Holly carb help

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Josh A

Josh A

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Hello all need a little direction on my 700 holley ive read every post i can find and its got my head spinning with all the information, as someone not very familiar with messing with carbs.
360-30 over if i remember right comp is 12 to 1, x heads, mopar single plane intake locked out timing at 36, purple shaft 508 cam, 700 holley dp, 1" spacer
904- 3500 turbo action converter , 3.91 gear
Car idles great in neutral about 1100, in gear will idle on the brake about 800 to 1000 about 13.5 to 14.0 ive got that part good finally without having to double foot it to keep it running in gear at a stop. Wide open is good between 12.5 to 13.2.
With the carb ive got the prim set square and am idling off the sec. things ive done to the carb is jet pri down to 69 and sec down to 80 and have 37 squirter front and rear blue cam on the front and the stock black one on the sec that the carb came with and a 10.5 pv in the front. Bleeds and restrictors are all pressed in so i havent messed with them
Problem im having is as soon as I'm into the gas off idle carb goes dead rich and stays there no matter what. light cruising thru town at low speeds, moderate throttle or even at speed doing 3100rpm @ 60 its between high 10s to low 12s. Ive had carb apart and clean everything on blown out all the orficies checked it all over still having this issue. I'm hoping someone can point me in some sort of direction with a little help.
Do i need to put some wire in the restrictors in the metering blocks to lean out the transfer slots, or possibly drill out the blades to get the blades more closed?
 
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There may be more variables, but I found that my race cars idle better in gear when the idle mixture screws are turned out about 1/2 turn from the best idle setting in neutral.
 
Blown power valve.
Why did you lock out the distributor advance on a carbed street motor?
 
Idle screws are aout about 1 1/4 all around seems to be happy in neutral and gear so ive left them there.
Power valve is still good sucked on it to make sure it was working. Distributor was this way when I bought the car was already locked out so ive left it
 
Josh A said:
Hello all need a little direction on my 700 holley ive read every post i can find and its got my head spinning with all the information, as someone not very familiar with messing with carbs.
360-30 over if i remember right comp is 12 to 1, x heads, mopar single plane intake locked out timing at 36, purple shaft 508 cam, 700 holley dp, 1" spacer
904- 3500 turbo action converter , 3.91 gear
Car idles great in neutral about 1100, in gear will idle on the brake about 800 to 1000 about 13.5 to 14.0 ive got that part good finally without having to double foot it to keep it running in gear at a stop. Wide open is good between 12.5 to 13.2.
With the carb ive got the prim set square and am idling off the sec. things ive done to the carb is jet pri down to 69 and sec down to 80 and have 37 squirter front and rear blue cam on the front and the stock black one on the sec that the carb came with and a 10.5 pv in the front. Bleeds and restrictors are all pressed in so i havent messed with them
Problem im having is as soon as I'm into the gas off idle carb goes dead rich and stays there no matter what. light cruising thru town at low speeds, moderate throttle or even at speed doing 3100rpm @ 60 its between high 10s to low 12s. Ive had carb apart and clean everything on blown out all the orficies checked it all over still having this issue. I'm hoping someone can point me in some sort of direction with a little help.
Do i need to put some wire in the restrictors in the metering blocks to lean out the transfer slots, or possibly drill out the blades to get the blades more closed?
Click to expand...


You need T slot restrictors and probably need to look at the power valve channel restrictors.

The wires you reference are for idle. If the idle mixture screws are working they throttle isn’t open too far. It may not be optimal but they aren’t open too far.

You need to get a vacuum gauge on it and check to see what your cruise vacuum is. You may need to open the power valve a bit later.


A 37 squirter seems awful big for what you have.
 
Ya I added the 1" spacer this yr as last yr my carb was getting really hot and once i got the car up and going with the spacer I had a lean spot when I would floor it fast so i went up from 35s to 37s and it went away
Ya ive seen they make metering blocks already that have restrictors in them for adjustability, I may have to get some of those
 
I'm gonna throw my 2 cents in.....I had similar issues with my dual quad set up. The idle and cruise (high speed) bleeds are probably wrong. The pressed in bleeds probably need to be changed. To what I can't say. DP is really not a street carb. It is a race carb.You would probably benefit from a vacuum secondary carb with an automatic. It sounds like you have an oxygen sensor. I'd suggest first dialing in the carb for max performance. Let's say 70s and 78s jets. Now if 70s is too fat at cruise dial it down in front till you get what the engine wants. Let's say 65s. So you dropped the primaries down 5 numbers for proper cruise mixture. Now you need to up the power valve circuit the 5 jet sizes so when you romp on it the primaries are dumping the equivalent of 70s. You can either drill out the power valve channel restriction to make up for it or buy a metering block with a replaceable power valve restriction. There are formulas to determine the size the orifice needs to be now to make up the 5 jet sizes. Now when you stomp on it you are back to the correct A/F ratio for max performance.
I hope this helps and isn't too confusing. If you are set on keeping your 700 DP you will need to drill out the bleeds and tap them for replacement bleeds. Make sure you find out what the original restrictions are and use that as a starting point. But I think the PV restriction will definitely need to be messed with so you can get the cruise ratio where you need it and that the primary side can be jetted down .
 
