Trans_AM_88

i just finished fine tuning my holley 750 double pumper mech. secondaries carb. i put in 62 primary jets, 64 secondaries. 9.5 powervalve and 32 shooters for front and back. my base timing is a 12* advanced. i have a noticable bog/hesitation when i stomp on the throttle and i was told that i should look into accelerator pump cams. i dont know anything about them but jegs has an assortment kit here

how can i find out which one i need?

RB83L69

Buy the kit and try them until you find the one that your motor likes best.

Trans_AM_88

i dont even know where the cam is or what it looks like. is it easy to change? what does it do exactly?

RB83L69

www.holley.com

bluegrassz

iTrader: (3)

here is what you need to read.accelerator pump system

Here is an exploded view of a 4150. Check out part #172. That is the pump cam.
exploded view

five7kid

iTrader: (14)

More specifically, http://www.holley.com/HiOctn/TechSer...o/4150-60.html .

#172.

bluegrassz

iTrader: (3)

LoL. You posted the same time I edited my post. Looks like we are on the same track.

Trans_AM_88

well i guess i'll have to buy the kit then. i hope this will be the end of my holley tuning trip. it's cost me damn near $100 to tune this beast lol

on a side note:

a few 'problems' with my carb while the car is running.

1. i cant seem to get the idle under about 900rpm . the idle screw on the throttle is backed all the way out and the engine is humming along at 1000rpm. when it warms up it come down to about 900-950. is that normal?

2. everytime (and i DO mean everytime) when i start my car in the mornings (or anytime after the engine has cooled down completely) then engine refuses to idle. it just starts, revs up to maybe 1100rpm and then dies right out. like clock work i tell you. i have to use the choke to get it going and i usually have to rev the engine until it get up to about 200 degrees, then it'll idle with the choke open. again, is that normal? its not like its freezing out...it could be 60-70 degree weather, nice day, and it still happens.

3. i dont know if this is normal either...in the mornings or if the engine has cooled down completely, if i put the choke on more than about 25% the engine just stalls out. it will only run on minimal choke. normal?

bluegrassz

iTrader: (3)

my car idles at about the same. Should be about normal.

Funny thing is, I dont even have a choke.lol. I even removed the choke flap for more air. Car starts right up with 3 pumps on the gas then I start it. I have to stay on the throttle for a few seconds, but then it is fine. May idle at 1000 rpm for a minute or two, but then comes down to say 850 or 900.

I am running my timing at 10*base. Might change your timing. Then readjust your idle.

Chickenman35

1: Not Normal. You should be able to kill the engine with the idle screw speed screw backed out. Either you have a vacuum leak, the primary butterflies are hanging up or the Secondary idle setting is too high ( Yes there is one. Carb has to come off to adjust it )

2. Not normal. Probably a result of jetting down waaaaayyyyy too far. 62 Primaries and 64 Secondaries on a 750DP??? Something doesn't sound right there at all. What is the list number on your carb? What jets were in it originally ( New or used carb )? A 305 ( mild cam ) generally cannot run anything smaller than a 66 primary without having problems. A 350 ( mild cam ) usually requires a minimum of a 68. Secondary between a 76 to an 80. Changing more than 4 sizes from the base setting usually is an indication of some other problem with the carb. At 60 to 70 degrees you should not even need the choke. The engine is starving for gas...that is why you are having to run the choke.

3: 25% choke is normal...when it is freezing outside. And only then for starting. When running you need very little......again only when it is very cold outside. Holleys generally don't even need a choke in warmer climates. The engine is trying to tell you something...IE: I want more fuel!! .

Jet the thing back up. You're not even in the ballpark if that is a 4779 series. A 4779-8 series comes with 71 Primaries and 80 Secondaries. If you have a list 4779...then you're nearly 10 sizes away from stock on the Primary side. Not even close. Please supply list number of carb so that we can check stock jet sizes and make an informed recommendation.

The only reason that the car probably is drivable at all is because you changed the Power Valve to a relatively high number. Most DP's come with a 6.5" PV. By going to a 9.5" valve you are likely opening the PV under light accleration, which is not normal...but in your case is probably the only saving grace because the Primary ( and Secondary ) circuit is far too lean. Put a 6.5" PV or lower ( Which is what a properly tuned DP requires ) and you would probably have a horrible lean surge throughout most of your driving range.

