Quadrajet Inlet Filter GF 470

[Richard T.]

My 68 L 36 has the original quadrajet and runs fine. My issue is the cold start after it sits a few days. It requires lots of cranking and pedal pumping to get gas back in the bowl. I'm told the GM inlet filter (GF 470) has a check valve inside to prevent the fuel from siphoning back out of the fuel bowl which seems like a great idea . Lots of people recommend it but others say that the valve will swell up and restrict fuel flow at high rpm or in worst case block it completely . I'm told this is due to poor materials used in the valve. I can understand this happening in a Chinese knockoff part but normally GM is very careful about these things. I'd like to get opinions from users about this filter before buying some. Seems it's been discontinued so it will be the NOS market for originals.
Thanks in advance.

[Mark E.]

Re: Quadrajet Inlet Filter GF 470

Richard,

Your car may be operating normally. Welcome to the era of ethanol gasoline. It evaporates more quickly, hence it only takes a few days for the small fuel bowl in the Q-Jet to dry up. I consider cranking before starting as a charming quirk of yesterday's technology using modern gasoline.

This has been discussed before. Search here and the forum at cliffshighperformance.com to read more about this phenomenon.

[Mark E.]

Re: Quadrajet Inlet Filter GF 470

Found a couple of relevant threads on Cliff's forum:

https://cliffshighperformance.com/simplemachinesforum/index.php/topic,3602.msg15579.html#msg15579

https://cliffshighperformance.com/simplemachinesforum/index.php/topic,497.msg2095.html#msg2095

[Edward J.]

Re: Quadrajet Inlet Filter GF 470

Rich there is no way to siphon the fuel from the carbs float bowl (the bowls fuel level is below the needle and seat). as Marc states the new ethanol fuels evaporate when sitting. Your car I believe has a in-line fuel canister that needs to be also filled first before the carb.float bowl is filled so may require a littler longer crank time.

[Ed D.]

Re: Quadrajet Inlet Filter GF 470

I have also experienced the empty bowl syndrome with my 72. I just changed my Q-jet internal filter, the one in there did not have the check valve. The new one is a Wix filter with a check valve. I did not notice any difference in the starting. I am also told that the fuel pump has a check valve in it, that needs to work. I have the original fuel pump and am not sure if it has a valve or if it is working.
Ed

[Joe L.]

Re: Quadrajet Inlet Filter GF 470

My 68 L 36 has the original quadrajet and runs fine. My issue is the cold start after it sits a few days. It requires lots of cranking and pedal pumping to get gas back in the bowl. I'm told the GM inlet filter (GF 470) has a check valve inside to prevent the fuel from siphoning back out of the fuel bowl which seems like a great idea . Lots of people recommend it but others say that the valve will swell up and restrict fuel flow at high rpm or in worst case block it completely . I'm told this is due to poor materials used in the valve. I can understand this happening in a Chinese knockoff part but normally GM is very careful about these things. I'd like to get opinions from users about this filter before buying some. Seems it's been discontinued so it will be the NOS market for originals.
Thanks in advance.

Rich------


GM never specified the GF470, aka GM #5651802, carb inlet filter for any 1953-82 Corvette. That filter, now discontinued, was certainly in their "parts bin" during the period. On something like this, I hate to second-guess those that originally designed the system.

[Bill S.]

Re: Quadrajet Inlet Filter GF 470

Starting Fluid. If the car has been parked for a few days pop the hood, remove the air cleaner top, and spray some starting fluid down the carb throat, set the choke, and it will start on the first crank. It may not stay running, but if it stalls out the fuel pump has pumped enough gas into the fuel bowls and if you pump the gas a few times it will restart. Saves wear and tear.

[Ed D.]

Re: Quadrajet Inlet Filter GF 470

Starting Fluid. If the car has been parked for a few days pop the hood, remove the air cleaner top, and spray some starting fluid down the carb throat, set the choke, and it will start on the first crank. It may not stay running, but if it stalls out the fuel pump has pumped enough gas into the fuel bowls and if you pump the gas a few times it will restart. Saves wear and tear.

Bill, While this may help someone who is running a car all the time, I dont think this will work on an Operation Test, or a PV. My 72 does not start hard enough that I would go to that degree to help start it, but maybe some need that much help.
Ed

[Mark E.]

Re: Quadrajet Inlet Filter GF 470

Starting Fluid. If the car has been parked for a few days pop the hood, remove the air cleaner top, and spray some starting fluid down the carb throat, set the choke, and it will start on the first crank. It may not stay running, but if it stalls out the fuel pump has pumped enough gas into the fuel bowls and if you pump the gas a few times it will restart. Saves wear and tear.

Bill,

Your post made me wonder which starting method is better: Crank it until it starts or starting fluid.

Cranking is less work, safer (less chance of carb flare up and fire), and maybe causes less engine wear because oil pressure builds before starting.

But the starter fluid method is less taxing on the battery and starter.

I think the advantages of the first method outweigh the second method, especially regarding safety.

[Shane F.]

Re: Quadrajet Inlet Filter GF 470

I somewhat agree with all that has been discussed. Whether it be fuel evaporation or leaking float bowl plugs, most Q-jets will eventually dry out. My LS-5 starts fine sitting after several days. Any longer than a week or two, a small syringe of petrol down the carburetor vent tube and she starts first crank every time.

[Ed D.]

Re: Quadrajet Inlet Filter GF 470

I somewhat agree with all that has been discussed. Whether it be fuel evaporation or leaking float bowl plugs, most Q-jets will eventually dry out. My LS-5 starts fine sitting after several days. Any longer than a week or two, a small syringe of petrol down the carburetor vent tube and she starts first crank every time.

I am not what has changed over the years, we know the fuel is different. But I dont remember having this issue when the car was new, and did not have the problem when I did my PV in 1996. The carb was rebuilt and the pugs were epoxied in 1995. The carb has not been touched since then. To start the car after standing several days; I have to set the choke, crank it for about 4 seconds, then pump it 3-4 times and then it will start.
Ed

[Mark E.]

Re: Quadrajet Inlet Filter GF 470

I am not what has changed over the years, we know the fuel is different. But I dont remember having this issue when the car was new, and did not have the problem when I did my PV in 1996. The carb was rebuilt and the pugs were epoxied in 1995. The carb has not been touched since then. To start the car after standing several days; I have to set the choke, crank it for about 4 seconds, then pump it 3-4 times and then it will start.
Ed

Same experience with my car. And back in the day, it took longer for the fuel bowl to evaporate.

[David C.]

[Mark E.]

Re: Quadrajet Inlet Filter GF 470

I've used them on several Q-Jets. They may help with drain down, but won't help with evaporation.

If you think your fuel bowl is drying up prematurely, you can check it for internal leaks. The bowl and main well plugs are known to leak. If they are leaking, a common symptom is a flooded engine that's hard to start.

[Joe L.]

Re: Quadrajet Inlet Filter GF 470

I've used them on several Q-Jets. They may help with drain down, but won't help with evaporation.

If you think your fuel bowl is drying up prematurely, you can check it for internal leaks. The bowl and main well plugs are known to leak. If they are leaking, a common symptom is a flooded engine that's hard to start.

Mark------


...and applying epoxy to the soft plugs may not be as "forever" as some folks think.