Hot Rod Forum banner
101 - 120 of 120 Posts

·
Registered
Joined
·
4,239 Posts
Had to edit as I read to fast. I would do the Holley route and get a 600 Holley vacuum secondary with the adapter to put on your intake and it would be easy to work with and is so common that you can get stuff for it almost at any parts store.

To me simple is using a basic carb build and basic ignition system and all things being equal not going over fancy on things and having it all setup good. The Holley 600 vacuum secondary carb is a very good carb to use and you can get them all over ebay for sometimes less then a $100 bucks for a good one that just needs cleaned up and rebuilt. I did that route for a 305 many years ago and that combo ran excellent for the life of the car and only cost me a $150 bucks for the used Holley and a new skip white distributor and a rebuild kit.

In your situation you would have to use one of those adapters from spread bore to square bore if your intake is a factory Q jet intake and they are not the best for performance wise but on my brothers old 305 it seemed to not hurt anything and he got good mileage still.
 

·
Registered
Joined
·
254 Posts
Discussion Starter · #102 ·
/i would never consider wires an option………..just saying simple is better. Honestly the side hung bowls, Holley is the best option. The shorter version with rear meter plate vs meter block should give more space w/6 cylinder distributor.

IMHO A old carter WCFB rebuilt would be my first choice. Generally pretty cheap at swap meets and e bay. I’m not too sure about adaptor to Q-jet pattern, so that might nix it as an option.
i'll try to get a pic asap, but with the stock factory hi-rise manifold, q-jet, and hei ignition there is already not a whole lot of room between the back of the carb and distributor cap. So, a 4175 might not work here. However, like you said, a square bore carb might work here.

i do know, for sure, that the edlebrock performer manifold and square bore holleys/holley type carbs WILL work with an HEI although even here there is not a whole lot of room.

i would rather not go that route if possible because it's too many parts to change out / i like the factory hi-rise----it's only about 7 lbs heavier than the edelbrock aluminum manifold.
 

·
Registered
Joined
·
254 Posts
Discussion Starter · #103 · (Edited)
If it was me I would go the Holley route. Troubleshooting a carburetor in most terms is a lot more simple then fuel injection throttle body to troubleshoot if you have enough experience to tuning and fine advance tuning a carb. Yeah the FI units will give you information on your handheld or laptop whichever you use and stuff but there is a lot more to the whole system vs a carburetor in my opinion. I have seen and watched videos where folks spent a lot of time on those fuel injection units and they did not get it so easy even with information from there handheld device.

But that is with performance motors and other factors in place there as well vs a bone stock motor. To me simple is using a basic carb build and basic ignition system and all things being equal not going over fancy on things and having it all setup good. The Holley 600 vacuum secondary carb is a very good carb to use and you can get them all over ebay for sometimes less then a $100 bucks for a good one that just needs cleaned up and rebuilt. I did that route for a 305 many years ago and that combo ran excellent for the life of the car and only cost me a $150 bucks for the used Holley and a new skip white distributor and a rebuild kit.

In your situation you would have to use one of those adapters from spread bore to square bore if your intake is a factory Q jet intake and they are not the best for performance wise but on my brothers old 305 it seemed to not hurt anything and he got good mileage still.
Yeah, this is a possibility; i actually originally had a Rochester 2GC on this engine----using a transdapt q-jet to 2bbl adapter. The only reason why i switched to q-jet is because the 2g flooded and i figured since the manifold is q-jet, it would just be simplier to use a q-jet. So, i'm not opposed to trying a square bore holley on this factory q-jet manifold. The carb i really like is the "old" holley 4010/4011 which, of course, they don't make anymore. BUT, summit has a new copy of the 4010......:)

So, actually, another possibility is to go back to the 2G. My only concern MIGHT be the CFM----will it be enough? My goal for this engine is 240-250hp probably with nitrous (and here i can't even get the engine started......)

So, i think that 2g's flow what------435 cfm, some i've seen flow 500cfm. Now the 4.3 is 262 inches and there's no way i'm going to rev it past 5000rpm with stock internals. So the 2g with 435 to 500 cfm's may very well be enough?
 

·
Registered
Joined
·
4,239 Posts
The 600 Holley with the side hung fuel bowls and with the secondary metering plate is pretty compact and leaves a lot of extra space and that is why many use them on tunnel rams as they don't take up as much space vs say a Holley with a pair of center hung bowls and a secondary metering block in some applications and the style of intake tunnel ram manifold being used. On a regular Qjet factory intake that the old 305 had with the adapter and all it left a lot of room between the Hei distributor and the back of the carburetor.