Pump cams. Shooters about right. Primary side try a Blue Cam in the #2 hole or a Green Cam in the #1 hole.

Again...post back with List number of carb and some Engine specs... IMHO you're out of the ball park with your basic settings.

bluegrassz

iTrader: (3)

might want to check out one of his other posts. One of there reasons he jetted down the carb.

Trans_am_88 other post

Plus he was getting like 21-22" of vaccum. That is why he went with a 9.5 powervalve.

Trans_AM_88

19" of vacuum. that should mean little or no leaks right?

i bought the carb brand new. its in fact a 4776-5, not a 4779. i must have misread it, sorry about that. the specs for this carb (stock) are as follows: 600 cfm with mechanical choke, mechanical secondaries and double pumper. 66 primary jets, 73 secondaries. power valve is a 6.5 and the squirters are 28. right now i have 62 primaries, 64 secondaries, 9.5 powervalve and 32 squirters. the carb is on top of a bone stock L98. theres an edelbrock performer intake. holley blue electric fuel pump at 6psi.


do you guys think that the stock jets would work now that i have a 9.5 powervalve? before, with the carb straight out of the box, i was running rich...my plugs were black. other than what i have lsited above, the carb is still stock. other than that, my mechanic messed with the mechanical secondaries and made them come on later which kinda feels too late now (if that means anything)

and how do i change the secondary idle? how do i know what i need?

my car just feels all around slow right now. it feels as if the power is being held back by something. i'm really hoping to wake the car up by tuning the carb.

thanks for the replies guys.

Chickenman35

One thing I noticed right away in your other post is you said that your air cleaner top was getting sucked down when you revved the car. That is definately not good. The air cleaner lid is too close to carb airhorn. If it's pulling the air cleaner lid down then you have a HUGE restriction to air flow. It would be like running with the choke on all the time. Has this problem been addressed?

Get a good drop base air cleaner like a Moroso 14" unit. You can run a 3" air filter with no hood scoop. You need 2" above the air horn to the top of the air cleaner lid minimum. The Moroso unit has a contoured top that smooths the air flow and provides the necessary clearance.

Baseline settings. After you have installed a proper air cleaner!!

62 on the Primary may be OK. With a stock cam that's 4 sizes down from stock. May be a tad lean once you fix the air cleaner problem ( If you haven't already replced air cleaner ).

IMHO. Secondary is too lean still. Remember..... 4 sizes plus or minus from baseline should be all that you need to adjust. Anything more indicates some other problem. I'd bump the secondary up to a 68 or 69.

9.5" Power Valve may be Ok with a stock cam...so should a 6.5". I take it that you're pulling some pretty high idle vacuum?

I'd do the jetting changes then switch back to the 6.5" PV for testing.. You really don't need the PV coming in too early...that will kill fuel economy. It's really a Power Enrichment circuit for WOT or heavy pulls at large throttle openings. Under those conditions your engine vacuum should be below 5". You don't want the PV coming in under light acceleration...that will kill fuel economy.

PV tuning should be last thing you do. Really finessy stuff. I do my PV tuning with a in dash vacuum guage and a long hill. PV recommendations are for minimum levels below idle vacuum. If you've got a 6.5" PV and 10" of idle vacuum ( in gear with Auto) you're good. If you have a 6.5" PV and 22" of idle vacuum, you're still good. You don't have to change the PV. When you open all four barrels or even lean on it on the Primaries the vacuum will plummet...well below 6.5".

The only time you really need to step away from the stock PV size is if you have really low vacuum ( Huge cam for instance ). Let's say a 6.5" PV and 7" to 8" of idle vacuum ( Auto in gear ). Fluctuations in idle speed can cause the PV to open at idel...you definately do not want that. Car will go pig rich. In that scenario you would probably want to change to a 4.5" or 3.5" PV.

Float levels. With engine running. 1\8" below sight plug threads. I find that this stops a lot of excessive fuel slosh under hard braking. Also helps if you autocross. Make sure that fuel pressure at carb inlet does not exceed 6PSI. Remove the sintered filters under the carb inlet fittings and throw them away. Danged restrictive. Run a good quality fuel filter of sufficient size to fuel log. A Fram HPG1 is good. With fuel filters...big is good...bigger is better!!

