Edelbrock carb swap from Quadrajet

[mudweiser]

Still fighting the troublesome Q-jet carb issues. Hesitates when the secondaries open, poor starting, idiling etc... I have rebuilt the carb several times as well. I found an Edlebrock #1409 i believe 600cfm carb new for $150. I might have the model number wrong, but it is the marine 600 cfm version. Wondering what i might gain/lose going to this carb. I know the q-jet has very, very large secondaries compaired to the edelbrock. I do question if this engine can even breath that much where it needs the large secondaries. Any opinion n doing this switch?

 

[WizeOne]

Re: Edelbrock carb swap from Quadrajet

Not even sure if the bolt pattern is the same between a square bore (edelbrock 1409) and the spread bore Q-jet. If not, it will not fit on your spreadbore intake mani.

However, some Chebby experts will probably chime in here.

 

[J JACKSON]

Re: Edelbrock carb swap from Quadrajet

you would have to run a adapter plate to get it to bolt up then you would have to deal with bending a new METAL fuel line the rest shouldn't be a problem

 

[jimmbo]

Re: Edelbrock carb swap from Quadrajet

First issue is why can't you get the q-jet to run right? It is a very good carb. When you say you have rebuilt it several times, does that need you took it apart, used some solvent on it and, using new gaskets put it back together? Or, when reassembling it you checked all the settings and condition of the float, vacumn controls, checked for warpage and loose throttle shafts, etc?

Spreadbore vs. squarebore. The Edelbrock is a squarebore design and depending on the intake manifold might or might not fit. Adapters are available but none flow well. Just for your info, Q-jets were only made in two sizes, the small version flowed 750 cfm and the larger flowed 800cfm. The difference was the size of the primairy venturi. A 350 cubic inch engine, unless spinning over 8000rpm is never going to use that much airflow.

In theory, the Q-jet should offer better low speed torque because of the small primaires. I did experience that when I swapped the 500cfm 2bbl Holley for a 650cfm spreadbore Holley on my 5.7 VP. It increased my top end enough I had to increase the pitch on the prop to keep the rpms in the recommended range. Normally more pitch reduces hole shot but the smaller primaires helped keep the bottem end the same as the 2bbl was with the smaller prop.

 

[rthomas]

Re: Edelbrock carb swap from Quadrajet

i did it, unfortunately i never ran mine with the original q-jet so i cant say witch i prefer, ive done this same swap many times on gm cars and always been pleased with the results. its probably worth noting that using an edelbrock manifold along with the carb will yield far better results than just the carb alone

 

[wca_tim]

Re: Edelbrock carb swap from Quadrajet

I had an edelbrock 1409 (their marine 600 cfm version) on my 4.3 and had zero problems with it once it was dialed in for that set-up. Although a lot different to set-up and tune than a quadrajet, it was easy to get set up.

I also have the 750 cfm version on my current 383, and although it was tougher to get the jetting right on, think I've finally got it. The engine builder I used for the 383 has run side by side comparisons and had no doubt that the edelbrock marine carbs made just as much or more power than any out of the box marine carb they tried.

For a stock or anywhere near stock small block, a 600 cfm carb has plenty of flow capacity. no worries there.

The 1409 version has a dual bolt pattern for borad compatibility... but you'll need the adapter plate to match the square bore base up with the stock manifold spread bore pattern.

150 is about half what the edelbrocks go for, are you sure it's new and not something that could be screwed up from the start? as long as your sure about the new one, i think you woulc be pleased with the result.

 

[mudweiser]

Re: Edelbrock carb swap from Quadrajet

I rebuilt the q-jet myself with a kit. Cleaned everything with carb cleaner, set float levels, adj linkage and what not. I do know the bushings on the butterfly shafts have some wear. Had to replace that plastic cam on the secondary upper butterfly shaft and noticed the wear. Most likely i missed something, after the first rebuild i went through it again and found the bad cam. I'm not a carb guru by any means but i have read up a bit on the q-jets. Seems like they are a nice carb when properly set and from what i have heard, their performance is hard to beat when properly set-up. I'm sick of messing with it.