Valiant that all makes sence actually on getting my cruise dialed in, id like to try to make the 700 work so i guess I'll have to look into taps and buying some blanks to drill out
 
Good luck. It's a pain but worth it. My twin 450s took 5 primary side changes and 1 secondary side change. Car runs great. Before you drill anything try dialing in the primary side to get the cruise A/F ratio where you want it. If it won't dial in you need to mess with the bleeds.
 
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Josh A said:
locked out timing
Click to expand...

Josh A said:
Problem im having is as soon as I'm into the gas off idle carb goes dead rich and stays there no matter what
Click to expand...

Professor Fate said:
Why did you lock out the distributor advance on a carbed street motor?
Click to expand...
Still think your issue starts with the ignition. With a locked out distributor, when you accelerate it goes dead rich because it's not getting any advance, so you're getting an incomplete burn. You've got to have an advance, be it mechanical, vacuum or both. Locked out distributors are for engines with computerized engine management, like EFI or Lean Burn systems.
 
Ok I'll look into tearing apart this distributor aswell to see if I can get it back to being adjustable
 
I once ran that cam in my 11.3 scr 360 with alloy heads
If your Carb does NOT have a 4-corner idle , then I know exactly what's wrong, Ok rephrase; I think I know Almost exactly what's wrong, lol
Firstly; IMO your compression ratio is too high for pump gas on the street. I highly recommend you do a compression test and post up the results. Crank at WOT, until you get two consecutive pulses of same or similar pressure.
Then;
#1, forget trying to set the Idle Afr with that cam, there is far too much monkey-motion in the intake until about 2000/2200 rpm.
#2, you have way too much idle timing
#3, your secondaries should be closed tight but not sticking
#4, your transfers are NOT open far enough
#5, she is gonna want some idle-air bypass with the closed secondaries
#6, your idle speed is way too high.
#7 your jets may not be not quite right, depending on your elevation.
#8 Your cruise timing is waaaay not enough

My 367 idled at 750 real steady, and I could drag it down to 550 with the clutch. It did not care about the cam-timing. I ran it every 4*, from 8 advanced to 4 retarded, all on the same carb settings and timing, it just did not care.
Here's what I ran; 360+.040, OOTB Edelbrock alloy heads, Airgap, 750DP, no spacer, 292/292/108 Mopar cam. TTIs and dual 3" all the way.
As to Ignition;
I started with the ORANGE box, and a well-used standard Junkyard 318 Mopar distributor, with a 20* cam, and the 318 springs one of which had the one-long loop. I set the Power-timing to 34* which resulted in 14* of Idle-timing. The curve resulted in 28*@2800, then slowed down to 34* at 3400.
I modified the V-can to get 22*, as fast as possible.
Full cruise-timing at 2800, was 28+22=50* which was not quite enough but the best I could get.
At these setting I was able to run 87E10 full-time.
As to the Carb; (750DP)
I flipped the carb over, Set the Transfer slot to just noticeably taller that wide, maybe 30%. I reset the Holley mixture screws to 3/4 turn. I closed the secondaries up tight but not sticking. I drilled one Idle Air bypass in each Primary throttle-plate of 5/32. I put it on the front side, between the idle discharge port and the T-slot, and about .25" back from the front edge. I lightly deburred the holes on both sides.
If your carb does NOT have a 4-corner idle system, and if you crack the secondaries for bypass air; I did that, and I struggled with a crappy idle for quite a long time. Finally I said chuck it and started drilling the blades. I got up to 7/32 before you know it, but that was too big. I had to solder them closed, move over, and try again. Do NOT drill more than 5/32, and DO NOT drill thru any solder plugs.
Other
>If you have power-brakes, do NOT route the vacuum hose to any single runner. Instead, route the hose to the hose-barb on the secondary side of the carb, or if none there, then drill/tap a hole into the plenum at about that location. Do not use fuel line for this hose; you need a thickwall vacuum hose.
If you run that hose to one runner, I guarantee two problems at 750 rpm idle; 1) it will idle rough every time you step on the brake, and 2) the booster will run outta boost at slow speeds.
>The PCV is whatever I pulled out of the junkbox that fit (probably off a 318 but IDK). Make sure you use only PCV hose on that circuit.
>With my alloys I run a coolant temp of 207*F, but I suggest you run no more than around 185 at the stat-house with your iron heads.
>I have adjustable valve gear, and run 1/2 turn lifter preload.
>I ran 78/86s with a 10.5PV@930ft.
>Plugs are the Champion coppers heat-range of 12, IIRC
> If you ever need to buy a coil, I highly recommend the Accel square top SuperCoil.
>If you have an AirGap, I doubt the 1" spacer will do any good.
Lemmee see what I forgot.
Ok done
Ok wait, That is what I ran, lol, and it worked for me. Car ran fantastic but could have used a lil more pressure. I ran 3.55s with a standard A833.
 