Secondary idle. Remove carb from manifold. Turn upside down. You will find a small set screw underneath the thottle base plate for adjusting secondary idle. Secondaries should be just "cracked" open a hair. While it's upside down, check that the Primary throttle blades are fully seating with the idle speed screw backed off all the way. If not...find out why.

With a stock cam you should not have any problem of having to open the Primary butterflies too far. This can be a problem with big cams. Uncovering the Transition slots more than .040" cam cause a transition stumble. You don't have this problem...in fact you have the opposite. Car won't die when idle screw backed off. Chcek the things that I have noted.

Also make sure that you are running decent throttle return spring setup. A weak spring may not be pulling the butterflies closed all the way. I like to run two return springs. One pulling backwards from the bottom of the throttle linkage and one pulling forwards from the top of the linkage. This evens the load on the throttle shaft so that it doesn't wear uneven.

PS: I really think that air cleaner issue is your main problem. When you rev the engine it is so restrictive that the mixture is being artificailly enriched. So you jet the carb down to compensate ( not realizing the real problem ). Now when you start the car...it is so lean that it doesn't want to run properly. That all goes out the window as soon as the revs come up...then the air cleaner lid acts like a choke. You simply cannot properly tune the car with that restriction messing up the air flow.......

Hope this helps.

Chickenman35

Snip: Not necessarily. With a 350 and stock cam you could have a small leak at the carb base or even a vacuum port on the carb unplugged. Car will still pull lots of vacuum...but you will not be able to get the idle down. make sure that all ports are hooked up or capped off.

One other thing. You say you have a Performer Manifold. What Part #? 2101 or 3701 by any chance? When useing a Holley Square bore carb on one of these manifolds you should use the Edelbrock adapter plate Part# 2732. #2101 and #3701 are designed for Q-jets and have a spread bore. Now you can bolt on a Square Bore carb such as a Holley or Edelbrock ( Dual bolt patterns ) , but the casting on the Secondary side is so thin that you can easily get a vacuum leak there. Thus the need for the 1\16" thick Steel adapter plate, #2732. Depending on core shift, you may get away without one....but I personally wouldn't chance it.

Interestingly, Edelbrock has a misprint in some of their catalogs:

Quote from my 2000 Catalog.

Square-bore to Spread-bore adapter plate ( 1\16" thick for Edelbrock manifolds only....#2732.
Mounts sqaure-bore carbs to speard-bore carb pad on Edelbrock intake ( Except 2101 and 3701)

The bracketed part "( except 2101 and 3701 )" is a misprint. 2101 and 3701 intake manifolds ( pre 1986 heads ) have the EXACT same carb pads as #2104 and #3706 manifolds ( 1987 and up heads ). With the 1987 and Up Performers, if you want to mount an Edelbrock square-bore carb, they have a notation that Part #2732 is required.

My 1998 Catalog shows that Part #2732 is required for manifolds 2101 and 3701 to mount a square bore carb. Nothing like a misprint in a Catalog or parts book to really mess things up

Trans_AM_88

I love long replies

Ok, Chickenman35 I'll try to answer all your questions in order:

I changed the air cleaner before I started jetting down. I'm running a 14x3 k&n with a 1 1/4" drop base. Good to go in that department.

I have a pair of 66 jets lying around. Do you think that would be good enough for the secondary jets? Or would it be best to go with 68 or 69 like you said?

As for the PV, what you said is very interesting. Now I really understand how it works and what it is for...makes a lot of sense . And what you said about not needing to get a bigger PV makes a lot of sense too. I will put the stock 6.5 PV back in and see how that works out.

My idle vacuum is slightly over 19"

Float levels: I tried checking them a while back with the engine running, but when I took one side off, the engine stalled . I haven't tried it recently, so I will try again. When you say to set the level at 1/8" below the sight plug threads, do you mean 1/8" below the opening of the sight plug hole? If so, how do I know then the level is at 1/8" without being able to see the actual level?

Throttle springs: I do have 2 springs already, but they are both pulling backwards on the bottom. Should the 2 springs be exactly the same strength? I think I bought a universal kit that had 2 different springs and I just put both on. If that is true, I suppose that the stronger spring should stay on the bottom pulling backwards, and the weaker spring should be on the top pulling forwards.

And your next post:

I have the spread bore intake manifold and I already bought the adapter plate. So I have the carburetor on top, then a gasket, adapter plate, another gasket, and then the intake manifold. How is that?


