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K5's with Carburetors (want your opinions)

Chief Brody

Chief Brody

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As you mostly know my passion was in restoring my Blazer to factory stock. That meant getting a Rochester Quadrajet. I didn't modify any of the fuel delivery system.
Fast forward almost 5 years and it has not been driven as much as I like because of a lot of things...but those aren't important.

I would be interested in hearing your opinions, particularly those that still have carbs.

1. Do you still use the factory Quadrajet fuel filter? What is your experience with replacement intervals and any issues with the stock filter or those with the anti flowback valve.

2. Those of you who have trucks with carbs and are not daily drivers, what have you seen as regards to truck setting for maybe months?

3. What carb products do you use? cleaners..etc..

4. How many of you went with an external fuel filter and have you put it on the suction side (between the tank and the fuel pump (mechanical)?

5. What "tune up" items go bad when the truck is sitting for weeks at a time?


Thanks for your input in advance.
 
I try to use ethanol free gas in three that I have which don't get driven weekly. But I used to only rely on Stabil gas treatment before that.
My Q-jet truck has a filter just ahead of the rear mounted tank, before the electric pump, so my filter in the carb doesn't have to catch it all. I haven't used many of the anti-drainback valves as I had experienced problems with them at WOT , but had also found them stuck halfway open too.
Now my '72 C10 longbed has a K5 tank in the rear, manual fuel pump with a inline filter under the cab. It has an Edelbrock carb which seems to let the gas evaporate out easier. If I let this truck sit for a couple of months with the fuel tank too low, it won't pull gas and start without putting some air pressure to the vent on the tank. I don't know if this problem is made worse by the filter in the suction line, but you would have a shorter line anyway, so maybe it wouldn't cause you issues.
I have used Seafoam in the tank for cleaning, but too much can make it smoke. (As my Dad found out) I have seen better results in a buddy's truck from BG products.
I don't know of tune-up items that go bad from sitting weeks at a time, but I know that stale gas can foul spark plugs easier.
I hope that you find some information in this long post.
 
2) dead batterys :dunno:aaaand mice. Crank for a few seconds, 2 pumps and it will usually start.
3) BG. 44k and ethonal defender (this stuff goes in all the trucks at least twice a year.)
4) clear in line filter between mechanical pump and carb. I still use a filter in the factory location also.


I try to be in the habit of starting everything on the 1st of the month, usually forget or get caught up in other things and they get done every other.

My k5 has a mechanical pump. I have a k20 that the po used a cheep electric in the wrong place that has been changed twice (and now moved and replaced with a better pump for the 3rd). Filter is built in to the pump and it still has a filter.in the stock location on that one also. If I run it dry I have to prime it(complete pita, who runs out of gas at a good time). Definitely want to replace the mechanical.
 
Granted, I don't run a Q-jet any longer. But I get where you are coming from, and sticking with that tech is more challenging today than "EFI everything!". lol

Never had an issue running the factory setup. The tank has a filter in it. Unless that has failed, and your fuel line has rust in it, nothing should get to the carb anyway.

The factory filter at the carb is a good design (IMO) as it can't stop flow...if it gets plugged up, it unseats and bypasses. What's the worst that happens then? At some point a piece of junk MAYBE gets in a carb passage. Take carb off, disassemble, blow it out, reassemble, done. Big deal. And I never had to do it. I ran Q-jets on a few cars and trucks, I'd say combined 10+ years of operation never changing the filter more often than the first time I rebuilt the carb. Personal opinion, and I'm ok with people disagreeing, is that additional filters are a waste, and more dangerous than the problems they purport to solve or prevent. I have a hard time believing many of the stock fuel filters were EVER changed. You knew, because normally people crossthreaded the fitting for them if the tried. Since the filters unseat, not sure how you could ever blame a problem on the filter anyway.

Today, I'm not sure who is making ethanol compatible floats, needle, seals, and filters. My assumption is that ethanol may eat all that stuff over time. There is so much cheap crap from china out there, who the heck knows anymore. Maybe Edelbrock if they still sell their Q-jet stuff? Any components older than probably the early 2000's is questionable IMO, and I have a feeling there are a LOT of those components out there to be found, still new.
 
1) Yes. Not much experience with changing them out, maybe every 2 yrs? No issues (yet) with the filter or flowback valve.

