What kind of carb tuning am I looking at?

[Beach Goat]

Sorry to be such a noob, but I am completely new to carburetor tuning. I have a 580" wedge motor, Indy heads, huge 290/290 .800" lift cam with tons of overlap, AED 1000 Holley 4150 carb, 14:1 compression. I'm having the motor detuned to 10.5:1 and a 268/272. 650" cam with much less overlap. I'm trying to get it a little more reliable on parts, a little easier on starting, and use 93 octane.

Besides changing the primary and secondary jets, what kind of changes am I going to be needing? I know that's a pretty broad question, but I'm reading a book "How to Tune and Modify Holley Carbs" by David Vizard, and I'm wondering if I'll have to change EVERYTHING he talks about.....power valve, air bleeds, four corner idle screws, jets, etc.

Not that I mind, it's going to be a fun experience, I just want to get a general idea before I start paying for dyno time.

 

[super-bee_ski]

Wow!
Race motor for the street?
Well,
I for one would say jetting would be the FIRST thing you would wish to address
BUT:
1. I would wait until your CAM is changed and Compression is lowered
2. Sell that RACE Carb, then purchase a 750 Holley or Edelbrock?

You mention Dyno time....
Speak with the Tech's at the Dyno shop, they will help you get the Street combo you desire.

 

[oldbee]

+1, except maybe an 850cfm?

 

[Beach Goat]

Thanks for the reply, I'm kind of in a strange spot. The engine is at the shop getting the pistons and cam+springs changed as we speak, but I am pretty much tapped out financially on this project and I have to keep the AED carb for the time being. The car is actually very streetable, with good manners, beside the hilariously bad fuel economy and not really wanting to cruise below 2000rpm. I hope the carb will still have good manners with less camshaft.

 

[oldbee]

Ok I can see the spot you're in so ur probably gonna have to do some leaning out on jets, at the very least!

 

[Zeppelin264]

No offense, but your asking for help on tuning a carb when you are running a full blown race motor?

I'd find a local dyno shop or carb tuner and get some help. Your going to go through a lot of trial and error trying to learn how to tune that carb, and in the process might destroy the motor.

 

[AR67GTX]

Thanks for the reply, I'm kind of in a strange spot. The engine is at the shop getting the pistons and cam+springs changed as we speak, .

Well - changing out the pistons in addition to the cam is a positive move. Trying to run 14:1 pistons with a smaller cam would have been a huge issue (especially for your starter). The carb changes may depend on how it was modified to cope with that huge cam and compression. I suspect some accommodation was made in the carb to get it to idle halfway properly - changed the idle or transition air bleeds, drilled the throttle plate, lower number power valve, opened up the secondaries closed position some, etc. You will probably have to reverse some of those to get a steady idle and off-throttle response. You probably need to do a complete disassembly of the carb (or have someone do it for you) and catalog what you have and what needs to be reversed or corrected.

 

[Beach Goat]

I am doing the tuning on a dyno, so I'll have access to plenty of experience and assistance.

 

[HEMI-ITIS]

Nice to get my crank pulled 1st thing in the morning

 

[super-bee_ski]

No offense, but your asking for help on tuning a carb when you are running a full blown race motor?

I'd find a local dyno shop or carb tuner and get some help. Your going to go through a lot of trial and error trying to learn how to tune that carb, and in the process might destroy the motor.

You are correct Zeppelin264
That is Exactly what I told him in Post #2

Post #2: "You mention Dyno time....
Speak with the Tech's at the Dyno shop, they will help you get the Street combo you desire."

Gee, you can sell that Bathtub of a Carb and pick up a Nice 850 CFM carb here on the Forum!

 

[super-bee_ski]

Here are a couple of Carbs for sale on the Forum right now:

1. HOLLEY 750: Used, will probably need rebuild. What you see is it. It was on an 440 ran rich.
$150 plus shipping. Open to offers.
2. Edelbrock 1805 carb. Manual choke. This carb is practically new. With about 10 miles on it. It's been sitting on a shelf for some time. Has the mopar throttle bracket installed. $275 shipped in the states.
3. Here ya go! For Sale: Demon 850 I bought this from a fella in New England 5-6 years ago but haven't used it. Low hours but should be kitted as the gaskets and seals have dried out, other than that a nice carb...$450 plus shipping from Northern Calif. PM me here if you have an interest, thanks!

 

[super-bee_ski]

Nice to get my crank pulled 1st thing in the morning

there is nothing like getting your CRANK pulled and a good polishing job first thing in the morning Big Al !!
Ps: got pics of the damage?
Again, 5 years was a "good run"

 

[HEMI-ITIS]

Is the timing locked at 70*?

 

[Beach Goat]

Is the timing locked at 70*?

Negative, timing is currently set at 25* advance at idle, 35* total.

 

[66Satellite47]

If you really have 14:1 CR, can't imagine how you'd get by on 93 pump gas. That's 114 territory. If you cut the pistons or increased chamber volume to get down to 10.5 you're OK. My GUESS is that with 580" you still need at least 1050 or 1150 CFM just to give it some air to work with.

 

[doublekrossd]

I've been working with pro systems for all my carb work. They aren't the cheapest but they really aren't much more than an off the shelf Holley. I know you mentioned about funding a new carb may be an issue but my experience has been to get what's right first instead of trying to limp along with mis matched parts.

My new carb is amazingly responsive, flows around 1000 real cfm, and is 100% street driven. The guys at pro systems are great to work with, give them your motor specs and what you want to do with it and they'll build a carb for you and your motor that's ready to run out of the box.

Good luck!

 

[66Satellite47]

OK

 

[HEMI-ITIS]

Pro systems has a great product.Be sure to buy from a legit dealer and some hack working out of his garage!