Chickenman35, thanks a lot for the detailed replies! They are greatly appreciated. Thanks

Chickenman35

Problem with long replies is when you spend 30 minutes typing away and looking things up....then lose it all when the attached picture is too big!!! Guess what just happened to me....Grrrrr

Air cleaner change good

I'm still thinking that you'r too lean on the Secondaries. That's what is holding the car back. I'd jet the Secondaries back up to 73's or 71's and see how it responds. Make only one change at a time . Keep a log book and write the results down.

Put in a fresh set of plugs and drive it around a bit, using only the Primaries. A nice cruise on a Freeway would be good. Make sure that you are not getting any poor driveabilty issues such as lean surge. You shouldn't have to use that choke at all in temps over 60 deg. Pull the plugs and make check that you have some good color. Lumps of coal not good...neither is bone white.

Then tune the Secondary jetting for max power at WOT. Generally you want things lean and clean on the Primaries for good driveability and economy...and slightly rich on the Secondary side for max imim power with some safety margin ( Detonation is bad ).

An Air Fuel meter, such as a K&N unit, is very usefull for establishing baselines. Very helpfull for setting things like cruise mixtures and getting you in the ball park for baseline jet settings. Just don't rely on it as gospel. Always go with what the engine wants...particularily at the extremes of mixture ( Lean or rich ). If the engine seems to want more fuel, but the A\F meter already says that it is rich....then give the engine more fuel.

Float levels: Yes 1\8" below sight bowl hole ( engine running )is good, for the reason's I mentioned. I use a small Mag light to shine in the hole so that I can see the level.

Couple of tips. Make sure that the float bowl screws are tight. Not snug...Tight . Not ham fisted tight and don't strip out the threads..... but the gaskets will take a " set " on a brand new carb or after chnaging gaskets. If you don't re-tighten the float bowl screws the gaskets can leak fuel between circuits ( cross talk ). This results in excessive richness.

Also, every couple of months, give the air bleeds in the air horn a shot of carb cleaner. They get gummed up with fuel varnish after awhile and this will riccen the mixture. Often overlooked.

Adapter plate good. Use the pump cams as I mentioned in other post.

Chickenman35

Return springs. A picture is worth a thousand words. Here's my setup. I use two stock Q-Jet springs. Top one go's into one of those universal throttle spring adapter. What you can't see is the forward bracket that bolts to the two front boplt holes on intake. Simple little chrome jobby from Mr. Gasket. Tons of mfg's make these. Will clear all drop base filters.

Chickenman35

BTW...just came across this article on PV tuning. Troy Patterson of TMP carbs is an great guy and he also builds awesome carbs. He is now the sole distributor for Weber Power Plates.

Troy Patterson Tuning Article

Notice the section on Power Valve tuning, Particularily the issues with having too high of a Power Valve. You do not want the PV to open under light acceleration...that is not it's purpose.

With 62 Primary jets you were probably relying on early opening of the PV ( 9.5" ) to mask a probable lean surge. Going back to a 6.5"( or lower) PV may require increasing the Primary jet size slightly. But that is the correct way to do it.

BTW...you might want to check out TMP's catalog's . Those Weber Power plates give drive ablility and throttle response like Fuel Injection. Awesome!!

Troy Patterson
TMP Carbs
10030-1 Canoga Ave.
Chatsworth, CA 91311
(818) 885-0410
E-mail: yorts@aol.com

I do not believe his website is up.

Cheers.

Trans_AM_88

Hey when I type up a long reply, I ALWAYS copy the entire thing, so that if something funny happens I can just paste it again. We all know how frustrating it is when a long thought-out reply gets deleted

I think I should also mention that the only way I can tell that my secondaries have opened is by the sound. I cannot feel a damn difference in acceleration at all. The engine just gets loud. So it probably makes sense that they are jetted down too far.

Alrighty. This is what I will do tomorrow:

1. Put the stock secondary jets back in (73)
2. Put the stock 6.5 power valve back in place of the 9.5 PV
3. I’ll try to set the float levels again, but like I said earlier, when I pulled off the sight plug the engine stalled out. I still haven’t figured out why that happened .
4. Set the secondary idle so that it is just cracked open a hair
edit: I also rigged up my throttle return springs so that they pull against each other. It's temporary, but for now it should work.

