Holley carb help please!

I was running a 650 edelbrock on my engine and my car ran 12.6 in the 1/4 mile but I bogged off the line and couldn't spin the tires. I Put a Holley 750 DP with a Proform main body on it that should flow well over 800cfm, now the problem is that I spin the tires off the start and don't bog but now I have no high RPM power and the car only runs 13.1 with the Holley. This really boggles my mind because I thought the larger carb would give me the exact opposite results. My first runs with the 750 were with 72/82 jets and I ran 13.5, then I put in 76/86 jets and it ran 13.1. All my 60' times suck and are in the 2.0-2.1 range. Should I try even bigger jets? It feels like I lost all the high end power when I switched carbs. Also my mph dropped from 112 mph with the 650 to 108 with the 750.
Please give me some advice on what I should try.
Thanks.

Did you put the air bleeds in the correct place?

The air bleeds on the Proform mainbody are the same way as it came new.

what are your plugs telling you?

My first runs with the 750 were with 72/82 jets and I ran 13.5, then I put in 76/86 jets and it ran 13.1. All my 60' times suck and are in the 2.0-2.1 range. Should I try even bigger jets? It feels like I lost all the high end power when I switched carbs. Also my mph dropped from 112 mph with the 650 to 108 with the 750.
Please give me some advice on what I should try.
Thanks.

If you are losing MPH, you are too rich. You are going the wrong way in your Holley tuning. Put in less jet. 76/86 is wayyy too rich for what you are doing. I ran 11.70's @ 115+ with the stock 72 front, and 80 jet rear, and that was in a 3310 vacuum secondary 750. Go back to the 72 in the front, and put a 78 in the back. See how that works for you. 86's are way too rich unless you're running without the power valve.

Are you running a sticky tire at the track? If not, you'd better get a set of DOT or slicks. Trying to tune the car with jetting and inconsistent launches on street tires will be a nightmare.

Try 73 primary 81 seconday assuming there is no power valve on the secondary side.

What are your air bleed sizes? The outside is your idle bleed. A 750HP has .075 idle bleeds, and 0.036 high speed bleeds. A smaller high speed bleed will act like a larger main jet and start the main circuit sooner. The opposite is also true.

This should be a good baseline that mimicks a stock 750HP jetting. Though your metering blocks are different this should get you close. Jet for MPH at the track and make sure your timimg is very close before you start working too hard. Don't spread the front to back jetting more than 8 sizes. Chances are you'll end up being around a 6 size spread.

Thanks for the info, Sounds like I have a lot of tuning to do. I just got in from the garage and I fixed my linkage problem, my linkage was too short and wasn't opening the butterflies all the way. Now that I can get full throttle it is bogging a little if I gun it off idle. I checked my plugs though and they look normal, not white but not fouled with fuel on them. I am going to try different jets and see what size my air bleeds are.

Boy does that sound familiar. I had the same in another vehicle, put the DP on and lost performance. Went back to examine what could be going on and came up with a number of ideas. Went back to the Edelbrock and never looked back.
Are you running vacuum adavance or pure mechanical? Do you have a vacuum gauge on the intake? What is the initial timing? The Edelbrock should be able to spin the tires with no problem, but depending on you vacuum signal to the carb at different RPMs you may need some tuning. Holleys don't offer the range of tuning here that the Ed will, Holleys have their place, I have several.

All of my carbs have mechanical secondaries. My timing is good, 20 degrees initial, 20 mechanical advance. I think that my carb gasket between the main body and the butterfly plate is leaking and sucking in alot of air. I am going to tear it apart and make sure all the gaskets are good and I am going to try different jet combos. I am also going to get new air bleed screws and try that. I am surprised that the DP carb would make such a negative impact on the top end power.

Make sure that the accellerator pump check valve needles are in place under the screws. Its not the carburetor itself, you just haven't nailed the tuneup down yet.

I drove it today after making sure there weren't any leaks and it drove like crap, I rechecked the plugs and now it looks like its running rich. I swapped my large accelerator pump for a stock one and tommorrow I will set the jets lower but I tried the jets low before and it ran real slow. What else should I check for besides the jetting and air bleed screws? Could the squirters be too large? Could a 750 DP with a proform main body be too big of a carb for a 350 with a 236/242 roller cam, trick flow heads, etc.?
I appreciate all the advice and help you guys are giving.
Thanks.

