Edelbrock 1405 carb running rich

[AuroraGirl]

Dsitributor as far as I know is the original hei, looks like photos you sent, I take manifold appears factory, has the firing order on it. Was an egr manifold but has a block off now. Could distributor gasket cause a vacuum leak? I didn’t replace it when I had the distributor out I didn’t figure it would harm anything such as a vacuum leak. I can check the linkage I don’t recall any play though. The mixture screws are set to the best vacuum I could get, averages 18-20 at around 600 rpm idle. But if you recall I had a random vacuum leak(12 ish vacuum) and truck idled weird and off idle ran fine? I noticed that there’s oil pooling on the intake manifold. I was reading the middle bolts can have oil seep through the threads? Could that be the case? Could that be a vacuum leak?

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I think it means your intake gaskets may need to be serviced. its okay because that EGR port means its probbably something like @SirRobyn0 had inside his manifold lol

Good time to improve it

also you have mechanical choke still or did you put a electric on? whats that hose doing there in pic?
and you may try a POWERBLAST plate upgrade to your carb

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they are on sale. makesy our mixture more easily vaporized and then the engine can have better throttle response and take off from idle and closed throttle, common issue on edelbrocks
what CFM is that? here is 750-800, if you have less they have a product for that too but you need to find that on their products page https://thompsonperformance.com/products/pbp-ec-78

 

[iamtherealJayy]

That clear hose is a vacuum gauge, I think edelbrock 1405 is 600 cfm but not 100% positive. Choke is still manual and it’s getting old having to pull it half way for starting and slowly let it off after a bit.

 

[AuroraGirl]

That clear hose is a vacuum gauge, I think edelbrock 1405 is 600 cfm but not 100% positive. Choke is still manual and it’s getting old having to pull it half way for starting and slowly let it off after a bit.

make sure your cable is fully openign it when you think it is and make sure its not slightly out of adjustment or have a weird behavior lol, iirc you had to get the piece to screw down onto the wire to hold it instead of a z bend

 

[iamtherealJayy]

For the lack of better explanation, the choke is say three inches of pull? The first inch is easy, second inch is hard(opening throttle? More you pull it raises idle to a certain point, and last inch is easier again. The last part isn’t needed since it’s warm weather so I usually press gas pedal once pull choke whole way out and it fires first rotation, but you have to instantly push the choke back in which like I said it doesn’t move easy the middle inch. I could press throttle to close it but if you’ve got the pedal pressed and set the choke it doesn’t raise the idle like it would if you pulled it to that position. If you even slightly understand

 

[iamtherealJayy]

I mean pull the choke whole way while pressing pedal so it’s easy to just close it for the first start, I don’t pump it again throughout the day I just pull the choke a little bit past where it starts having tension. And it fires first rotation.

 

[SirRobyn0]

OMG, I have not visited this thread in sometime, so if anything I say has been said before I apologize.

So @iamtherealJayy Lots of things can cause the WOT hiccup, but I will say one thing about that. If it happens at lower RPM, the advance mech in the distributor is not likely to be at fault. Think about it, if your turning say 1,500RPM or at idle, you nail the gas, vacuum drops so the vacuum advance is not advancing and the mechanical advance is not into play yet, or it's just starting. That is normal and is designed that way to prevent severe pinging. So if the timing is set correctly and your accelerator pump in the carb is working it is mostly like the sudden vacuum drop, caused by the secondaries opening to quickly. The flapper thing above the secondary throttle blades is counter weighted and the reason for that is so that vacuum has to overcome that counter weight before the secondaries will flow air though it, to prevent bog. So essentially it slows the rate at which the secondaries come in, so at low RPM when air flow is low it doesn't bog. In Taylor's picture on post #511 you can see the secondary air valve in the bottom left corner. If you stick a pencil or something in there you should be able to move it. It should not be missing or stuck open.

On the thunder series & AVS Edelbrock's that secondary valve is spring loaded and adjustable, but on the 1405 it's just a counter weight, and sometimes guys will grind them down to make the secondaries open faster. You'd have to remove the carb top to see the counter weights.

I'd pretty much bet this is your problem. If it's not pinging you could try adding a couple degrees of timing into it.

Jacob, post #510, your picture of the intake. See how there is oil pooling around the intake bolts? Those are the center intake bolts. It does not look like it's been trailing down from the valve cover gaskets, and frankly it's hard for the valve covers to leak on the intake side. More likely oil is making it's way slowly up those bolts from the valley. Even if it's not what you can see of the intake gasket looks terrible, much like mine did when I refused to believe I had an issue there. I'm not telling you pull your intake just telling you to keep that in mind.

