The Stovebolt Site Forums The Shop Area Engine Shop 1969 C10 - Engine Blow-By Pressure Vs. Fuel Pump (Pictures posted)

Greetings to all. I have owned my 69 C10 for about 30 years. Engine was rebuilt about 30 years ago, and it only has about 20,000 miles on it since that time:
(I uploaded 4 pictures, and hope that they will attach here)

The pictures show the engine and the fuel filter which is about a foot from the carb. The close-up shot shows the filter almost totally empty.

The truck was beginning to show signs that the fuel pump was not delivering enough fuel up to the carb. It still has the original style pump on the lower side of the engine, and a push rod from an engine cam pushs back-n-forth to make the pump work. The truck would idle fine, but when a good load was put on the engine (shifting somewhat agressively from 1st to 2nd and with a desire to "Getty Up"), it would bogg down, and act as if it wasnt getting fuel. Got so bad, that the engine would stall out. I raised the hood and saw that there was very little gas in the see-thru filter.

So, I logically assumed that the fuel pump was bad. I installed a new fuel pump, and at the same time I pulled the tank sending unit and installed a new filter on the tip of the pick-up line, and blew air through the fuel lines to verify that they were not getting clogged up. Lines were not clogged. I started the truck, and I could see that the pump was working......but during a quick test drive, I got the same "bogging down" and then stall out. Raising the hood, I could see that the fuel filter was again almost empty.

I then thought I would try removing the gas line above the fuel filter and try priming it with fuel. When I loosened the clamp and pulled the hose off, there was a "hissing" noise, and the high pressure blew gas in my face (no damage done). So, Im thinking there is something wrong to create so much pressure inside the fuel filter.

To rule out the possibility of a "bad" new fuel pump, I ran the hose into a 2 liter bottle, and started the truck and let run 5 seconds, and shut her off. There was a good 2 inches of gas in the bottle, so Im pretty confident that the pump is fine.

I tried to "prime" the fuel filter with gas, but it just would not work. I put the filter back on, and let it sit overnight. When I looked the next morning, the fuel filter was almost full......so, I guess the pressure of the fuel tank gas was enough to push the gas down, thru the pump, and up into the filter. I started and did another test run, and the same "bogging down" happened.......and an empty fuel filter. Stalled out in my driveway, and I managed to squirt alot of gas on the air filter to get her back in the garage.

So my question to all the experts here:

Is it possible for engine pressure (blow-by pressure) to build up and maybe push its way up through the PCV line and into the carb. From there, could it put an insane amount of pressure back down the fuel line and out-power the fuel pump? I have not yet tried pulling off the large rubber line from the valve cover to the bottom of the carb. I did remove the PCV valve that fits into the top of the valve cover, and cleaned in gas......the metal ball in it was working fine.

And I will toss in some more history that might help: For the past few years the truck has been starting up great when "cold", and running fantastic.....plenty of power, idles great, etc. However, after 10 minutes of running, if I turn the engine off and try to re-start, then I only get a "grunt" from the engine.....has no desire to turn over. If I let the truck sit overnight, then it starts immediately and runs great. But as soon as she warms up, then its almost impossible to start. (And I have replaced almost everything.....battery, battery cables, plugs, wires, points, condensor, rotor, etc.). Someone then mentioned that it might be "vapor lock". So, with this added info., is it possible that the carb. is just old and needs replacing? Is something inside the carb worn out, and allowing too much blow by pressure to go backwards to the filter, and at the same time, allows too much gas/fumes back into the cylinders after running which causes vapor lock?

I have almost pulled out all my hair on this one.........and suggestions would be much appreciated.

There is a cone-shaped sintered bronze filter behind the fitting where the gas line attaches to the carburetor. They're notorious for getting clogged up and causing exactly the symptom you're describing, and that's something that hasn't changed for the almost 60 years I've been fixing vehicles. I believe the big nut that's visible in the third picture on the top line has 1" diameter wrench flats. Remove that nut and you'll find the bronze filter right behind it. There's a small nylon gasket attached to the nut- - - -put a new one on when you change the filter, and be careful how tight you snug the nut. Too much force will strip the threads in the carburetor and then you'll be looking for another carb.