Check needle and seat o-rings. Make sure you don't have nozzle drip with the engine sitting there idling.
Stock 750HP squirters are .031 pri/sec. After the pump shot is used up the circuit doesn't effect wot mixture unless your check valve needles are missing, then you get massive fuel pullover at the upper rpm. What metering blocks are you using? Are they from a 4779 750 double pumper?

What power valves are you running, sounds like they mat be opening too soon.

Holleys don't offer the range of tuning here that the Ed will, Holleys have their place, I have several.

Holleys are very tunable carbs, *if* you know what you're doing with them. The Edelbrocks are all vacuum seconday carbs, which makes them great on the street. Holley also makes a number of vacuum secondary carbs, like the venerable 3310 750, which work fantastic once properly set-up.

A guy I know had a 1980 Z28, 355ci with the Performer RPM cam & intake, with ported camel-hump heads, 3000 stall and 4.10 gear. Started off with the Edellbrock 750 carb, and another bud loaned him a Holley 750 with the choke horn milled off and he picked up 2 tenths and 2+ mph at the track.

Did you make sure to get the Proform main body for the 4779 and not the 3310?

I would look more into your accelerator pump, put the 50cc pump in the rear and front and tune it with diff cams that come with the kit. bogging off the line means too much pump. you need to tune the pump to not run out like it is before the enrichment system kicks in..Accelerator pump cams come in various sizes and are color coded and number coded by Holley. The cams have different shaped ramps that the arm from the accelerator pump rides on. By changing the size and shape of the arc on the cam, the pump shot can be tailored to start early or later as you go from off idle to full throttle. Changing the cams can have an effect on the way a vehicle leaves the start line in a drag race. If you leave the line off idle or at a higher RPM (while foot braking or when using a tranny brake or when using a clutch with a manual transmission) experimenting with the pump cams can help. There is no set rule for use, you just have to experiment with the different cams and the different cam positioning holes in the throttle linkage of the carb. Holley sells individual cams or you can buy their kit which includes an assortment of cams to choose from. Pump shooters are another area of experimentation. Holley carbs come with a standard shooter size which differs by carb list#. If you are experiencing a bog or hesitation off idle, you can try a larger, higher # shooter size. The bog or hesitation may be caused by a momentary lean condition when the carb goes from the idle throttle position to the main metering system. The shooters help richen this momentary condition and eliminate the stumble. Keep going up in shooter size until a puff of black smoke comes out the exhaust, then go back one or two sizes.

Playing with the shooter sizes is particularly helpful, when you have an intake with a large plenum area, such as a large open plenum or a tunnel ram. Keep in mind that as you increase the shooter size, you may also need a "hollow" screw to hold the shooters in the carb. At shooter sizes over .039, Holley recommends that you use the "hollow" screw (PN-26-12) which allows more fuel to flow to the shooters.

Holleys are very tunable carbs, *if* you know what you're doing with them. The Edelbrocks are all vacuum seconday carbs, which makes them great on the street. Holley also makes a number of vacuum secondary carbs, like the venerable 3310 750, which work fantastic once properly set-up.

Not to start an argument here, but I have tuned carbs for over 30 years. Started with single carb motorcycles and moved on to multi carb motor cycles and cars. My line of work is Industrial control systems, in which cars and plant equipment share many things in common.

The biggest let down of the Holley carb is the fact that the fuel metering system is through a venturi, which is not a linear flow device. All carbs have this drawback, but many of the other manufacturers have linearized the fuel metering by using tappered or staged metering circuit. Holley does not.

I always hear the stories of folks adding a bigger carb and getting a tad more or swapping to another brand and getting better results. So bigger must be better! But rarely do they look at the real reasons why they got better times. The design of the boosters and placement within the venturi are what can make a carb better or worse. The higher end Holleys use dog leg style boosters to get in the flow, the lower ends do not

As I said, Holleys have there place. If you are running down the strip every day then by all means run a Holley as that is what they are good at. If your are driving around town and an occasional run on the track then I would go with the Carters, Edelbrocks or Qjets. They take more time to tune in, but they will do a far better job overall.