I was thinking this was on a v8 but it sounds like this is on a 4.3 v6 which I am not familiar with for carb setup wise but I would assume the Holley should clear the Hei on one depending on the intake design but I know its very close. If you need I have a room full of those and I can measure one from a certain point back towards the bowl if you want me too. If you post photos that would be awesome as I for one would like to see what your working with and see what you have for space. The Holley Qjet replacement is a little bit longer then the 600 Holley vacuum secondary square bore carb that is most common aka the 1850 manual choke or 80457 electric choke.
 

·
Registered
Joined
·
254 Posts
Discussion Starter · #105 ·


This isn't a great picture due to the angle, but about 5" from the air cleaner stud to the HEI cap.

Anyways:
Battery sitting = 12.56
Battery while cranking = 11.50 ish

Voltage at red/ ignition wire with key "on" = 12.56
Voltage at red/ ignition wire while cranking = 10.8 ish. Is this good enough for HEI to start engine?
 

·
Registered
Joined
·
4,239 Posts
Yes that is normal as the starter depending on the power it has will draw quite a bit of amps while turning over. I measured a Holley 600 and with from the center of the stud to the back of the carb bowl its about 3 3/4 of an inch give or take an 1/8 of an inch but its under 4 inches. I don't know exactly how it would center on the stud wise compared to the Qjet. I would think it would be awfully close since they have the same air cleaner circle pattern size for the radius and stuff and the air cleaners pretty much swap out just fine.
 

·
Registered
Joined
·
254 Posts
Discussion Starter · #107 ·
UPDATE:
(Also, note i can't mess with the carb constantly due to work etc)

i somehow got it to start cold "normally"----it starts within 1-2 crankshaft revolutions.

The only thing different i did was to take the idle tubes out, blow compressed air thru them and run a wire thru them. Also, blew air thru the area below the idle tubes (idle wells?).

i'm not 100% convinced that this solved the starting problem as i did not see dirt or debris come out.

Neverthess, the cold start problem seems to be solved.

Remaining problems:
1) Stalls once you put it in gear. Can keep it running if i press the pedal, but this is unacceptable.

2) Won't start hot, although it seems to be improving----sounds like it wants to catch, but doesn't quite. Whereas before it would crank and crank and nothing.
 

·
Registered
Joined
·
4,239 Posts
If it won't start hot it sounds like you might have a fuel boiling issue as I had that several years back but it would start but the fuel bowls were always low as on my Holley I had on at the time had sight glass windows and I could see the floats sunk down. The biggest problem is I had to crank it a lot to get them filled back up after sitting for a short bit and the fuel boiled down. It was not enough to make it poor out the boosters but it was a headache. What fixed mine was a return line and adding a fuel pressure regulator and had to add a hood scoop to my truck to allow more air venting.

I doubt you have all the problems like I did but heat can make things a problem but I doubt to a certain degree that you have a major problem like that but I don't know for sure without being there checking things.
 

·
Registered
Joined
·
254 Posts
Discussion Starter · #109 · (Edited)
UPDATE 7/21:

i put a 2GC on there. i have a few 2G's on the shelf. In fact, the one i put on the engine was the original carb i used when i first got into 4.3's. about 4.5-6 yrs ago.

1) It does the same thing as the quadrajet:
Fairly easy to start cold.

Won't run below 1000rpm
(although with this carb i did not really try to get it to run below 900 because it started getting "a little" rough).

Stalls out once you put it in gear.

Can't re-start hot.



2) i put a vacuum gauge on the engine (although this one is connected to a vac pump---may not be as accurate?, and maybe i need to get a actual dedicated vacuum gauge?)

i got 13hg steady with the quadrajet using a front port that i'm pretty sure is manifold vac. This is at 1000rpm.

Then tried it again using a port on the intake (the one for the modulator on the trans). This read 15-17 but somewhat fluttering needle.

With the 2g, vac was 15ish hg and much steadier needle.

a) i should add that i have the stock cam for an LB4 4.3 v-6------178/195 @ .050". Wouldn't a smaller engine produce lower vacuum readings (i hope....?). i am near sea level.

3) Before i put the 2G on, i sprayed some carb cleaner around the carb base and intake/head area but couldn't find any leaks. i even sprayed a little down the carb throat----it slowed down briefly and went back to "normal." i also cupped my hand around the choke area and the engine did not speed up. i suspect rich.
 

