Thread: Thoughts about AED carb?

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We have a 355 with dart aluminum heads, flat tops, hurricane high rise intake, 2500 stall and the 750 AED/holley carb. the question is....it's sluggish at take off(small sputters and a little hesitation) but once it gets going it will freakin scream! but why could it be bogging down at take off? we also think the power valve could be blown to because we had some back firing going on when we first got it running....could the power valve cause it to be this sluggish? should i get rid of it and get something else?? maybe a different intake? any help would be appreciated! oh and this is my first post here...seems like a sweet forum...

Welcome to the forum. I wonder if you aren't just over carbed. Usually a 600 or 650 would be good for 355 cubes. Since you have thrown the Dart heads into the equation I'm not sure, but some of our engine guys will for sure.

Don

A blown power valve could contribute to your problem but my guess is that you need to fine tune the primary accelerator pump system. If you're running a 30cc pump you might want to go up to a 50cc pump. I would then get the pump cam assortment and primary shooter kit so you can tailor the pump shot. You also need a good book such as this one.

I forgot to mention that the smell of gas is a little strong when its idling sometimes...maybe it's not adjusted right? a friend adjusted it and he said he knew what he was doing....it done a little better after he adjusted it. also if you run it hard and then go to park it....the idle is bogged down kinda like it's flooding or loading up...rev it up a little bit and it's fine. it's weird lol

And i need to get a new dual inlet for it...is it a -6 or -8 fitting? it's a 750HO

the size of carb, and the intake configuration depend on what you expect the engine to do. If you want low end torque, and snap off the line, then you are over carbed. If you are looking for a high revving engine you are in the ball park.

The easiest way to explain this is to start by establishing that air moves through the intake as a liquid. By making the venturis in the carbs smaller, you increase velosity. This increase of velosity flowing through a dual plane intake is what is needed for efficient torque. The idea here is that the air will gain so much momentum that when the piston reaches bottom, the air flowing through the carb will flow all to the way into the cylinder, and thus start compression before the valve closes.

A larger carb, and a single plane intake work best at higher RPM ranges. At higher RPMs the engine is moving so mush air, that a smaller carb just makes resistance

When you understand velosity, carbs will be much easier to tune. When the velosity is greater (smaller venturis), the air flowing through the carb increases the low pressure in the jets, and more fuel is drawn through. When the velosity is slower (larger carb) the carb drafts less fuel. This is why an engine leans out when the carb is too large (engines often backfire in the intake when they are too lean) A larger accelerator pump can help, as well as changing jets. When a carb is too big you have to go with larger jets because there is not enough of a low pressure area created to draw the gas through the smaller jet, This will cover the problem, but you still lose some of the low end torque

I hope this helps. This is over simplified, and is just the tip of the iceberg, but to go into this subject in depth could take hours and many pages

I have never ran an A.E.D. carb. but bought one of thier kits for a holley. Looked like good parts and seems to function correctly. I had a simular problem with a hesitation recently on my Holley. took the air cleaner off and ripped the throttle a couple times. Noticed i was not getting fuel coming out of the secondary squirters. Turned out to be that little orange mushroom under the accelerator pump, it had broken.

Originally Posted by DennyW

Pretty much what was said. How ever, you can try a 1" spacer with the 4 holes (closed), not open. This will speed up the velocity for take off.

This the manifold you have ?

I was reading my Holley handbook and in chapter 8 it was talking about adapters. They claim that a 3310 rated at 780 cfm drops to 640 cfm when an adapter is used.
I've got the 650 dp mounted on the 289 in the Mustang with a 1in spacer. By their calculations that must drop the cfm to somewhere around 525. Does that make sense?

That does make sense. I was under the impression that carb cfm was set in stone. BTW, the manifold is a stock Ford unit I picked up at the local swap meet for $80 a few years ago. I'll have to find the numbers on it to see exactly what it was originally for.