Car Bogs
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 774
Likes: 1
From: Round Rock Texas
Car Bogs
Ok...just to get you guys caught up. Awhile back I posted about putting a cam in my car and it was too big for the motor. I decided to scrap that and got a ZZ383. It was running really strong, but would bog down after while. I pulled the plugs and it was running really rich. I adjusted the carb and put new plugs and it ran great...for awhile. I had a Holley 650 on it and it started leaking like crazy ( brand new). I took it off and put on an 870 I had. I did jet it way down and it ran great and started bogging down again. Also has developed a vibration.
I can't figure out why.
Any help is always appreciated.
Thanks.
I can't figure out why.
Any help is always appreciated.
Thanks.
Instructor
Joined: Nov 2012
Posts: 219
Likes: 0
From: Irma Northern WI
More information would be nice. Do a compression test. The vibration is a hint that something is amiss someplace. It could be as simple as a bad wire or as serious as a burned valve or blown piston. Keep us posted.
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 774
Likes: 1
From: Round Rock Texas
Thanks.
Le Mans Master
Joined: Oct 2006
Posts: 6,842
Likes: 285
From: Palmdale CA
Yeah, it is too big. That's why I jetted it way down, but I am looking at 700 DP Holley for it now. I am getting it back from my son today and will look at the plugs again. I ran into the same probs with my 75 and 750 Speed Demon until I finally got the right size jets. It is a brand new motor. Roller cam, lifters and vortec heads. It's a brute. I am thinking the flexplate may be wrong. It is an old one that my old mechanic friend had laying around. I am ordering a TCI flexplate, externally balanced for it. I will put that in this weekend. Other than that it is abrute.
Thanks.
Thanks.
Smooth idle, smooth running, but tap on the pedal and that truck wanted to jump! The carb comes with extra springs for the vacuum advance and the vacuum advance, is super easy to get to. It's right on top of the carb, with a black plastic cover. Two screws and you're there!
The smaller carbs, actually are better for low-end torque than the bigger carbs (more hp at the top end), but most of us are looking for the torque, not the drag-race winning hp at the top.
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 774
Likes: 1
From: Round Rock Texas
Allow me to suggest an alternative; The Holley 670 Street Avenger with vacuum secondaries. They're ready to run, right out of the box and we put it on a 74' Short and Wide Chevy p/u, with a built 383 stroker (that had a waaay to radical carb on it, with a ton of problems, like surging, bogging, chugging at the lights...) and the first five seconds we drove it, it was instantly noticable, on how nice it drove.
Smooth idle, smooth running, but tap on the pedal and that truck wanted to jump! The carb comes with extra springs for the vacuum advance and the vacuum advance, is super easy to get to. It's right on top of the carb, with a black plastic cover. Two screws and you're there!
The smaller carbs, actually are better for low-end torque than the bigger carbs (more hp at the top end), but most of us are looking for the torque, not the drag-race winning hp at the top.
Smooth idle, smooth running, but tap on the pedal and that truck wanted to jump! The carb comes with extra springs for the vacuum advance and the vacuum advance, is super easy to get to. It's right on top of the carb, with a black plastic cover. Two screws and you're there!
The smaller carbs, actually are better for low-end torque than the bigger carbs (more hp at the top end), but most of us are looking for the torque, not the drag-race winning hp at the top.
Thanks for the help.
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 774
Likes: 1
From: Round Rock Texas
Put the motor in and dialed everything in with the 650 Holley on it. It ran really well for about two days. My son was driving it and he called and said it didn't sound right or run right. I went and looked at it and immediately pulled the plugs and they were black. I changed plugs and it ran right again. He called me again and said it was running badly again and shuddering with some vibration. I am supposed to get the car back today so I will pull the plugs and see if maybe the balancer is still in one piece. I do know I am putting the new flexplate on it this weekend. So I will see if the plugs are fouled again. At first the car just spun tires when you barely stepped on the gas. Now, he tells me, it has no power and sounds like it is missing. That's all I know until he gets me the car back.
I hope that gives you enough info.
Thanks.
I hope that gives you enough info.
Thanks.
