Swapping carbs, maybe Holley Street Avenger?

The hesitation you refer to is totally adjustable.
If it is dumping too much fuel like you say, all you do is go down with the squirter size.

That is the great thing about Holleys, they are SUPER adjustable, and it is simple once you see what each circuit does.

If you stomp it and have an issue, tune the accel pump circuit.
If you have issue at cruise, tune the main circuit.
Ect, so on...

 

Well, Rolandag just PMd me, and I might be able to borrow/buy his 750 dp come tomorrow...

 

I swear by the Holley Street Avenger carb. I've had one on my engine since it was rebuilt. Took it out of the box, bolted it on & ran it. Never had to make an adjustment. Still running damn good to this day. I do alot of daily driving. If I ever have to get another carb, it'll be another Street Avenger...Just my 02.....

 

That's exactly how my neighbor feels about his 770 SA.

 

Now, that is the kind of info I want. What works...

I bought the 1406 Edelbrock and it worked great out of the box...until I swapped heads, headers, intake, etc. Then I bough the calibration kit to make up for it, an was able to fix the problems as they came up. I just finally got to the point where the calibration kit no longer fixed the problems, so figured it was time for a bigger carb.

So, Mercurycruizers...what engine setup are you running?

 

A better choice with your combo would be either a 650 DP or a 670 SA. The 750 DP will be too big off the line and slightly too big on the topend. The SA has a secondary metering block, not a plate. Another good choice is an 80783 650 VS.

 

Now that I am this far into it...what is SA?

 

STREET AVENGER

 

I'll second that. Great for daily street and ocational run at the track, I would not go larger then a 670.

 

Well, I got Rolandag's 750 DP and put it on and am having pretty much the same problems...

It idles fine, runs decent, then right about the time the throttle gets "tight" when the secondaries are getting ready to open, it falls all over itself. Once the secondaries open, it runs GREAT...

Any suggestions at this point as to why it is sputtering and faltering right at this point?

Does it if I slowly accelerate to that point or if I get there quickly. If i just stomp it to the floor, it just hiccups and takes off. Same thing it did with the 600 Edel.

 

The secondaries on a DP start to open long before the throttle "gets tight", usually at about 30% opening of the primary if everything is adjusted correctly.

 

If it is sputtering before the secondaries open, the jets are lean.
If it is sputtering right as the secondaries open, the secondary accel pump linkage or pump cam are not tuned.
If it is sputtering while the secondaries are opening, the squirter size is wrong.

Check the primary squirter size too.
A smaller squirter could be a help...

A 700 DP comes equipped with a 50cc secondary pump, so it is much more forgiving on the rear squirter tuning.

 

What rpm does this sputter start ? Are you using the vacuum advance? If so have you tried unhooking the vacuum? This sputter is it a miss or a pop? If poping does it sound out the exhaust or through the intake? Plug Gap?

 

I was standing in the shower thinking...

And got on here and Blown is on the same wavelength I am, I think...

I was wondering if something happens with the vacuum in carburetors right at that point where I feel it getting "tight" and maybe the problem is in my advance in the distributor (since it happens with both carbs). So, I was thinking about popping off the vacuum advance tomorrow and seeing what would happen.

To answer some questions, it is not a pop. I wouldn't call it a miss either. More like it just stops firing (I guess that is a miss) until I move the throttle back a bit, or more forward. You know how it sounds when a diesel truck does that thing when they are slowing down where you still hear the engine sound but it sounds like they are cutting the engine off and letting it drag the truck to a stop. That is about the best I can describe what mine sounds like right then.

I wonder if the vacuum changes right where the throttle tightens, and the vacuum advance cuts out for just the little bit of the acceleration.

I admit, I don't know much about carbs, just enough to be dangerous

 

Lean pop sounds like what you describe.
That said, I lean more to the distributor every time you post!

Where do you have the advance line hooked to on that Holley?
It goes to the vacuum port on the passenger side, right over the idle mixture screw.
You probably know that, but I had to throw it out there... Don't want you to be retarding when you should be advancing!