Caprice 305 ci 1986 carburetor question

my project-engine is working less or more properly,
but I have a kind of fast creeping leak on top of the carb,
so properly might be the wrong word.
There are also five blocked in-or-out holes/tubes, things I don't need, for only the brake-vacuum is relevant for my car.
So I'd like to replace the carburetor.
The car is under 1200 lb, engine is standard, 165 hp,
so more than fast enough for street use.

Is a 4BBL the best choice, or are there other/better (straight fitting)options ?

Thanks in advance,

M.

 

An old Quadrajet might be better, or a different 4bbl carb. I though the 86 caprice had a computer controlled carb? with some wires going into it. But since you are in Belgium, things might be different?

If you could post a photograph of your carb, we might be able to help you figure out what it is that is leaking, and how you could fix it, or suggest a better carb for you

 

Hi,
there's no computer involved;
here some shots from different angles,
the leak is on top at the front, and also a little lower than "on top"; the joint is tight.






M.

 

First thing to do would be to overhaul the carb. Get a "carb kit" (repair kit with the gaskets), and a new float, and a spray can or two of carburetor cleaner.

You might be able to find some small rubber or plastic caps to put over the fittings you are not using. At least it would look better.

The intake manifold you have is a "spread bore" design, so most of the normal hot rod carburetors like the Holley and Edelbrock will not fit without an adapter.

If you want to spend some serious money, you could buy a different intake manifold and a new carburetor. That would be the best thing to do. But if it were my car, I would work on the carb you have to fix it.

 

Float level is too high or the float is saturated and is no good.
Fuel is not supposed to be that high in bowl.
If it's sloshing out during use, you need a new top gasket, minimum

 

a new carb and intake would "clean" that engine bay up a lot. i hated that whole generation of carbs/intake/emission controls.

 

Understand being in Belgium you're workin with what you have available. I'd go with a carb kit, get it running smoothly, then work on your timing curve, the emissions controls on that engine likely doesn't have a decent curve, an hei spring kit will help, a mild cam will wake it up if you can afford it, this will require carb changes and ignition changes so keep all the spare parts from your 2 kits to retune. If you can get in the mid 200 hp range with a mild cam and tuning a 1200 lb car will doing well

 

Hmmm.....i noticed you do have vacuum advance on the distributor as well as no wires running off the car, so no computer. Did you import this 86 caprice from somewhere else or was it originally sold in Belgium?


Trying to rebuild the carb is a possibility---i'm sure you can get a rebuild kit shipped to you.

OR i think jegs or summit can ship you a professionally rebuilt quadrajet from SMI.

The other possibilities are new carbs----the holley 4175 is a direct replacement. Everyone feel free to chime in on your thoughts on this carb. i don't have anyexperience with it, although it looks to be good.

 

P.S. i noticed that the fuel line is headed towards the rear of the engine? Where is it going to? And what is the material of the tube?

 

thàt is input !
thanks for the usefull advice,

the leak is here,



float level indeed seems to be too high;
And the vacuum advance on the distributer ... needs some leads, or a comp ..?
I bought the engine, running in this configuration, with blocked tubes etc.
The car had a licenceplate from the Netherlands; I got no clue concerning the history.

But it hasn't run for ten years, so maybe everything dried out or became a nice cake, blocking internal valves or whatever.

The fuelline is copper, and it goes backwards to the firewall and then down to the electric fuelpump.

I'll try to save the original carb.
When it's dismantled, I can modify the tubes and holes.
Meanwhile, I found (where I can order) an overhaul kit, gaskets and so on.
And some elbowgrease will do the rest


M

 

I would also look at replacing that copper fuel line with a material less likely to crack and leak, like steel or braided hose. And definitely get those spark plug wires away from the fuel line - petrol and electricity together outside the engine makes your car burn to the ground. Also use spark plug wire holders and not the zip ties that are currently installed; plastic zip ties on wiring can cut through the insulation and allow a short to ground, which would be the engine block in this case.

 

Looks almost like my '84 305sbc. I swapped out the Quadra-jet for an Edelbrock 600cfm. I probably could have used a 500cfm, but I got a deal on the 600. I just blocked off the emission stuff on the manifold. You will need the adapter plate that Edelbrock recommends. I'm happy with the stock manifold and after some paint, it looks nice. You could go with an after market manifold, but if your running the engine stock, the OEM works fine.

I am on a budget like you are, so other than a little weight savings, I couldn't talk my wallet into getting a new manifold.

 

the above advice on lowering the float level is dead on.
Also you need to get that fuel pump back near the tank at about the same level, it will vaporlock if you leave it up front like you describe.
It is designed to push fuel rather than siphon it......

 

Random question, but what would be the chances of you wanting to sell that Netherlands plate? My family's from there.


