Still no power and bogging down
Thread Starter
Drifting
Joined: Apr 2002
Posts: 1,716
Likes: 4
From: New Baden Illinois
Still no power and bogging down
If I go past 1/4 throttle, it just bogs down and wants to fall on its face. I can get it up past highway speed, but I have to do it by feathering the throttle to get it there. I can also still feel a miss in it.
Timing is at 35*, all in, with total timing at 51* all in. Carb adjusted about 1 1/2 times out on the screws to get 19" hg at idle. Sitting in park at idle, it revs up perfectly and smoothly. However, once I get driving it, if I give it much gas, it goes nowhere and just bogs down.
Carb is 770 Street Avenger. I did the paperclip trick on the secondaries and they are not opening, but I cannot even get it to WOT without it falling on its face. I also made sure that the throttle was opening all the way with the pedal and it is.
If I rev it up in the driveway, I am getting black liquid soot on the garage floor.
Engine is a new 385 ci with Sportsman II heads, Crane Powermax 272 cam, Weiand Stealth intake, Holley Street Avenger 770 carb.
Distributor is original with an Accel cap and rotor (replaced several years ago, but very few miles on it. Ignition module is a Wells (parts store aftermarket) and was replaced about 12 years ago, but...again...very few miles on it.
Not sure if it is something with carb, or if the ignition just cannot provide enough fire for the engine.
Timing is at 35*, all in, with total timing at 51* all in. Carb adjusted about 1 1/2 times out on the screws to get 19" hg at idle. Sitting in park at idle, it revs up perfectly and smoothly. However, once I get driving it, if I give it much gas, it goes nowhere and just bogs down.
Carb is 770 Street Avenger. I did the paperclip trick on the secondaries and they are not opening, but I cannot even get it to WOT without it falling on its face. I also made sure that the throttle was opening all the way with the pedal and it is.
If I rev it up in the driveway, I am getting black liquid soot on the garage floor.
Engine is a new 385 ci with Sportsman II heads, Crane Powermax 272 cam, Weiand Stealth intake, Holley Street Avenger 770 carb.
Distributor is original with an Accel cap and rotor (replaced several years ago, but very few miles on it. Ignition module is a Wells (parts store aftermarket) and was replaced about 12 years ago, but...again...very few miles on it.
Not sure if it is something with carb, or if the ignition just cannot provide enough fire for the engine.
Thread Starter
Drifting
Joined: Apr 2002
Posts: 1,716
Likes: 4
From: New Baden Illinois
I have not checked the flow at the pump. It is just an OE style pump, designed to feed a single feed Qjet. How should I go about checking it? I have checked to make sur the fuel bowls have the correct amount of fuel in them but that is at idle.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Take the fuel line loose from the carb and attach some hose and stick the hose in a container,remove the 12v power wire to the dist,crank engine and watch the fuel flow going into the container.
It should gush pretty good. There is a quantity of fuel per cranks but I can't remember what it is,if someone doesn't post it soon I'll look it up and post it.
I went through some of your previous threads ,did you use the old pump,did you get the preformed rubber fuel hose or the straight? If straight ,make sure its not kinked.
A dirty fuel tank sock could be at fault also.
Your flow test will help.
It should gush pretty good. There is a quantity of fuel per cranks but I can't remember what it is,if someone doesn't post it soon I'll look it up and post it.
I went through some of your previous threads ,did you use the old pump,did you get the preformed rubber fuel hose or the straight? If straight ,make sure its not kinked.
A dirty fuel tank sock could be at fault also.
Your flow test will help.
Thread Starter
Drifting
Joined: Apr 2002
Posts: 1,716
Likes: 4
From: New Baden Illinois
I did use the old pump. For the fuel line, I used the original metal line from the pump, cut it when it got to the top of the engine and then connected it to the carb dual feed line with regular rubber fuel hose.
I guess it could be the sock also because it sat for awhile without being run. Now the tank is about 3/4 full with new 93 octane. Gonna be hard to look at the sock.
When revving the engine up in park, should the spray from the primaries be a nice even spray or in a circular spray pattern? Mine isn't.
I guess it could be the sock also because it sat for awhile without being run. Now the tank is about 3/4 full with new 93 octane. Gonna be hard to look at the sock.
When revving the engine up in park, should the spray from the primaries be a nice even spray or in a circular spray pattern? Mine isn't.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Blown power valve(s).
Like i mentioned before, once u backfire through a Holley the power valve blows out and fuel dumps into the carb - yes even with check ball/valve protection. Minimum u need to remove the fuel bowls and test/replace the power vlvs. Reading liquid black soot on the driveway tells me more than a little rich.
That behavoir is similar to retarded timing but i see u are using plenty of advance. Here again it would be nice to have a "toolbox carb".
Good luck dg and it was nice to read u found the major vacuum leak,
cardo0
That behavoir is similar to retarded timing but i see u are using plenty of advance. Here again it would be nice to have a "toolbox carb".
Good luck dg and it was nice to read u found the major vacuum leak,
cardo0
Pro
Joined: May 2003
Posts: 593
Likes: 0
From: London England
I'm with Roger, this would have been my first suggestion.
