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Ok, this is a Holley 4150, list no. 4779-2, 750 DP (mechanical secondaries). I bought it used and it was extremely goofed up.

I put 70 primaries, 80 secondaries, and a 6.5 power valve (primary). The carb has no secondary power valve, nor any provision to add one without a drill.

I don't seem to have a very good pump shot on the primaries. I had 28 squirters, front and back. With the engine off, and you give it full throttle, there's a HUGE secondary shot and a wimpy primary shot. I changed both squirters for new ones, that came with my Holley Trick Kit and have the same results.

I also seem to have a slight hesitation off idle, probably due to the wimpy primary pump shot (I won't be able to road test it until tomorrow). It has the white cam on it, the pump shot is adjusted correctly, and the pump is brand new (I just rebuilt this carb).

So, finally, to my 2 questions ...

1) Why such a wimpy primary pump shot?

2) The Trick kit came with 3 types of squirters ... why? What's the difference? I put in the ones with the little brass nozzles, at least for now, but it had the kind with no nozzles, but without the "squares" on the sides.

(click on the pic for a larger version):
http://mach1.classic-mustang.net/misc/squirterss.jpg
 

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The one in the middle is an anti-pullover nozzle. usually found on 4165 series spreadbore carbs.It prevents fuel from being siphoned out of the pump circuit.It will provide no advantage in a 4150 carb.
 

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Johnpro,

Have you check the linkage? Is the cam "just barely" touching the primary squirter?

Is it set the same on the secondary one too?
 

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I had a hesitation like that as well and it was fixed by using a different cam from the kit that came with the Holley. Has not returned after nearly 2 years.

-bob
 

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Johnpro,

I'm not sure that your carb shouldn't have a power valve in the secondary. I'm wondering if a PO may have put a different secondary metering block on the carb.

Anyhow, why don't you give holley's tech service a call? They should be able to answer this and your pump squirter question. I've called them in the past and found them to be very usefull. Their phone # is 270-781-9741.
 

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The 4779 did not have a secondary metering block with a power valve.
There are 2 types of pump discharge nozzle check valves under the nozzle screw. #1 is a rectangular weight with a check ball. the ball goes under the weight.Many remove the ball thinking it will improve the pump shot.What you get instead is a wimpy pump stream. #2 is a needle valve type, it uses no check ball.
There is also 2 gaskets used one between the nozzle and carb body the other under the pump discharge screws head.
 

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I belive the correct squirter is squirter A, without the brass nozzles. I believe these brass dodads or extensions and are for some sort of trick racing situation and not for normal street use. I've read about them, but don't remember exactly their purpose. Something to do with the vacuum/airflow conditions in the venturis

The plastic cams change the shape of the pump shot, in terms of how much gets shot in when, but it does not change the over all quantity of fuel, as that is controlled by the accelerator pump circuit. The squirter determines how long the pump shot will flow. A bigger squirter will dump more fuel quicker, a smaller, less fuel. According to the Holley carb product catalog, the combination of cam and squirter, plus the size of the accell pump (30 cc or 50 cc) is what addresses the off-idle fuel condition. Thus, changing the cam alone, or squirter alone, will not necessarily get you where you want to go. I was running 28 squirters on my 302 with a 650 cfm carb. Here is the link to the holley page which has a chart demonstrating fuel flow at various throttle positions, with different colors of cams:

http://www.holley.com/data/Catalogs/Avenger%20Systems&Carburetion.pdf



I have a Holley 750 dp at home which is brand new in the box. I had it worked over by a carb shop for a supercharged application, but I never ran it. Paid $700 for it. Had the Edelbrock then the Speed Demo instead. It was too much carb for the 302 in naturally aspirated form. I did take it apart once to borrow the jets out of it, but put the jets back after buying a jet kit. This carb does not come from Holley with a power valve in the secondary metering block. A special secondary metering block is sometimes substituted for drag race applications which allows a secondary power valve. The Holley website will confirm this in their product description. If you want, you can borrow my 750 and try it on your car for comparison purposes. If it works better than what you have, you can copy the settings. I will be home early today from work so stop on by if you want. Heck, bring the car and swap it out in my garage.

My suggestion is to change to the stock type squirter, run a 72 jet and give it a try. If an off-idle lean condition persists, then I'd change the cam. Barry Grant starts with the pink cam. I think Holley starts with the white cam. I've had somewhat better results with the green and black cams. The chart at the above link will give you a better idea as to the matching ofcolor with progressive order of delaying or speeding up the pump shot.

You can call me at work for the next hour or so if you want. 372-1777.

good luck :)
 

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uh, whoops on that link. Once you open the link you need to scroll down to pages 84 (cams) and 86 (squirters). It is interesting to see that the .028 squirter is about 3 up from the bottom of the list of sizes and there are about 8 more sizes up. What about a .031 squirter? Of course you can buy the no doubt very expensive kit they sell which contains a variety of cams and squirters so that you can optimally tune the carb. haha.
 

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A friend of mine brought his car to me complaining about the same issue you have. Primary pump shot was "wimpy". I found the problem with his carb was the rubber check valve inside the accelerator pump. This is an umbrella type valve that allows fuel into the accelerater pump and then seals the inlet when the accelerator pump is engaged to allow fuel to flow to the squirters. The valve was slightly warped allowing the fuel to flow out the inlet instead of to the squirter. Just another thing you could check.
 

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I believe this is the orange-red looking thing in your photo of the repair kit.
 

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I agree with Bob. I had the same problem with my 4160. Tried the larger squirter, primaries, changed power valve, and accelerator pump.... and larger ramp pump cam finally fixed the problem.

My 4160 (vac. secondary) came with the 3rd squirter in pic with the brass extensions, cant say about the others, and what aps they are used for.
 
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