# Fuel filter question



## RMTZ67 (Mar 12, 2011)

So I don't know how restrictive oem quadrajet fuel filters are, but I think its a interesting discussion. So please chime in with your views. I prefer a clean hardline to my carb so I am limited on my options. While doing a search it seems chevelles had this filter. I notice the hard female fittings which intrigue me. But what's got me confused is the return line on the up side. What gives?


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## Lemans guy (Oct 14, 2014)

I had a filter like this on my Lemans, the small line if a return line to the fuel tank to prevent vapor lock. Pontiac used this system, but then went to a fuel pump that had a return line connection. Either one works.

I now turn a hard line return off the fuel log at the carb, not stock, that foes back to the tank, like having a fuel regulator. If the fuel never dead heads it won’t vapor lock from heat.

You must have a return line to the tank and a sender that has the fitting to accept it in the tank.


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## RMTZ67 (Mar 12, 2011)

Mine does have a return line. So these filters are meant for non return line fuel pumps? Do you think factory fuel filters are restrictive? Or only if you have a engine above a certain hp.


Lemans guy said:


> I had a filter like this on my Lemans, the small line if a return line to the fuel tank to prevent vapor lock. Pontiac used this system, but then went to a fuel pump that had a return line connection. Either one works.
> 
> I now turn a hard line return off the fuel log at the carb, not stock, that foes back to the tank, like having a fuel regulator. If the fuel never dead heads it won’t vapor lock from heat.
> 
> You must have a return line to the tank and a sender that has the fitting to accept it in the tank.


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## Lemans guy (Oct 14, 2014)

They used the return line filters on all cars with AC because the condenser dumps lots of hot air in the engine compartment, AC cars also got 4 row radiators, seven blade cooling fans and the fuel return line. These are all great cooling features and work to keep any engine and fuel system cool and not vapor lock.

so originally your factory car if it was without AC did not have a return line to the fuel tank. If it did in 66 it had this filter and it was 67 I believe when they made the return line come from the fuel pump, again on cars that had a return line.


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## Lemans guy (Oct 14, 2014)

If you have a 67 and a return line it is likely at the fuel pump returning to the tank. If so you don’t want another return, it would mess it up. You just want one return line. It is somewhere between the pump and the carb.....on 67 it was in the pump and returned to the tank, but it is on the carb side of the pump. It has a smalll orifice same as that filter like an 060, it does return liquid not vapor but in a small amount, just enough to keep the fuel constantly moving so it does not vapor lock.


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## Lemans guy (Oct 14, 2014)

Sorry yes, that filter was meant for fuel pumps that had no return line, but the car did and it returned from the fuel filter.


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## O52 (Jan 27, 2019)

As an FYI and to really confuse the subject, my 68 has a return line from the pump. No A/C, stock 350 HP 400. Maybe by 68 the return line was standard on all higher HP engines in addition to the A/C cars. 
Waiting for the rebuttal... LOL


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## RMTZ67 (Mar 12, 2011)

My 67 already had a return on pump and tank and had correct drive train still in it W/ no ac. Anybody have a opinion on how restrictive if any, a stock fuel filter is? I thought I read something from Geetoguy where he said something to the like of getting rid of them. Hope I did not misquote him. If so my apologies.


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## O52 (Jan 27, 2019)

I've never had any problem with them on my BB El Camino. And to the best of my failing memory I don't recall any problem with the in carb paper filter on my GTO back in the day. 
With that being said I'll be installing an inline canister filter at the fuel tank when the restoration gets to that point. I prefer not having to R/R the QJ fuel filter nut any more than I have to.


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## Lemans guy (Oct 14, 2014)

They put them on AC cars for sure, but like 052 said maybe other higher HP cars or on later versions.....Bottom line is a return line is good for cooling...


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## Lemans guy (Oct 14, 2014)

I use a fuel lab stainless steel mesh filter between the fuel pump and Quick Fuel Carb......

cleanable washable mesh, not stock, but works super.


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## Montreux (Mar 8, 2009)

I think it was a 1967 mid-year change from three-port filter to three-port fuel pump.


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## Montreux (Mar 8, 2009)

Today’s fuels leave a dusty tan residue when the fuel gets old and evaporates. This residue is as fine as talcum powder and will quickly clog the small paper filter built into the inlet fitting of a Q-jet. When you finally find the right filter (ask the old guy behind the counter), buy several. There cheap, but a PITA to find! Somehow they don’t show up in the computers at the parts houses.


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## lust4speed (Jul 5, 2019)

Never had a problem that I knew of with the sintered bronze Quadrajet filter until I dropped in a warmed up 455 and the car would nose over at the top of 2nd. Removed the small filter and ran an in-line filter and the problem went away. The 455 was just more thirsty than the stock 335 horse 400 it replaced.


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## RMTZ67 (Mar 12, 2011)

lust4speed said:


> Never had a problem that I knew of with the sintered bronze Quadrajet filter until I dropped in a warmed up 455 and the car would nose over at the top of 2nd. Removed the small filter and ran an in-line filter and the problem went away. The 455 was just more thirsty than the stock 335 horse 400 it replaced.