·
Registered
Joined
·
4,239 Posts
With that small of a cam and such your engine should have around 19 inches of vacuum and be super steady on average, as with any vehicle I have checked the vacuum on before regardless of the engine size. if it was a bone stock engine with no performance stuff what soever it would have around 19 to 20 inches of vacuum. With you having the one reading on the one port being lower and then the other port being higher it seems to me the lower reading might have and most likely been a timed port location and perhaps your primary butterflies are open just a hair to much allowing just enough air by to give a little bit of signal.

I know a Holley carb is different in design but similar function and on a Holley on the timed port off the metering block which runs through the main body and through the base plate that if you hook up a vacuum gauge to the timed port normally you won't get a reading but if your primary butterflies are open up just enough it will at times give a reading on the vacuum gauge but not a full reading. If you have another carb doing the same thing then one you have something else going on, or two, you have a carb issue that your not catching on both of them with out a proper adjustment on the mixture screws and other settings etc. You certainly been through a lot that is for sure. It not starting while its hot leads me to believe that maybe its boiling fuel perhaps as with Edelbock carbs they have an issue with heat soak at times and the fuel will boil in the bowl. I wonder if your carb regardless of which one your using that it might be boiling fuel.

Also is the fuel actually good in your vehicle? If you have bad fuel it can make it running a nightmare and with today's fuel it does not take no more then a few months for it to go bad. I wish I could think of something of what it could be and maybe perhaps you might have an intake leak somewhere making it almost not able to run at idle. So many things can cause an issue like this. Sounds to me you got a few things going on at one time. Hot start problems and then the problem not being able to stay running. Does your 2GC need a rebuild?
 

·
Registered
Joined
·
14,319 Posts
Actually it’s getting to sound like the timing set is worn out and the cam is running retarded as a result.

Manifold vacuum doesn’t have a lot to do with engine size, it is cam, rpm and throttle position tied. Your stock cam should generate about 19 to 20 inches at idle of about 500 to 600 RPM. It should take very little throttle opening. You low vacuum even on a 1000 rpm idle indicates retarded timing this can be ignition or camshaft or both.

Setting the ignition timing is independent to cam timing. As far as the distributor is concerned the cam is simply a jack shaft. The ignition timing is set to the crank position regardless of where the cam is in relation to the crankshaft. A sign that the timing set is failing is a frequent need to reset the ignition timing because as the timing set wears the cam falls typically retarded and takes the ignition timing with it until you readjust the ignition then the process starts over of the ignition fall retarded from you new setting as the timing set further wears till next time you retune. This can also be a characteristic of wear in the gears that drive the distributor. A test that is sometimes successful is with the timing light on number one raise the rpms up then snap the throttle closed while observing for wander about the timing marks, this is not always successful indicator but it is a decent and simple test to perform.

Bogie
 

·
Registered
Joined
·
4,239 Posts
Good one Bogie I forgot about a timing chain going bad and over stretched and thus causing a reduction in timing. I have never left an engine alone to let one wear out to come across those symptoms.
 

·
Registered
Joined
·
254 Posts
Discussion Starter · #113 ·
With that small of a cam and such your engine should have around 19 inches of vacuum and be super steady on average, as with any vehicle I have checked the vacuum on before regardless of the engine size. if it was a bone stock engine with no performance stuff what soever it would have around 19 to 20 inches of vacuum. With you having the one reading on the one port being lower and then the other port being higher it seems to me the lower reading might have and most likely been a timed port location and perhaps your primary butterflies are open just a hair to much allowing just enough air by to give a little bit of signal.

I know a Holley carb is different in design but similar function and on a Holley on the timed port off the metering block which runs through the main body and through the base plate that if you hook up a vacuum gauge to the timed port normally you won't get a reading but if your primary butterflies are open up just enough it will at times give a reading on the vacuum gauge but not a full reading. If you have another carb doing the same thing then one you have something else going on, or two, you have a carb issue that your not catching on both of them with out a proper adjustment on the mixture screws and other settings etc. You certainly been through a lot that is for sure. It not starting while its hot leads me to believe that maybe its boiling fuel perhaps as with Edelbock carbs they have an issue with heat soak at times and the fuel will boil in the bowl. I wonder if your carb regardless of which one your using that it might be boiling fuel.

Also is the fuel actually good in your vehicle? If you have bad fuel it can make it running a nightmare and with today's fuel it does not take no more then a few months for it to go bad. I wish I could think of something of what it could be and maybe perhaps you might have an intake leak somewhere making it almost not able to run at idle. So many things can cause an issue like this. Sounds to me you got a few things going on at one time. Hot start problems and then the problem not being able to stay running. Does your 2GC need a rebuild?
1) i know now, for sure, that i'm getting manifold vacuum because i'm now using the outlet on the manifold normally used for the vac modulator on the trans.

