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Discussion Starter · #1 ·
I've been working on my conversion from 2bbl to 4 bbl using and adapter plate :eek: and a used :tdn: Holley 570cfm Street Avenger :tup:. I've worked out some of the bugs on the primary side, but, I still have a problem. I have it at idle and just the lightest touch of the throttle and it does not respond and almost dies, which I can see the accelerator pump arm moving and there's new parts there, but not squirters. So if I grab the shaft for the vacuum secondaries and open them ever so slightly, the engine likes it, and then I can open the throttle and let it rip. I did not see fuel squirting in from the accelerator pump, but my vision or something is obstructing my view. Here's my video: And it is hard to start hot or cold:

https://www.youtube.com/watch?v=O17NDLgfu6s
 

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with the motor off and your head looking right down the carb pump the gas and see is it is spraying fuel ... it should look like your spraying a windex bottle... if not you have acc pump problems.
 

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i had same issue. Tried almost everything from every thread in the forum. Last thing I did, which I should have done first was look down in the carb (mine was a used Holley 650) when I manually moved the accelerator pump. I had just small drips of fuel. I took a screw driver and took off the jjets(?) that were dripping, blew them out with my mouth and put them back on. Sprayed great and that was my problem. I was messing with vaccuum ports, acc.pump spring, linkage, carb cam gear and everything but if I would done that first I would have saved myself alot of grief and time. In the end I just bought a new Holley 650 anyways for like $250. Took 1/2 an hour to put on my 390. And btw, that avenger is kinda small in my opinion cfm wise. Let us know what works
 

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I've been working on my conversion from 2bbl to 4 bbl using and adapter plate :eek: and a used :tdn: Holley 570cfm Street Avenger :tup:. I've worked out some of the bugs on the primary side, but, I still have a problem. I have it at idle and just the lightest touch of the throttle and it does not respond and almost dies, which I can see the accelerator pump arm moving and there's new parts there, but not squirters. So if I grab the shaft for the vacuum secondaries and open them ever so slightly, the engine likes it, and then I can open the throttle and let it rip. I did not see fuel squirting in from the accelerator pump, but my vision or something is obstructing my view. Here's my video: And it is hard to start hot or cold:

https://www.youtube.com/watch?v=O17NDLgfu6s
I just watched your video and really feel your frustration brother. I was in the same place right after buying my Galaxie last fall. Motor to the internet, to the motor, back to the help pages. It will get better and you will figure it out. If you have the money, couple hundred, I really suggest getting a new carb and hook up all the vacuum lines the right way by lookin on the forum for diagrams. Throw it on a credit card or something. You will save alot of time and searching and will be doing 100 foot burnouts by the weekend!
 

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Discussion Starter · #6 ·
i had same issue. Tried almost everything from every thread in the forum. Last thing I did, which I should have done first was look down in the carb (mine was a used Holley 650) when I manually moved the accelerator pump. I had just small drips of fuel. I took a screw driver and took off the jjets(?) that were dripping, blew them out with my mouth and put them back on. Sprayed great and that was my problem. I was messing with vaccuum ports, acc.pump spring, linkage, carb cam gear and everything but if I would done that first I would have saved myself alot of grief and time. In the end I just bought a new Holley 650 anyways for like $250. Took 1/2 an hour to put on my 390. And btw, that avenger is kinda small in my opinion cfm wise. Let us know what works
I think I'm well under 300hp still with this carb so it should be ok I think. I put a 780cfm on a 350 and it was terrible, but the 670cfm was just right, but it was more powerful with cam and heads. I'll be a few days before I get to it but I will check the squirters and post an update with success story I hope.
 

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I think I'm well under 300hp still with this carb so it should be ok I think. I put a 780cfm on a 350 and it was terrible, but the 670cfm was just right, but it was more powerful with cam and heads. I'll be a few days before I get to it but I will check the squirters and post an update with success story I hope.
Oh 670cfm. Your original post said 570cfm which I thought was light given your other specs. Good luck man.
 