The "grunt" on a hot start is caused by worn starter brushes. Invest in a good quality rebuilt starter, as 30-something years of faithful operation means the rest of the starter is also worn out. Don't waste time and effort putting new brushes into a worn out starter.
Jerry

Jerry.......Thanks for the quick reply. I will go out and check that bronze filter at the carb inlet, and let you know what I find.

I forgot to mention that I put a brand new starter on, in addition to all the other new parts. I have replaced everything, and am still getting that "vapor lock" thing. Starts perfect when cold, runs great, but turn her off after warm-up, and all I get is that "grunt", or sometimes barely turn over. So, if it is a "vapor lock" thing going on, is that a sign of a bad carb?
This carb is at least 30 years old, and that has been my next thought......get a new one.
What the heck is the cause of constant vapor locking?

Thanks.
Dwight

Vapor lock is a myth, invented by people who don't understand physics and are too lazy to learn. True "vapor lock" is extremely rare, and it's a condition where fuel lines, the fuel pump, and other associated parts get hot enough to boil the fuel, resulting in vaporized gasoline that can't be pumped like a liquid. It has absolutely nothing to do with a refusal to crank. That's an electrical problem you haven't discovered yet, probably a bad ground that heats up and won't conduct enough current flow to operate the starter efficiently. Start by running a heavy gauge new battery cable from the battery negative post to the engine block, cylinder head, or other location near the starter. Be sure to scrape away all the paint, rust, or other insulating stuff down to bare, shiny metal before bolting the cable on. Some people recommend using a copper-based conducting grease on the connections- - - -I've never found a need to do that since I began doing electrical work in the 1950's, if I do the rest of my job right.
Jerry

Jerry, the engine might be hydro-locked from liquid fuel leaking into the cylinders.

That would take quarts (or at least pints) of liquid- - - -not a few ounces from a leaky carburetor.
Jerry

Hotrod Lincoln/Jerry.....I actually started a thread on this site a couple years ago about the "no start" when engine is warm issue.......and I have yet to resolve it. I replaced the starter, bought brand new heavy duty cables, all the terminals are wire brushed/sanded down perfectly clean. Alternator is charging properly, and after running and I turn the key off, the battery has a great charge (around 13 volts).......so there is plenty of juice to crank, but she wont crank. I even had to try jump starting when I turned the key off by mistake at the local trash dump, and the brand new truck assisting with the jump barely made a difference....just a "grunt", and then a reluctant turn-over and somehow she started.

But, back to my first question: Is it possible for the engine to build up so much blow-by pressure that it goes up the PCV tube and into the carb base, and the pressure goes back down to the fuel filter? Here the high pressure would force the fuel pump to close, and not pump any gas up to the filter. Is it normal to pull the hose off the filter and have that intense pressure "hissing" and exploding fuel out into my face?

78 Buckshot......Yep, maybe "hydro locking" instead of "vapor locking". That would definately make the pistons not want to turn over. With time this should be dilluting the engine oil with gas, and I would think I would get a gas smell in the oil........I have checked and cant detect the gas smell in the oil, but will check again.

The situation you're describing is impossible. The carb bowl is vented to the atmosphere, so no pressure at all is able to get past the needle valve, and back into the fuel line. Blowby doesn't get into fuel lines- - - -period! The crankcase is also vented- - - -either to the atmosphere directly, or at least to the "clean" side of the air filter. Have you made any measurements of battery voltage and/or current draw while the engine is refusing to crank, or are you just guessing at what's happening and throwing random parts at the problem?
Jerry

I checked some of my old picture files, and see that I actually "rebuilt" this carb about 5 years ago. Here are some pics of the 2BBL carb on this ole 307:

See anything crazy looking that might be a clue to the problems?

Jerry......Thats what I thought when I pulled the hose off and it sprayed like a can of spray paint right into my face.....I didnt think there should be that much pressure building up in the fuel line. If the fuel pump cant force that much pressure into the fuel filter/fuel line, then its gotta be coming from the engine side. What if the carb bowl vent is clogged up?

You sure that the PCV hose coming off the valve cover and connecting at the base of the carb cant force alot of pressure up into the carb? I dunno.....just throwing out whatever idea I can come up with.

Yep, it does seem that I have been throwing alot of parts into the engine bay......but at the time, they seemed to be logical, and not "too random". But at this point, almost everything has been replaced except that ole carby.
I hate to just "throw another random part/carby" at the motor if it really doesnt need it.

Nope, I never had any extra hands around to help take voltage measurements while trying to crank the hot engine......but I did measure the new battery strength at that time, that is, I took a voltage reading after turning the warm engine off, and it was way up around 13 volts. When starting the cold engine, it was reading around 12.65, and she cranked with authority and fired up in a second. Also, the temp gauge is reading normal (actually to the cold side of normal), and not heating up during this process......so, were not dealing with a "Hot" engine or an over-heated engine during these "no starts".

If you can start it when it's warmed up does it act like it's flooded with fuel when it starts?, black smoke? Have you checked the static ignition timing to make sure it's not too far advanced? I wouldn't worry about the clear fuel filter only part full when running - that is very typical. Yes, some residual pressure in the fuel line is normal. You are correct with the assumption of fuel in the oil and the engine "making oil if it were leaking much into the cylinders. Also what Jerry is saying about crankcase pressure finding it's way into the carb/fuel line is right - can't happen.

78Buckshot.......On the times that I try to start her back up after driving for say 30 minutes, the engine will either just do a moan and not crank over, or she will crank reluctantly and very slow and somehow fire up and start. At that point, she seems to run fine, but if I turn her off, then the odds are strong that I will just get a "moan/grunt" from the starter and she will not crank over/start. Also, there is no black smoke after this "warm start up", and the temp gauge is normal.

(And during the entire time (say 30 minutes) that I am out driving the truck, it drives great, idles great, and there are no signs of issues. Well, that was true until this recent issue of no gas in the filter, and stalling out).

Yep, I checked the timing, dwell, etc. when I put new plugs, wires, rotor, condensor, points in her.

When you say "residual pressure in the fuel line is normal", about how much is "normal"? Im guessing its whatever the fuel pump is designed to push.......say 2-3psi? But when I pulled the gas line off the filter, it seemed like a good 25psi pressure exploding all that gas out.

Another relevant question is:
Is it normal for the fuel tank to push gas past the fuel pump and up into the fuel filter (filter is beside the carb) overnight when the truck is parked? The fuel filter can be empty and then I check the next morning and see that it is almost full.

It's time to apply the old Sun machine slogan- - - - -"We test- - - -not guess!" It's vitally important to test cranking voltage while the hot start problem is happening, not before or after. Then, once the cranking voltage is known, you can use a battery load tester to find out how much current draw is involved by loading the battery down to the same voltage reading. That's the diagnostic procedure I've been using for over 50 years, and I've yet to encounter a problem I couldn't solve. If you don't have the equipment or the experience to do that, it's time to turn the problem over to someone who can test the system properly. Tennessee's not that far away- - - -come on over! I'm sure the engine will be plenty warmed up by the time you get here! In the meantime, change that carb inlet filter and solve the "vapor lock" that isn't there!

Jerry

Hmmm. next time this happens, take both ground sides of your jumper cables. hook 1 to the neg battery terminal and the other end to a great ground with no paint or the starter itself. What your doing is duplicating the ground cable. If it starts, u got a bad ground cable. On the fuel issue, take the gas cap off carefully when problem is present, Is there pressure? run it without the cap, does it still happen? It should still crank tho regardless of the fuel. Unless its filling cylinders like previous stated. But more symtoms would be present.

If you work by yourself you need to make up some long test leads for you VOM so you can take readings while sitting in the drivers seat. I have some 25 footers in the shop for just such occasions.

I agree with Jerry...your engine failing to turn over has nothing to do with the fuel system, it's an electrical issue.

Next time it happens, slide under the truck and see if the starter motor is HOT...maybe you starter is hanging up on the flywheel and staying engaged...just a thought.