As for getting new spark plugs, I just bought new plugs like 2 months ago, but I have a spark plug blaster at school so I’ll try and clean most of my plugs.

I don’t know if I can afford an A/F meter right now...so I don’t know about that.


And back to the original reason for this thread: the pump cams. I bought the kit and I’m going to go pick it up tomorrow. But I think I will do the above listed things first, and then mess with the cams.

ALSO, about the carb plates. They sound interesting, do you have any pictures of them? Do you run one?

Chickenman35

Snip: Take a closer look at the picture with linkage.....

Trans_AM_88

Ok, update.

I put in the 73 secondaries, cracked the secondaries open a bit, put in the 6.5 power valve. Well guess what, I now I have even MORE hesitation...WTF. Now I am pissed. How can the hesitation get worse?

I didn’t get a chance to change the float levels but I don’t think that's the main problem here.

HELP!!

five7kid

iTrader: (14)

If your float levels aren't correct, there's no point in trying to "tune" the rest of the carb.

ljnowell

Precisely why i run an edelbrock

Chickenman35

How can the hesitation get worse?...because something was not right with your carb in the first place. That was the whole point of doing things step by step...and not straying too far from the baseline.

Maybe the float bowls were not tight enough. Maybe a bit of trash in one of the airbleeds. Float level could have been off. Power valve could have been leaking slightly.

For some reason your carb was running pig rich. So you jetted it wayyy down. Now, by taking the carb apart numerous times, you may have accidently fixed the original problem. Now I believe that with those tiny 62 jets in the Primary...you are running too lean

The 9.5" PV was helping to get you through this lean area by opening very early. It was masking a problem created when you jetted down so far.

Out of the box, that carb should have been pretty darned close setup wise. Something else was basically wrong with your carb or setup to make it run so rich. Then you started changing everything around without addressing the real problem. Now you have a mess on your hands


Here's what I would do.

1: Check the float level immediately. As stated. You can't tune anything unless that is right.

2: Put the stock Primary jets back in. Run it that way and see what it does.

3: Put the stock pump shooters and cams back in ( Just to get things back to the baseline ). What color cams are the stock ones?

Basically I'm saying put everything back to the baseline and start all over. Make only one change at a time!! You had some basic problem with the carb...then you hit it with the shotgun affect...changing numerous things at once. Not the right way to do things.

Did you get the idle fixed? Will the thing now die when you back off on the idle screw?

When is this hesitation taking place now? Actually..make the changes I mentioned above and start all over. Report back then how the thing is running.

Pump cams will make a HUGE difference. But they should only be changed once you get everything else back to the baseline.

Normally you do not have to touch the Secondary cams and shotters. That is one of the last things to change.

Once the float level is correct and the jetting is sorted I would recommend going back to the stock shooters and cam on the Secondary and try a #31 shooter and a Blue Cam in the #2 hole on the Primary side for a starting point.

Make sure that there is absolutely no play in the accelerator linkage at idle, but .015" travel left over at WOT. With the engine off, look at the Primary shooters and just crack the throttle a bit. You should have an immediate squirt of fuel from the shooters. If no fuel comes out or it just dribbles out ....then you have a problem.

I suspect that when you get things right, your jetting will be very close to stock.

Don't get frustrated. Take thing methodically and one step at a time


Report back with your progress.

Trans_AM_88

ok i have a problem. i put the carb together, back to stock form. 66 prim. jets,73 sec. jets, 6.5 powervalve, both 28 squirters. now the carb is exactly like it was when i bought it.


problem: big one. the car will NOT idle. it just starts up and dies immediatly. same problem as before but much more consistant. i was thinking that the bigger jets would solve this problem. i tried over adjusting the idle screw just to keep the engine running but that did not work. i tried messing around with the air mixture screws too but its hard when the engine stalls out right away.

the engine will keep running if i continually rev it but it will die as soon as i stop. therefore i cannot properly set the float levels either since the engine will not run.

anyone please jump in, i am at school and i need my car to go to work today. any help would be usefull

Trans_AM_88

Alright guys, I’m out of work now so I drove the car around for a while. It drives well when it’s warmed up. I need to use the choke to keep it running, though. Even fully warmed up, the engine will barely stay alive, if not just die with no choke on. The plugs are still clean, just browner than before. Again, no chance to set the float levels as we had an enormous afternoon shower. Looks like its going be raining for the rest of the night. Tomorrow is another day.