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Discussion Starter · #8 ·
Oh 670cfm. Your original post said 570cfm which I thought was light given your other specs. Good luck man.
You are correct. It IS a 570cfm. The stock cam is really only about .400" lift, so I should strickly be between 200-300 hp and that is exactly how I applied the "Holley Selector" applet on the website, since it is a street engine and still not a street/strip engine. It's like on motorcycles. It you add a header, you go up 1 size on the jets. Then remove the air box and go up 1.5 jet sizes with your new pod air filters. I still feel the 570 is appropriate but I will use a bigger one some day.

I'll check it out.
 

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Smaller carbs usually yield good torque and driveability. I love street avengers, they have always worked so well out of the box. I concur with the above statements: Move the throttle alot in a quick movement, and if you don't see a very nice spray in to the carb, you have something wrong with the accelerator pump circuit. The spray is very noticable.
 

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The stock 351W was rated at 250 hp, but that was still the old gross ratings. In current rating standards it probably much closer to 200 +/-. Is was having a lean stumble off idle with my 670 on my engine. I swapped in smaller squirters and that made a great difference in driveablility. With the adapter on the stock 2V manifold, it may be either a rich, or lean condition, but making sure the accelerator pump is functioning is the first step.
 

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So if I grab the shaft for the vacuum secondaries and open them ever so slightly, the engine likes it, and then I can open the throttle and let it rip.https://www.youtube.com/watch?v=O17NDLgfu6s
ok- going off this statement alone...
if adding air (by opening the secondaries) makes things better- then you've got too much fuel.

perhaps the squirters are too big, or the accelerator pump is too aggressive?
 

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Discussion Starter · #12 ·
ok- going off this statement alone...
if adding air (by opening the secondaries) makes things better- then you've got too much fuel.

perhaps the squirters are too big, or the accelerator pump is too aggressive?
Biggest problem I corrected today was the check valve for the squirter down in the throat was seized closed. No fuel was squirting at all. I fixed the problem today, which I attached the latest progress in a video. It is still not running good on the street. I need an alternator, since that is not connected via a belt right now as it has a bad bearing, and I am installing new plugs since there was a lot of smoke in the past monthes from something. Either the lean/rich condition or bad fuel etc etc etc.

Holley Accelerator Pump Video - YouTube
 

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Discussion Starter · #13 ·
ok- going off this statement alone...
if adding air (by opening the secondaries) makes things better- then you've got too much fuel.

perhaps the squirters are too big, or the accelerator pump is too aggressive?
The check valve was seized, causing no fuel flow. The 2nd's are definitely acting peculiar. They are actually opening 100% when the car is not moving (? / -I rev engine in PARK-). Usually, I thought, the primaries had sufficient flow to satisfy an engine when the tranny is in park, which just rev's it up with virtually no load. But they do open for some reason on this setup when the engine is fully rev'ed up and tranny in park (?). I thought I saw a silver spring in the vacuum diaphragm housing. I will address that issue soon and let you know. I know I like fuel flowing thru there right now though (re: cleansing, a used carb). It will assure me the whole carb is running as intended. I might sell it on Ebay and tune another one in for my specific purposes. :bow: Thank you ladies and gentleman.
 

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I don't know how your secondaries are hooked up but if they are vacuum activated they need to be on the proper circuit. E.G. venturi vs manifold vacuum. If they are opening at idle I think they are actuated wrong? AT wot manifold goes to almost zero as all vacuum is felt at the venturi.
 

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Discussion Starter · #15 · (Edited)
I don't know how your secondaries are hooked up but if they are vacuum activated they need to be on the proper circuit. E.G. venturi vs manifold vacuum. If they are opening at idle I think they are actuated wrong? AT wot manifold goes to almost zero as all vacuum is felt at the venturi.
I don't really know right now. I don't remember a vacuum port on the 2nd's metering block. I thought it's just the difference in pressure (basically) on the 2nd's throttle plates which opens them. Crude, simple, and effective. I might be wrong.
 