Dryseals is thinking about it way too hard. If you take your time and have selected the proper size carburetor you can have a fine running engine. I have been tuning carburetors with my wideband for several months now and can tell you that you are able to get pretty close to an optimum fuel curve if you put your heart into it. Especially since you have adjustable air bleeds. Metering rods are not necessary for a proper metering carburetor. While they offer a finer grained enrichment circuit for part throttle driveability a good running holley is hard to beat. It may end up a bit fat at places, but it will run and drive well. I have spent days on end with an AFB and AFR monitor and was unable to get the metering rods where I thought they should be, even with a toolbox full of the right parts.
Every family of carburetor has its advantages/disadvantages. None do it all perfectly, but at least a carburetor is a reactionary device and can think for itself to a degree. When a person specifys "double pumper" they need to realize that its primary focus is competition when you need to know the carburetor is at WOT when your foot is down.
I for one enjoy tuning QJets and AFBs but the Holley 4150 will always be close to my heart and is my personal favorite. I have never been "let down" by the performance of a holley I have tuned on.

I'm not trying to put down Holleys, I have several sitting in the shop along with others. Holleys will run a tad fat and thats due to the metering circuit. For the others, I tend to custom ground the rods to get were I want. My primary focus is not to get caught up in a one carb world, they all have their place. If I'm running primarily on the strip, its going to be Holley, thats why I have them. For the street, its a toss up. A finely tuned Qjet is the best, but they sure look ugly. :D

Not to start an argument here, but I have tuned carbs for over 30 years. Started with single carb motorcycles and moved on to multi carb motor cycles and cars. My line of work is Industrial control systems, in which cars and plant equipment share many things in common.

Sounds good. I myself have been working on musclecars since 1974. So I've been at it 31 years or so myself.


The biggest let down of the Holley carb is the fact that the fuel metering system is through a venturi, which is not a linear flow device. All carbs have this drawback, but many of the other manufacturers have linearized the fuel metering by using tappered or staged metering circuit. Holley does not.

I always hear the stories of folks adding a bigger carb and getting a tad more or swapping to another brand and getting better results. So bigger must be better! But rarely do they look at the real reasons why they got better times. The design of the boosters and placement within the venturi are what can make a carb better or worse. The higher end Holleys use dog leg style boosters to get in the flow, the lower ends do not.

The higher end Holleys use an annular booster, not just the dog leg boosters. According to Dave Vizard, an annular booster equipped Holley is the best for all around power on the dyno, bar none. He's used all carbs and the Holleys with annular boosters are the best it gets. The annular booster atomizes the fuel emulsion to a fine misted spray which makes even the most thermal-barrier coated single plane intake manifold responsive at lower RPM's. I believe NASCAR engines use the Holley 830 annular carbs.


As I said, Holleys have there place. If you are running down the strip every day then by all means run a Holley as that is what they are good at. If your are driving around town and an occasional run on the track then I would go with the Carters, Edelbrocks or Qjets. They take more time to tune in, but they will do a far better job overall.

I agree the Q Jet is a fantastic street carb, and I've built many of them over the years for myself and friends which have worked superb. However - I have also found from experience the 3310 750 Holley vacuum secondary has worked excellent as well, in fact in higher-HP applications its a lot easier to get the power output with the Holley than the Q Jet. Q-Jets need extensive reworking (ie drilling of passages) once the cam duration goes over about 224-230 @ 0.050" and manifold vacuum drops significantly. Otherwise they tend to run lean and not deliver the power they should.

Overall, in a street/strip application, the 750 Holley vacuum secondary 3310 is pretty tough to beat, even with it's straight-leg boosters. I've run 115+mph while running in the 11.70 range on radials in my street Camaro Z28 with a 3310. It would take a *lot* of modification to get a Q Jet to run that well with my engine set-up.

markinkc69z is pretty much right on the money with his comments about the 4150 Holleys. I agree they are simply a terrific carb once they are dialed-in. They are easy to work on, and tune, and unlike other carbs don't require extensive modifications to make them work properly on a hot street ot strip engine.

We all have our opinions, these are just my own based on experience.

