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914World.com _ 914World Garage _ Is the PRE fuel filter necessary?

Posted by: Steve Pratel Apr 26 2015, 07:25 AM

I'm about ready to wrap up the under carriage of my project, and take it off the jack stands, and have a bit of a quandary as I put my fuel system supply together.

I've already replaced the fuel lines front and rear, new filter in the rear, and installed the new fuel tank.

The last piece of the puzzle is to attach the fuel pump, but there is a REAL mismatch in the sizes of the nipple on the tank and fuel pump. The fuel outlet on the tank is about 12mm (1/2 inch) and the nipple on the CB performance low pressure fuel pump is about 7mm (1/4"). I made up a barbed fitting, but is now too long to fit comfortably and the fuel pump is pushed off to the side rather than center of the front suspension cross member.

I know these tanks have a decent fuel screen/sock in the tank, and as this tank is super clean inside, am thinking about eliminating the pre filter. The barbed fitting is just about as long as the filter, and will fit perfectly.

Can this pre (in pic) filter be eliminated and run the normal just before the carbs?

Attached image(s)

Posted by: rhodyguy Apr 26 2015, 04:59 PM

I tossed the metal filter. Then the fittings on the pump will be the same on both ends. You can then use a common sized fuel line and a fi filter with the same nipples. The cap'n suggests a bmw filter but I don't remember what the part# is. I take it you have carbs. OOOPS double post.

Posted by: SirAndy Apr 26 2015, 05:48 PM

No filter before the pump is a BAD idea but as Kevin suggested, you can use a filter that has different sized fittings.

When i had my carbed 2056 i used that exact same CB pump and filter and i don't recall having any fitment issues.

However, i mounted it in the stock rear location, maybe that is why it fit for me.

Posted by: rhodyguy Apr 26 2015, 06:00 PM

sorry, i meant to imply the common nipple filter would be upstream of the pump. in my car the single tank outlet, ss tunnel line, filter, pump and carb fittings all accept the same sized fuel line.

Posted by: Steve Pratel Apr 26 2015, 07:15 PM

The issue is the size of the fuel outlet on the tank, it is almost 1/2" about 13mm. The nipples on the rest of the fuel system all to the carbs are the standard 7mm.

When I first saw the filter, I thought is was on the outlet of the pump, but I was surprised to see it is on the inlet side. The fitment issue is this is going on a 912E (basically a 76 911 with a 914 engine)

Posted by: Andyrew Apr 27 2015, 10:40 AM

I typically have had just the pre filter. I have had issues with running multiple filters, but thats on my v8..

Unless your running a carb, I would not even consider no filter. With a carb I would still run a filter... Just think in 5 years when your tank starts to rust a little bit..

Posted by: rhodyguy Apr 27 2015, 11:05 AM

when it's time to change the filter that comes attached to the pump, the pinched clamps make replacing the filter a pain. if you're going to use the metal filter swap the clamps out for some shouldered ones before the install. easier than lying on your back with the fuel left behind dribbling down on you.