2) i'm not absolutely ruling out boiling or percolation, but i'm leaning away for the following reasons:
a) Both carbs were able to start and re-start hot before this problem started. How could the problem all of a sudden just appear out of nowhere? Not saying it's not possible though....

b) Even before the engine gets up normal temp it will stall out if put in gear. And with my recent testing i'm only running the engine for a few mins, not for miles and miles. So it's not like were getting the engine REALLY hot.

c) The adapter for the 2g really raises the carb up from the manifold and this is on top of the fairly thick q-jet base carb to intake gasket. i don't think in this case the carb is getting warm enough to boil the fuel.

d) i've run a return line since last summer.

3) Some of the fuel was in there since last october-ish, but i've since added 2 gallons of recent fuel.

4) i sprayed carb cleaner around the carb base and between the intake and heads and couldn't find any leaks. Also, how likely is it that a leak just happened right after i did the carb adjustment? Not saying it absolutley could not happen.....
 

·
Registered
Joined
·
254 Posts
Discussion Starter · #114 ·
Actually it’s getting to sound like the timing set is worn out and the cam is running retarded as a result.

Manifold vacuum doesn’t have a lot to do with engine size, it is cam, rpm and throttle position tied. Your stock cam should generate about 19 to 20 inches at idle of about 500 to 600 RPM. It should take very little throttle opening. You low vacuum even on a 1000 rpm idle indicates retarded timing this can be ignition or camshaft or both.

Setting the ignition timing is independent to cam timing. As far as the distributor is concerned the cam is simply a jack shaft. The ignition timing is set to the crank position regardless of where the cam is in relation to the crankshaft. A sign that the timing set is failing is a frequent need to reset the ignition timing because as the timing set wears the cam falls typically retarded and takes the ignition timing with it until you readjust the ignition then the process starts over of the ignition fall retarded from you new setting as the timing set further wears till next time you retune. This can also be a characteristic of wear in the gears that drive the distributor. A test that is sometimes successful is with the timing light on number one raise the rpms up then snap the throttle closed while observing for wander about the timing marks, this is not always successful indicator but it is a decent and simple test to perform.

Bogie
You mean timing chain?
 

·
Registered
Joined
·
14,319 Posts
You mean timing chain?
Yes, the timing set consisted of the crank gear, the cam gear and the timing chain.

The factory timing set consists of crank gear that is generally make of sintered iron. It will show wear grooves made by the harder steel timing chain. The cam gear is cast aluminum with nylon teeth. With age the nylon hardens and cracks and will spontaneously come apart at some point in the failure cycle. It also becomes grooved by the harder teeth of the timing chain. The timing chain is what is called a silent link, it is made of stamped sheet metal pieces that are stacked to make a toothed link; the links are riveted together to make a toothed chain. The chain wears at the riveted joints ovalling the holes the rivets pass through and grooving the rivets, this allows the chain to stretch in length.

The mix of these wear and failure points allow the cam to fall behind the crank shaft as the cam has the substantial resistance of the valve springs when there is ordinary wear on the gears and chain. The timing gear with plastic teeth is subject to sudden failure of one or more teeth as the nylon hardens and fatigue cracks with age.

I don’t recall if we’re dealing with a Buick or Chevrolet V6 here, while both are subject to this wear pattern the Buick is particularly sensitive and at some point in the failure mode it will collide valves and pistons; then it gets really expensive as you’ll be adding valves and possibly some pistons to the replacement parts list.

Bogie
 

·
Registered
Joined
·
254 Posts
Discussion Starter · #116 ·
Chevy v6----so basically SBC timing set.

Another clue i'd like to reiterate:

---Approximately april 18th----ran "normally." No stalling whatsover. Truck had been sitting for about 5-6 months

April 19th, got the secondary plates, not air flaps, plates on the quadrajet to open to 80% (35 degrees or so) from 0%.

April 20th, when on the way to work, did some "sprited testing" (ok i FLOORED IT, but there's no way i went past 5000rpm)

IMMEDIATELY after the acceleration test i noticed the problems-----wanting to stall out, couldn't re-start hot etc.

And here we are today.
 

·
Registered
Joined
·
14,319 Posts
From here it’s not possible to say for sure but if this is a high mileage engine above 60,000 miles especially if it’s been or is run hot the chances are pretty good something inside the timing case is in failure mode.

Signs include hard starting, needs fast idle to keep running, if still operable on the street it has no power. It needs a base timing adjustment either suddenly or frequently. The idle vacuum is low although this might be hidden by needing to speed the idle up. Plug fouling may be present but this is more often tied to not being able to run the engine long enough to burn deposits off the insulators.

