I am thinking about putting an inline filter by the tank on my 72. I am currently doing a frame off and while it is easy to get to it now, will I still have access to change it later once the exhaust and spare are back in place?

 

Yes, but you need to keep it close to the rear frame rail, close to the pick-up/sending unit. You may need to drop the spare to replace it, no biggie...

 

If you are using a mechanical fuel pump, I wouldn't put a fuel filter before it. The pump will not have the suction to pull enough gas through the filter.

 

I saw in the September issue of Corvette Fever in the article on 3x2's they recommended putting an inline filter by the tank. I was more nervous on getting to it if I ever needed to change it. Never thought about not enough pump suction. Any other thoughts on this?

 

IMO, the fuel filter will fill by gravity..Suction not really needed. If you had it mounted above the fuel level, I guess it could be a restriction.....

 

Thank you....

 

A fuel filter near the tank will add some restriction to the inlet of the fuel pump whether it is located above or below the tank's fuel level.

There is little restriction when a fuel filter is new. If you have a new or clean tank the filter should not clog up for years. You will just need to be watchful if your fuel pressure drops since the inline suction filter will look similar to a shot or weak fuel pump.

 

Yes, I can see the reasoning on a filter at the tank on tri-power vettes, as I have a 435- 69, and I dread changing the in-carb bronze filters if they were to plug up..a real PITA! If you have room for a filter after the pump, (at the carb perhaps),it is better there, and much easier to service.

 

The tripower car article is probably because they are rare, and assuming the individual wants to maintain an oem appearance under the hood. If this isnt a concern, I would definately do it conventional and put it between the pump and carb. Depending on where you put it, it could still be kept out of sight down by the oil filter, or up top where its easy to see. Just remember, when a filter after the tank gets clogged, you are out of gas. The pump starves and you're dead. The stock Qjet filters, as crummy as they are, are still designed to bypass in the event of a clog via the spring, and at least limp you home.

 

I have been leaning towards going with the Holley 4150. If I go that route, are the two bronze fuel filters that are in the carb sufficient or should I have a second inline filter also? If I go with just the bronze filters, will that filter 99% of the impurities out?

 

Even with the inline bronze filters in the carb I've always read that you should still have another filter. Those are a last resort. Lars has a good writeup on building a hard fuel line that goes from the pump to the carb with an addition of an inline fuel filter between the two.

-dath

 

I'd say no. The paper ones are supposed to catch more then the bronze but they are adaquate for final filtering when used with a larger filter. I'd put a good quality inline before the carb. I had another car that I had a Holley 4150 on, and did exactly what was mentioned above. I constructed a nice hard (aluminum) fuel line with blue Earls fittings and added a matching blue anodized inline fuel filter in it with a small fuel pressure gauge so you could see when it was getting dirty. I liked this better than those "see through" type because they tend to leak. Plus it just looked cool. Easy job. I'd go this route since your going with a non oem setup anyhow.

 

If your going to add a filter place it where you can get to it without dissembling the car. The fuel line should attach to the frame rail at some point so try a location around this area. Clear of mufflers and other blocking objects. You can place it anywhere convenient where you can get to it. This is important. You have to be able to get to it to change it. Its actual location with a mechanical pump is not important.
Mechanicals suck and electics pumps push. A mechanical pump can easily suck through a filter.
If your not sure where to put it with the frame off do it last. It should be just as easy to install it as it is to replace it.

On mine the sender/feed tube are on the bottom right so thats where I put the filter first and then the electric pump.

 

i have been running an inline fuel filter on my 72' lt-1 for years with no problem. i have it mounted on the inside of the right side frame rail, but then i am also running the off road side exhaust so access is no problem. i change it every spring.

 

I agree. I installed one in my '73 many years ago on the rubber hose that goes from the bottom of the tank to the right frame rail. There is a clamp on the rear crossmember that holds this hose up in the crossmember just before it kicks up and runs down the right frame rail. I installed a small glass filter with the replaceable insert in the hose between the tank and the clamp. It keeps everything tucked up tight and is easily accessable without removing anything.

Well almost anything, I do unbolt the clamp to make it easier to service the filter a couple of times a year. The nice thing about the glass filter is you can see if there is any debris in the filter and even see water should any get in there.

GUSTO

 

hey gusto, you a helo jockey in the corps?

 

Sleazy Rider...

For twenty years... then ten more in King Airs... but that was in another life... Now I get to play with the V-22 boys...

GUSTO

 

semper fi that was the only thing i liked about the corps, being a member of an air crew and flying. when i got back from nam, i got a back seat license for an f4. those planes will rock your boat
i can only imagine a v-22

 

Don't put a fuel filter on the suction side of the fuel pump, i.e. at the tank. This will cause you nothing but problems.

The mechanical diaphragm pump is not a positive displacement pump, and it has poor suction capability. If it is exposed to vapor instead of liquid, output pressure immediately drops to zero. When you put a filter between the tank and the pump, you create a pressure drop across the filter - not so much when the filter is brand new, but once the filter has seen some service. With this pressure drop, you see a lower line pressure on the suction side of the fuel system. With modern fuels, the vapor pressure is very high, and your lowered line pressure on the suction side will induce voporization of the fuel in the suction line, especially when travelling up-hill on a hot day or at WOT when fuel delivery requirement is high.

If you intend to retain your mechanical pump, install the filter between the pump and the carb (that's why GM did it that way). If you really need to install a filter between the tank and the pump, you might want to consider use of a small electric boost pump at the tank to keep the filter pressurized and eliminate the suction side problem (notice that the GM-installed filters located in the frame rail between the tank and the engine are used only on fuel injected cars that have a tank-mounted pump, keeping the fuel filter pressurized).

I've seen a lot of problems caused by suction-side fuel filters. I suggest you not do it...

 

You make a lot of valid points lars and I would agree with the benefits of using a small electric pump in the rear to preclude fuel delivery problems. I did however run this setup for many years with no problems, others may not be so lucky.

On the other hand, because my '73 sits for weeks at a time without being started, I found myself having to crank the engine excessively to get it started whenever I wanted to use it. As a result, I did recently install an electric pump near the tank that has done a good job of eliminating the cranking problem... it may also prevent me from having the problem you mention above in the future as well.

Thanks... GUSTO