I rebuilt the Holley, put the stock size air bleeds in it, new accelerator pumps, 73/81 jets, and it still doesn't feel as powerful as the edelbrock on the top end and it doesn't cruise right on the expressway, if I gun it from a standstill its ok, but if I gun it on the expressway it hesitates. I have my timing at 39 degrees total, my curve gives full advance by 2500 rpm. I am stumped here! The only other recent change to the car was that I took off the bullet mufflers and put on Hooker Aero chamber mufflers, true dual 2.5". Apparently I still need to figure something out with this Holley DP. :(

After driving the car it appears to be running lean. Any help or advice is appreciated.

put your car in drive and parking brake applied, check the vacuum from a vacuum source on the carb, the full vacuum port, now from that measurement find a power valve that is 2 inches lower i.e 6.5 inches in drive, need a 4.5" power valve.. also when changing jets, you need to change them in 2 size increments, start over from the beginning and get your vacuum first, then start from the stock jets, do some W.O.T, not feeling it? go up 2 jets, and do it again, and again, and again til you get it, otherwise you are beating yourself up and us answering this question you have.

40 degrees of timing? Is it possible that's killing your top end?

I always ran between 38 and 40 degrees timing before and it ran good. I have been experimenting with the carb a little each day, I had the 73/81 jets and it ran crappy, just for the heck of it I changed the primaries to 67 and the car wouldn't even make it around the block because it just sputters so I am going to put in size 80 jets in the primary and go from there, I didn't realize how much of a difference a few jet sizes can make but I'm new to holley carbs so I will just keep trying things to see what gets better or worse. Thanks for all the advice guys.

To tell you the truth, it really sounds more like your float level is too low. The stock jetting should be producing you good power, tweeking in the extra comes from rejetting. Measuring the floats gets you in the ball park, but I always found that setting results in the fuel level way below the mark.

I have sight plugs for the fuel bowl settings and I have the fuel level just at the bottom of the sight plug. I have been driving it with 80/90 jets and it drives nice, but still seems lean, I'm going to go larger and see if I can't pick up some more power.

I think your airbleeds are backwards. If you have a primary powervalve your tuneup should be pig rich. If the airbleeds were swapped your main system would be very lean and have a tough time starting up. What are the bleed sizes and is the smaller bleed installed towards the center of the carb? (next to the pump squirter)

The air bleeds are 36 in the center 4 and 75 on the outer 4. It doesn't have a bad problem starting, I have to pump the pedal a few times but that is normal with my motor. As I said I am new to Holleys but this is odd because I am running relatively large jets and the bigger I go the better it performs. I am bumping it up from 80/90 to 82/94 to see how it runs. I know that the proform main body flows more air but with these jets this is getting rediculous.

Ok, this is strange but it runs even better with the 82-94 jets, I know this is too big of a gap so I need to go with a 84-92 or something but it seems to run better. I have no idea why it needs such large jets to run right? It doesn't bog if I gun it or have any driveability problems now and I haven't seen any black smoke from the exhaust so I don't think its running too rich.

I don't get it, somebody help me out here. With 76/86 jets it ran way too lean and bested a mph of 109, with 80/90 jets it ran better, with 84/94 it ran 111 mph and with 88/98 jets which I thought would be a huge overkill it ran the exact same 111 mph. I used the 88/98 jets and it didn't even run rich!!!!!! It didn't bog off idle or show any sign of black smoke. It ran the exact same as it did with the 84/94 jets. 4 runs in a row with jetting between 84/94 and 88/98 were all 12.7 @ 111 mph and all were with a 2.1x 60' time. It feels weak at higher rpm and the only thing I can think of is that my fuel pressure must be dropping or something except for the fact that it doesn't run rich when I first take off.
Any advice or ideas????????????????????

Looking for help??? In all my years rebuildin and running Holley carbs, this article(s) was the most helpful in the world, This will be the last time I post to you unless you can prove that you followed the basic principles.

Start over from the beginning!!!!!!!!!!

Put the carb back to stock, set your timing, set idle to stock, i.e 1 1/2 turns out. set the float level. Put car in gear, then get your manifold vacuum reading. I it's lower then 7" you need a 5" power valve. (example)The specs of your engine must be completely known before carb tuning actually works, no vacuum leaks, no exhaust leaks,
timing dead on, e.t.c You are beating yourself up without even attempting to solve the problem.

you can run a holley carb with 90/100 jets and it will still run, you need to run the leanest size jets to achieve the best power in a mechanicAL CARB.
Read this article, then come back to us after you did the steps....Good Luck.

