Name that CARB! (please)-gctid362507

[Guest]

Hi All-

I think what I have on my hands here is a Quadrajet 4 barrel on top of my mercruiser 454, but not too sure. I have the carb. Have the rebuild kit. Have the time. Even have instructions and a manual! Has anyone ever rebuilt one? Is it easy? Better left to the pros? In between? I'd appreciate an advice or accounts on the rebuild. THANKS!:livid:

Attached files [img]/media/kunena/attachments/vb/665513=25571-photo (2).JPG[/img]

[2850Bounty]

Yep, the ole Rochester Quadra-Jet. Probably the 4MV since I don't see an electric Un-choke.

Darn good carburetors if you understand them.

Here's a 4ME with the electric heating element style.

[Guest]

I'd personally call it an "in-between" to rebuild. But best left to the pros to do it right and get the best out of it. (In that, I mean I would personally love tackling that job, but I know an old guy or two that would do it much, much better than I could.) Good carbs when set up right imho. And, as I can see with the tube angled toward the throat, you even have an older style marine version. And it's ALWAYS good to see people having the marine version carb for their boats.

[Guest]

Generally, they don't need "rebuilding" because they don't get that much wear-not like on an automobile where you're constantly using the throttle. They get dirty and gunked up from fuel sitting in them over winters, float needles stick, passages get clogged. I've disassembled, cleaned, and reassembled several Rochesters, both two barrel and four using the kits available at the local auto parts store and they have worked great afterwards. Take it apart carefully, soak it/spray it down with carb cleaner, brush all the crud out with an old toothbrush and blow out all the passages. Reassemble it with the new parts and gaskets you get with the kit (you will wind up with extra stuff that doesn't go on our carbs.) You shouldn't have to make any real adjustments other than the idle mixture screws you took out on disassembly. Seat them gently and back them out about 1 1/2-2 turns to start. There are all sorts of sites out there on the Quadrajet for help, however many of the auto sites that deal with them also talk about jetting modifications that don't really concern us here. I say GO FOR IT!

[Chief_Alen]

Welcome aboard !

Below is a post i made to a different site copied and pasted here.

Get yourself down to a auto parts store, get a can of berrymans carb soak comes with a screen in the can, like a deep fryer.

Also get a can of compressed carb cleaner.And a carb rebuild kit.

With a clean area on a table or bench i place a old cookie sheet with sides.

Break down the carb and remove all the rubber.

Remove the jets they should just screw out.

Everything goes into the berrymans, let soak for a few hours.

Remove the parts from the berrymans, start with the lower carb housing and blow it dry with compressed air, it clean?

Piece by piece build it, make sure every passage is clean blow it dry and use compressed can carb clear blow it dry again.

Jets clean, Float, floating no gas in it ?

Push the float under water and if you see bubbles it's time to replace it.

Ok when you install the pin in the forks that hold the float are they pressing on the float tounge and not allowing the float to move freely ?

So if you did your job correctly the carb should operate freely, and when you install the adjustment screws be gentle.

Do not bend the tips. All the way in with them gently and out 2 turns to start.

Final adjustment on the water.

Have someone else drive about 2000 rpm maybe a little more and you do the final adjustment.

If you take your time and there are no distractions, you should be ok.

Good luck !

[2850Bounty]

mainecoast wrote:
Generally, they don't need "rebuilding" because they don't get that much wear-not like on an automobile where you're constantly using the throttle. They get dirty and gunked up from fuel sitting in them over winters, float needles stick, passages get clogged.

I'm with Mainecoast. I think the term "rebuild" is a bit of a stretch in some regards.

Short of replacing a float, needle/seat, power valve, accelerator pump piston (or Holley diamphram), inlet filter and all gaskets ( IOW the kit )......, most of what we're doing is a good cleaning.

[captharv]

Rick:

There is no curled tube on the vent horn. Are you sure its marine?

If not, that the OPs problem...

[2850Bounty]

captharv wrote:
Rick:

There is no curled tube on the vent horn. Are you sure its marine?

If not, that the OPs problem...

Harv, many of the early Marine Q-jets had an angled cut to the vent tube as well as a wall or dike around the base of the vent tube.

This qualified these in this respect.

Here's a Qjet with the straight but angle cut vent tube.

Note the wall or dike around the base of the vent tube.





Here's one that uses the J-tube.

Note that there's no wall or dike around the base of the J-tube.

[Guest]

Thanks Rick.

This is great to get this kind of support. I think I will attempt it. The kit had so many parts and instructions and specifications I thought "Oh no" but the manual cleared things up. It really does not seem that difficult. On the Car Talk scale of difficulty I think it is well below "You've built your own nuclear reactor out of wood"- I do think I will try a short boil in vinegar.

[Guest]

i remember theres some plugs in the bottom of your carb that tend to leak and should be epoxied. if you've had your carb rebuilt before it may already have been done. i rebuilt my carb last year and it was pretty simple of you take your time and clean all the passages. mine was already epoxied.

http://www.carcraft.com/howto/57178/index.html

about half way down the page is a photo and arrows pointing to where needs to be epoxied

[2850Bounty]

FWIW, the Marine Q-jet does not undergo nearly as many throttle plate open/close cycles as does the Automotive version.

The illustrations show how to remove the throttle plates, remove the throttle plate shafts, and how to re-bush the main base plate, etc.

I highly doubt that you'll have to do this for the Marine version.

If you were to do this...... DO NOT install the new bushings as shown in the illustration.

This is a recipe for accidentally breaking the throttle base plate.



Instead, try clamping a correct diameter steel shaft into your bench vice.

Then slide the throttle plate bore over the steel shaft, and allow the shaft to absorb the shock while installing the bushings.

And again, I'd advise against hammering on any carburetor component without backing it up with something.... especially a die-cast component.



.

[BLCarl]

Two tricky areas for assembly are getting the main metering rods to pass through the gasket and drop into the jets without getting tangeled and bent, at the same time the choke linkage also has to pass through and connect. You just have to be careful not to bend anything and make sure everything is where it should be before tightening the screws. On very old models the well the main jets are in had plugs between the throttle plate and main body that would sometimes leak and cause mixture problems. It was usually cured with epoxy or JB weld. The newer ones had O rings around the plugs. If they were leaking you could see fuel stain evidence.

It's a well designed carb. Once you get things the way they should be they work great.

[Guest]

Those secondaries have a nylon (or something like that) cam that lifts those needles when secondaries open.If the rebuild kit has that cam, replace it just in case.

I once had a head-scratching session when that cam broke and the engine went ultra-lean when the secondaries started to open.It first felt like a blocked fuel supply or other fuel starvation.

Timo

[Guest]

http://www.youtube.com/watch?v=4BU7FfDXXi8&feature=related

I found this video helpful... maybe you will too!