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Le Mans Master
Joined: Jan 2006
Posts: 6,506
Likes: 139
From: Butler Pa
Put the motor in and dialed everything in with the 650 Holley on it. It ran really well for about two days. My son was driving it and he called and said it didn't sound right or run right. I went and looked at it and immediately pulled the plugs and they were black. I changed plugs and it ran right again. He called me again and said it was running badly again and shuddering with some vibration. I am supposed to get the car back today so I will pull the plugs and see if maybe the balancer is still in one piece. I do know I am putting the new flexplate on it this weekend. So I will see if the plugs are fouled again. At first the car just spun tires when you barely stepped on the gas. Now, he tells me, it has no power and sounds like it is missing. That's all I know until he gets me the car back.
I hope that gives you enough info.
Thanks.
I hope that gives you enough info.
Thanks.
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 774
Likes: 1
From: Round Rock Texas
I don't think so. My 75 was the same way until I finally got to the right jet size. After I got there I never had another problem. One of my mechanic friends said to me "870 is not too big...just jet it down" so I took his word for it since he gave me the carb and builds motors all day long. He is just so far away to have him look at it. Can't get the guy that built the motor out to look at it until he gets back in town.
Le Mans Master
Joined: Jan 2006
Posts: 6,506
Likes: 139
From: Butler Pa
Le Mans Master
Joined: Jan 2006
Posts: 6,506
Likes: 139
From: Butler Pa
I don't think so. My 75 was the same way until I finally got to the right jet size. After I got there I never had another problem. One of my mechanic friends said to me "870 is not too big...just jet it down" so I took his word for it since he gave me the carb and builds motors all day long. He is just so far away to have him look at it. Can't get the guy that built the motor out to look at it until he gets back in town.
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 774
Likes: 1
From: Round Rock Texas
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
Just a thought but do you have a performance fuel pump? It might be pushing to much pressure.... Sometimes it's right on the edge of too much psi and it creeps in and starts flooding the bowls. You should be around 5psi. 6 or higher and you have too much....
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 774
Likes: 1
From: Round Rock Texas
No. it has a Chevrolet fuel pump and it sits at 6 psi. It came off the 350 that was in it.
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
That might be your problem. Most stock Chevy fuel pump put out about 3psi and performance was about 5 psi. Guys with the expensive carbs with all the good stuff can handle 6 but our everyday street carbs it's a gamble. Do you have the glass sight windows on the bowls? After running it for a while you can see if the level is raising.... It should be less than half way up on that window on most carbs.
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 774
Likes: 1
From: Round Rock Texas
That might be your problem. Most stock Chevy fuel pump put out about 3psi and performance was about 5 psi. Guys with the expensive carbs with all the good stuff can handle 6 but our everyday street carbs it's a gamble. Do you have the glass sight windows on the bowls? After running it for a while you can see if the level is raising.... It should be less than half way up on that window on most carbs.
Thanks for the feedback.
Melting Slicks
Joined: Oct 2012
Posts: 2,156
Likes: 273
From: Dunedin NZ.
Ever thought of putting a O2 meter on it and see what is really going on? I fitted a bung just past the collector on my 350 exhaust and can plug the gauge in there anytime and check the fuel mixture even while driving. Much easier than pulling plugs all the time to check the A/F ratio and much more accurate. Just my opinion like, but the motor can sound like its running okay and the A/F ratio can be rich, it will run okay for a while then eventually foul the plugs especially if cruising or running slowly like around town.
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 774
Likes: 1
From: Round Rock Texas
Ever thought of putting a O2 meter on it and see what is really going on? I fitted a bung just past the collector on my 350 exhaust and can plug the gauge in there anytime and check the fuel mixture even while driving. Much easier than pulling plugs all the time to check the A/F ratio and much more accurate. Just my opinion like, but the motor can sound like its running okay and the A/F ratio can be rich, it will run okay for a while then eventually foul the plugs especially if cruising or running slowly like around town.
Thanks.
Safety Car
Joined: Jan 2009
Posts: 4,000
Likes: 299
From: New York
The bog may be timing .
Not sure how you decided what jet size to run but it sounds like your making changes with no rhyme or reason to see if they stick.
Go back to basics , button up the ignition side.. Set float level , set transition slots , , start car set idle and a/f mixture..
Not sure how you decided what jet size to run but it sounds like your making changes with no rhyme or reason to see if they stick.
Go back to basics , button up the ignition side.. Set float level , set transition slots , , start car set idle and a/f mixture..