ACCELERATOR PUMP SYSTEM

The accelerator pump system consists of three main components: the pump
diaphragm, the pump cam and the pump nozzle. This is the carburetor system
that is most responsible for having good, crisp, off-idle throttle response.
Its purpose is to inject a certain amount of fuel down the throttle bores
when the throttle is opened. By accomplishing this purpose it acts to
smooth the transition between the idle and main circuits so that no stumble,
hesitation or sluggishness will be evident during this transition phase.


The first adjustment to check is the clearance between the pump operating
lever and the pump diaphragm cover's arm, at wide open throttle. This
clearance should be around .015". The purpose for this clearance is to
assure that the pump diaphragm is never stretched to its maximum limit
at wide open throttle. This will cause premature pump failure. Once this
clearance has been set take a good look at the pump linkage and work
the throttle. Make sure that the accelerator pump arm is being activated
the moment that the throttle begins to move. This will assure that pump
response will be instantaneous to the movement of the throttle. These
adjustments can be made by turning the accelerator pump adjusting
screw that is located on the accelerator pump arm together with the
pump override spring and lock nut.


The amount of fuel that can be delivered by one accelerator pump stroke
is determined by the pump's capacity and the profile of the pump cam.
The period of time that it will take for this pre-determined amount of
fuel to be delivered is affected by the pump nozzle size.


A larger pump nozzle will allow this fuel to be delivered much sooner
than a smaller pump nozzle. If you need more pump shot sooner, then
a larger pump nozzle size is required. During acceleration tests, if you
notice that the car first hesitates and then picks up, it's a sure bet
that the pump nozzle size should be increased. A backfire (lean condition)
on acceleration also calls for a step up in pump nozzle size. Conversely,
if off-idle acceleration does not feel crisp or clean, then the pump
nozzle size may already be too large. In this case a smaller
size is required.


Holley accelerator pump nozzles are stamped with a number which
indicates the drilled pump hole size. For example, a pump nozzle
stamped "35" is drilled .035". Pump nozzle sizes are available from
.025" to .052". Please note that whenever a .040" or larger accelerator
pump nozzle is installed the "hollow" pump nozzle screw, P/N 26-12,
should also be used. This screw will allow more fuel to flow to the
pump nozzle, assuring that the pump nozzle itself will be the limiting
restriction in the accelerator pump fuel supply system.

NOTE: When changing the pump nozzle it's best to jump three sizes. For
example if there's currently a off-line hesitation with #28 (.028")
pump nozzle, try a #31(.031") pump nozzle. If you must use a #37 (.037")
or larger pump nozzle, then also use a 50cc pump.


The same applies to the accelerator pump cams. Once a pump nozzle size
selection has been made the accelerator pump system can be further
tailored with the pump cam. Holley offers an assortment of different
pump cams, each with uniquely different lift and duration profiles,
that are available under Holley P/N 20-12. Switching cams will directly
affect the movement of the accelerator pump lever and, subsequently,
the amount of fuel available at the pump nozzle. Lay out the pump cams
side by side and note the profile differences. This little exercise may
help to better explain the differences between the cams and their
effect on pump action.


Installing a pump cam is straighfforward. It's a simple matter of
loosening one screw, placing the new pump cam next to the throttle
lever and tightening it up. There are two and sometimes three holes
in each pump cam, numbered 1, 2 and 3. Placing the screw in position
#1 activates the accelerator pump a little early, allowing full use
of the pump's capacity. Generally, vehicles which normally run at
lower idle speeds (600 or 700 RPM) find this position more useful
because they can have a good pump shot available coming right off
this relatively low idle. Positions #2 and #3 delay the pump action,
relatively speaking. These two cam positions are good for engines
that idle around 1000 RPM and above. Repositioning the cam in this
way makes allowance for the extra throttle rotation required to
maintain the relatively higher idle setting. Pump arm adjustment and
clearance should be checked and verified each and every time the
pump cam and/or pump cam position is changed:


Lastly, a 50cc accelerator pump conversion kit is available under
Holley P/N 20-11 when maximum pump capacity is desired.

