who is the goto guy on holleys

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ok quick up date... after finely getting to drive the dart.. after about 10 or so mins of running seemly good its starts, hesatating at stop lights, the gets worse to where it stalls and seems to flood i have to hold it to the floor to get it running..and it dropped the gas gauge from the trip..i thought it was vapor locking added a return line back to the tank, no help...so i put my old 750 back on there made the same trip..gas needle bearly moved. ran great no issues to speak of...this is where it gets crazy...when i took the 850 off i noticed that if i tipped it just a little front to back gas poured into the body of the carb...i dropped it off at a carb shop, they ran it said it ran great floats set right af gauge read right...but they didnt know anything about the percy adjusta block or why it leaks gas when moved back and fourth... they are still looking into it....any thought or ideas thanks
 
stock fuel pump 6 psi... the first time i drove the car with the carb in plase it ran good for the first 20 min, then starts hesitating at stop lights.. and when i limped it home it would die and had to hold it to the floor to get it started, but wouldnt idle...thought it was vapor locking so ran a return line back to the tank, test drove same route...same thing happen.. put on my old 750, ran the same route no issues...took the carb to a carb shop, they ran though it...and tested it on their engine made adjustments, said it was all good tested it today...same as before runs great for 15 to 20 mins, the runs like crap..i.do not have the heat exhaust plenum under the intake plugged off..i was thinking its getting hot....but why does the 750 run great...?
 
AJ/FormS said:
Sounds like she's flooding as the engine warms up;
Wild guess is a leaky PV
Just swap the one over from the 750

You need the special tool and a vacuum pump to test it.
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pv is blocked off...what if i block the exhaust ports that runs under the carb on the intake...and why doesnt the 750 do it?
 
1968FormulaS340 said:
It is very easy to check and set the float level on these.
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it just cam back from the carb shop its been checked adjusted and ran on their engine...said the all good... my 750 works great, 850 goes to until it get hot.. it was sujested to block off the exhaust port in the intake that goes under the carb... i cant explain why the 750 doesnt act that way..
 
I am not familiar with the Percy stuff. Never saw a need to stray from stock Holley parts. Sorry.
 
RustyRatRod said:
I am not familiar with the Percy stuff. Never saw a need to stray from stock Holley parts. Sorry.
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thanks, i do have another question...if you dont mind...the heat riser in my edelbrock intake is not blocked off, if that was the issue with the heat wouldnt it make the 750 do the same thing?
 
flathead31coupe said:
thanks, i do have another question...if you dont mind...the heat riser in my edelbrock intake is not blocked off, if that was the issue with the heat wouldnt it make the 750 do the same thing?
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I would certainly think so. I don't think that's going in the right direction. I am thinking it's in the carburetor.
 
thanks i did want to note that when i first took off the 850 i noticed if i rocked the carb from front to back just a little, gas would pour into the center of the carb...i asked the carb guy he said he noticed that as well be had no idea as to why...and said the carb was set up right including the float levels...
 
I would still check the floats. I really don't care what they tested, I only care how they are on my car.

The needle and seat are also susceptible to dirt which will also flood out the float bowls.
 
1968FormulaS340 said:
I would still check the floats. I really don't care what they tested, I only care how they are on my car.

The needle and seat are also susceptible to dirt which will also flood out the float bowls.
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Good point..People don't check this, on weekend hot rods....
 
If you can prove it's flooding,you will be well on the way to solving the problem.

I think there are about 5 ways that flooding at or near idle can happen;
1) choke-blade closed or nearly so.
2) too high a float-level
3) leaking PV
4)restricted air bleeds
5) misadjusted carb, or wrong gaskets installed
6) porous circuits
>I would mention valve lash, but you clearly state numerous times that it runs fine with the 750
> I agree with Rusty on concentrating on the carb. I believe, at this time of year the heat passage under the carb is actually beneficial.
> keep in mind that the secondaries could also be the source of your troubles.
> Also keep in mind that running rich can be one of two things; A) too much gas, and B) not enough air,

> proving a flooded, or flooding, condition is not hard.
> you can adjust the float level by pinching the fuel line shut, and waiting for the engine to pull the fuel level down. When she begins to run right, then the level is near to right. Shut the engine off. Look at the float level. Figure out why the fuel level was not there to start with. If the float level thus determined does not agree, or very nearly agree, with the known proper spec, find out why and fix it. Take the metering block apart if you have to, or swap on one that is known to be good. Idle-air bleeds would be a prime target as would be the emulsion holes in the idle-well.
And of course my favorite; the T-port sync. If your throttle blades are too far open the transfers will be dumping pretty good. You are running a PCV right?
 
yes to the pcv... i will try the sujestions its crazy that its about 10 mins after the car reaches 190 that the 850 acts up.... until then its ideal hard launches, part throttle, start ups.. if it makes any difference the 750 is a single pump and the 850 is a dp...someone mention kill bleeds but i have no idea.
 
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flathead31coupe said:
yes to the pcv... i will try the sujestions its crazy that its about 10 mins after the car reaches 190 that the 850 acts up.... until then its ideal hard launches, part throttle, start ups.. if it makes any difference the 750 is a single pump and the 850 is a dp...someone mention kill bleeds but i have no idea.
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Well that just reeks of valve lash or very rich
Why are you running the 850? Big power? Hi rpm? Or just cuz?

