I'm curious if most folks are running with the original 1/4" gas tank fitting. I am, but since I converted to fuel injection, I wondered if I should upgrade to one of the larger #6AN fittings. I suspect not (1776 cc), but I was wondering what some of our larger engine or Subie conversion folks had done.
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I'm not 100% sure, but I think the stock 1/4" line will support darn close to 200 hp.
I know it will support up to at least 150. I did some research, but I don't remember the numbers. My car has a 5/16" line, which is good over 200hp, so I'm in the clear. I'm just going to add another 5/16" line, and adapt to 6AN on either end to the pump, rails, and regulator. It would be nice to keep it all the same size throughout, but it's really not necessary.
AN-6 is 6/16" or 3/8" which will support over 400 hp. Overkill for anybody unless they have some kind of a turbo/boosted setup. So overkill for any NA 4 or even 6 cylinder.
Check the ID of the tank inlet, it may require drilling out to make it bigger(and make all that larger fuel line worth changing).
Thanks so much, Danny. There's little that you don't know!
In drag racing the stock fuel pump and lines will get a car down deep into the 12's, but this is in part because 48 IDA's have such large float bowls; this isn't necessarily the case with 48 IDF's or Dellortos (which don't have the same storage capacity). Glenn Ring's high 12 second, Berg 5 equipped '74(?) Beetle (180? 190? hp 2180- FK8, 42x37 heads, IDA's, 1 5/8" exhaust but stock fuel pump/lines) drains the float bowls just shifting into 5th gear (well over 100- 110? mph) when running wide open from a standing start. A half second wait, the bowls have gas and he's going again, but the cure is a larger fuel line (and probably a higher volume pump).
I don't know at what point with larger IDF's or Del's the pump and line need to be upgraded (160? 170? 180 hp?- I expect it's less than with the IDA's because of the smaller float bowl volume) but if I talk to someone I think knows any time soon I'll post what I find out. Al
I talked to someone last night- IDA's don't have bigger float bowls than IDF's or Dellortos (sorry for the misinformation) and that all 3 carbs have roughly the same limits. First upgrade should be to increase fuel line size to type 3 (7mm/5/16"); for a lot of street cars this cures fuel delivery problems.
This chart is from Summit racing:
| Recommended Fuel Line Size (from the tank to the pump) | ||
| Engine Output | Size (inches) | Size (AN) |
| 350 hp or less | 5/16 in. | -5 |
| 350-450 hp | 3/8 in. | -6 |
| 450-650 hp | 1/2 in. | -8 |
| 650-1,000 hp | 5/8 in. | -10 |
So, like I said before, 5/16" is plenty for just about any 4 cylinder application.
I think it's weird that fuel lines are sized according to OD, but the wall thickness is taken into account.
AN lines are usually just available in even numbered lines though, so that's why the 6AN size rather than 5AN.
Mike, I believe in what Einstein said about knowing where to look things up rather than keeping it all in your head......I don't really know that much, I just look it up.
Great information, everyone! I'm going to declare the stock gas tank fitting adequate for my modest 1776. I don't even want to think about what this car would be like if I changed the fuel pump inlet to 6AN and suddenly had 350HP. Great Caesars Ghost!
"I believe in what Einstein said about knowing where to look things up rather than keeping it all in your head......I don't really know that much, I just look it up."
I don't know, either. I just listen to Harry:
Stock fuel tank outlet on Bridget feeds the F-150 fuel pump to the Subie 2.2 no problem. As long as I don't toss anything in the tank that will slide over it.
