1989 5.7 Quadrajet to Edelbrock 1409 swap help

[vetting]

I have a 1989 mercruiser 5.7 with what I'm pretty sure is a Quardrajet carb on it. I'm tired of fighting carb issues every other year and really dont have the patience to deal with a carb rebuild. So I want to upgrade to a Edelbrock 1409 carb. I'm just wondering if Im going to need an adapter plate and if I need any brackets for the throttle or not. I dug up some old pictures for reference.

Also, I know that I'll have to redo the fuel line. I would like to put in a flexible line to make it easier to working on the motor - like taking the inline filter off and being able to remove the valve cover for rocker adjustments. I was thinking about putting braided hose in - do you know what size the fittings are?

 

[Bondo]

Ayuh,.... The 1409 is a dual patterned carb, so it should bolt right on,....

The linkage should/ might work, with little to no modifications,....

The fuel line from the fuel pump to the carb is 3/8",....

 

[Rick Stephens]

The cable bracket will drop right on. You'll either have to make up a steel line or use marine fuel line with 'push on' fittings/connectors. Your autoparts store will have the fittings.

 

[Fishermark]

The cable bracket will drop right on. You'll either have to make up a steel line or use marine fuel line with 'push on' fittings/connectors. Your autoparts store will have the fittings.

If you use rubber hose, just to be more specific, make sure it is marine type A1.

 

[NHGuy]

If you use flexible hose do yourself a favor and get some insulated padded clamps to keep it from bouncing around. Especially near the belts and pulleys.

 

[vetting]

So I dont need a Edelbrock 2696 Four-Hole Square-Bore to Spread-Bore Carburetor Adapter?

 

[Rick Stephens]

That adapter goes the other way. It takes a square bore intake and adapts it to a spread bore carb.

Generally speaking, a square bore carburetor like the 1409 has dual mounting/screw holes and can be attached to either a square bore or a spread bore intake. It is not quite as efficient sticking a square bore carb on a spread bore intake. Or vice versa, using an intake designed for a spread bore with a square bore carb is not quite as efficient. That efficiency is lost through minor difference in airflows as compared to using intake and carbs designed together.

 

[vetting]

So I guess I dont understand when one would even use that adapter with a 1409 then but it comes up in almost every post out there regarding mercruisers and 1409s. I was under the assumption that you need one unless you already had a weber cab (91+) which is already hooked to a square bore intake.

 

[Rick Stephens]

So I dont need a Edelbrock 2696 Four-Hole Square-Bore to Spread-Bore Carburetor Adapter?

So the way you phrased that was confusing to me. Looks like what you said was Square-bore (intake) to Spread-bore carburetor.

I do not believe you have to have the adapter for the 1409 to fit the spread bore intake because the carburetor has both sets of screws. I did not try to do that though. I have a square bore Performer intake. And I do not know what efficiency is lost via either method: A) square bore carb directly on spread bore intake or B) through an adapter plate.

 

[Fishermark]

I went from a Quadrajet to an Edlebrock square bore carb on my 56. I have the Performer spreadbore intake. I did not need the adapter... but it is close. As long as the the barb and gasket covers the opening then you are good. You will have to take a look and see once you get the carb.

 

[carrera205]

I'm looking at doing this swap also! Anyone have pics of the 1409 on their Merc 5.7 with the bracket and cables setup?