If that's ok, then Dick's suggestion seems likely, if it's running massively rich already then when you accelerate and the accelerate pump squirts it may be making it so rich it's flooding.
If that's ok, then Dick's suggestion seems likely, if it's running massively rich already then when you accelerate and the accelerate pump squirts it may be making it so rich it's flooding.
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Thread Starter
Drifting
Joined: Apr 2002
Posts: 1,716
Likes: 4
From: New Baden Illinois
I'm not very familiar with Holley's and this is my first one. The only thing that I have done internally on the carb is to swap out jets. I cannot remember what sizes off hand I did, but I followed Lars advise in moving one set to the other position and then bumping up the previous set. If I get some time tonight, I will disconnect the rubber fuel hose and see how much it flows into a cup with measurements.
cardo0: According to Holley's site, you can test the power valve by seating the mixture screws and the car will die. When I was adjusting the screws previously to try to get the correct a/f mixture, when I seated them, the car started to die and then I backed them out so that it didn't die. Is there any other way to test it?
Also, after I drove it yesterday, I sat in it in the garage with it idling and even in park I could still feel what felt like a slight intermittent miss. (Maybe it's from too much fuel being dumped in??)
cardo0: According to Holley's site, you can test the power valve by seating the mixture screws and the car will die. When I was adjusting the screws previously to try to get the correct a/f mixture, when I seated them, the car started to die and then I backed them out so that it didn't die. Is there any other way to test it?
Also, after I drove it yesterday, I sat in it in the garage with it idling and even in park I could still feel what felt like a slight intermittent miss. (Maybe it's from too much fuel being dumped in??)
Thread Starter
Drifting
Joined: Apr 2002
Posts: 1,716
Likes: 4
From: New Baden Illinois
The choke is fully opening.
Burning Brakes
Joined: Sep 2009
Posts: 1,003
Likes: 48
From: hickory NC
C4 of Year Finalist (appearance mods) 2019
2017 C4 of Year Finalist
I haven't checked the pump with a feeler gauge. What effect will it have if it is not correct?
Thread Starter
Drifting
Joined: Apr 2002
Posts: 1,716
Likes: 4
From: New Baden Illinois
Is this the area in which I am supposed to be able to fit a .020 feeler gauge? If so, I could not fit it in at full throttle. At no throttle, it would squeeze in. If I could fit a feeler gauge in there, how would it be depressing the pump?
Also, I disconnected the fuel line and cranked it. It was putting out some pretty good fuel. In 5 seconds, it put out 4 oz., plus whatever splashed out of the cup onto me.
It was too late to start it up and see if I could kill the engine by running the mixture screws in.
Also, I disconnected the fuel line and cranked it. It was putting out some pretty good fuel. In 5 seconds, it put out 4 oz., plus whatever splashed out of the cup onto me.
It was too late to start it up and see if I could kill the engine by running the mixture screws in.
Le Mans Master
Joined: Oct 2000
Posts: 8,897
Likes: 1,357
From: Santa Ana CA
You never mention your air cleaner.
The symptoms could indicate that like the air cleaner lid is too close to the top of the carb, the air cleaner is too small, or something is cutting off the air flow.
I once had to flip over my air cleaner lid blocking off too much air and it did this same thing.
The symptoms could indicate that like the air cleaner lid is too close to the top of the carb, the air cleaner is too small, or something is cutting off the air flow.
I once had to flip over my air cleaner lid blocking off too much air and it did this same thing.
Thread Starter
Drifting
Joined: Apr 2002
Posts: 1,716
Likes: 4
From: New Baden Illinois
You never mention your air cleaner.
The symptoms could indicate that like the air cleaner lid is too close to the top of the carb, the air cleaner is too small, or something is cutting off the air flow.
I once had to flip over my air cleaner lid blocking off too much air and it did this same thing.
The symptoms could indicate that like the air cleaner lid is too close to the top of the carb, the air cleaner is too small, or something is cutting off the air flow.
I once had to flip over my air cleaner lid blocking off too much air and it did this same thing.
Thread Starter
Drifting
Joined: Apr 2002
Posts: 1,716
Likes: 4
From: New Baden Illinois
Burning Brakes
Joined: May 2008
Posts: 860
Likes: 0
From: Stratford Ontario
Two other things to look at is make sure all the vent tubes on top of carb are clear, not just the two big ones to the bowls. And try running with the gas cap loose to see if vacum is building up in tank and trying to starve engine at higher loads. It will have to be driven like this so be carefull of splashing fuel out. I would also try running car once with no breather once if cap doesnt work, just to be sure your not restricting airflow.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Because you have to pump the gas is why I think that you have a vacuum leak somewhere. Get the motor running and spray all around the base of the carb with something flammable like wd-40 and see if the idle changes.
The worst kind of vacuum leak to find is from the cam valley to bottom edge of the intake manifold.
Thread Starter
Drifting
Joined: Apr 2002
Posts: 1,716
Likes: 4
From: New Baden Illinois
I'm not following you...do you mean I have to pump the gas to start it? I only have to pump it a few times when I first start it cold. After that, I can usually start the car by just reaching in and turning the key.