Holly 600CFM Adjustments , 72' 390

[fastEdsel]

I chased a dead spot on my 390 for 7 long years! I literally tried everything, I thought. I came to this site often and had a ton of replies and I still am grateful for all your input. I too replaced all the components and accessories on that engine. Even tried different carbs, cam settings, jets, accelerator pumps and still the dead spot wouldn't go away. My neighbor said give the damn Holley a Vikings funeral and put on an Edlebrock but I have so much experience with Holley I just knew it couldn't be the carb, and it wasn't. It turned out to be a defective distributor and a major vacuum leak on the advance diaphram. It really wasn't big enough to show up on a regular vacuum test but when I pulled off the vacuum line into the carb and blew into it back through the advance pod, there was no restriction. I replaced the distributor, replaced the Pertonix Ignition I had already installed into it and problem is gone. Just another suggestion, Good Luck.

[DGrant09]

Thanks!! I did find one leak off of the carb, the distributor is new with a duraspark ignition from a 76 earlier this year. I have been wondering about the Edelbroke lately (maybe I should have gone that route)... We used a Holley last year simply because that was what was on the truck. Oh well, this will work fine once it is gone through on Tuesday!! Fingers crossed!!
Thanks again!
Dan

[fitzwell]

ok...cyl 1-4-6-7 fuel soak. Are those cylinders on the same "level" of the intake? If so, check the air bleeds at the top of the carb.

[DGrant09]

1 & 4 are front and rear on the passenger side, 6 and 7 are center on the drivers side. It would make sense for balance purposes if one side of the carb fed these problem cylinders.
I wish I had enough smarts with carbs to have fixed this one. I think your on the right track though.
Thanks
Dan

[AK F100]

I have no imput to your problem, just a quick hello from a neighbor. HELLO.

Good job on putting the fire out quickly. Fire is a living creature and tends to quickly over-eat every time it gets fed.

[binder56jd]

no expert here, but all the stumbling/hesitation problems i have experienced with ford,gm or ihc-using primarily holley,but some with carter or Roch-have been timing related--whether worn dizzys or leaking vac advance--i would have another look at the timing

i realize that should not cause a fuel soak & i have never seen that problem on 4 cyl and opposing sides

if you go e-brock b sure to get a phenolic spacer or u will be cussin the percolating problem

good luck

ps- i advocate holley


pss- does your's have the externally adjustable float feature--that is the one thing that they have started doing on some models--no external adjustment--i don't like that at all---i didn't see any mention of correct float adjustment in the previous post

[cdeal28078]

1 & 4 are front and rear on the passenger side, 6 and 7 are center on the drivers side. It would make sense for balance purposes if one side of the carb fed these problem cylinders.
I wish I had enough smarts with carbs to have fixed this one. I think your on the right track though.
Thanks
Dan

It does work that way on a dual plane intake.
As for the A/F screws not shutting down the engine when turned all the way in you may want to check the secondary set screw and make sure it isn't holding the secondaries too far open. I would also check the base plate of the carb and make sure it is not warped causing a vacuum leak.
I bought 3 different Holley Street Avenger carbs about 3 yars ago. Everyone of them had a warped base plate. I ended up rebuilding an older 1850 I had laying around.
Every Holley built in the last 10 years or so has the power valve blow out protection to the best of my knowledge.
The spring on the accelerator pump arm also has an affect of it's operation
I have worked a lag out of my engine before just by adjusting the arm.
Can't say what would flood only one side of a carb like that, seems like it would affect both sides unless it was an internal leak and your intake has the divider bar at the top of the intake. Some do some don't
clint

[fitzwell]

1 & 4 are front and rear on the passenger side, 6 and 7 are center on the drivers side. It would make sense for balance purposes if one side of the carb fed these problem cylinders.
I wish I had enough smarts with carbs to have fixed this one. I think your on the right track though.
Thanks
Dan

It does work that way on a dual plane intake.
As for the A/F screws not shutting down the engine when turned all the way in you may want to check the secondary set screw and make sure it isn't holding the secondaries too far open. I would also check the base plate of the carb and make sure it is not warped causing a vacuum leak.
I bought 3 different Holley Street Avenger carbs about 3 yars ago. Everyone of them had a warped base plate. I ended up rebuilding an older 1850 I had laying around.
Every Holley built in the last 10 years or so has the power valve blow out protection to the best of my knowledge.
The spring on the accelerator pump arm also has an affect of it's operation
I have worked a lag out of my engine before just by adjusting the arm.
Can't say what would flood only one side of a carb like that, seems like it would affect both sides unless it was an internal leak and your intake has the divider bar at the top of the intake. Some do some don't
clint

Have had it happen...one of the air bleeds gets a chunk of crap in it & half the motor is fat. Good call on the accel pump linkage. When you adjust it, you need about .015 clearance betweeen the arn & the lever, at the wide open position.

I feel your pain on the Street Avenger. Put 3 of 'em on my 69. Each one did smoething different, none ran right. I still look for early 01850 stuff at the swap meets.

and, as always...

[DGrant09]

We got the carb back and it's doing good!! The gasket that goes between the mixture screw body and the float body was the wrong one!! NAPA kit there, at least they returned my 75.00 for the kit! I guess there was supposed to be several different gaskets and mine was short what we needed.. If I would have looked closer before installing it I could have saved a bunch of time and energy. I did pick up some good info on carbs though!!
Thanks for all of the ideas and teaching me!!

[Thunderfoot]

Good deal, always good to here a happy ending!

[Clarko]

ALWAYS use Holley parts and gaskets when dealing with a Holley carb!

I'm very happy that you got your problem fixed and as far as carbs go, I'll use nothing but a Holley or an Autolite/Motorcraft.

Another thing that clears up a dead spot in a Holley is to install an extended accelerator pump discharge nozzle (aka tube type).

They help straighten out the flow so that under higher venturi vacuum, the accelerator pump shot breaks on the side of the venturi.
The stock one looks like this:


I've used the same 770 Street Avenger for a while (and will continue to use it on the new engine) and have had no issues with it.

[DGrant09]

A quick answer to the carb issue. Come to find out the gasket between the metering body and float area was the incorrect one! I guess my carb kit was shorted and I did not catch the differences. Since the carb shop found and replaced this, the truck has done good..
Thanks again
Dan

[Jake11]

Holley carbs are fuel leak looking for a opportunity.
Their great on race cars and when a fireman is handy. I learned
this 30yr's ago. Go ahead and run one. When the flood-o-matic
wipes out your rings or bursts into flames, buy a new Holley. Tell
yourownself how wonderful they are. Good luck. Jake