POWER ENRICHMENT SYSTEM

The power enrichment system supplies additional fuel to the main system
during heavy load or full power situations. Holley carburetors utilize a vacuum
operated power enrichment system and a selection of power valves is
available to "time" this system's operation to your specific needs. Each
Holley power valve is stamped with a number to indicate the vacuum opening
point. For example, the number "65" indicates that the power valve will open
when the engine vacuum drops to 6.5" or below. An accurate vacuum gauge,
such as Holley P/N 26-501, should be used when determining the correct
power valve to use. A competition or race engine which has a long duration
high overlap camshaft will have low manifold vacuum at idle speeds. If the
vehicle has a manual transmission, take the vacuum reading with the engine
thoroughly warmed up and at idle. If the vehicle is equipped with an automatic
transmission, take the vacuum reading with the engine thoroughly warmed up and
idling in gear. In either case, the power valve selected should have a vacuum
opening point about 2" Hg below the intake manifold vacuum reading taken.


A stock engine, or one that is only mildly built for street use, will have high
manifold vacuum at idle speeds. To determine the correct power valve the
vehicle should be driven at various steady speeds and vacuum readings
taken. The power valve selected should have an opening point about 2" Hg
below the lowest steady speed engine vacuum observed.

POWER VALVES

The power valve is a key component of the power enrichment system of Holley
performance carburetors. The power enrichment system supplies additional
fuel to the main system during heavy load or full power situations. Holley
utilizes a vacuum operated power enrichment system and a selection of power
valves is available to "time" this system's operation to your
specific requirements.


Each Holley power valve is stamped with a number to indicate its vacuum
opening point. For example, the number "65" indicates that the power valve
will open when the engine vacuum drops to 6.5" Hg, or below.


An accurate vacuum gauge, such as Holley P/N 26-501, should be used when
determining the correct power valve to use.


A competition or race engine which has installed a long duration, high overlap
cam will have low manifold vacuum at idle speeds. If the vehicle has a
manual transmission, take the vacuum reading with the engine thoroughly
warmed up and at idle. If the vehicle is equipped with an automatic
transmission, take the vacuum reading with the engine thoroughly warmed
up and idling in gear. In either case, the power valve selected should have
a vacuum opening point about 2" Hg below the intake manifold
vacuum reading taken.


A stock engine, or one that is only mildly built for street use, will have high
manifold vacuum (17" to 21" Hg) at idle speeds. To determine the correct
power valve, the vehicle should be driven at various steady speeds and
vacuum readings taken. The power valve selected should have an opening
point about 2" Hg below the lowest steady speed engine vacuum observed.
Holley has a 6.5" Hg power valve, P/N 125-65, which usually works out
well for most driving situations.

Believe me, I have triple checked all the basic stuff and I have already tried everything suggested. I checked the manifold vaccum with it in gear and it was bouncing between 7 and 8 so I installed a 5.5 power valve. I have always had my timing set at 38 degrees and I have tried 36 and 40 with very little differences and I don't have any vaccum leaks. I tried several different pumps and the stock size seems to work just fine, I don't have any throttle response issues or hesitation or bogging off the line. I have my fuel pressure set at 7 psi. I have torn down my carb and cleaned/rebuilt it and so have others that know more about holley carbs than I do, nobody has been able to figure out why it runs this way. I have tried different air bleed screws on the proform main body and nothing changes. I have sight plugs on the float bowls so I can see that the float level is set right. I have tried all stock settings and my car won't even drive without backfiring and sputtering if I have the stock jets in it, I have tried 68/78, 70/80, 74/84, 76/86, 80/90, 82/92, 84/94, 86/96, 88/98. It ran the exact same times at the track from 84/94 to 88/98 jetting. I have borrowed and tried different squirters, etc. I am at my wits end and I think I am going to just part out the proform main body, the only thing I can think is that it flows too much for my engine or that fuel pressure drops too low but that wouldn't explain why it runs fine at launch and while cruising. I had a friend who is good with carbs look at it and he couldn't find what is wrong, when I had 80/90 jets in it he drove it around then shut it down right away and we removed all the plugs and the plugs showed we were running lean. I thought that with jets that were so much larger than stock that it atleast wouldn't run lean.

timing set at 38 degrees, what is the initial? try 12 advanced initial, I found that my 750 proform loved 76/81, I also ran no vacuum advance, you are probobly running into a big timing issue more then carb. Actually what type of cam is it, the lift, the duration, what type of heads, the flow numbers, what type of intake, single plane or dual, what type of stall if your an auto, what type of motor, bore, e.t.c.... what type of distributor, what type of plugs, what type of headers, factor these in for me and I can get it running.. ;)

