ptroxx

I Was wondering if its better to not put the org fuel filter back in my quad jet, and install an inline fuel filter.. This was suggested to me by someone and was wondering what everyones thoughts are...???

And if inline is better what is a good place to install it ?

Thanks..

HamadUP

markdtn

Have to wait for Lars to come back to get a good answer, but I'm pretty sure I have read from him that the one in the carb is important. Maybe for the anti-backflow valve?

Glassbowtie77

Also I read somewhere that if you were God forbid in an accident and the car was to overturn it will shut the gas flow to the motor off and prevent a fire or an explosion. Another good reason to go with the filter in the carb in my opinion is that you don't cut the 1 piece steel fuel line from the pump to the carb and put rubber hoses and a filter in there which has been known to be a potential fire hazard on these cars.

jamesd2

My 73 had an in line fuel filter mod when i bought it, and when I sent my Q-Jet to Lars for a rebuild, he stressed the importance of returning the filter to its original inside carb location. Thats all I needed to hear..............................

70Yellowbird

I've seen quite a few in-line filters in engine pics on this Forum ... I assume they are using both the carb filter and an in-line. That's what I have on mine.

skipinhouston

It has been my experience that in addition to the filter at or in the carb, you should put an in line filter in front of the fuel pump and as close to the fuel tank as possible, especially if you have an electric pump.
Now, with so many problems arising from ethanol in the fuel, it's more important that ever before.
Just my opinion.
Skip in Houston

skipinhouston

Duplicate post. Sorry.
Skip

ptroxx

Thanks for all the posts everyone...... Yeah I was told to not run the carb filter at all... saying it restrics the carb and to just run a inline filter...This really didnt sound right to me.. seem like they wouldnt have put the filter in that location if it didnt work...

Thanks again everyone...

lars

Just a few comments and facts on the subject of fuel filters... most of this has been discussed and debated here on the Forum on a few occasions, and there are some differing opinions. But the following are a few facts on the subject:

• GM used in-carb filters on the Q-Jet and on many of the the factory-installed Holley carbs. The in-carb filter actually flows pretty good, and will easily meet the flow demands of a high performance engine. If you're putting out less than 500hp, the in-carb filter is not restricting your performance unless it is defective. Due to its small size, it's a good idea to change the filter at regular intervals to assure free-flowing performance.
  
• Due to the needle/seat assembly in the Q-Jet being placed in the bottom of the float bowl (Holley and AFB carbs have the assemblies in the top of the carb), it is possible for fuel to drain back through the needle/seat after engine shutdown and empty the float bowl. By using an in-carb filter with a checkvalve (NAPA part number 23051 for the pre-'75 short filter and 23052 for the 75+ long filter), you can keep the fuel from draining out of the bowl.
  
• The GM intended purpose of these checkvalve filters was for vehicle roll-over fuel spill protection - it was a safety feature that has some questionable merits, but there was a saftey reason for the in-carb filters...
  
• An in-carb filter allows the use of a one-piece all-metal line between the pump and the carb. Having an all-steel line with no splices on the pressure side of the fuel systemn is a huge safety advantage.
  
• Running 2 filters serves little or no purpose. Run one or the other, but skip the 2-filter idea - it has no merit.
  
• All of the automakers, whether they had in-carb filters or in-line filters, always placed their filters on the pressure side of the pump - never on the suction side. The reason is that the mechanical diaphragm pumps do not "suck" well, and any restriction on the suction side will adversely impact fuel pump performance (both pressure and volume capability). Also, a restriction on the suction side of the fuel system greatly increases the probability of vapor lock on hot days due to the low pressure being applied to the suction line (this causes the hot fuel to vaporize in the line, giving the pump a slug of fuel vapor and terminating its output). Even today, with the advent of high pressure electric pumps for fuel injection systems, the automakers install the filters on the pressure side of the system (the pump is in the tank, and the filter is usually installed someplace along the frame rail between the pump and the engine). Both our old carbureted cars and the new injected cars have a suction side screen: There is a pickup "sock" in the tank to eliminate the big chunks that could hurt the pump, so any additional suction side filter is not required.
  
• If you run a good electric pump back near the tank, you can successfully use a high-flow, high performance filter between the pump and the tank. The good electric pumps are positive displacement vane pumps, and will pull fuel through a filter on the suction side without problem. The stock mechanical pumps do not share this design feature.
  
• Little-known fact: The stock paper and bronze in-carb filters will stop and prevent sugar from entering the carb.... If someone puts sugar in your gas tank, the stock Q-Jet inlet filter will plug up solid from the sugar, but it will not allow the sugar to pass into the carb or into the engine. Most in-line aftermarket filters are screen-type filters, and they will allow the gas/sugar mixt to pass through.
  
• Most people install in-line filters using sections of rubber hose. Rubber hose on the pressure side of a fuel system is simply a bad idea, and countless collector cars have burned to the ground as a result of rubber line on the pressure side of the system. If you elect, for whatever reason, to install an in-line filter, be sure to use all metal line components and screw-on connections. Photo below shows an in-line filter system I built and installed betwen the pump and the carb using all metal connections on a custom engine setup. Such a system is not necessary on a stock engine:

So whichever route you take, keep the filter on the pressure side and do good workmanship to keep your installation safe and reliable. The factory in-carb system is safe and reliable...
Lars

ptroxx

Thanks for all the input on this issue..

sweethence

samer here, stock in line set up with filter in carb

CheezMoe

I recommend to read Lars' words of wisdom and heed them! One filter and no rubber on pressure side! I run the in-carb filter w/ check valve on my Q-Jet with a solid steel supply line.

Allen_396

On a similar subject, I replaced the inline fuel filter on my '69 and the bracket doesn't fit around the new one. The new filters must be a larger diameter. Is there a replacement bracket/clamp that fits these?

RunningMan373

Of course I tend to agree with Lars, seeing as if the set-up isn't done carefully, you could wind up going to a barbeque, with you car as the main course, but I believe that if done correctly, and if you watch the condition of the hoses and seal them well and strongly, you will not have a problem. I would like to convert my current set up to a all steel one, but to do it you would need a flare tool and a bender, which I currently don't have, so I am satisfied with this work i just completed yesterday. Note the STEEL filter and the carefull securing and routing of the lines, away from any hot surfaces OR moving parts/belts, and the clamps and not too tight, but installed with a good pinch. The fuel line was cut back a while ago, as it was badly twisted at the carb, as i've seen most of them are at this point, just the twist was cut off at this point. I then re-Removed it, flushed it out with water, then recut it to just below the last curve, filed it smooth, removeing all burs and sand paper cleaned the tube outside body in a circular patern, where i intended to install the line. You want any grooves running around the tube, not along it. re-flushed it with hot water to remove the metal dust, Then installed the flexy about 3" onto it, and put on two screw type hose clamps, torque to just till the rubber wants to come through the groves, but doesn't. Installed a fitting in the carb to replace the line from the local autorama fitting tree, it has 4 stepped bevels on it's line side, 3/8" line, it will not come off of it w/o cutting.This is critical, if useing rubber lines on the engine, it must be done near perfect. Then installed the filter, which has 3/8" lines. pics-

lars

You don't have to buy all the tools if you don't have them: You have a stock carb on a stock setup, and the correct, factory, steel line is available for only $20...