles, oil systems etc. Liquid Teflon can be bought at any modern plumbing store. It will not breakdown in the presence of any automotive chemical except carb cleaner will wash it away.

[sideoilerfe]

Regular fuel filters work just fine. I'd put one inline before the pump and use the one inside the canister as well. You can also put another inline one before the carb if you like.

I have a spin on one that someone installed at one time to the frame that works extremely well. It uses the Wix 33121 Detroit diesel filter. Wix 24309 is the assembly. You just bolt it to the frame, install lines and spin on the filter. 30 micron.

[robroy]

Regular fuel filters work just fine. I'd put one inline before the pump and use the one inside the canister as well.

Hi SideoilerFE! Thanks for your reply. I think the fuel pump on my engine may not have a canister--is this likely? Here it is:



Thanks!
-Robroy

[sideoilerfe]

You don't have the stock pump. However, you can still add an inline (or two). I would add one before the fuel pump and after the pump. Works fine. Just use the plastic ones they sell at the auto part store that way you can see when they get dirty. 3/8 before the pump and 5/16 after. Just buy the Wix equivalent beings that Fram sucks!

[DuckRyder]

Alternately if you like RobbMc's filter you should be able to get a standard NPT to nipple fitting.



Incidentally, is that a rubber line all the way up to the Carb? If so I don't like that AT ALL. My advice is to bend a steel tube all the way up to the Carb, and connect it with two short pieces of high quality rubber hose (which you check and replace often) and the filter.

If it has a Holley, you can also get filters that screw into the inlet, as used on 390/428 Mustangs.

[cdherman]

Regular fuel filters work just fine. I'd put one inline before the pump and use the one inside the canister as well.

Hi SideoilerFE! Thanks for your reply. I think the fuel pump on my engine may not have a canister--is this likely? Here it is:



Thanks!
-Robroy

That is a very fine engine there!!

Why go to lots of trouble to recreate what Ford actually designed as a stock feature -- a nice big can under the fuel pump was the orignal design? $60 gets you a new Bosch pump that would bolt up and have a nice caninster for a cartidge fuel filter.



I was never real clear why Ford went away from the big can pumps -- likely they are a little more expensive than a piddly inline filter.

I also second the solid line to the carb comments. In 65 at least, Ford ran a hard line all the way. Its just 5/16" double flair line. Use a tape measure and get your approximate distance, then pick up a piece of premade line and loan a tubeing bender from them too. A little patience and you'll have a hard line that will stand 2-3 inches away from heat sources, keeping your fuel line cooler and reduceing the risk of vapor locks and melted hoses. With a nice bid filter at the pump, you don't need that piddly inline filter before the carb -- make the whole engine look cleaner too, less parts, peices and splices to look at.

[robroy]

Just use the plastic ones they sell at the auto part store that way you can see when they get dirty.

Hi SideoilerFE! I may wind up doing this. Part of the reason I was liking the idea of the RobbMc filters is that they look more durable, and I'm not entirely convinced of the benefits of the clear filters.

I guess some forms of contamination will show up visibly in the clear filters, but from what I've seen, it usually has to get extremely bad before this will happen. My father had several of those clear filters on his old Suburban, and the car had a rusty gas tank that pumped lots of flakes up the fuel line--enough to completely clog the filter. But on the outside the filter looked 100%; you could only see what was clogging it when you cut it open with a knife.

Maybe this experience was unusual, and most contaminations will show up?

Alternately if you like RobbMc's filter you should be able to get a standard NPT to nipple fitting.

Hey Robert! This might be what I'll wind up doing. I'm really curious though--if the AN fittings are extra work to adapt to regular cars/trucks, why has RobbMc made them? And why hasn't he made the nipple fittings?

I suppose I should be asking him that question, but maybe it's obvious to experienced folks.

Incidentally, is that a rubber line all the way up to the Carb? If so I don't like that AT ALL. My advice is to bend a steel tube all the way up to the Carb, and connect it with two short pieces of high quality rubber hose (which you check and replace often) and the filter.

