Rebuilding my Quadrajets on my 4.3

[MolsonCanadian]

I took off my Q-Jets a couple days ago while the weather was warm. I have an engine running a little rich, and they are both 1990's so they're probably due anyhow. I'm going to tear into them in the next week or so. Anything out of the ordinary I should know? I plan on leaving all the settings as they are now and tune once back on the engines in the spring.

 

[RogersJetboat454]

Re: Rebuilding my Quadrajets on my 4.3

Pay close attention to how the accelerator pumps are going together. Some of the parts for the accelerator pumps included in various kits can leave allot to be desired. Try to get a name brand kit.

As far as leaving all the settings as they are, I wouldn't do this because it won't give you the opportunity to clean the idle mixture passages. Not hard to properly set the idle mixture once it's all done. Just a vacuum gauge, and the tach.

If you want a good book on the carb, this will tell you EVERYTHING you need to know and then some;BARNES & NOBLE | Rochester Carburetors by Doug Roe | Paperback

 

[Don S]

Re: Rebuilding my Quadrajets on my 4.3

You can't rebuild a carb and keep all the old settings. With new gaskets, accelerator pump, needle valve and seat, everything needs to be reset or at least checked. You so realize you have to disassemble, soak in carb cleaner, blow out all passages with compressed and and verify they are open don't you?

 

[MolsonCanadian]

Re: Rebuilding my Quadrajets on my 4.3

Yes. thank you Don. I may not have articulated it correctly, I didn't mean leave them there. Everything will be cleaned properly and returned to merc specified adjustment. (I think it called for 2 turns out, which is what they are at now)

Thank Rogersjetboat454, I actually got Cliff Ruggles' book "How to Rebuild and Modify Rochester Quadrajet Carburetors". From the reviews I have read, it is pretty good. Though I have never rebuilt a carb alone, I'm confident I can tackle it.

 

[Don S]

Re: Rebuilding my Quadrajets on my 4.3

When you do them, here are the Merc specs on the settings for that engine.

 

[MolsonCanadian]

Re: Rebuilding my Quadrajets on my 4.3

Thats great, thank you Don.

 

[MolsonCanadian]

Re: Rebuilding my Quadrajets on my 4.3

I was originally going with plain ole Carquest carb kits, but have now ordered kits from Cliffs High Performance out of Ohio. From the reviews, they are good quality parts, and include a new float.

 

[achris]

Re: Rebuilding my Quadrajets on my 4.3

Q-junks can be very finicky, so follow the book to the letter, check every setting twice and don't force things together. If it doesn't want to slide back, then something is wrong.

HTH...

Chris.....

 

[MolsonCanadian]

Re: Rebuilding my Quadrajets on my 4.3

Thanks Chris, I've heard the same thing. Good thing I have a few months to fiddle with them. No rushing.

 

[RogersJetboat454]

Re: Rebuilding my Quadrajets on my 4.3

IMHO Q-Jets have an undeserved reputation. It's not a slap it on and run it carb like a Holley.
A little bit of patience, and fine tuning will reward you with superior fuel economy, and kick a** secondaries.

 

[achris]

Re: Rebuilding my Quadrajets on my 4.3

IMHO Q-Jets have an undeserved reputation. It's not a slap it on and run it carb like a Holley.
A little bit of patience, and fine tuning will reward you with superior fuel economy, and kick a** secondaries.

Agreed...

 

[tinkerguy70]

Re: Rebuilding my Quadrajets on my 4.3

IMHO Q-Jets have an undeserved reputation. It's not a slap it on and run it carb like a Holley.
A little bit of patience, and fine tuning will reward you with superior fuel economy, and kick a** secondaries.

They've gotten this reputation because most people are to impatient to set them up properly, or they rebuild them incorrectly. As long as the throttle shafts or the throttle plate aren't worn out, there is no reason to change it to a Holley IMHO.

 

[RogersJetboat454]

Re: Rebuilding my Quadrajets on my 4.3

They've gotten this reputation because most people are to impatient to set them up properly, or they rebuild them incorrectly. As long as the throttle shafts or the throttle plate aren't worn out, there is no reason to change it to a Holley IMHO.