On another note, I checked what cams I have of the carburetor. They are both pink/tan.

No hesitation anymore, but then again the engine will only run > 1100rpm (with the choke on)

Snip:

Well, there is a tiny bit of play when I first open the throttle, but then they squirt. How can I measure how much play I am getting?

five7kid

iTrader: (14)

Sounds to me like it is massively mis-jetted. If you have to have the choke on to make it run, it's lean.

Trans_AM_88

Then why did it run better before with smaller jets?

This is very confusing.

THEGENERAL

welcome to the fine world of holleys ...lol.....go buy an edelbrock and then the problem will be solved....

Chickenman35

That's a big help.....

Chickenman35

If you can't keep the thing running to check float level, you can do a rough setting with the engine off.

I'm betting that your float level is way low now. That's why it won't run unless you have the choke on.

Start the engine...let it run for a minute then turn it off. Grab a little flashlight ( a Mini Mag light is good ). With engine off, undo botth float sight plugs. Does fuel flow out? I'm betting it doesn't. Report back please.

Look into the Primary float chamber and see if you can see the fuel level. Nudge the fender a bit to make it move. If the fuel level is wayy down, then lossen the float screw with a screwdriver and turn the 5\8" Hex Nut a couple of " flats" . Check the Secondary side as well.

Start her up see, where the float level comes to. Keep adjusting till the fuel level is just below the site plug bottom. The thing should be running now. Idle mixture screws: 1.5 turns to 2 turns out from fully seated is a good starting point.

Once the darned thing idles, change the Primary pump cam to a Blue Cam in the #2 hole. Adjust out the freeplay with the screw adjustment on the accelerator pump spring. You want zero freeplay to 1 turn of preload on the cam. Use a #31 or #32 pump shooter. Leave the Secondary Pump shooter as stock....but could you recheck that Secondary pump cam color please. I's either Pink or Tan....can't be both.

Check out these Holley Tech Articles. They will tell you precisely how to adjust things.



Holley Tech Articles

Holley Accelerator Pump system

Chickenman35

Because something was screwed up with it.....

By taking it apart numerous times you may have inadvertantly " fixed " the original problem. I've had this happen a few times to me. Carbs, Computers...girlfriends. It doesn't matter...they all can be a PITA at times

Trans_AM_88

haha, that's so true

i'll do what you said and report back, thanks buddy

THEGENERAL

and that helps a lot too huh

Trans_AM_88

Actually yes, it does.

And for what it is worth, I had an edelbrock before this and that was even worse. What a piece of junk. In any case, if you read the thread fully, and you understood it, then you would realize that it is not the carb that is causing problems. Just because a piece of gunk may have gotten caught somewhere doesn't give you the right to denounce Holley

Edit: and please don't come into this thread and start a little flame war. I would appreciate it if you would either keep your negative posts out of this thread, or perhaps rephrase your statements and try to be helpful and constructive.

ljnowell

OK, this is how i see it. You started the thread, the general made a JOKE to you about selling it and getting an edelbrock. He like them, you dont. Big deal. Someone else made a smartass comment back, because everyone here apparently has no sense of humor, so the general responded. If you dont like it, too bad, this is the internet, and this is how things work. Until you become a mod, you really dont have any right to tell someone to leave the thread, get over yourself.

THEGENERAL

i was tryin to be helpful i have had nothing but problems out of holleys and nothing but good luck out of edelbrocks and i wasnt tryin to start a flame war i believe the other guy was the one that started the *** hat comments i just replied so go and make him sit in the corner not me it wasnt me that started it i just simply suggested to buy an edelbrock never once did i start a fight about it until i was flamed up on

Daz

iTrader: (1)

bunch of clowns..

Have you checked the float level yet?If it would only stay running on a higher RPM,turn up the idle screw.The float level should be the first check you have made.I was having the same problem with my Holley and it made a world of difference after I adjusted the foat.

Daz

Trans_AM_88

ok sorry I missed the joke. No harm done



Alrighty, back to the issue at hand.

I'm trying to adjust the float level for the primary side but I'm having trouble. If I try and adjust it while the car is running, fuel comes out of the adjusting screw. I tried the oppposite extreme, with the screw all the way OUT and fuel started coming out of the pointy tube towards the middle of the carb (I don't know the technical name). I am assuming when that happened the float level was way to high. So I'm guessing the other way (turning the screw in, clockwise) would lower the level. Correct? right now i got it pretty decent, a little more that 1/8" below the sight threads. Is that way too low? I'm having trouble getting the level back up without going too high. Also, I'm having trouble getting the adjustment screw tight enough to seal it (i can see some bubbles seeping through)

Edit: Oh and the pump cams. I put the blue one in, but there are 2 holes on the cam and 2 holes on the carb. Chickenman, you said hole #2, I am assuming you mean the hole marked #2 on the cam. What about on the carb? Right now I put the screw through hole 1 on the carb, into hole #2 in the cam. I haven't driven it yet, but i will report back later tonight and tell you how is drives.

Chickenman35

Clockwise on nut lowers level, Counter-clockwise raises level. If it's leaking you may have damaged the little gaskets underneath the screw and nut. Time to get some spares.

Start the car...check the level...shut the car off...adjust the nut one flat...restart car and re-check level. Repeat until the level is where you want it. More than 1\8" below sight plug threads is really a bit too low. 1\8" below is about the maximum.

Pump Cams. #2 hole on Cam must match up with #2 hole on Carb ( and if using #1 hole on Cam use #1 hole on carb )..so you've got it wrong on the carb side. Sorry...I should have mentioned that. The different hole positions alter Cam timing for different profiles. Unless you have a chart ( which I do ) giving degrees of Cam lift per degrees of throttle opening it's a bit hard to understand. A lot of charts just give you pump volume inforamation...they don't tell you what the shot timing is.

IE: A Pink Cam has a lot of pump shot, more than most street cars require...but it's a very specialised cam. It is meant to be used on Trans-Brake cars or cars with high stall convertors that are being held on the brake before launch ( 3,000+ RPM ). Thus it has very little pump shot initially ( I call it a lazy cam ), because the throttle is open fairly far to hold RPM's against brake...then it has a huge whack of pump shot towards the end. Exactly the opposite of what a street motor requires.

Through experience, I've found that most street driven SBC's want a fairly quick fat shot right of of idle. Especially Auto cars. The shorter the rear gears...the less Pump shot you need. A #31 Primary shooter with a Blue Cam in the #2 hole achives this. With Auto cars you may need to go up to a #35 shooter.

The cam controls the amount of shot and the timing of the shot. The shooter does not affect the total volume of the shot, but it does alter the timing. IE: Same cam...changing to a larger shooter will shorten the duration of the shot, dumping the fuel in quicker. Changing to a smaller shooter will still inject the same volume of fuel ( Volume cintrolled by Cam profile ) but it will spread it over a longer period of time.

The trick is to get the right balance of shooter size and cam profile to meet the requirements of the engine when you accelerate.

Cam profile is the first choice. Then you adjust shooter size. A stumble off idle then the car goes usually indicates too small of a shooter and\or a cam profile that is not aggressive enough in early part of throttle opening. A car that initially accelerates well, them stumbles, then goes... usually indicates too large of shooter size. The pump shot is being dumped all at once and you empty the pump chamber before the mains come in fully. This is usually accompanied by a puff of black smoke out the exhaust as the engine goes overly rich initially. Car may feel 'lazy" as well.

Always use the minimum pump shot that you can get away with. Excess pump shot wastes fuel and can foul plugs.

Note: Primary side is usually all that require tuning. Secondary size should be left alone untill Primary side is set. Usually the Secondary side is pretty good as it comes from the factory. For novices it is best to leave the Secondary side alone until you get a better " feel " for things.

A good book to get is :

Holley Carburetors by Dave Emauel
ISBN 0-931472-08-3

This is one of the few books that gives you a chart, not only of pump cam volumes, but more importantly...pump cam timings.

Chickenman35

Here's a couple of threads that you may find helpful. Warning....lots of intense reading here!!!

I Really need help with my Holley

Holley Tuning

THEGENERAL

lol

Trans_AM_88

Ok, new update. Sorry I haven’t posted in a while but I got really pissed off at my car and I had to stay away from it for a few days. But today I went back at it.

Today I put the blue pump cam on the primary side of the carburetor. The secondary side still has the stock pink cam. I put the screw through both #2 holes. I also discovered that the smooth side of the cam goes against the throttle linkage . That is good to know .

I also set the float level for the primaries. I think I got it damn close to 1/8" below the sight plug hole, so I think I’m all set there.

I adjusted the linkage to the primary squirter so that it's JUST touching at idle. I also check to make sure it squirts the second the throttle moves, and it does.

I also did the same for the secondaries, even though maybe I wasn't supposed to, but I noticed the spring was really tight.

And now for the new problem: I discovered that the secondary venturi's (the things that hang in each barrel, or is it called a pilot tube?) and DRIBBLING gas...a damn good amount too. I figured it must be flooding because the float level is too high. So I did as you said, and turned the float adjustment nut clockwise. I almost ran out of thread and the float level sight plug still spills fuel out and the venturi's still dribble. Is my float stuck or broken? How could this happen? I tried tapping the secondary fuel bowl to get the float unstuck but that didn't do anything.

If I let the car sit for 15-20 minutes it will run rough at about 1300 rpm (idle screw isn’t even touching) and will momentarily rise up to 1500rpm, but quickly start to fall with the engine shaking violently. It will eventually stall out. I think I’m flooding. What’s going on here?

Chickenman35

Oh yeah...it's flooding. Big time. Those are the venturi boosters....and gas should NOT be dribbling out of them at idle.

Could be a bit of trash in the needle and seat. Take it out ( unscrew it all the way counter-clockwise ) and blow it clean.

I've seen some pretty rough handling of carbs when shipped. This is a new carb right? Sometimes what happens is they get tossed about and placed upside down. Then the float can get stuck. Sometimes all that is necessary is to take things apart and blow them out with compressed air. But come to think of it...you've changed jets on the Secondary side a couple of times. Make sure the float isn't sticking in the down position. Check it's movement very carefully for any binding.

You could also have a defective needle and seat Check things out one more time. Don't forget to use new gaskets every time you take the float bowls and metering blocks off. Actually, you might get away with re-using them once if they are the blue or black non-stick gaskets and you are carefull when you disassemble things.

If the float is a white Duracon float I've seen these crack. Then they fill with gas. Brass floats and Nitrophyl floats ( Black ) are usually bulletproof when new.

Man this is a lot of head-aches for a new carb. I feel your pain If the SOB doesn't come right pretty darned soon I'd be asking for a replacement. Other than setting float level...which you're just getting around to...that thing should have run fairly good straight out of the box. But....I don't think you ever got the float levels set correctly ( Edit: previously ).

PS: Just a thought. You didn't perchance add a fuel filter and cut the metal line did you? Sometimes metal filings will get flushed through the line and cause a mess of problems. Sounds silly...but we've probably all done it at one time or another.

Trans_AM_88

Well, as luck would have it, this happened the day i took out the sinter filter in my fuel line. I didn't cut any metal lines either.

so the venturi boosters unscrew? I'll try and take them out and clean them. Then I'll pull off the secondary fuel bowl and make sure everything is ok in there. As for the gasket, it's a blue one, and I am very careful so I don't break it.


Hmm I was just looking at Holley's website and i noticed that there are filters inside the carburetor. Did you mean those filters and not the one in my fuel line? Or does it matter?

EvilCartman

iTrader: (1)

Take out the needle and seat assembly not the boosters. You don't even have to pull the fuel bowls off to do it. The picture below shows what it may look like when pulled out.

Trans_AM_88

Where is it ? Are you talking about the idle mixture screws?

Trans_AM_88

Wait a sec, is the neeedle and seat in the float adjustment? Can i pull the needle and seat out without messing anything up with the float?

Chickenman35

Yep...just unscrew the N&S as mentioned. It will come out straight out the top.

The Needle and seat is the float level adjustment. When you turn the 5\8" hex nut back and forth, the Needle and seat moves up and down. That's how it adjusts the float level.

Trans_AM_88

Alright. I took out the needle and seat. There was some junk on the needle so I cleaned it with carb cleaner. Put everything back together, now the car backfires like nuts. A few through the carburetor (just very small ones) and a whole bunch through the exhaust. The rpm's just rise and fall randomly by themselves when running. It will still die out if I do not apply a little throttle. I blew out a bunch on chunks of my cat too lol. This doesn't sound too good. Should i get new spark plugs? Why is the car backfiring so much? I tried to let it run for a few minutes to clean up the plugs which helped get rid of the backfire through the carburetor. But it keeps popping through the exhaust. Why?