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Old 07-27-2011, 07:08 PM
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Holley 850 DP running very rich flooding engine

Hey Guy's need some help with tuning a Holley 4150 with Mech. secondaries. The carb is on a 462 Pontiac with a Comp xe284h cam. The car has yet to be taken out on the road since it was dynoed. I'm thinking that the jet's might be the problem? I have checked the floats and they appear to be set properly. The car is stock with the exception of jet changes and a Proform base plate that I had to install because the stock base was cracked in shipping. LMK what you think.
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Old 07-27-2011, 07:35 PM
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Usually this comes down to Needle stuck open due to trash in seat. Fuel pressure too high, Float level too high. Possible broken gasket in the carb itself such as power valve gasket. If it`s just running too rich then jet it down about 4 sizes. If it`s sure enough flooding then the issue is in one of the areas I pointed out.
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Old 07-28-2011, 03:09 AM
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Ymmv I'm thinking this might have something to do with the fact that my fuel pressure has been creeping upand down? I think its time to replace that regulater? Can the regulators be re built?
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Old 07-28-2011, 12:02 PM
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Quote:
Originally Posted by Schoust
Ymmv I'm thinking this might have something to do with the fact that my fuel pressure has been creeping upand down? I think its time to replace that regulater? Can the regulators be re built?
Check pump linkage adjustment.
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Old 07-28-2011, 12:30 PM
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If it's running rich, barely idling, puking black smoke and symptoms of that nature pull the power valve(s) out and check to see if they are blown. Even if the carb has built in blowout protection check them out anyway.
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Old 07-28-2011, 03:06 PM
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Not sure what you mean about the linkage Bug? Are you refering to accelerator pump shot linkage? If so how does one check this? As far as the power valves go I did have some backfires while getting the distributor right. I thought that they were safe if you have blow out protection? The idle isn't that bad it's rough but I think that might be do to the 240/244 duration cam..... I will say that the engine is pig rich without a doubt! Can this be from the builder looking for big number's on the dyno thus installing more jetting than needed on the street? The engine was diagnosed with a different distributor with the timing locked out.....
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Old 07-28-2011, 03:45 PM
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What is the model number of the carb?. What mods to the carb?

What is the present jetting? two power valves or just one?

850 carb jetting:
Two power valve carbs jetting should be 80 to 84 square.

One only power valve carb versions jetting should be 80 pri ad 86-88sec.

Your jetting should be within 5 jets +/- of this range.

You will need to install a 3.5" or 4.5" power valve with that cam.
The power valve must stay closed at idle.

You will need to fix the distributor timing curve to get it to idle clean with that cam. search my posts on it.
You need a minimum of 26deg timing at idle

I run with locked out mechanical timing with that same cam. Idles clean and runs like a top. Ya, it needs that much idle timing.

Locked out mech advance works real good with the XE284H-10 cam..

This will allow you to set the pri and sec throttle opening correctly at idle for proper idle transfer slot exposure at idle. Or it will run rich.

Fix the timing curve, remove the carb and reset the thottles at idle and swap the power valve.

Idle fuel pressure for a holley carb. 7psi. a return style regulator w/ return line will not creap.

Until you make these changes it going to idle rich and run like crap and load the plugs.

Last edited by F-BIRD'88; 07-28-2011 at 03:53 PM.
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Old 07-28-2011, 03:58 PM
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Now were getting somwhere! Not sure what numbers are on the carb but it's a standerd double pumper with the choke horn (manual choke) The only mod that it has is a Proform base plate I had to change the original because it broke during shipping. The jet's that it made the most power with were 79's the timing was set at 37 degree's locked at 3000rpm...
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Old 07-28-2011, 04:12 PM
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Before screwing with power valves, take time to determine what you engine needs. Its impossible to determine what opening you need in a PV without first reading your vacuum. Don't assume you need a certain PV based on your cam. Many have found that a valve opening at about half your vacuum reading at idle works quite well. e.g. vacuum reading 12-13 = PV of 6.5. Your current flooding could very well be a low vacuum condition that is causing the PV to open early.
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Old 07-28-2011, 04:20 PM
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When you say that it could be a Vac. problem are you saying that there might be a leak??I was hoping to find someone with a similar combo and work it out with them but I sure would like to learn how to come up with the proper combo too...
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Old 07-28-2011, 04:49 PM
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Quote:
Originally Posted by Schoust
When you say that it could be a Vac. problem are you saying that there might be a leak??I was hoping to find someone with a similar combo and work it out with them but I sure would like to learn how to come up with the proper combo too...
Thanks
No. Just that your current PV may not be right for your current setup.
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Old 07-28-2011, 04:54 PM
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Yea I realized what you were saying after I read it a second time. Idono,maybe my pump is causing this issue? It has been bouncing around for some reason? I run a Holey Black with matching holley regulator and as of late the pressure is moving around? I have to pull the filter and then check the regulator. I was kicking around changing the regulator to a return style,never did like the idea of dead heading the pump.....
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Old 07-28-2011, 05:17 PM
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if you want to run dead head, get a carter P4070 or P4594 pump.

No regulator is needed. Cheaper and more reliable than a holley pump.
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Old 07-28-2011, 05:24 PM
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37 deg timing is good but thats not "locked" Locked is when you remove/disable the mech advance.

The timing does not move with rpm, when its locked

You can lock it out and keep the vacuum advance system too.

#79 jets square are fine in a 850 thats got both a primary and a sec power valve.

If the sec power valve is not there now,sec jetting should be 86 to 89

power valve(s) should be a 3.5 or 4.5" rated.

Pontiac V8's usually like 32 to 36deg timing. if the pointer is accurate atTDC.

Last edited by F-BIRD'88; 07-28-2011 at 05:29 PM.
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