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The 2nd's are definitely acting peculiar. They are actually opening 100% when the car is not moving (? / -I rev engine in PARK-).
whew...man that's weird.
i'm not familiar with the Street Avenger specifically- but vacuum secondaries open when the vacuum drops. its pretty much impossible to get the vacuum to drop in park (because there's no load), so i'm not sure what would be causing the secondaries to open...but i'm pretty sure they shouldn't be.
 

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Discussion Starter · #17 ·
whew...man that's weird.
i'm not familiar with the Street Avenger specifically- but vacuum secondaries open when the vacuum drops. its pretty much impossible to get the vacuum to drop in park (because there's no load), so i'm not sure what would be causing the secondaries to open...but i'm pretty sure they shouldn't be.
I LOOKED AT THE "2ND'S TUNING SPRING" assortment and the guideline refer to initial opening rpm (ie: 2400rpm) until 100% open (ie: 5000rpm). I removed a spring which was about silber and tried the lightest (white) and heaviest (black) and both seemed to make the engine perk up. Conclusion: The car sat for many years thru its life so it might be just about anything.

I tried to make a video of my "improved" condition but my Sony Bloggie video camera just got ruined in the heat of my glove box, and usb recharging heat. It served me well during it's 2 year lifespan.
 

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i think something is wrong- this is quoted from the Holley Street Avenger instructions:
The secondaries will not open by free-revving the engine. The engine needs to be under a load before they will open.

here's the link- the good stuff starts at the bottom of page 11.
http://static.summitracing.com/global/images/instructions/hly-199r10219-3.pdf

it doesn't say anything about rpm in regards to initial opening- the stiffer vs lighter springs would allow the secondaries to open at different vacuum levels.

where are you seeing guidelines on rpm? i'd like to read through it.
 

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If it's sat a few years, I would get a Holley brand (only) kit and re-do it to set everything to spec. Everything. Note for example, that the secondaries should be locked at idle. No opening with the finger. See the linkage on page 4 of the link cutthrell gave above for how the linkage blocks the secondaries. Taking everything back to stock is a straightforward process, and buying a new carb is (in most cases) totally unnecessary. If you do toss it - toss it my way. BTW - 570 is an excellent CFM for that engine, and capable of about 400hp if you mod it later.

Also note that adding air for improved running means the idle mixture is set way off. After you have re-set the carb, be sure to tune your idle mixture with a vacuum gauge, tune your primary cruise, then tune your accel pump circuit, then do the secondaries. Unless parts have bee lost, changed or modified, you should be pretty close to good after you rebuild the carb following the instructions to the letter.
:tup:
David
 

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Discussion Starter · #20 ·
i think something is wrong- this is quoted from the Holley Street Avenger instructions:
The secondaries will not open by free-revving the engine. The engine needs to be under a load before they will open.

here's the link- the good stuff starts at the bottom of page 11.
http://static.summitracing.com/global/images/instructions/hly-199r10219-3.pdf

it doesn't say anything about rpm in regards to initial opening- the stiffer vs lighter springs would allow the secondaries to open at different vacuum levels.

where are you seeing guidelines on rpm? i'd like to read through it.
http://www.holley.com/data/Products/Technical/199R8219-2rev.pdf

There is some information here about the opening rpm.

I had a 670 Street Avenger on my Z28 and they never opened when the car was stationary. I never checked if they opened on acceleration, but they must have they way it ran. It was a 4 speed.

My XL is an automatic, and I was thinking today, and there is a torque convertor spinning on the end of the driveshaft, and there is fluid in there, and it is a load on the engine. It's at least worth thinking about a little. That amount of load might require the great torque requirement and the greater power output.

My co-worker worked in a marina on Long Island, and they did used to work on the boat carbs, and he says they will open even with no load.

I appreciate your guy's input. Thanks.
 
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