2) It doesn't get daily driven during the winter (due to the rust potential). No issues after being parked for a while. i have an electric fuel pump, so i might let that run a few seconds before cranking if it's been sitting for more than 2-3 weeks. i think the bigger issues for me is to avoid flatspotting the tires. So, every 3-5 weeks or so, jack it up and rotate the tires 180 degrees or something...

3) None yet.

4) i have a screw on canister type filter before the electric pump in addition to the stock, in carb filter.

5) none yet.

Really, i think if the carb is tuned/adjusted right, they GENERALLY run as good as injection. Yes, i know injection IS better, but you know what i mean----for general daily driver use.

Really, TBI kinda/sorta is an "electronic carb."
 
Ethanol is not your friend. If ethanol free gas is not available use something in the tank regularly. I've found if they are driven regularly the ethanol isn't as much of an issue but over time it's eating away at the rubber/plastic bits in the carb. So still use the fuel treatment.

The sitting for long periods of time is where ethanol does it's best work. Usually you'll see white crusty garbage left behind. That will effect needles/seats jets/rods and the float. Run it dry or treat the fuel before you long term park it.

As far as the Edelbrock q-jet stuff. It's not all the same as the original q-jet stuff. My Dad is rebuilding an Edelbrock q-jet right now for a buddy. First off the carb kit price is over $100. Right out of the box the gasket for the top of the carb to the main body don't match up. It don't match an original q-jet either. He's been fooling around with their tech department to get the right gasket. 2 weeks he's been dealing with them, sending pics and part numbers and they still can't get him the stuff. So don't anybody get their hopes up that just because Edelbrock would be the savior on all things q-jet.

Even with treatment of the fuel I think with continued running on ethanol you could be rebuilding the carb a little more frequently. Unless someone has a source of ethanol compatible carb parts that is.
 
For all the hassle and worry, it would probably be best to simply run an infrequently driven truck on non ethanol gas if it's got non ethanol rated fuel components. Who cares if its 30 cents a gallon more, better than worrying about leaving it sit with fuel in it, finding ethanol rated components, etc. Just a thought. I know I have to look a little bit, but it seems MORE common to find a non ethanol pump now than it was even three years ago. And as I recall, some website even lists stations that carry it. Gasbuddy might.

I'm guessing edelbrock took the qjet and either backwards engineered one model and based everything off of that, or simplified an existing qjet pattern to save money. The qjets were never really good in regards to interchangeability as the years went on anyway.
 
I do run non ethenol gas, but they might have water in their underground tank...
 
Usually when water gets in gas there is a national news story on it. I dont think it's a common occurrence. Water wont go through the in tank filter fyi.
 
I got some carb cleaner and some new filters, ones without the anti-passback flap. I don't want any restrictions in the line...I read where that flap decreased the flow some...also got new spring.
 
I don't really know what it is...i'm just trying to troubleshoot a sputtering acceleration. Last fall I set the timing and fuel / air mixture. The exhaust still smells rich to me but I'm not sure. But I do know that it didn't used to sputter or be sluggish.
 
I know it's not asked in your questions but is it the accelerator pump? The carb kit I just put in mine had a funky issue with the pump shaft being too long but still fit. I swapped the rubber parts from the rebuild kit pump to the old pump shaft to fix it. (tip to @Fastereddie)
 
Desert_K5 said:
I know it's not asked in your questions but is it the accelerator pump? The carb kit I just put in mine had a funky issue with the pump shaft being too long but still fit. I swapped the rubber parts from the rebuild kit pump to the old pump shaft to fix it. (tip to @Fastereddie)
Click to expand...

I didn't take the air horn off to look at it...I just looked down into the carb and cranked the accelerator and it pushes gas through the jets..it "accelerates" as I push the pedal down. I suppose it could be...but not sure. Easier changing filter first than taking carb off
 
what does the pattern supposed to look like coming out of the jets? It is not a "mist"
 
Strong stream out of both nozzles
 
Might want to check the vacuum advance if it has the old can style --if the diaphragm failed it wont get advanced at idle (when hooked to manifold vacuum),and that could cause a bog on acceleration..

Usually when an accelerator pump doesn't work well it'll want to bag down badly and almost stall when you stab the throttle fast,especially under a load..if you see two streams squirt out into the venturi when you work the throttle by hand it is probably OK..
Low fuel pressure can cause a bog too..usually a bad fuel pump shows up by hard starts with long cranking periods to get it fired up after sitting first..
 
On a truck that sits a lot, I would start with fuel drier and a little fresh gas. Then drive it. Mine run better after driving a while, especially with fresh gas.
 
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