Mike B

Hotrod Linc......OK, so when you ask about the cranking voltage, are you saying that I merely have to have the voltage meeter clamped on the posts, run the meter to my windshield, and just watch how low it drops as I crank? I can do this test when the engine is cold (and it will start right up), and when its warm (when the engine grunts "say what?") when I turn the key. This will show how low the battery drops while cranking. How do you measure the amps/volts being drawn by the starter?

Yep, I could drive the ole c10 down to Tnn (as long as I dont turn her off), and have you roll up your sleeves and figger this puppy out.

Carb inlet brass filter: Did not have time last night to check this, but will do today.......will take pics and post. I hope you are right and its just clogged with some crap.......and that will solve the "vapor lock" and "hydro lock" that isnt there. ha ha

GlennsT.......OK, easy way to "double up" and test the negative ground cable. My ground cable is only a few feet long and goes straight to the ground bolt on the top of the engine. The cable ends/and ground location/bolt were thoroughly cleaned/wire brushed. But a test worth doing.

I sent a pic in the last post of the gas cap.....it has a pin hole in the middle, and still lets air in/out. If I have a full tank and park off-level, the gas will slosh up to the top and start dripping out. Plus, there is never any "hissing" sound as I remove this old-fashioned gas cap.......never any vaccuum building up inside.

MikeB.....Yes, I have 2 seperate issues going on. The most pressing one was the "lack of fuel" getting to the carb, as this causes me to break down on the side of the road.
The other issue "No Start when warm" does not leave me by the roadside unless I do a Homer Simpson "DOH" and forget and turn the key off......then, I am stuck, and just have to grab a pillow and take an hour nap in the truck bed until the engine cools off......then, Im on my way again.

But I would love to solve both these riddles and leave all these gremlins and Murphey' Law hoblins behind.

Starter hanging up and getting hot.....I guess thats a possibliity, but there are no typical sounds of a starter turning as the engine revs up/down. With a discerning ear, you can pick that noise up pretty clear. But never hurts to reach past those hot exhaust pipes/mufflers and check the temp of the starter......just remember that I have a cheap laser temp reader.....could just shine that up on it to get some readings.

Lets clear somethings up before this goes much farther,
1) Blow-by will not effect fuel system, ever! Blow-by is vented to atmosphere.
2) Fuel pressure build up in tank will flood the engine, NOT keep it from turning over. It will not cause it to hydrolock with fuel.
a) Hydrolock with fuel will cause oil to thin with fuel, oil to smell of fuel, and oil to be way over full, and likely low oil pressure.
3) Fuel pressure in tank is caused by bad vent or cap, you will notice pressure or vacuum when opening tank.
4) Fuel filters are never full, 1/2 or less is normal.
5) Battery cables should be as short as possible and 4 gauge or bigger. Bigger diameter is better.
6} Timing, dwell, points gap, do not change when hot. Timing can cause a hot start problem if set to high.
7) Crappy carburetors will not keep the engine from turning over, EVER. They make for hard starts or no start, but the engine will turn over.
8) Carburetors very rarely wear out and need replaced, but they do get dirty and need cleaned.
9) Vapor lock is fuel boiling, turning to a vapor and venting out carb.
10) Vapor-lock will NEVER EVER keep an engine from turning over.


Moving on, when the engine refuses to start when hot, have you tried to turn the engine by hand? Will it rotate or is it physically locked up?
Will the engine start when hot if you jump across the starter solenoid? ( Batt terminal to [ S ] terminal on solenoid )
Have you tried pouring water on starter when hot? If cooling it down causes engine to start, you have a heat soak problem.


Easy things to check,
Voltage at ( S ) terminal on starter solenoid when hot,
Voltage at starter with key in start position. Not at solenoid, but at point where voltage enters the starter case after coming out of solenoid.

Harder things to check,
Starter amp draw, hot and cold,
Hot battery amp test,
Hot cable amp test, similar to battery amp test only through cables to battery.

Ground cable should go directly to engine block with 3/8" bolt/stud and star washer. Frame and cab should be grounded from engine block or separate ground lead off battery. You CANNOT have to many ground cables or straps, BUT, you should only have one cable per terminal at battery with a solid crimp, not the bolt on DIY cable ends. Positive cable should be same size as ground, short as possible and run directly to BATT terminal on starter solenoid. Battery shut off switch should be able to handle 200 amps.