There isn’t a really good test that is simple. The simplest is with a timing lighting one hand is to run the rpm’s up and drop them quickly while observing if and how much the timing marks drift, This does take removing and plugging the source of vacuum advance and securing the centrifugal so you‘re observing slop in either or both the timing set and/or the distributor gear mesh.

I certainly realize that this is a PIA job to do for simply going exploring inside the timing case. And certainly the next best test is putting a degree wheel on the crank, removing a rocker cover then hooking a dial indicator to the number one intake lifter if hydraulic or to the valve spring retainer if the lifter is solid or you shimmed a hydraulic so it is solidified, then reading the degrees to see if the events happen where they should is also a big job.

So basically if you’ve been through a carb change with no effect then if it’s fuel it’s in the supply system or carb internal settings. It could be ignition, with HEI it can be the pickup or the module. The distributor can simply be mounted out of time, this is common with reinsertion of the distributor on chevy 90 degrees V6’s as it is on their parent V8’s. Another thing can be the failure of one or in this case I’d expect more than one cam lobe and tappet failure through wear. This might show on a compression test, but at cranking RPM usually not. It often presents as the affected cylinder‘s spark plug always wet fouled. It shoul be visible with the valve covers off and the engine running the affect rockers and valves not moving much if at all.

Ignition may be the hardest to check for as a common HEI module failure is sparking late this without a distributor testing machine can be hard to detect.

You’ve been coming through these tests with no improvement to that it was running decent before your spirited drive then problems started. All we can do is make a list starting with the low hanging fruit then work our way to the more difficult

Bogie
 

·
Registered
Joined
·
254 Posts
Discussion Starter · #118 ·
From here it’s not possible to say for sure but if this is a high mileage engine above 60,000 miles especially if it’s been or is run hot the chances are pretty good something inside the timing case is in failure mode.

Signs include hard starting, needs fast idle to keep running, if still operable on the street it has no power. It needs a base timing adjustment either suddenly or frequently. The idle vacuum is low although this might be hidden by needing to speed the idle up. Plug fouling may be present but this is more often tied to not being able to run the engine long enough to burn deposits off the insulators.

There isn’t a really good test that is simple. The simplest is with a timing lighting one hand is to run the rpm’s up and drop them quickly while observing if and how much the timing marks drift, This does take removing and plugging the source of vacuum advance and securing the centrifugal so you‘re observing slop in either or both the timing set and/or the distributor gear mesh.

I certainly realize that this is a PIA job to do for simply going exploring inside the timing case. And certainly the next best test is putting a degree wheel on the crank, removing a rocker cover then hooking a dial indicator to the number one intake lifter if hydraulic or to the valve spring retainer if the lifter is solid or you shimmed a hydraulic so it is solidified, then reading the degrees to see if the events happen where they should is also a big job.

So basically if you’ve been through a carb change with no effect then if it’s fuel it’s in the supply system or carb internal settings. It could be ignition, with HEI it can be the pickup or the module. The distributor can simply be mounted out of time, this is common with reinsertion of the distributor on chevy 90 degrees V6’s as it is on their parent V8’s. Another thing can be the failure of one or in this case I’d expect more than one cam lobe and tappet failure through wear. This might show on a compression test, but at cranking RPM usually not. It often presents as the affected cylinder‘s spark plug always wet fouled. It shoul be visible with the valve covers off and the engine running the affect rockers and valves not moving much if at all.

Ignition may be the hardest to check for as a common HEI module failure is sparking late this without a distributor testing machine can be hard to detect.

You’ve been coming through these tests with no improvement to that it was running decent before your spirited drive then problems started. All we can do is make a list starting with the low hanging fruit then work our way to the more difficult

Bogie
i figure the more things we do, the more we find out/less to figure out---i has to be something......?

i am working on checking timing now----have to let it cool off as i forgot to plug in the pcv line-----i REALLY couldn't get it to keep running below 1200 rpm that way!
 

·
Registered
Joined
·
254 Posts
Discussion Starter · #119 ·
Ok, base timing is between 8-10 deg btdc (i couldn't see EXACTLY what the timing is because the tab wasn't really easy to see, but it's definitely between 8-10 btdc)

i flicked open the throttle a few times and the timing stayed rock solid--didn't move.

i'm leaning towards vacuum leak--because an hour ago i forgot to plug the pcv opening and could not get it to keep running. Plug it and it will idle all day at 900 rpm.

But where?
 
101 - 120 of 120 Posts
Top