Anyhow I'm exhausted, hopefully this all made sense. I'll make sure to pop into this thread tomorrow so let me know if anything I wrote is unclear.

 

[iamtherealJayy]

You made a great point explaining the vacuum advance since vacuum drops with the sudden throttle opening, the advance is set to full since whoever on here said it was better I can’t remember. Makes sense tl me, runs fine accelerating and then wam timing is too retarded to keep up. And yes the intake bolts are the middle ones, I completely degreased and cleaned the top of this engine so that oil is fresh. I think it’s coming from those two bolts and not the valve cover. If the bolts are the culprit is that something fixable without removing the intake? Could the intake manifold cause the random vacuum leak I’ve had a couple times? Somewhere in the rear is leaking too and covering the starter and dropping off rear of the oil pan, flywheel has some oil so I figure rear main.

 

[AuroraGirl]

You made a great point explaining the vacuum advance since vacuum drops with the sudden throttle opening, the advance is set to full since whoever on here said it was better I can’t remember. Makes sense tl me, runs fine accelerating and then wam timing is too retarded to keep up. And yes the intake bolts are the middle ones, I completely degreased and cleaned the top of this engine so that oil is fresh. I think it’s coming from those two bolts and not the valve cover. If the bolts are the culprit is that something fixable without removing the intake? Could the intake manifold cause the random vacuum leak I’ve had a couple times? Somewhere in the rear is leaking too and covering the starter and dropping off rear of the oil pan, flywheel has some oil so I figure rear main.

Manifold* vacuum yes.
Also your intake gasket is prob origiinal, your intake had EGR , its time to pull it off and clean. your truck isnt too hard to reach the engine is it? if you want a tip, pull the hood I had troubles doing intake becuase everything was distant from the sides to reach. I actually beenefited from my plow beinf on because i kinda climbed on that lol.plus you can look at the valley and push rods and make sure its all ok. and yes that can be the leak. interimittently.

also, teh rear may be your distributor since you said you didnt do that sealBut you are gonna wanna still check your weights

OMG, I have not visited this thread in sometime, so if anything I say has been said before I apologize.

So @iamtherealJayy Lots of things can cause the WOT hiccup, but I will say one thing about that. If it happens at lower RPM, the advance mech in the distributor is not likely to be at fault. Think about it, if your turning say 1,500RPM or at idle, you nail the gas, vacuum drops so the vacuum advance is not advancing and the mechanical advance is not into play yet, or it's just starting. That is normal and is designed that way to prevent severe pinging. So if the timing is set correctly and your accelerator pump in the carb is working it is mostly like the sudden vacuum drop, caused by the secondaries opening to quickly. The flapper thing above the secondary throttle blades is counter weighted and the reason for that is so that vacuum has to overcome that counter weight before the secondaries will flow air though it, to prevent bog. So essentially it slows the rate at which the secondaries come in, so at low RPM when air flow is low it doesn't bog. In Taylor's picture on post #511 you can see the secondary air valve in the bottom left corner. If you stick a pencil or something in there you should be able to move it. It should not be missing or stuck open.

On the thunder series & AVS Edelbrock's that secondary valve is spring loaded and adjustable, but on the 1405 it's just a counter weight, and sometimes guys will grind them down to make the secondaries open faster. You'd have to remove the carb top to see the counter weights.

I'd pretty much bet this is your problem. If it's not pinging you could try adding a couple degrees of timing into it.

Jacob, post #510, your picture of the intake. See how there is oil pooling around the intake bolts? Those are the center intake bolts. It does not look like it's been trailing down from the valve cover gaskets, and frankly it's hard for the valve covers to leak on the intake side. More likely oil is making it's way slowly up those bolts from the valley. Even if it's not what you can see of the intake gasket looks terrible, much like mine did when I refused to believe I had an issue there. I'm not telling you pull your intake just telling you to keep that in mind.

Anyhow I'm exhausted, hopefully this all made sense. I'll make sure to pop into this thread tomorrow so let me know if anything I wrote is unclear.

The reason I say the advance check out is he has a stock 78 K10 distributor and This is what

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These are all from the era, some more worn than others, one i cleaned up, but the point is to look at the wear, rust. if thats even possible to exist in his distributor, the whole idea of consistent ignition is out the window, especially sticking weights or worn pivots that dont let the advance correctly start. I still think its most likely carb being primary thing like you say, but im saying this is probably a problem at the same time

 

[iamtherealJayy]

Intake has been off before, there’s rtv on China walls. I was going to get a new cheap distributor because I don’t wanna spend $200 on a distributor but the cheap ones just seemed like more problems than I need to spend $50 on.