I see in the first group of photo's, the ground cable has the battery shut off switch installed, remove it for testing.
I also see you are running headers, does the starter have a heat shield? or heat wrap? Old headers create more heat due to thinning metal.

Joe

All good points, Joe! I missed the battery disconnect, which, unless it's the NASCAR approved 1,000 amp model, is worthless. ANY source of potential resistance in a starting circuit must be avoided like the plague- - - - -even 1/10 of an ohm is way too much to allow good current flow. The reason for measuring cranking voltage is simple- - -it gives you an indication of the current flow (or lack of it) during the "no crank" episode. Let's say you have an intermittent open or high resistance circuit on a hot start- - - -the battery terminal voltage during the "grunt" will still be fairly high, 11 volts or more since little or no load is being placed on the battery by the starter. A too-tight engine, or a shorted starting motor will place a HEAVY load on the battery which will drop the terminal voltage down to 9 volts or less. Armed with that information, the rest of your diagnostic procedures will take a drastically different turn. A "new" starter doesn't necessarily mean it's "good", but guessing and swapping parts without a detailed diagnosis rarely if ever works out well.

Edit: I just reviewed the photos again, and Joe is right on target. Dump the Mickey Mouse battery disconnect, and either fabricate a heat shield between the starter and the header, or go to one of the gear reduction "high torque" starters available on Ebay to get more torque on a hot start. It's a definite possibility that the starter armature is getting heat-soaked by the exhaust and is getting enough drag on the pole shoes to try to lock itself up after a fairly short drive. I've got a crippled leg, but I'd probably be able to outrun anyone who tried to GIVE me a set of headers if I had to run them on a street engine.

I had a severe problem with heat soaking a full size Delco starter on a '55 Chevy w/full length headers. Didn't have much success with a wrap around heat shield. Just the proximity was to close. As mentioned...switched to a high torque mini starter.


Also, for the sake of conversation what condition are your plugs in? Their appearance can diagnose what you can't see or what you are guessing at.

Joe H......Lots of good info. It has been raining all day here, and I had the truck outside under a tarp, so I couldnt do any wrenching today. I will first check that brass carb filter screen, and then follow up with all the other comments/suggestions.

Hotrod Linc......I understand the concern with the Battery Disconnect. However, the "Fail to Start when Engine Warm" issue started long before the disconnect switch was put on the battery.......at least 2 years before. I had another gremlin issue over the past 6 months:

One day I suddenly heard someone blowing a car horn. I went outside and found my 69C10's horn just blowing away. So, I raised the hood and pulled the wire off the horn. It had a super sensitive horn contact at the steering wheel, but it was freaky to just have the horn start blowing after sitting for a few days. Then I found a voltage drain, even with the horn wire off the horn, so I assumed the steering wheel contact was still touching, causing a drain, and was removing the battery cable to stop the drain. (When I removed the battery cable, I could hear a relay turning off up under the dash.....and that turned out to be the horn relay turning off when the battery juice was taken away. I then slapped on the disconnect switch to make life simplier. Sometime after, I pulled off the steering wheel to investigate the problem, but could not find any issues. Put it all back together, and now the horn seems to work fine, and the horn relay is not clicking on/off when I turn the battery disconnect switch off.

Removing the battery disconnect switch will not solve the "Warm/No start" issue....but I do understand the fact that I am perhaps losing amps at the switch, and corrosion will be an issue over time. The truck sits for weeks w/o starting, and I prefer not to have a dead battery when I want to run her......and am not yet 100% certain that I have eliminated all voltage drains (I found the old Kraco radio was draining juice, even with the power off, so I yanked those wires from the fuse box).

So, I will do more investigating when the rains stop, and get back with more info.
That was a good thought about the headers making the starter too hot.....I will check into that, and get a picture of how close it is to the pipes. However, for over 25 years, the old starter worked fine, hot or cold engine, and I made some long road trips and had no "fail to crank" issues.