I had a bog at the top of second even with a new filter. I guess I should have tried it w/o...anyway I bought a high flow needle and seat and a accelerator pump from cliff Ruggles an the bog is gone but now I am getting what I will call a flutter. Kinda like va va va voom.lol So I am trying to figure out the solution. I also raised the float 1/8 from specs.


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## Montreux (Mar 8, 2009)

How much gas do you have in the tank? New car reviews (back in the day) found out that if you have 1/4 tank or less, all the fuel runs to the back of the tank under hard acceleration, and the fuel pump starts sucking air. The fuel in the carb will get you about to the top of second gear. Then the motor lays down. A well-known and oft-forgotten problem. 

Holley is selling a fuel pickup “rug” that replaces the sock on the end of the fuel pickup. They claim it will solve this problem, and deliver fuel if any part of the rug/mat is touching fuel. 

It’s a little pricey, and I haven’t tried it yet. But I have seen a convincing demonstration at a car show.


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## RMTZ67 (Mar 12, 2011)

Montreux said:


> How much gas do you have in the tank? New car reviews (back in the day) found out that if you have 1/4 tank or less, all the fuel runs to the back of the tank under hard acceleration, and the fuel pump starts sucking air. The fuel in the carb will get you about to the top of second gear. Then the motor lays down. A well-known and oft-forgotten problem.
> 
> Holley is selling a fuel pickup “rug” that replaces the sock on the end of the fuel pickup. They claim it will solve this problem, and deliver fuel if any part of the rug/mat is touching fuel.
> 
> It’s a little pricey, and I haven’t tried it yet. But I have seen a convincing demonstration at a car show.


I will have to double check that next time I take it out. I used to have a bog after shifting to second at wot. I installed a high flow needle and seat and a accelerator pump per Cliff Ruggles, and raised my float 1/8" ... it removed my bog but now I have a slight flutter. Kinda like va va va voom...for lack of a better description. If I can clear that up it will be the perfect beast lol.


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## BearGFR (Aug 25, 2008)

I run two of these (the large ones). One just after the tank, the second just before the carb.
RobbMcPerformance Fuel Filters
100 micron at the tank, 40 micron before the carb.

Bear


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## lust4speed (Jul 5, 2019)

Uncovering the fuel pickup is a problem on to itself, but if you have half a tank or more of fuel and are experiencing the dropout or softness at the top of second, then it is a fuel delivery problem. A mechanical fuel pump can only suck so much fuel through a 5/16" line, and the bad part is you can be loosing horsepower but it doesn't get bad enough to really let you know. The flutter could be the clue that you are still right on the line of running the bowl out of fuel. Everything you did is a step in the right direction and helped, but you might have to continue chasing the problem.

The fuel starvation is accumulative and each separate minor restriction adds up. Start back at the fuel sock in the tank and check what shape it's in. Any porosity in the fuel hoses back at the tank will allow air to be sucked in the line, and any kinks will severely restrict flow. The fuel pump itself might not be functioning at 100%. You did the right thing with the larger needle valve in the carb, but it's only a start. Reducing each bottleneck is the only solution as long as you keep the mechanical pump and small line.

Fuel filters themselves cause restrictions so you have to be careful stacking them up. If an inline filter is added at the carb, then the carb filter should be removed. If a 100 micron filter is added back at the tank, then the sock is usually removed. Depending on horsepower which pretty much determines fuel consumption, there is a point where even a RobMc pump won't suck hard enough to deliver enough fuel. As fuel needs rise most of us just take the easy way out and go to a healthy electric pusher pump back at the tank because it's a lot easier to push fuel than suck it. Negatives are noise, relatively short life of the pumps, and the continually escalating cost of the new electric pumps.

BearGFR had a good point with the size and location of the filters. On the vacuum side of the pump you basically just want a large screen with minimal resistance and the 100 micron has the larger screen. It is necessary for an electric pump and possibly a little overkill for a mechanical, and a new sock over the inlet in the tank is hard to beat. The 40 micron up front after the pump works well and filters much smaller particles. The big filter is just a little hard to blend in if you are going for a stock or near-stock look in the engine compartment.


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## PontiacJim (Dec 29, 2012)

RMTZ67 said:


> I had a bog at the top of second even with a new filter. I guess I should have tried it w/o...anyway I bought a high flow needle and seat and a accelerator pump from cliff Ruggles an the bog is gone but now I am getting what I will call a flutter. Kinda like va va va voom.lol So I am trying to figure out the solution. I also raised the float 1/8 from specs.


Fuel pump may be simply going bad on you, so don't discount that.


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## RMTZ67 (Mar 12, 2011)

PontiacJim said:


> Fuel pump may be simply going bad on you, so don't discount that.


Its about 8 months old (Carter) but was looking to buy another just to be sure. If not...got a xtra.


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## PontiacJim (Dec 29, 2012)

RMTZ67 said:


> Its about 8 months old (Carter) but was looking to buy another just to be sure. If not...got a xtra.



OK, read on another post somewhere that the fuel issue was solved once a new pump was installed. Stuff goes bad, even fairly new. Rock Auto could be a good source for an inexpensive pump should you just want to purchase a back-up to have if the extra pump gets used. Some things I just like to have an extra on hand and on the shelf. 

