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post #1 of 25 (permalink) Old Jul 21st, 03, 01:22 AM Thread Starter
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I've replaced my Rochester Q-jet with the famous Holley 4160 600cfm vac. sec. carb. But i have serious problems with the Holley.

Problem:
When i hit the pedal to the floor, the car goes like a rocket to about 2500 rpm, and the it seams to flatten out to about 4000 rpm, and then i get a real kick and it goes like a rocket again.

I bought the Sec. Quick Spring Kit and tried all the springs for the sec. vacuum. I can get it bog with the weaker springs, and it works best with the hardest spring. I also jumped up 2 sizes for the acc nozzle sience it hesitated with the stock nozzles.

The carb is brand new.

List No. 80457-s

Or is this how a Vac. secondary carb is supposed to work?

Must also say that the Holley's quallity and precision was the worst thing iv'e seen. There is on the metering block on the primary side, 2 small brass nozzles(not the jets, smaller)that is "stamped" in the aluminum, and the other one is about 1 mm more down in the hole than the other one, and also oval and "sqeezed".

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post #2 of 25 (permalink) Old Jul 21st, 03, 06:41 AM
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I think you are describing the curb idle air bleed and the high speed air bleed. They can be 2 different sizes. If one or both are damaged I would bet the carb was used, played with and returned and just stuck back on the shelf.

As for your "go - bog - go" your own trouble shooting tells me it's not the secondary opening causing the problem. You went with a bigger pump squirter and all that does is change how the pump shot is delivered. The accl pump os good for a fixed amount of fuel with each pump. The bigger nozzles let the whole shot kinda just dump that pump shot all at once. A smaller nozzle streches out the shot a bit longer, again it's the same amount of fuel. When you step on the throttle air rushes into the throttle bores much faster than the fuel does. The accl pump is there to avoid a lean condition while the fuel catches up with the air.

Go back to your stock nozzle and see if that helps. If the bog goes away go one sec spring at a time lighter until the bog or kick comes back and then go back one.

If the prob didn't go away with the stock nozzle, there's a whole lot more that could be causing this. Get a accl pump cam kit and try a different cam. It's not a bad idea to put the heavy sec spring in when playing to remove the sec's from the problem and when fixed find the right spring...

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post #3 of 25 (permalink) Old Jul 21st, 03, 09:19 AM
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Holley's are great carbs, primarily due to their adjustability. However, that feature can also make them tricky to setup. If you're not carefull, you'll end up chasing your tail. Just keep track of where you've been and where your going with the adjustments. Usually, the best setup isn't too far from the published baseline settings. Don't give up, you'll get it figured out and we'll help.

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post #4 of 25 (permalink) Old Jul 24th, 03, 02:46 AM Thread Starter
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Hi

I replaced the stock accs nozzle(31) and the hesitation come back big time. And i also replaced the main jets back to 65 and also putted the cam in pos. 1. Thats factory basic. And the carb hesitates from 600-1400, above that it works fine in the response. But then it has a bigger loss of power in the mid range. And as usual that kick comes around 4000 rpm.(still the hardest spring in sec.)

So, then i reinstalled the 66 main jets and bought an expensive 50cc pump kit. And "Whola" the hesitation disapeard. and i also got more power in the mid range, and can feel that kick at 4000 rpm, but not as before, what i hope indicates that i got more power in the mid range, and not got a weaker kick. [img]smile.gif[/img]

Im going to go down in the springs now for the sec. till it bogs and then go up one spring. If this dosent help. Im going to try the #67 or #68 main jet.

One more good thing with the 50cc pump is that it has a really good response in cruising speed. [img]smile.gif[/img]

Im posting the results later.


To bad we dont have a 1/4 mile strip where i can test the car on, i know the car did 1/4mile in 14.7 sec with the carb stalling and boging.

Hmm, maybe i'll buy a G-tech.

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post #5 of 25 (permalink) Old Jul 26th, 03, 08:58 PM
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if i remember correctly the 50cc accelerator pump delivers fuel throughout the rpm range.this being the case it sounds like it is covering a lean condition right in your primary jet range.if this is a 350 try #70 jets and the #31 squirter and see where that gets you.also you didn't say what color pump cam you are using.i believe the 50cc pump is designed to work with the brown cam,this is a pretty huge shot of gas for a near stock motor.i would try the jet/squirter combo i reccomended with the original acc pump setup and the orange or blue cam in pos.1.don't forget to set the pump arm linkage for .015 clearance after wide open throttle,this is much easier with two people(one to hold throttle open and press down with a flathead screwdriver on the pump arm,and the other measuring and adjusting the gap).also be sure your mechanical distributor advance isn't bindingand that your idle air bleeds are free of obstructions.
good luck!
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post #6 of 25 (permalink) Old Jul 26th, 03, 09:15 PM
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That isn't how a vacuum secondary should work. If you have your timing dialed and the carb set up right, a vacuum secondary carb should feel like it has no transition to the secondaries. Check your timing. Check your float level on level ground. Look in a Holley book and find out what jet size came stock in that carb. If you have to jet up more than 4 sizes from stock you have another problem.
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post #7 of 25 (permalink) Old Jul 26th, 03, 09:20 PM
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Also, there should be no reason to have a 50cc pump on that carb. If using one does make your car run better, there is another problem other than the accelerator pump. Lastly, make sure that the secondary butterflies are cracked open slighty. If they are closed it will definetly cause a bog. Adjust the small screw under the carb untill the transition slot looks like a round hole if you are looking from the bottom of the carb. I think Holley's website shows how to do this.
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post #8 of 25 (permalink) Old Jul 27th, 03, 06:20 AM
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What is the rest of your combo? It really sounds like you have a vacuum leak or are running a large single plane manifold.
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post #9 of 25 (permalink) Old Jul 27th, 03, 11:17 AM
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Before you go and blame the carburator make sure your timing advance is setup correctly. I experienced this exact same symptom once and it turned out that the mechanical advance was sticking.