Wait-a-minute!
The gas sloshes into the carb? That is not supposed to be able to happen; the vent stack goes into the airhorn, some nearly 2 inches higher than the fuel level. I think this is a big clue! You're talking exactly which 850?
Notice the carb shop said it was all good, I bet they ran it on a stationary engine,while you are in a moving vehicle, with the fuel constantly sloshing.
I wonder if that Percy block is not routing the vent properly, or the 850 itself has a defective vent system.

If you take the carb off,plug both vent stacks and the inlet, then you should be able to turn that carb upside down with no loss of fuel. The only way out for the fuel, when upside down is, or should be, thru the stacks.
Well; the main lines and the accelerator circuits might dribble a bit until they are empty.
Each bowl holds about 50cc, and if all or most of it drains, that is a big issue! Find out why!
 
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Are the vent whistles present?

Never seen a car with that adjust a jet stuff work right.
 
AJ/FormS said:
Well that just reeks of valve lash or very rich
Why are you running the 850? Big power? Hi rpm? Or just cuz?

Wait-a-minute!
The gas sloshes into the carb? That is not supposed to be able to happen; the vent stack goes into the airhorn, some nearly 2 inches higher than the fuel level. I think this is a big clue! You're talking exactly which 850?
Notice the carb shop said it was all good, I bet they ran it on a stationary engine,while you are in a moving vehicle, with the fuel constantly sloshing.
I wonder if that Percy block is not routing the vent properly, or the 850 itself has a defective vent system.

If you take the carb off,plug both vent stacks and the inlet, then you should be able to turn that carb upside down with no loss of fuel. The only way out for the fuel, when upside down is, or should be, thru the stacks.
Well; the main lines and the accelerator circuits might dribble a bit until they are empty.
Each bowl holds about 50cc, and if all or most of it drains, that is a big issue! Find out why!
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it was suggested the 850 would be ideal...the engine is a 70 440 has 906 heads, the cam is one under the 509, 30 over flat top pistons, fender well headers, mild built 727, eddy preformer 440 intake.. the carb iam using was used on a blower set up....the carb shop looked inside and ck it all out so iam not sure,also the car is a beast all around until 20 to 30 min into a drive....then sux....the 750 does good
all the time.
 
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From cold to warming up, rich is a good thing. The warmer it gets the leaner it will want to be. Well that is somewhat misleading.If you had a near perfect mixture when at normal running temp, then;as the engine cools off, it will want to be richer as she goes. This is because,as the engine cools, not all the gas is atomized small enough to burn, to burn properly, or to burn on time.Or it falls out of suspension and sticks to cold parts, and gets to the party late. So it takes more fuel to overcome flatspots,hesitations and bogs.

On the street;
Up to about 5000 rpm, a 650 might be fine.
By 6000rpm, a 750 might be taxed.
The 850 might be getting a workout by 6600.
Notice I say "might". There are various schools of thought on what happens with a too small carb, and what a too-small carb might be. I have found on the street, almost anything will work until it really is Too-Big, or it really is Too Small.
According to the formula, my 367 should be using a 700. I found a 600 unacceptable. I found an 850 TQ very good.
I am currently using a 750, and I think it's just right. According to the formula that so many poo-poo, a 750 should be good to 7050 rpm on my 367. So I run it up to that on a regular basis,lol.

I'll tell you a secret; if your tires are spinning to 65 mph, then you have more than enough carburetor for the street.Whether an 850 or a 750 or a 500 it no longer matters, cuz 65mph is the cut-off point.
With a 727(2.45-1.45-1.00), and 28 inch tires, and 3.23s, you will hit 65@about 6500 with 5% TC slip,at the top of first gear.
If you have 3.55s, you will want to shift into second, and then you will hit 65 in second gear @4200ish.If you spun all the way through first with the 750, then you already have more carb than you need.If you spun all the way through first with a 650, you already have more carb than you need.
If you had 3.91s, second would be about 4650, and your engine would be very lightly loaded and probably spin thru first gear with a 600(or less), and, needs just a 600 to get to 65 mph@4650.

So, how far can you spin in first gear? and What rpm are you regularly turning? Choose accordingly.
 
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IMO the 850 is fine for your 440, I ran one years ago on one and it was fine. As mentioned when it starts screwing up check the fuel level in the bowls. It sounds like the fuel level is creeping up as you run it, may be time for new needles and seats.
 
this is a work in progress...havent beet on the strip yet... just trying to drive it to get use to it....trying to find out when i had the carb off. what would make the gas go into the center of the carb just by rocking it front to back a little...and why it starts to crap out after running great until its gets hot about 20 mins into a drive...i have to hold it to the floor to get it started and will not run well until it cools down...
 
The fuel bowls are full is why it's overflowing.
 
justinp61 said:
The fuel bowls are full is why it's overflowing.
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lol i know that...its somethings not right, it shouldnt leak gas into it just by moving it front to back a 1/2...thats why i took it to the carb guy he checked it out said the needle and seat and float levels were on the money.. guess if he doesnt know i sure dont..
 
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