Agreed...

You brought up a good point too, it would be prudent of the OP to be sure there isn't any excessive wear in the throttle plates. I'm sure this would probably be covered in the book he bought, since it's a pretty common problem.

 

[NHGuy]

Re: Rebuilding my Quadrajets on my 4.3

I did my quadrajet this fall using Cliff's book & parts. I am certain you will be thrilled with the results. Just take your time and it will come out right.
If you are into appearance, only soak the air horn for an hour or two so you don't discolor the finish on the secondary flaps and the choke plate.
There's a cadmium gold finish under the spray black of the external linkages. It's not a functional thing but I cleaned off the black from the linkage cause I like things shiny. Then I redid the black carb paint with most of the links off and the remaining ones masked.
When I put it back together it looked great cause of the paint, some new gaskets, the bright finished links and a new white vacuum break. I hope it runs as good as it looks. I really expect that it will. I used the factory jet sizes, cleaned out the idle channels and replaced the idle tubes, did everything by the book.
Oh, here's something to watch for. Before you remove the upper secondary flaps make note of the position of the adjustment screw. There is a picture of the parts in Cliff's book on page 84. The Mercruiser book describes how to set it using a weird gram force scale that shows how many grams of weight it would take to push open the flaps. I did not see any mention of how to set it up in Cliff's book.
He has a nice forum where you can ask questions, I'm going to hit him up for some info in the spring when I put my boat back in service. If he says to just play with it that's fine too, full throttle runs are a lot of fun!

 

[MolsonCanadian]

Re: Rebuilding my Quadrajets on my 4.3

Thanks folks, I will be looking for wear on the throttle plates. Thanks for the tip about the secondaries, NHGuy. I'm not too concerned about the appearance of them. They are under the spark arrestors, which are under the plastic covers. When I check the oil etc, I only open a small portion of my engine bay, and only the dipsticks and belts are visible.

 

[ol belly up]

Re: Rebuilding my Quadrajets on my 4.3

...

 

[RogersJetboat454]

Re: Rebuilding my Quadrajets on my 4.3

Hello folks. I hope you don't mind if I jump in for a uestion. My 4.3 has a 4brl carb. Don't know the brand since it is in winter storge. My question is when I floor it to pull up a skier it hits a dead spot and falls flat for a couple seconds. This makes it hard for the skier to get up because of the sudden momentum loss. I don't know much about carbs. Any ideas?

Start you're own thread on it. Not polite to hijack someone else's thread, and you will get more specific answers..
When you do that, post the serial number of your engine, and a picture of your carb if you're not sure what it is.

 

[MolsonCanadian]

Re: Rebuilding my Quadrajets on my 4.3

Took apart one of the carbs last night. Two things that I noticed right away:

ALL the screws were loose! Once I pulled off the airhorn, the base plate pretty much fell off. The two Philips screws were only in a few threads each.
Also, the carb was CLEAN! Other than a little bit of blackening on the plates, all looks factory fresh. I'll be putting it together over the weekend and tearing into the other one.

Rogersjetboat, the primary and secondary plates were good and solid. No lateral movement.

 

[RogersJetboat454]

Re: Rebuilding my Quadrajets on my 4.3

Rogersjetboat, the primary and secondary plates were good and solid. No lateral movement.

By lateral movement, I'm guessing you mean back and forth, as in pushing their shafts back and forth on their axis?
It's not necessarily back and forth movement you worry about (if thats what you mean), the throttle plates more or less prevent that. It's the overall gap between the shafts and the holes they pass through in the throttle body. The steel throttle shafts will wear down the aluminum holes in the throttle body, and allow vacuum leaks if the holes are excessively worn oversized...

 

[MolsonCanadian]

Re: Rebuilding my Quadrajets on my 4.3

I mean they are not loose in the holes. No need for bushings. The whole unit actually looks brand new. It was surpringsingly clean.