Initial timing is at 17 degrees with 21 degrees mechanical advance, I changed the springs and it reaches total advance at 2500 rpm. It is a MSD distributor with 6AL box. As for the engine it is a 350 ZZ4 shortblock, heads are new trickflow (I'll have to look up the flow numbers), cam is a Comp cam extreme energy hydraulic roller with 236/242 @.50, lift is .520/.540. 110 degree lobe separation. Intake is a gasket matched Edelbrock performer RPM dual plane. Hedman 1 5/8 long tube headers, dual 2.5" pipes with hooker aero chamber mufflers. B&M TC that only stalls at 1500 rpm but it is the high rpm power that I lost from the edelbrock 650 carb to this holley DP. AC-delco plugs gapped at .050
I am going to try and rig a fuel pressure guage to my hood temporarily so I can see if my fuel pressure drops off too much when I get on the throttle.

TOO MUCH TIMING!!! You have too much initial timing. The more advance, the less higher RPM's, the less, the more RPM's. That is why you are hitting a brick wall up high and surging at cruise RPM's. Start the carb back to stock, set the timing to 10 degrees and bolt it down, take a ride. If there is pinging or it doesn't have power, set the timing up 2 degrees in 2 degree increments. I guarantee once you have the timing dead on, that carb is gonna be like playing pocket pool.. When I had timing issues I blamed the carb as well, once I set my timing correctly there was a huge gain and change.. It's going to take up a lot of time and gas to get right, but devote one day to it and let us know how it worked out

Also the intake is killing you as well, Mechanical carb and the lift/LSA/duration needs more of a single plane. You also need a 2800 stall to get you into the traps faster.
Trade someone for the Edelbrock torker2 or a team G and right there you will feel a big change. I tied the performer RPM and hated it, I lost 35 horses switching from the team G.

frist guys you should check your fuel flow the guy said he went to bigger carb he has a 12sec car on a 12sec car the fuel pump should flow a gallon of gas in about 35 seconds this is the frist thing you check if its ok then start tunning the carb i had the same problem got the fuel flow right the car went from 12sec to 11.40et-(388LT1 750dp gm dual plain intake)

First I'd like to thank everyone for their input and advice. Second I want to kick myself for trying too many things. I played with my timing until I came to the conclusion (seat of the pants feeling only, not at the track) that timing was best at 13 initial and 35 total timing. I bumped up the fuel pressure at the same time to 8.5 psi. Then the car ran pig rich so I re-jetted it to 76-81 and it cruised fine and ran well except under wide open throttle so eventually from playing with the jets again I have come to the conclusion that the 76-86 combo seems to work well. Again, I haven't been to the track to verify this but my car wouldn't even cruise with 76-86 jets before I retarded the timing and increased the fuel pressure. Now the car cruises great and accelerates pretty hard. I don't have any driveability issues (except a vibration which I hope to solve with a new trans yoke). I'll have to wait until I get to the track to verify if this helps my times because I don't think I can feel the difference between 1/2 a second or not on the street.
Thanks guys.

First I'd like to thank everyone for their input and advice. Second I want to kick myself for trying too many things. I played with my timing until I came to the conclusion (seat of the pants feeling only, not at the track) that timing was best at 13 initial and 35 total timing. I bumped up the fuel pressure at the same time to 8.5 psi. Then the car ran pig rich so I re-jetted it to 76-81 and it cruised fine and ran well except under wide open throttle so eventually from playing with the jets again I have come to the conclusion that the 76-86 combo seems to work well. Again, I haven't been to the track to verify this but my car wouldn't even cruise with 76-86 jets before I retarded the timing and increased the fuel pressure. Now the car cruises great and accelerates pretty hard. I don't have any driveability issues (except a vibration which I hope to solve with a new trans yoke). I'll have to wait until I get to the track to verify if this helps my times because I don't think I can feel the difference between 1/2 a second or not on the street.
Thanks guys.

Told you it was the timing :p

I'm glad you found the problem, good luck at the track :cool:

Told you it was the timing :p

I'm glad you found the problem, good luck at the track :cool:

Thanks for the help. :bow:

Interesting thread and results.:)

Nice to see it drives better for now. If you can't drive it..ya might as well get rid of it. :cry: