Quadrajet Clarification

[HotRodPC]

What are you saying there is no vacuum advance ? on a 74. I thought all HEIs had vacuum advance.

Oh no, there certainly is. Everytime Vac Advance and where to hook it up comes up, it's major arguement time. Everyone has different opinions about that. It's like politics and religion.

 

[firebane]

I don't think its a choke issue. usually a choke issue revolves around high revs that wont come down to idle. Or it never works. which is maybe what you mean lol

The foot to the floor is from hot soaking. so when you run it and then leave it for 30-45 min its a freakin pain in the asss to start. There are multiple reasons that contribute to hot soak.

Hot soak is where your fuel bowl is heated to the point that it creates enough vaporization pressure that it pushes fuel out every passage that it can and flooding your engine. It also can be caused by having already high temperature fuel being delivered to the fuel bowl.

base insulator problems, cast iron manifold doesn't help either, high float setting, needle and seat issues, boiling gas by having fuel lines too close to heat sources. or high fuel pressure. although not usually a problem with quadjets and stock mechanical fuel pumps.

The thing is ive never seen a quadjet of your era having slotted straight blade screws, usually its only the older ones with the divorced choke that used those, all the later model ones used tourqe bit screws. So I wonder if someone didn't already monkey with it.

Oh ya. Another thing im wondering is which vacuum port on your carb is the vacuum advance from your distributor connected to ?

Lots of good info and sounds a lot like issues I'm having. I'm not sure how accuracte my temp guage is but when I'm driving around I notice it usually hovers around the 180 mark and sometimes closer to the 200 mark. I also noticed that I don't have a clutch for my fan so I don't know if that plays into it as well.

You mention the heat soak issue and that sounds exactly like my issue and that has me thinking about what I said above and where the truck runs what I think is a tad warm. I'm going to be swapping thermostats as I have a new one already just haven't had a chance to do it. Also the entire manifold is covered in a nice thick layer of grease/oil/dirt which I'm going to say as well doesn't help with heat issues.

You mention divorced choke and I have seen this brought up through my searches and don't quite understand what this means can you elaborate a bit more.

The vacuum advance for the carb I forget where that is at the moment as it wasn't even hooked up and working properly. There was a port on the front of the carb that you can't see in the picture that doesn't have any vacuum at all. But when I did move it the idle jumped considerably.

Regarding the history of this carb all I can say is that the guy who owned it before me I have no double in my mind did monkey with it. I am trying to see to what degree and possibly fix the issues but as too many people in the past have done I may swap it for a eddy or holley.

 

[MadOgre]

Lots of good info and sounds a lot like issues I'm having. I'm not sure how accuracte my temp guage is but when I'm driving around I notice it usually hovers around the 180 mark and sometimes closer to the 200 mark. I also noticed that I don't have a clutch for my fan so I don't know if that plays into it as well.

You mention the heat soak issue and that sounds exactly like my issue and that has me thinking about what I said above and where the truck runs what I think is a tad warm. I'm going to be swapping thermostats as I have a new one already just haven't had a chance to do it. Also the entire manifold is covered in a nice thick layer of grease/oil/dirt which I'm going to say as well doesn't help with heat issues.

You mention divorced choke and I have seen this brought up through my searches and don't quite understand what this means can you elaborate a bit more.

The vacuum advance for the carb I forget where that is at the moment as it wasn't even hooked up and working properly. There was a port on the front of the carb that you can't see in the picture that doesn't have any vacuum at all. But when I did move it the idle jumped considerably.

Regarding the history of this carb all I can say is that the guy who owned it before me I have no double in my mind did monkey with it. I am trying to see to what degree and possibly fix the issues but as too many people in the past have done I may swap it for a eddy or holley.

Well, see if you have an automatic quadjet with non worn throttle shafts. If you don't then the Edelbrock may very well be the way to go as they are a lot more user friendly. If you buy a brand new one its still about the same cost as doing a major overhaul on a quadjet. And if you install a pressure regulator to make sure you get no more then 5-5.5 lbs pressure and a good heat insulator gasket, you should never have to worry about the hot soak problem ever again.

 

[MadOgre]

This is what a divorced choke looks like

You must be registered for see images attach

This is the carb im working on

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

 

[MadOgre]

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

 

[MadOgre]

I'm not sure how accuracte my temp guage is but when I'm driving around I notice it usually hovers around the 180 mark and sometimes closer to the 200 mark. I also noticed that I don't have a clutch for my fan so I don't know if that plays into it as well.

You mention the heat soak issue and that sounds exactly like my issue and that has me thinking about what I said above and where the truck runs what I think is a tad warm. I'm going to be swapping thermostats as I have a new one already just haven't had a chance to do it. Also the entire manifold is covered in a nice thick layer of grease/oil/dirt which I'm going to say as well doesn't help with heat issues.

Your thermostat wont help much with the hot soak problem. What you really need to do is isolate your carb and fuel lines from the heat radiated from your engine.

You should have a thick heat insulator gasket under your carb. RPC sells a quadjet plastic spacer that would probably help a lot if used in conjunction with the heat insulator gasket.

usually guys tighten the piss out of the carb to manifold bolts and they compress that base gasket so much that it doesn't really do what it was designed for. Not to mention causing warpage in the carburetor itself.

The trick is not to run your engine cool but to keep your carb cool instead. That's why Aluminum intakes help in this area.

Having no fan clutch ? do you mean it is a fixed fan blade like this ?

You must be registered for see images attach

If so that will keep your engine cooler because the fan is always cooling according to engine rpm. The only draw back is that it is always cooling even when its 40 below and it sucks 10-15 horsepower. maybe a little more.

 

[MadOgre]

Oh no, there certainly is. Everytime Vac Advance and where to hook it up comes up, it's major arguement time. Everyone has different opinions about that. It's like politics and religion.

Oh OK LOL

 

[firebane]

I'm not sure how accuracte my temp guage is but when I'm driving around I notice it usually hovers around the 180 mark and sometimes closer to the 200 mark. I also noticed that I don't have a clutch for my fan so I don't know if that plays into it as well.

You mention the heat soak issue and that sounds exactly like my issue and that has me thinking about what I said above and where the truck runs what I think is a tad warm. I'm going to be swapping thermostats as I have a new one already just haven't had a chance to do it. Also the entire manifold is covered in a nice thick layer of grease/oil/dirt which I'm going to say as well doesn't help with heat issues.

Your thermostat wont help much with the hot soak problem. What you really need to do is isolate your carb and fuel lines from the heat radiated from your engine.

You should have a thick heat insulator gasket under your carb. RPC sells a quadjet plastic spacer that would probably help a lot if used in conjunction with the heat insulator gasket.

usually guys tighten the piss out of the carb to manifold bolts and they compress that base gasket so much that it doesn't really do what it was designed for. Not to mention causing warpage in the carburetor itself.

The trick is not to run your engine cool but to keep your carb cool instead. That's why Aluminum intakes help in this area.

Having no fan clutch ? do you mean it is a fixed fan blade like this ?

You must be registered for see images attach

If so that will keep your engine cooler because the fan is always cooling according to engine rpm. The only draw back is that it is always cooling even when its 40 below and it sucks 10-15 horsepower. maybe a little more.

Well you definitely have given me a lot of information regarding all this and clearly tells me what I originally thought that something about this carb setup was not done properly causing grief with the truck.

Regarding the fan I have I think a 5 blade fan with no clutch on my truck. And since I live in a cold climate during the winter probably be a good idea to pickup a clutch fan for my truck as well.

 

[firebane]

I'm not sure how accuracte my temp guage is but when I'm driving around I notice it usually hovers around the 180 mark and sometimes closer to the 200 mark. I also noticed that I don't have a clutch for my fan so I don't know if that plays into it as well.

You mention the heat soak issue and that sounds exactly like my issue and that has me thinking about what I said above and where the truck runs what I think is a tad warm. I'm going to be swapping thermostats as I have a new one already just haven't had a chance to do it. Also the entire manifold is covered in a nice thick layer of grease/oil/dirt which I'm going to say as well doesn't help with heat issues.
Your thermostat wont help much with the hot soak problem. What you really need to do is isolate your carb and fuel lines from the heat radiated from your engine.

You should have a thick heat insulator gasket under your carb. RPC sells a quadjet plastic spacer that would probably help a lot if used in conjunction with the heat insulator gasket.

usually guys tighten the piss out of the carb to manifold bolts and they compress that base gasket so much that it doesn't really do what it was designed for. Not to mention causing warpage in the carburetor itself.

The trick is not to run your engine cool but to keep your carb cool instead. That's why Aluminum intakes help in this area.

Having no fan clutch ? do you mean it is a fixed fan blade like this ?

You must be registered for see images attach

If so that will keep your engine cooler because the fan is always cooling according to engine rpm. The only draw back is that it is always cooling even when its 40 below and it sucks 10-15 horsepower. maybe a little more.

Well you definitely have given me a lot of information regarding all this and clearly tells me what I originally thought that something about this carb setup was not done properly causing grief with the truck.

Regarding the fan I have I think a 5 blade fan with no clutch on my truck. And since I live in a cold climate during the winter probably be a good idea to pickup a clutch fan for my truck as well.

 

[firebane]

So I just wanted to update this thread with some findings that i found.

First finding is that the motor in my truck isn't a 350 as I thought it was but in fact a 305 as designated by the C2R stamp on the pad behind the alternator.

Second the carb on the truck is for a manual transmission as per the number sequence but only 1 of the other 2 I have are for an automatic and the other is manual.

So I'm thinking with the automatic I can take a look and possibly make it work? But we'll see as I have no clue what status its in.

And finally I have discovered it would seem someone has either taken the manifold off this truck at one point in time or didn't properly torque down the manifold bolts as some were extremely loose and when I cinched them down you could see oil seeping out from the crack.

So now it basically looks like it'll be time to replace intake manifold gaskets and valve cover gaskets.

Some slightly dissapointing news but looks like I'll need to be saving up to drop a 350 into this old girl next year and dropping the 305.

Call me crazy but I knew there was a big power loss in this truck.. I know what a 305 vs 350 feels like and I knew something wasn't right.

 

[MadOgre]

Well post up some pics of all three carbs you have and did you check the throttle shafts on all three for excessive wear?

 

[firebane]

I haven't had a chance to get any pictures of the carbs yet but I found this for a cheap price and its aluminum. I know its not a Edelbrock intake like a performer but I didn't feel like spending a whack of money on a intake. This is still an aluminum intake for the quadrajet.

 

[HotRodPC]

I haven't had a chance to get any pictures of the carbs yet but I found this for a cheap price and its aluminum. I know its not a Edelbrock intake like a performer but I didn't feel like spending a whack of money on a intake. This is still an aluminum intake for the quadrajet.

Cheap??? Not wanting to spend a whack of money on an Intake? Bud, you might check into it, but that might just be a gold mine and be more valuable than a Performer. Not sure if that's one of them, but a facorty GM Aluminum intake usually means Whack Money. That could very well be off a Vette, or Z28 camaro or some other performance engine that a guy restoring a car will pay good money for. Hell without even looking it up to see the value, I woudln't mind having it, and if it's indeed a useable one and not fugged up, I'd be willing to trade a used Performer for it.

Edit: Oh now I paid attention and see the EGR port. That'll make it not one of the valuable ones for sure, but still very worthy of using.

 

[HotRodPC]

From what I see it's not a valuable one. If the info is incorrect it appears to be for 82-92 Caprice and Camaro on 305 and 350 engines. Seems it has ask prices of $80-$150 depending on condition. That's the ask price though, doesn't mean it sold. I'd still use it though. Lighter and discipate heat better for sure.

 

[HotRodPC]

Am I seeing in the pics that you tapped, threaded and used threaded plugs in the well plugs rather than epoxy? Or is that not the well plugs notorious for leaking?