Flutter could also be an ignition problem - ie too much advance coming it from the vacuum advance. Maybe plug it up and try without it just to see if it changes anything.

Make sure your choke is not "fluttering" or oscillating open and closed at the higher RPM's when the engine is sucking hard on the carb. And, I would check the secondary air flap for the same thing - too loose and fluttering.

Undo the gas cap just to make sure it is not a plugged up vent issue of some kind and you are creating a vacuum within the gas tank and can't suck the amount of gas needed.

One of the modifications I used to do to the Q-jets is to open up the fuel wells for the secondaries. It was a modification shown in one of the pamphlets I had on blueprinting the Q-jets. There are these tiny holes that are fed by the main bowl that fill the small fuel wells for the secondaries. The secondaries can drain them faster than those tiny holes cans fill them up - so the carb would lean out and you get a surging as they fill/empty/fill/empty etc.. The recommendation was to drill them slightly larger to 1/16" to provide adequate fuel supply. I always did this on any Q-jet I rebuilt for myself and never had any issues - just a thought.


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## RMTZ67 (Mar 12, 2011)

PontiacJim said:


> OK, read on another post somewhere that the fuel issue was solved once a new pump was installed. Stuff goes bad, even fairly new. Rock Auto could be a good source for an inexpensive pump should you just want to purchase a back-up to have if the extra pump gets used. Some things I just like to have an extra on hand and on the shelf.
> 
> Flutter could also be an ignition problem - ie too much advance coming it from the vacuum advance. Maybe plug it up and try without it just to see if it changes anything.
> 
> ...


Hey Jim, so I was gonna take it out for a test drive yesterday and had plenty of gas in the tank to eliminate the issue Monteux mentioned. Had a plug for the vacuum advance to try that. I had the get down to close the garage door manually because the sun was messing with the sensors and on the way back to the car I noticed it was leaking fuel pretty good from the pump hardline to carb. I tried tightening but nothing changed. Ordered another fuel line and see what happens, if it looses that much fuel idling... I wonder how much at wot? My problem? maybe.


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## PontiacJim (Dec 29, 2012)

RMTZ67 said:


> Hey Jim, so I was gonna take it out for a test drive yesterday and had plenty of gas in the tank to eliminate the issue Monteux mentioned. Had a plug for the vacuum advance to try that. I had the get down to close the garage door manually because the sun was messing with the sensors and on the way back to the car I noticed it was leaking fuel pretty good from the pump hardline to carb. I tried tightening but nothing changed. Ordered another fuel line and see what happens, if it looses that much fuel idling... I wonder how much at wot? My problem? maybe.


It could be possible that it is sucking air? I don't think you would lose that much pressure or the gas would be spraying out and you would have noticed it sooner, but..........

Are you sure it is the line and not the pump housing? Sometimes the fittings can get overtightened and crack the housing. If it is a stainless steel line, apparently they have a tendency not to seal very well at the flare - which has been posted several times with regards to brake lines. I have never used a stainless line on anything, so I have no experience, but the stainless is harder and if the flare is not just right, I can see how it could leak. I prefer a typical steel line and do make my own as I have the tools to do all this.

So check your pump for any cracks. I would go with steel line if you happened to have used stainless. Then see if any difference - it can't hurt.


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## RMTZ67 (Mar 12, 2011)

Well bought a new pump and line and.... line did not fit. I removed the hose because of the chrome clamp end and still would no go on. The only way is to remove the thermostat housing. Then how do I change my fuel filter.. Looks like the made it to long at the carb. Anyway I just used fine sandpaper on the ends of my old line rinsed it off and worked fine with no leaks. Took it for a ride and the flutter seems to be gone, but I will need to run a few more times before I am convinced. Here is how mine runs and the other that goes behind the housing. How are yours?


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## PontiacJim (Dec 29, 2012)

RMTZ67 said:


> Well bought a new pump and line and.... line did not fit. I removed the hose because of the chrome clamp end and still would no go on. The only way is to remove the thermostat housing. Then how do I change my fuel filter.. Looks like the made it to long at the carb. Anyway I just used fine sandpaper on the ends of my old line rinsed it off and worked fine with no leaks. Took it for a ride and the flutter seems to be gone, but I will need to run a few more times before I am convinced. Here is how mine runs and the other that goes behind the housing. How are yours?
> View attachment 138708
> View attachment 138709


Yippie! Your fuel pump was probably going south. The fuel line issue is that the line is probably for a short type Q-jet fitting (picture) that has the bronze/paper filter inside the Q-jet housing. You have one of the long style filters on yours - I think later type.


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## RMTZ67 (Mar 12, 2011)

PontiacJim said:


> Yippie! Your fuel pump was probably going south. The fuel line issue is that the line is probably for a short type Q-jet fitting (picture) that has the bronze/paper filter inside the Q-jet housing. You have one of the long style filters on yours - I think later type.
> 
> View attachment 138710


Well that's good to know, Never seen this one. Think i'll order that and a filter and just keep the line. Thanks


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