Quadrajet fuel filter - Chevelle Tech
Engine General Engine Discussion.

 8Likes
  • 4 Post By dyno jonn
  • 1 Post By Robinls5
  • 1 Post By BillK
  • 2 Post By Vintage Musclecar
 
LinkBack Thread Tools Search this Thread Display Modes
post #1 of 13 (permalink) Old Jul 10th, 20, 11:31 AM Thread Starter
Tech Team
Dave
 
Join Date: Sep 2013
Location: OH IO
Posts: 771
Quadrajet fuel filter

Does the fuel filter in the inlet have a built in check valve to keep the fuel from draining back to the tank when not running.
25C 70 is online now  
Sponsored Links
Advertisement
 
post #2 of 13 (permalink) Old Jul 10th, 20, 11:50 AM
Senior Tech Team
Eric
 
Join Date: Aug 2011
Location: Poteau, Ok
Posts: 4,932
Re: Quadrajet fuel filter

Technically fuel cannot drain out of the bowl through the inlet as its the highest point on the carb.

You're just jealous because you can't hear the voices!

1967 Olds Cutlass 468 BBC/T400
1963 Plymouth Fury 440/Torqueflite
2007 Ford Mustang GT (momma's car)
oldcutlass is offline  
post #3 of 13 (permalink) Old Jul 10th, 20, 11:56 AM
Team Member
Bill
 
Join Date: Jan 2018
Location: Boston Area
Posts: 1,185
Garage
Re: Quadrajet fuel filter

Quote:
Originally Posted by 25C 70 View Post
Does the fuel filter in the inlet have a built in check valve to keep the fuel from draining back to the tank when not running.
It depends my porous bronze filter does not but the paper ones do have a small flap inside that may act like a check valve but not a very good one. The small round rubber seal goes against the fuel line entry direction and not towards the carburetor. Why are you asking? Eric's statement above is correct. However Rochesters have a problem with the lead plugs in the main body to leak and drain all the fuel into the intake. That will dilute the oil too. Most rebuilders including me will use a fuel resistant epoxy on the plugs to seal them.
Billdini is offline  
 
post #4 of 13 (permalink) Old Jul 10th, 20, 12:01 PM
Tech Team
 
Join Date: Jun 2019
Posts: 236
Re: Quadrajet fuel filter

The ACDelco GF 471 Quadrajet filter does (or at least always did) have a check valve installed in them, other brands likely do too. Usually if a QJ is "losing prime", it is the main well floor of the carb leaking, which is easily repaired.
Droptop72 is offline  
post #5 of 13 (permalink) Old Jul 10th, 20, 12:15 PM Thread Starter
Tech Team
Dave
 
Join Date: Sep 2013
Location: OH IO
Posts: 771
Re: Quadrajet fuel filter

I had the carb apart and sealed the main well floor. I don't have the filter in the inlet, the threads are worn and it's not leaking so don't want to disturb it. I use an inline filter. The car requires what I consider excessive cranking after sitting a few days. Does anyone make a check valve that can be installed in the fuel line at the tank or before the pump.
25C 70 is online now  
post #6 of 13 (permalink) Old Jul 10th, 20, 12:31 PM
Senior Tech Team
Jon N.
 
Join Date: Jan 2003
Location: back in the "Hew-Hess-Hay"
Posts: 4,359
Re: Quadrajet fuel filter

What good will a check valve do if fuel is evaporating from the float bowl?

Answer: nothing.
77 cruiser, 71350SS, von and 1 others like this.

Jon N. ~ What doesn't kill you makes you stronger.

The only reason someone would want insurance is if they want to pay someone elses bills or want someone else to pay their bills.