It is a new carb. My friend ordered it from Edlebrock himself years ago but it was a project boat that fell through.

 

[Mkos1980]

Re: Edelbrock carb swap from Quadrajet

You will only need the adapter plate if your running the low rise 4bbl intake. The 350 Magnum motors run a highrise with duel bolt patters for both spread and square. You will also have to run a new throttle cable bracket. I picked up a universal one at AutoZone for about 15 bucks. Other then a new fuel line mentioned above, thats it. I tried the metal line but it was way to hard to bend 3/8 around everything so I went with the A1 hose. I was always under the impression it had to be metal until I walked over to the USCG in Cleveland and they said no and handed me a book with rules and such. This was from their site.
FEDERAL LAW

183.558 - Hoses and connections

(a) Each hose used between the fuel pump and the carburetor must be ?USCG Type A1? hose.



If a hose is used in the fuel line running between the fuel pump and the carburetor, the hose must be ?USCG Type A1? and so labeled as required by 183.540. This requirement is applicable whether the fuel pump is engine mounted or mounted remotely from the engine, as permitted by 183.566.

Oh BTW I switched from the Qjet to the Edelbrock 1409 and I am in love with it.

 

[mudweiser]

Re: Edelbrock carb swap from Quadrajet

I suppose i should have mentioned it's a 1989 5.0 not the 5.7 motor. Wish it was the 5.7.

Interesting about the fuel line, always thought it had to be metal.

 

[jimmbo]

Re: Edelbrock carb swap from Quadrajet

On a 305 the Holley 500cfm 2bbl is the perfect size, airflow wise. When it is flow rated using the spec for 4bbl carbs it flows 375-380 cfm which is what a 305 uses once Volumetric Efficiency is taken into account. Easy to set up, no worries about the secondaires.

Shown here on a real nice 4bbl manifold Volvo put on the Vortec 5.0 litre and 5.7 litre engines

 

[rodbolt]

Re: Edelbrock carb swap from Quadrajet

on the type A1 fuel lines, type A1 simply refers to its gasoline permeability and its open flame resistance.
keep reading the regulations and you may find that hose clamps and slip connections are not allowed on the pressure side of the fuel system.
seirra makes some nice flex lines that have 3/8ths male flare fittings swaged on that are USCG compliant.
bring me a rig with hose clamps on the pressure side and either thats the first repair I make or you simply pick the rig up and take it down the street.
but simply slipping on a hose labeled A1 and some clamps may not be in compliance.

 

[Mkos1980]

Re: Edelbrock carb swap from Quadrajet

May not be, but I'll go back and reread some of the stuff. When they did a visual last month during a safty check I passed and got a nice little sticker to put in my window showind that I passed and not to stop me in the future (this year at least)

 

[Willyclay]

Re: Edelbrock carb swap from Quadrajet

Just sent you a PM.

 

[Mkos1980]

Re: Edelbrock carb swap from Quadrajet

You can still use them as long as the hose slips over a regualor connection part. Not just cut steel fuel line.

FEDERAL LAW

183.560 - Hoses clamps: Installation

Each hose clamp on a hose from the fuel tank to the fuel inlet connection on the engine, a hose between the fuel pump and the carburetor, or a vent line must:

(c) Be beyond the bead, flare, or over the serrations of the mating spud, pipe, or hose fitting; and (see 183.560)

 

[mudweiser]

Re: Edelbrock carb swap from Quadrajet

Ahhh, he ended up selling the carb over the weekend. Should got it right away. Wasn't sure about the performance so i waited. It made for some good reading anyways. I always learn something new with each repair, or in this case, attempted repair. Stuck with the Q-Jet for now i guess. Thanks to all wh offered advise.