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*** If the timing is locked at 36*, then that is GOOD & not your problem.***

Is it rich just off idle &/or all the way to full throttle?
 
Aj- ya its has 4 corner idle screws, and I gave up setting the idle by afr and vacuum because in gear it wouldnt idle without me also tapping the gas too. I have my idle up as once I put it in gear my converter pulls my rpms down about 3-400 lower and the motor just slowly putts out anything less then 700rpm in gear.
No power brakes I'm running just one pcv off the drivers side cover to the underside of the carb like normal.
Also have 180° thermostat aswell.
For ignition I already have a msd 6a box and blaster coil.
 
Bewy- ya idle is good but as soon as im on the gas to start to move carb goes dead rich afr and stays there all the way up to and even at speeds.
Then if I'm at a stop and flat foot it and watch afr gauge it'll go right up to high 12s low 13s and just bounce around up there as I'm full throttle going thru the gears.
 
Josh A said:
I gave up setting the idle by afr
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Good. You shouldn't be tuning to a number but a state. When you get the idle right you can get it so it only drops 50 rpm from neutral to in gear.
 
RustyRatRod said:
How will that affect idle?
Click to expand...
Because it will spark too early to build maximum pressure when spinning at low rpms. Slow idle in this case may be 800 to 1000 rpm. A lean mixture that burns slower will work well with that initial BUT only when there's no load other friction.
This is why its dropping 3 to 400 rpm when going into gear.
An engine heavily loaded needs a somewhat rich mixture and timing to match.
In this respect the engine needs at idle are similar to the engine needs for near max power for other purposes.

Josh
In terms of sequence, first need to get the transfer slots set to the middle of their working range. .020 to .030 on the primary maybe a bit less on the secondary. With these newer 4 corner idle carbs often the transfer slots are a bit wider or longer than older Holleys, but even those Holley said no more than .040" exposed below the plate. Keep notes so you'll know the relation of thurning the idle speed screw to the amount the slots open. Otherwise you'll have to take the carb off each time you adjsut it. Thats nuts.

Go to the B_G ballpark initial timing suggestion chart posted in the howto section here. That will give you a range of initial idle timing for a starting point. Details depend on when the intake valve closes, overlap, crank arm position so what works out as best in the end varies with these and other factors that put heat into the combustion chamber at idle. Once you get strong idle, then you can fool with a short timing curve. Do it right (like DC/MP did) and there's some 'free' power at the top.
 
Mattax said:
Because it will spark too early to build maximum pressure when spinning at low rpms. Slow idle in this case may be 800 to 1000 rpm. A lean mixture that burns slower will work well with that initial BUT only when there's no load other friction.
This is why its dropping 3 to 400 rpm when going into gear.
An engine heavily loaded needs a somewhat rich mixture and timing to match.
In this respect the engine needs at idle are similar to the engine needs for near max power for other purposes.

Josh
In terms of sequence, first need to get the transfer slots set to the middle of their working range. .020 to .030 on the primary maybe a bit less on the secondary. With these newer 4 corner idle carbs often the transfer slots are a bit wider or longer than older Holleys, but even those Holley said no more than .040" exposed below the plate. Keep notes so you'll know the relation of thurning the idle speed screw to the amount the slots open. Otherwise you'll have to take the carb off each time you adjsut it. Thats nuts.

Go to the B_G ballpark initial timing suggestion chart posted in the howto section here. That will give you a range of initial idle timing for a starting point. Details depend on when the intake valve closes, overlap, crank arm position so what works out as best in the end varies with these and other factors that put heat into the combustion chamber at idle. Once you get strong idle, then you can fool with a short timing curve. Do it right (like DC/MP did) and there's some 'free' power at the top.
Click to expand...
I still fail to see how the power valve can affect idle. It's on the power circuit. But I won't argue it here. Don't wanna sidetrack. Yall carry on.
 
RustyRatRod said:
I still fail to see how the power valve can affect idle. It's on the power circuit. But I won't argue it here. Don't wanna sidetrack. Yall carry on.
Click to expand...
LOL Need more coffee. Was answering about locked timing at 36.

Power valve number would not be an issue in a properly set up carb.
Power valve damaged would allow fuel from the bowl to get pulled straight into the intake. Also if the PV gaskets are damaged. I'm sure you've seen both.
 
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