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Old 05-21-2012, 09:48 AM
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Low-throttle good, high throttle different story

Hey all;
75 Monte Carlo, 400sbc, mild cam, aluminum heads, edelbrock carb. Nothing special. About 14* base idle. Around 34* total.

I've got the car running pretty good. She's little rich right now at the moment but will be fixing that this week (always like to run richer to start off, just in case). I was out driving her Friday night and she loves the gas at low to mid-throttle. Hauls ***, shifts fine, likes to spin tires randomly. Just tends to buckle a little at very low throttle from a stop, mostly after a good amount of throttle. I assume that's being caused by warm temps, or still excess fuel leftover. Just have to lean out some and I believe that will be all good then.

Anywho, anytime I've ever tried to go WOT, she not only buckles but wants to die completely. Last year she was bad, but had different timing. This year, no backfires or anything else, but just wants to straight die. I'm assuming the first place to check on why this is happening would be the carb. I'm assuming that the primaries are working fine, but maybe the secondaries aren't doing their job? They open, that's for sure. But honestly not sure if spraying properly.

Is there anything else that I should look at? Anyone else had anything similar to this problem? Thanks!

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Old 05-22-2012, 06:04 AM
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Might be way to lean at WOT,check plugs.Mine does the same thing idle is rich but leans out at WOT,but it doesnt die just a slite power loss.I need to do a jet & rod change.Get a O2 sensor an gauge they help alot.Ive got one on mine.
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Old 05-22-2012, 09:57 AM
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Need more specific info.
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Old 05-22-2012, 10:10 AM
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Quote:
Originally Posted by F-BIRD'88
Need more specific info.
Needs more specific info on what info you need.
Did my best to describe problem and what was being ran.
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Old 05-24-2012, 09:16 AM
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Update

Ok so I think I figured out why this is happening. I went to the car yesterday and was looking at the carb. Playing with the linkage, the secondaries open up fine no problem once it gets past a certain point. But looking into the carb, it looks like fuel has never been sprayed in there. There is a clear difference between the primaries and secondaries. I've attached pics below. 1st one you can see moisture from the fuel and it sprays fine when there's pressure and you open the throttle. However, the back does not do that. They look like fuel has never been sprayed in there nearly ever.

There is some fuel in there though. The 2nd pic I was trying to get a close shot of where it is. It looks like there's weights on the secondaries to close them back up when not in use. I can see fuel sitting next to it, and seems like the weight almost dips into it. If you look at the 2nd pic, it would be right between the weight and round part where the filter connects, but kind of far down in there.

The carb came with the car when bought it and was apparently on it before the previous owner ripped it all apart.

Why would the secondaries not be spraying? And how can I fix this? Thanks
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Old 05-24-2012, 11:01 AM
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Some critical factors with this carb.
Carb body and intake plenum heat.
Heat riser passages in the manifold often meed to be restrictied
to control the plenum heat.
Edelbrock makes wood carb spacers that really help.

Fue pressure: This carbs do not like more than 6psi at idle.

5 to 5.5psi fuel presssure is best.
This is crical.

These carb always need specific fine tuning to make then work just right.
download and read the edelbrock carb tuning manual.

http://www.telusplanet.net/public/gi...delbrock_1.htm

This is your bible.

what is the model number of your carb.?
stamped on the front of the carb base.
EG 1407 1405
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Old 05-24-2012, 11:42 AM
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Thank you for the info.

I was going to write down what model it was yesterday and completely slipped my mind. I know I got it at home somewhere too written down.

Lots of good info in that bible.

According to the specs the fuel pump is no more than 8psi. I know that's still over 5.5, and will look into buying a gauge to see what I really am working with.

I have a highrise intake, and a 1" aluminum carb spacer in there. Same results on the carb before and after the spacer.

It really seems like there should be fuel at least flowing at some point into when the flappers are open. And is the fuel where I talked about normal? The carb sat for about 4 years or so in a a garage, so was thinking maybe dirt got somewhere. I'll go through the whole manual there and see what I can clean.
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Old 05-24-2012, 12:07 PM
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Sounds like you are expecting a pump shot in the secondaries when you bump the throttle, this will not happen, accelerator pump shots are on the front primaries only, forgive me if I read this wrong.

The flapper you see is a secondary metering air valve, it only opens when the motor wants the CFM. It is unlikely you will see any gas actually flowing through a venturi opening unless the engine is pulling allot of air.

These carbs are relatively easy to clean up and calibrate, most likely you will benefit from the manual and a good cleaning and some tuning to get the rod jet combo correct as mentioned, then they work great.
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Old 05-24-2012, 12:21 PM
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Quote:
Originally Posted by Custom10
Sounds like you are expecting a pump shot in the secondaries when you bump the throttle, this will not happen, accelerator pump shots are on the front primaries only, forgive me if I read this wrong.

The flapper you see is a secondary metering air valve, it only opens when the motor wants the CFM. It is unlikely you will see any gas actually flowing through a venturi opening unless the engine is pulling allot of air.

These carbs are relatively easy to clean up and calibrate, most likely you will benefit from the manual and a good cleaning and some tuning to get the rod jet combo correct as mentioned, then they work great.
I suppose you are correct. I'm expecting it to be like the primaries. I was originally working with a Demon that did the same, but that thing was impossible to tune. What's the best way to figure out what I need?
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Old 05-24-2012, 12:34 PM
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read the bible. Ditch the open spacer. Get a wood spacer.
is this manifold a dual plane or single plane.?
If its dual plane with divided plenum get a divided spacer, not open.

wood is a very good heat insolator.
makes the best carb spacers for heat isolation.

What "mild" cam? What converter? You need to give info.

"I have a motor" I don;t like the way it runs, Whats wrong?
The thingy doesn't do its thingy?

We are not mind readers.

The accelerator pump shot and timing linkage will need work

The ignition timing curve will need a lot of work.
Check the jetting and rods in the carb.

get a fuel pressure regulator and set to 5psi at idle.
edelbrock carb are very sensitive to heat and fuel pressure.
read the carb bible. Google search Carter AFB carb tuning.
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