Apache.......Good thought about the plugs. The plugs were replaced when all this "non start" issue started, but I will try to pull them out and label and get some close-up pics......maybe some good clues there.
I will also check the oil dip stick again and make sure the level is not increaseing (due to gas leaking down past the pistons/rings), and see if there is any gas smell to the oil.

Next time I will also try to remember to make a quick Youtube video of the engine "Cold starting", and then the "Warm start" issue in all its grand glory.

Maybe all this discussion will help another poor soul down the road.

I understand the battery cutoff switch, I have one on my truck. I used the biggest amperage switch I could find, 2500 peak amps, 250 continuous amps. Yours is rated for 135 amps, thats why I suggested removing it till you solve the heat problem.

While waiting for the rain to pass, pull the battery and have it load checked, do it three times to simulate real use. If it still good the third time, you know it's not the battery.

OK, Some pics and an update:

First, the Carb filter: You were right......it took a big 1" wrench to loosen the nut where the secondary fuel filter is located. There is a little "barrel" filter right at the inlet, which is held in place by a spring. Beyond this filter is a brass or stainless screen about an inch deep inside, and I think removal is done by taking the carb apart. However, I shined a light in, and it was not clogged. I used a few Qtips dipped in gas to lightly clean the screen, and no particles came off, only a bit of grime.

As you can see in the pics, the barrel filter did have some black sludge laying in the bottom of the filter. Amazing that all this crud gets past the larger filter that is a foot from the carb. When gas is pumping up and through this barrel filter, it would mix with the gas, and could possibly restrict the gas flow going into the carb. So, I cleaned it all out in gas, and put it back.

In the pictures, you might also notice the "wet gleam" all over the intake manifold......appears that there has been excess gas leaking here. Possibly a carb float not closing properly?

The last pic shows a pic of the oil dipstick......oil was changed 3/2018, and only has 750 miles on it. It is right at the Full mark (a wee bit above), and "seems" to have a very slight gas smell. Also a bit on the thin side, but I did add a quart of Marvel Mystery Oil during the last oil change.

Next post will show the starter/headers.

Now for the starter/headers:

Kinda hard to get decent shots without jacking the truck up, but the pics show that the headers do come within just over an inch from the starter motor. You can see the new starter/solenoid. I admit that the header pipes are a bit close, and probably should have some type of heat shield to keep the heat away from the starter. However, the old starter was on for over 25 years without any issues.....and due to this 2 yr-old "No Warm Start Issue", I replaced it with a new one.......and had the autoparts store test it with their machine, and it was still "good". So, I dont think the heat from the headers is the problem causing the "No Warm Start".

Its the extreme heat from the headers...trust me I've been down this road. In picture No. 3 left to right again the armature and stator of the starter are exposed to intense heat saturation. The clearances inside the starter are very, very close. Very little natural air across the starter causes it to swell.
Question... were the headers installed 25 yrs. ago?

There's an accepted way to clean that bronze filter, and you haven't done it yet.

1. Find a large flat rock
2. Place bronze filter in the exact center of the rock
3. Using a 3-lb. hammer, take a full overhead swing, and hit the filter.
4. Repeat step #3 a minimum, of 3 times.
5. Buy and install a new filter.

Sintered bronze filters ARE NOT intended to be "cleaned". They're a throwaway item.
Jerry

Apache......Yep, I bought the truck about 30 years ago, just as you see it now. The 307 engine had been rebuilt and the headers installed shortly before I bought it. What perplexes me is that the truck ran fine for 27 years just like you see it, with the header pipes about an inch from the starter......never had a problem, even on long trips (even one trip to upstate Pa. to trailer home a fat 55 Nash......no issues at all).

One thought is "what if" the carb is now running too lean, causing the header pipes to get hotter than in the past....maybe an added 25 - 50 degrees from the pipes would make the difference? Seeing the intake manifold under the carb looking wet makes me want to point the finger more at the carb, which then pushes the heat level from the header pipes over the edge, making the starter freak out.

Alright that rules that out. BTW...that's a good set of headers, most deteriorate especially after 30 yrs worth of service....but running lean enough to dramatically increase header temps? I would think pistons would have holes in them. Infrared temp gun time...GREAT diagnostic tool.

