GF432 fuel filter (and fuel pump)

[Mark J.]

I just bought a GF432 fuel filter for my 68 L36. There is currently no inline fuel filter. The filter came in a box labeled GF432. The filter itself has AC and the numbers 982 334 in black lettering (no red letters, no GF432 on the filter). The body (excluding fittings) is 2 3/4 inches long. It has the 2 lines out the top, and one at the bottom. On the bottom is etched, " MADE IN USA" FL 11, AND "OUTLET". That last part is very confusing! so, 1. Have I described the correct filter? My fuel return line is currently capped off. 2. Is it possible to install this filter and cap off the return line on the filter, or will that interfere with the functioning of the filter or otherwise create a hazardous situation?

I replaced the fuel pump. The fuel pump that came off the car has AC stamped on it, and the number 206Z40482. Any idea what this fuel pump was original to? Last 5 digits match the L88 fuel pump # from judging manual but I sure don't have an L88!

Final question. Judging manual states that cars equipped with add on external filters that should not be there should be discouraged for safety reasons. I assume it is the Holley equipped cars that have no inline filter. What is the safety hazard of adding an inline fuel filter to those cars?

Thanks, Mark Jackson

[Joe L.]

Re: GF432 fuel filter (and fuel pump)

Mark-----

The GF-432 filter which you have described sounds generally correct to me, although I don't have one here in the office to confirm your dimensions. With respect to the lettering on the filter, the current GM service replacement part, GM #5651480, may very well differ in that respect to original filters.

Your filter should have identical threaded female fittings permanently welded to the center of each end of the cannister. On one end of the cannister, which is the top in the as-installed position, should be a small, nipple-type fitting. The filter assembly mounts vertically in a bracket attached to the smog pump mounting bracket. A pre-bent, steel fuel line with threaded male fittings at each end connects the filter to the fuel pump and another, differently configured steel fuel line with identical threaded male fittings connects the fuel filter to the carburetor. I do not understand why the filter that you have would be embossed "outlet" on the bottom (or inlet) side of the cannister. For this filter, the end opposite the end with the small "nipple" connector is the inlet side.

The fuel filter nipple is connected via a short section of rubber fuel line to a small diameter section of steel fuel line which has a u-shaped bend at the top and connects via another short length of rubber fuel line to the car's fuel return line near the fuel pump's inlet line.

All of the steel fuel lines and GF-432 bracket are avilable in reproduction. If you wish to use the GF-432 filter and are missing any or all of these parts, I suggest that you obtain them before trying to mount the filter.

Also, I strongly suggest maintaining the fuel return line in its factory-original function and configuration. This system is designed to help alleviate vapor lock conditions and is engineered for use with a QuadraJet carburetor fuel system. GM engineers did not put it on the car because things would have worked just as well without it.

Fuel pump AC type 40482, GM #6416741, which is what you apparently have, is the correct SERVICE fuel pump for ALL 68-69 Corvette 427 applications, including L-88, L-68, L-71, and L-36.

With respect to you last question, understand that any fuel system modification, including the addition of in-line fuel filters to applications not originally so-equipped, represents a NON-ENGINEERED installation which has an inherent safety risk.

[Jeffrey S.]

Re: GF432 fuel filter (and fuel pump)

Mark: I can't tell you what you did describe but I can tell you that a GF432 filter is silver and has "GF432" written inred on it. There is one very good reason to re-connect the return line to the filter aside from the original "clean air" use of the line. That is that the return line will help prevent "heat soak" and vapor lock on a hot day. I have seen some big block Chevelles that never came with vapor return lines install them for this reason. My friends 69 small block had a chronic vapor lock problem until I re-connected his line and the problem was solved. Did you buy this filter from a reputable source? Eas it sold to you as a new, correct part? Seems awfully strange.

I'm sorry that I can't shed any light on the fuel pump questions. Hope this has been helpful

Jeff

[Mark J.]

Re: GF432 fuel filter (and fuel pump)

Joe and Jeff, Thank you very much for your responses. My fuel return line needs a little work (maybe replacing) before I can reattach it. I also don't have a smog pump to attach a bracket to. The filter I have has all the correct female parts, and I have asked Mr.Goodwrench (on the GM AC Delco website) if the one I have is the current GM service replacement.

[Jeffrey S.]

Re: GF432 fuel filter (and fuel pump)

Mark: First, I don't know what you have. If someone was to take the trouble of sending a counterfeit it would at least look like the original. Perhaps someone accidently switched some other application part with GF432 and didn't check what was in the box before sending it. I certainly would not install this part. Real Gf432's are readily available from reputable people like Paragon, Corvette Central, etc. Second- you don' need the smog pump to mount the filter bracket securely. You do need the smog bracket (casting) which bolts to the engine. However, since the lines from the fuel pump to the filter and from the filter to the carb are hard lines you might not need anything else.It's your call. It would be safest to have the filter firmly attached to the engine.

[motorman]

Re: GF432 fuel filter (and fuel pump)

blocking off the return line will cause a increase in fuel pump pressure and this will cause carb flooding under some conditions. on fuel pumps with a return line to the tank you can increase the fuel pressure by blocking off the return line. this is a trick to use when you pump gets weak,you just block off the return line and you can drive on you merry way.