Thanks for this advice! Yes, it's a rubber hose all the way to the carb. I like your tubing idea better too, but I probably wouldn't have thought of this because I ran my old FE for years with a rubber hose.

Regarding your suggestion to use two short hose sections on the ends, is this just to make it easier to form the tubing? Or is it easier to deal with sealing problems when it's just a rubber hose making the actual connection? Or does it protect against vibrations somehow? Thanks!

If it has a Holley, you can also get filters that screw into the inlet, as used on 390/428 Mustangs.

It's an Edelbrock 750CFM with a manual choke. I had the option of using a Holly for a little more cash but I heard that they're a little more touchy and difficult to keep tuned than the Edelbrock. I also heard that they have better throttle response and top end, but I figured I'd be happy enough with the "stock" setup. Good tip though!

CDHerman, your suggestion on replacing the fuel pump with a canister model is probably a good one, but I couldn't bear to pull off a brand new part! I do like the idea of a larger filter though; RobbMc makes a large model of their filter that I could install.

Thanks very much for all the excellent and experienced replies folks!
-Robroy

[Dragon]

Hey Robert! This might be what I'll wind up doing. I'm really curious though--if the AN fittings are extra work to adapt to regular cars/trucks, why has RobbMc made them? And why hasn't he made the nipple fittings?

Probably because he got the Aircraft style filter housings from an aircraft supply house. You don't have to use AN fittings with those filters anyway just MIP x SLIP 3/8 x 3/8

Incidentally, is that a rubber line all the way up to the Carb? If so I don't like that AT ALL. My advice is to bend a steel tube all the way up to the Carb, and connect it with two short pieces of high quality rubber hose (which you check and replace often) and the filter.

Even us Ford techs replaced the metal lines. Metal lines crack because they are free floating from the pump to the carb. Yes they look good but besides weight no racer would use them because of the cracking at the fittings.

Regarding your suggestion to use two short hose sections on the ends, is this just to make it easier to form the tubing? Or is it easier to deal with sealing problems when it's just a rubber hose making the actual connection? Or does it protect against vibrations somehow?

That is what it does. Stops the ends from cracking. Plus most people cannot flare the ends at home to fit the inverted flare that is inside the carb and on the metal fitting that comes with the metal tube pump fitting.

[cdherman]

Take the current new pump off and sell it on ebay or in the for sale section. It won't go wasted and the difference in prices is likely to be a lot less than the RobbMc setup, plus you'll not have a bunch of new sittings and connections to deal with (and possible leak.

Just my $0.02

[Dragon]

I have the canister pump and 2 inline filters. One inline is under the truck and is huge as the mechanical pump is not designed to suck. The canister is then followed by a clear housing inline filter so I can look for junk and water.

[sideoilerfe]

I never suggested all rubber lines. The stock pump only costs $24 not $60. I just suggested another inline before the carb because you'd have to connect the line to the carb with a small piece of rubber hose anyway so why not put a filter there. I personally like the canister filter in the pump and an inline before the pump. Easy and inexpensive.

[sideoilerfe]

Even us Ford techs replaced the metal lines. Metal lines crack because they are free floating from the pump to the carb. Yes they look good but besides weight no racer would use them because of the cracking at the fittings.

I've never had a metal line crack. Besides, "free floating" The metal line screws into the fuel pump on one end and screws into the carb on the other (unless you have an Edelbrock or Holley then a short rubber piece is needed to make the connection).

[Dragon]

Free floating means it is not supported along it's length. An example in an aircraft hydraulic and fuels lines, they are tied to every other frame to prevent cracking. That works out to every 24 inches the more bends the more clamps. Run the Baja 500 or 1000 and you will see no solid metal lines for fuel and sometimes even for brakes.. Braided flex lines sure.

[sideoilerfe]

Free floating means it is not supported along it's length. An example in an aircraft hydraulic and fuels lines, they are tied to every other frame to prevent cracking. That works out to every 24 inches the more bends the more clamps. Run the Baja 500 or 1000 and you will see no solid metal lines for fuel and sometimes even for brakes.. Braided flex lines sure.

Oh, I misunderstood you. I apologize.