Hot Linc..........Hillarious for sure! Actually, that barrel filter at the base of the carb was a plastic one......so instead of wasting my energy with a 3LB hammer, the technical manuals mandate that I douse it with gas and toss a match on it.
Funny.......I get your drift, but at this point Im still diagnosing the issues, and doing my redneck "fixes" at times.

The bronze screen filter that is inbedded over an inch beyond the barrell filter looked good, and the only way to remove that is to tear down the carb (I believe).

But back to the barrell filter, do you think that was enough crud in it to restrict the gas flow enough to cause the engine to die on hard acceleration?

Apache.....OK, I can measure the header pipe temps next time I get her going. What would be a "normal" and a "too hot" temp reading on the pipes?
(If they are glowing red/white, then thats probably too hot).

I've been watching that happen for over 50 years- - - - -so- - - - -YES! Also, headers and full sized GM starters don't mix- - - - -I've also seen hot-soak no crank problems on header-equipped engines since the 1970's or so. You either need a heat shield, or a racing type gear reduction starter that has more pipe clearance. There's also a really good header fix involving a cutting torch and a set of rams' horn exhaust manifolds.
Jerry

HotLinco.........Oakkie Doakkie......well, we might have solved the stalling problem with the "hammerd-clean" used barrell filter. Will give her a test run tomorrow and let you know if it solved that problem.

That is a standard GM carb, the only filter is what you pulled out. No filters inside. There may be a piece of something you are seeing so try and pull it out. Again, no filter or screen inside the carburetor!

This is the type of filter it could have, https://quadrajetparts.com/sintered-bronze-carburetor-fuel-filter-p-80.html or this type, https://quadrajetparts.com/short-paper-carburetor-fuel-filter-with-check-valve-p-79.html . The screen you pulled out is for marine use or racing.

Headers pipes thin with age from heat, so your problem could be a combination of low voltage and heat soak. One place to check for voltage drop is the large bulkhead on the firewall with all the wires coming out, the engine harness unhooks from engine side. I have seen more then one have a bad connection.

A semi easy test is to attach a heavy wire to the ( S ) terminal on the starter solenoid, ( while engine is cool ) and secure it close to the battery but not touching anything. When the truck won't start, touch the wire end to the battery ( with key in RUN ). This will bypasses all wires, connections, and key switch, if it still does nothing, you are down to heat soak or low BATT voltage to starter.

As a side note, running lean will dry out the spark plugs, they should be pretty clean and colored. I have seen my 250 inline 6 run 700 to 900 degrees about a 16" from the exhaust valves, measuring the down pipe while driving.

Slightly late ignition timing will also increase exhaust temperature pretty dramatically. I've seen cast iron exhaust manifolds get red hot from late timing, and those headers are going to be close to cherry red on a long uphill pull, even with normal timing. On the dyno runs we did we would have to swap the headers side to side and turn them upside down, facing the collectors forward to keep the heat away from the dyno operator. I could actually see the flames dancing around inside the header tubes when we got above 500 HP on some of the circle track engines we built.
Jerry

Joe H.......from you links for the Rochester Quadrajet parts, I was trying to find a parts breakdown to see if there is some type of metal flat screen imbedded in that barrel filter housing......but so far have not found the breakdown on my old Rochester. The Carb No. is 7029125, so let me know if you stumble accross a link showing the carb parts breakdown. I tried watching Youtube videos of the carb tear-down, but so far have not seen them get to that spot.

Large bulkhead on firewall (over behind the master brake cylinder)......so, you are saying its a good idea to unplug it and try cleaning the contact areas?

Good idea with the heavy wire from the S terminal for testing during the "No Warm Start" issue.

Plugs.....I do need to pull all of them, label location, shoot some pics, and also do a compression test while Im at it. Will also keep the air cleaner off while the engine is running so I can better look for gas leaks around the carb.

HotLinc.....So, I better not leave my foil-wrapped hot dogs on the headers forks for too long. So, with those cherry red headers with flames flashing on the inside, the temps must have gotten up over 1500 degrees. HOT. Comparable to NASA's solid rocket booster engines on lift-off.