BIGOT is a word used by people that can't use logical reasoning to prove that you are wrong when you don't agree with them.
dyno jonn is offline  
post #7 of 13 (permalink) Old Jul 10th, 20, 1:26 PM
Lifetime Premium Member
Bob
 
Join Date: Mar 2005
Location: Jeannette Pa. near pittsburgh
Posts: 8,890
Re: Quadrajet fuel filter

Here is what I have done for many years,,, AND it works. FIRST,, I never change the filter in the Q-JET. WHY..??? Since I have owned my LS-5/ M-22 since 1970 I installed a metal fuel filter at the fuel tank, AGAIN, WHY ???
Screwing with a Q-Jet, You may have trouble with striped threads, Line from fuel pump leaking.
In 1970 I installed a Metal fuel filter at the tank,, Then after the filter a Bendix Electric pump at the tank, On a toggle switch.
Move ahead to the 1990s ( after the frame off) Now its a trailer Queen.
After the frame off a Metal fuel filter at the tank, Then a $35.00 electric fuel pump from Advance ( mounted at the tank) and a toggle switch, Under the dash. My SS 454 ElCamino sits for MONTHS. ( I fired my El Camino last week, It sat for over 14-16 months,Spins over 2-3 times and fires up, YES ,,, I use the electric fuel pump) Turn on the key, Then the fuel pump,,, When it quits clicking real fast, Then I hit the key. It will spin over two or three times and fires right up. I did pump out the old fuel and changed fuel filters at the tank.
In my lifetime, I have found out......... When I keep my paws OFF of the Q-Jet, It is happy! NO BIG wrenches on my Q-Jet since it was new. Due to the fact I have SCREWED UP a Q-Jet or two.
Bob
vortec710 likes this.


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
1970 SS LS-5/M-22 El Camino- Org. Owner-AACA 2016-Senior Grand National Winner---MCACN-GOLD-2013
1970 ( FRAUD) SS 468 Station Wagon - Driver.
Robinls5 is offline  
post #8 of 13 (permalink) Old Jul 10th, 20, 3:10 PM Thread Starter
Tech Team
Dave
 
Join Date: Sep 2013
Location: OH IO
Posts: 771
Re: Quadrajet fuel filter

Bob the electric pump would probably be the best solution.
Dyno John, I agree the check valve won't stop fuel from evaporating from the bowl. It may stop the fuel from siphoning back to the tank after enough fuel evaporates to cause the needle valve to open, since the needle valve is low in a quadrajet.
25C 70 is online now  
post #9 of 13 (permalink) Old Jul 10th, 20, 3:55 PM
Super Mod
Mr Bill
 
Join Date: Aug 1998
Location: Waldorf Md. USA
Posts: 12,573
Re: Quadrajet fuel filter

Dave,
I had the same exact problem with the Q-jet on my Wife's Rivera for a couple of years. I have probably done a couple of hundred Q-jets over the years so I am familiar enough with them to know all of the common fixes. Nothing seemed to work. When I had the engine out of the car 2 years ago to rebuild it I looked at everything I could think of on the carb and simply could not find anything wrong. I had it sitting on my bench at the shop with the top cover off and the bowls full of fuel and it didnt lose a drop in over two weeks. So I got the engine done and put it all back together and darn if I didn't still have the same issue.

Went on E-bay and started searching and found the same exact part number carb as was on her car. Bought it for $25, cleaned it up and put a kit in it, put it on the car and the problem is basically gone. I do not have a clue what was wrong with the original carb but there must have been something.

I will add that it seems like her car and my S-10 both have to crank a bit longer than "normal" if they sit for a week or so. As near as I can tell from all of the research I have done that it is the ethanol fuel evaporating a lot more than non ethanol fuel and it is apparently happening when you shut the engine off and it is still hot. They will both start up almost instantly if they just sit for a day or three but much more than that and it takes 15 seconds or so of cranking.
von likes this.

Bill Koustenis
Advanced Automotive Machine
Waldorf Md


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


1971 Heavy Chevy - original owner
1984 Buick Riviera - original owner (Wife's car)
Team Chevelle #100
BillK is offline  
post #10 of 13 (permalink) Old Jul 10th, 20, 6:31 PM
von
Lifetime Founding Member
Von
 
Join Date: Oct 1998
Location: Mooresville, IN (Indianapolis)
Posts: 14,568
Re: Quadrajet fuel filter

Quote:
Originally Posted by BillK View Post
Dave,
I had the same exact problem with the Q-jet on my Wife's Rivera for a couple of years. I have probably done a couple of hundred Q-jets over the years so I am familiar enough with them to know all of the common fixes. Nothing seemed to work. When I had the engine out of the car 2 years ago to rebuild it I looked at everything I could think of on the carb and simply could not find anything wrong. I had it sitting on my bench at the shop with the top cover off and the bowls full of fuel and it didnt lose a drop in over two weeks. So I got the engine done and put it all back together and darn if I didn't still have the same issue.