 

[SirRobyn0]

Intake has been off before, there’s rtv on China walls. I was going to get a new cheap distributor because I don’t wanna spend $200 on a distributor but the cheap ones just seemed like more problems than I need to spend $50 on.

If you get a new distributor Look at Davis Unified Ignition, if that is more than you wanna spend then look at getting a Spectra unit from your local parts store. The spectra uses two manufactures for their distributors, Ritchporter of Canada, and WIA which is Korean. Both units are good quality.

@AuroraGirl No un touched distributor that is 40 years old is going to be up to snuff, and I agree he'd see benefits from a new unit, it's just not likely to be the cause of what he is complaining about.

 

[iamtherealJayy]

I’m thinking most of my issue is not knowing the history of the truck lol. My 87 I know the history on it. This 78 I bough from some drunks in a trailer park. I don’t know why anything is how it is. It runs great, other than poor fuel mileage, I don’t know what kinda mpg it’s getting but I’ve noticed the odometer showing 30x18 so I know it’s atleast 18 miles and the gauge shows 3/4 of a tank. Don’t know accuracy of either gauge since neither worked when I got the truck. The speedometer is pretty much dead on according to gps on my phone but about 20mph off according to my girlfriend who followed me home and said I was doing 70 in 45. Phone said I was going 48 so I’m sticking with I wasn’t speeding. My only complaint other than the possible 3mpg is the secondaries dropping vacuum and my advance dropping out. I could change the advance to ported instead of manifold but then I’d possibly have to redo the timing to advance it a couple of degrees.

 

[iamtherealJayy]

Also I don’t suspect the distrivutor gasket for the leaking in the rear, could be intake manifold but not positive. It wasn’t wet like fresh oil all around the distributor. Granted, it was oily but it wasn’t like on the intake manifold where it left oil on your finger, it just made your finger dirty.

 

[SirRobyn0]

You made a great point explaining the vacuum advance since vacuum drops with the sudden throttle opening, the advance is set to full since whoever on here said it was better I can’t remember. Makes sense tl me, runs fine accelerating and then wam timing is too retarded to keep up. And yes the intake bolts are the middle ones, I completely degreased and cleaned the top of this engine so that oil is fresh. I think it’s coming from those two bolts and not the valve cover. If the bolts are the culprit is that something fixable without removing the intake? Could the intake manifold cause the random vacuum leak I’ve had a couple times? Somewhere in the rear is leaking too and covering the starter and dropping off rear of the oil pan, flywheel has some oil so I figure rear main.

I assume what you mean is you have the vacuum advance hooked to manifold vacuum instead of ported like the factory did. Ported was for emissions control. The main point to running ported was so there would be extra wasted fuel at idle, which would help the cat warm and stay warm at idle.

It's perfectly fine to run it on manifold vacuum, but might make your idle emissions a little higher, so that is something to keep in mind if you have to do an emission test. But the engine will like manifold vacuum better.

Technically yes you could pull those two intake bolts, put thread tape on them and reinstall. Even though you have said it's had it's intake done in that picture I quoted earlier this intake manifold gasket does look crusty. Again not saying you have to change it, but keep that in mind. It's kind of a pain to replace, but I'm sure you see some benefits.

 

[iamtherealJayy]

I may just keep “bandaiding” stuff until I can pull a 350 out of something else and do a fresh rebuild because there’s no point in my mind to fix the intake manifold if the rest of the engine is tired and junk. This is a work truck not a race truck. I only noticed the hiccup when doing dumb stuff you shouldn’t do in your work truck lol. I’m just trying to get the best mileage I can. My 87 tbi gets almost 13 I’d like 8-10 atleast in this truck.

 

[SirRobyn0]

I may just keep “bandaiding” stuff until I can pull a 350 out of something else and do a fresh rebuild because there’s no point in my mind to fix the intake manifold if the rest of the engine is tired and junk. This is a work truck not a race truck. I only noticed the hiccup when doing dumb stuff you shouldn’t do in your work truck lol. I’m just trying to get the best mileage I can. My 87 tbi gets almost 13 I’d like 8-10 atleast in this truck.

I get it. Totally. So what are you currently getting for mileage? I would expect you to at minimum 10MPG unless you have a ridiculously low rear end and drive it on the highway a lot.

Low mileage, that could definitely be in the distributor. So if that's your primary concern then yes, I'd go after a replacement distributor.