A quick check with the timing light will show you how much advance you have at the problem RPM's. Your advance curve should be full in at about 2500 RPM, with roughly 36 degrees total timing.

Once you verify it is (or is not) the carburator, I would look at the vac secondary diaphram and spring. If you are running a healthy 350 or bigger that carb is a hair on the small side so it will need that secondary to open fairly quick --- a lighter spring can fix that. Too quick will also cause a flat spot until the engine revs enough to pull the air available to it. Running WITH an air filter will cause the secondaries to open faster than without an air filter.

I would put the stock accel pump back in and try to find the reason you are lean in the midrange. Timing CAN screw with your carb performance too.

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post #10 of 25 (permalink) Old Jul 27th, 03, 12:23 PM Thread Starter
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Thanks for all the suggestions and help.

The thing is that the engine was working fine with my old carb on it, Q-jet. But then i was told that the holley was much better and easier to adjust for more performence(which i have not noticed yet).

The timing advance is working properly, im not sure what the total timing is yet because i dont have a timing tape on it, just the factory "0" mark.

But im more into that vacuum leak thing. Or should i say air leaking into the vacuum.
When i driving about 70-80 mph and press the pedal to the floor and then releases it when the eninge is on a heavy load, i hear a reversed air sound, like Swisch. I can hear it on lower speeds aswell, but the sound comes at about 4000 rpm and thats where my damn th350 shifts.

And if i got a vacuum leak, could that cause so the secondarys are opening too early and the hardest spring is't enough to hold it? And that also is causing that boging/lack of power?

I actually strats to think that it is the headlampswitch for the RS-lamp-doors that is leaking. Because when i have a passenger in the car, he cant hear that sound i hear. Or it could be the powerbrakes?

Im going to spray some starthelper spray over the area tomorrow and see if the Rpm is increasing.

The intake i have on it now is a stock dualplane.

And the stock nozzle and jets that came with the carb is ragarding to holley:
Prim. jets: 65
Sec. plate: 65
Accs nozzle: 31
powervalve: 65 (if i have a vaccumleak, could this one cause problems?)
Vacuum spring: black

thanks

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post #11 of 25 (permalink) Old Jul 28th, 03, 02:12 AM
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I'm sure you're using the adapter plate between the Holley carb and Q-jet manifold. One can be bought from Summit, marketed by Edelbrock, 1/16 inch thick. Large vacuum leak if not done.

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post #12 of 25 (permalink) Old Jul 28th, 03, 02:53 AM Thread Starter
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Hi Everett.

Yes im using an adapter, squarebore &lt;--&gt; spreadbore. [img]graemlins/thumbsup.gif[/img]

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post #13 of 25 (permalink) Old Jul 28th, 03, 03:14 AM
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Vacuum leaks typically hurt at idle most and have little effect on WOT. Although if your carb was already on the lean side a vacuum leak could push it over the edge high end, but it wouldn't suddenly get richer at 4000. I dunno.

Just curious, how do you know your advance is working correctly if you cannot accurately read the timing?

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post #14 of 25 (permalink) Old Jul 28th, 03, 09:48 AM Thread Starter
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Hi Eric.

I could see that line (where the timing is at) moving when we pulled the throttle upp to about 2600 rpm and then it stopped moving, and when we went back to idle, the timing line was about 8 or 10 on the original timingmark, so i guess the advance works then? or am i wrong?

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post #15 of 25 (permalink) Old Jul 31st, 03, 10:01 AM Thread Starter
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Hi

I tooked my car to a guy that have been doing US cars for a long time, and had him to adjust my holley. And i was not happy at all, and he said then it has to be something wrong with the engine because the timing and vacuum was correct.

So i just rebuilt my old Q-jet, and guess what, all my old Q-jet power was back + the power of headers and straith flow mufflers. [img]graemlins/thumbsup.gif[/img]

Now im going to change the intake and write some "for sale" notes for my Holley 4160 vac.

Thanks for all help guys.

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