Sent from my iPhone using Tapatalk

 

you need a top gasket and a new accelerator pump.Thanks for the last picture.You can leave the carb on and just take off the top and replace these parts......

 

If you go with the Edelbrock, you'll need a fuel pump that pumps 6psi.

 

If it set for 10 yrs., it needs to be pulled and cleaned and kitted for sure, you should either do that or replace it. Always put a new float in a quadrajet.

 

I have a Dutch plate for you if you want, PM me for details

Hennie

 

I am with the squirrel on this one. You can repair the carb or as he suggested go with an older quadrajet.

That is a smog engine. It has an EGR valve. See arrow in picture. it can be blocked, just remove the valve and make a little plate to cover the hole.

You can also make it a little snappier by getting an advace curve kit for the distributer, there are better distributers but if you must work with what you got the advance curve kit will help a bit. Maybe this is a future modification.

Good luck with it whatever you decide to do.

 

I would try to find an older QJet, anything '79 and older doesn't have the computer chips in them. Holley makes a very nice spreadbore carb as well, pricey but nice carbs.

Bob

 

My Daly is a 86 Caprice wagon Olds engine from the factory but same carb. Switched to the edelbrock improved performance and milage.

 

well,
considering the tips and tricks, I opened it and closed it sucesfully,
with the right result.
The choke doesn't work - maybe because some disconnections -, so I pulled it manually backwards.
The engine starts, the car runs; after a couple of minutes, I shut the engine off, just to avoid what can happen after years of inactivity.
To cope with the remarks about the tie-wraps : they were temporary, just to keep them away from the exaust-pipes; real separators are on their way.
At least the engine is +/- ok, so I can look further;
I'm still wondering wether I need a return or not ; maybe the pressure of the electric pump will eventually blow out something; I have no idea of the initial pressure of the original mechanic pump ( it had to be discarded in favor of the chassis-rail )
since performance is more than sufficient, I don't want to take the risky/exotic route.
as far as I know, my carb fs. 600 cfm. seems fair enough ( and I have no idea of the mileage )

bobss396 suggested a '79 carb : http://www.rockauto.com/catalog/moreinfo.php?pk=1126106
would this do the job ?
http://www.jegs.com/i/Holley/510/0-80457S/10002/-1
or is this the one ?
regards,

M

 

The choke requires a "hot air" tube from the intake manifold to the choke housing. The lower end of the tube is shown here:



the upper end connects to the place where there's a bolt stuck in a short rubber hose on the housing on your carburetor.

Also there is a thermal spring in the choke housing, attached to the round plastic piece. You can adjust how much for the spring exerts by loosening the 3 screws and rotating the plastic piece. It should just close the choke plate when the engine is cold, and should open by itself as the engine warms. It is a complicated mechanism, and takes some work to get it adjusted properly.

The fuel pump should produce about 5 psi or so of pressure, more than 6o r 7 will probably cause problems. Most normal electric pumps designed for use with carburetors do not require a regulator. Racing type pumps usually do need one.

 

as always a matter of taking and giving ...

the pressure - dixit the box - is around 5 psi, and since the pump has only to push the petrol and 1.5 ft up and 3 ft away, it will be 5 psi; at least the carb doesn't leak anymore under "full pressure"

thank you, Squirrel

M

 

and since the world never stops turning ..
the carb nr is 17058204
which learns it was built in ' 78
M

 

I can't understand why you'd want to remove the choke, rather than make it work. I guess if you don't drive the car when it's cold, you can get away with no choke, but I still don't understand why.

 

Put an adapter and run a large (500 cfm) rochester 2bbl. Thats what I do on all my small blocks that are just for daily driving. You will be amazed at how great it will run compared to the quadra-shit. That, or put a Holley on it. Quadra junks and Edelbrock/webers suck no matter how fresh and tuned they are.

 

I'm not discarding the choke, Jim, not at all;
I'm still trying to understand and save the carb!
I removed a vacuum thing,





to test it with a vacuum-euhh-sucker,
choke-housing is next,
and slow but shure I'll see what it's about and how it works.
But, yes, but, I'm still considering other options
M

 

The vacuum thingy has two jobs. It opens the choke under some conditions, and it also helps control the secondary air valve. The secondary air valve is the plates over the secondary side, which open "on demand".

The Quadrajet is an engineering marvel, lots of guys don't understand it and consider it junk. If you take the effort to figure out how it works, and get it working as designed, it is great.

 

The Q jet will get better mileage than a big 2GC when built properly , plus you will have the secondaries on demand.
The Q jet is the apex of American production carburetion.
You owe it to yourself to learn about them , rather than yanking them off and thinking up names for them LOL


BTW, the 1-3/8 2GC's flow about 400 CFM when corrected to the same in. of vacuum as the Qjet...In other words ,about half of a late model Q jet.