Went on E-bay and started searching and found the same exact part number carb as was on her car. Bought it for $25, cleaned it up and put a kit in it, put it on the car and the problem is basically gone. I do not have a clue what was wrong with the original carb but there must have been something.

I will add that it seems like her car and my S-10 both have to crank a bit longer than "normal" if they sit for a week or so. As near as I can tell from all of the research I have done that it is the ethanol fuel evaporating a lot more than non ethanol fuel and it is apparently happening when you shut the engine off and it is still hot. They will both start up almost instantly if they just sit for a day or three but much more than that and it takes 15 seconds or so of cranking.
I've done a few Q jets too and the ones I've done for myself do the same thing as yours. I'm also told the modern fuels evaporate quickly. After playing around with a Q jet apart, I saw the float bowl needs to be about half full before the accelerator pump gets fuel. It seems most Q jets when cold need a little squirt from the acc pump to start the engine. So to get that squirt the bowl has to get up to about half full which takes a few seconds of cranking (with just a mechanical fuel pump). BTW Q jet fuel filters are sold with or without a built-in check valve. I've heard the ones with check valve restrict fuel flow somewhat.

von '69 Malibu Team Chevelle Member #15


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
von is offline  
post #11 of 13 (permalink) Old Jul 10th, 20, 9:00 PM
Lifetime Premium Member
Beth
 
Join Date: Oct 2010
Location: Nashville TN
Posts: 1,787
Garage
Re: Quadrajet fuel filter

Here's the short filter with a check valve.

It says the check valve will restrict fuel flow above 350 hp or so

https://quadrajetparts.com/short-pap...0rcb86hfa2h611

Are you sure your carb isn't getting hot ? Maybe a better insulator under it would solve your problem.

67 Chevelle convertible, 138 vin, original 4 speed, bucket seats, Marina Blue with black interior
nashville beth is offline  
post #12 of 13 (permalink) Old Jul 11th, 20, 12:52 AM Thread Starter
Tech Team
Dave
 
Join Date: Sep 2013
Location: OH IO
Posts: 771
Re: Quadrajet fuel filter

Thanks for all of the replies. I am going to start it cold then shut it off and let it set for a week and see what happens. This should tell me if heat is causing fuel evaporation.
25C 70 is online now  
post #13 of 13 (permalink) Old Jul 11th, 20, 8:22 AM
Senior Tech Team
Eric
 
Join Date: Jan 2006
Location: SW Ohio
Posts: 1,311
Re: Quadrajet fuel filter

First, if this is any sort of a performance application, forget about the anti-drainback filters, they WILL cause issues. I have personally A-B-A tested them in my +/-375 HP small block in my `83 Malibu wagon test mule which is equipped with a `77 Qjet (uses the long paper filter).

Standard filter = 0 issues.

Swapped in an anti-drainback filter, took it for a test hit--top of 1st and into 2nd it started burping & farting something awful, abandoned the run. Repeated a couple more times with the exact same results.

Brought it back home, stuck the standard filter back in and presto, the car's right back to normal, no more burping & farting.

Second--for the most part, the issue of QJets going dry in a few days is vastly for the most part due to simple evaporation, not draining through the bowl (esp. on later model QJets or earlier units which have been properly sealed). The QJet on my wagon goes dry in 3-4 days, and it's properly sealed up.

Keep in mind a QJet holds maybe 1/2 the fuel volume of a Holley or Carter, so they'll evaporate out more quickly. I have also verified that regular pump fuel will evaporate out of a Holley in a week or so (verified both on my wagon and on my Chevelle), while the 100LL Avgas I normally use in my Chevelle is good for weeks.

Lastly, I have verified rapid evaporation from the 3 gallon fuel cell I use on my carb live test engine stand. With an open vent on the cell, I can see the pump fuel evaporating out of the cell on a daily basis.

$.02 worth from someone who builds carbs for a living.
77 cruiser and von like this.

Carburetor Rebuild & Restoration

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


Check out
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
on Facebook
Vintage Musclecar is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Chevelle Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address. Note, you will be sent a confirmation request to this address.

Email Address:
OR

Log-in










Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome