Carb tuning / Timing issues???
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From: Ft Hood TEXAS
Carb tuning / Timing issues???
Okay, have a 76 with the L48. I recently changed out some stuff and the car is driving me nuts. Here is the list of mods:
Holley Street dominator aluminum intake manifold
Holley 600 CFM carb
Accell Distributor, Cap and rotor
Accell high output coil
Mid America True Dual Kit and Flowmasters
I finally got the carb to where it seemed to be doing really good. Had great throttle response, decent on the upper end as well. This morning after taking the slow drive home from work, it backfired and died on me while pulling into the driveway. Idle in Park or Neutral is about 700 rpm and in gear, it is about 500 rpm. At times if you hit the gas too hard from a stop, it will stumble really hard. Other times, it will go without missing a beat. When driving, sometimes if I do a heavy take off, it will try to die on me like it is starving for fuel. have a brand new mechanical pump and new fuel filter on there. I am going to try to mess with the timing some more today. Does this sound like a timing issue or more like a carb issue? Any help at all will be apprecated. I am leavng for the sand box soon and just wat to be able to enjoy my Baby for a little while before I go.
Thanks,
Glen.....
Holley Street dominator aluminum intake manifold
Holley 600 CFM carb
Accell Distributor, Cap and rotor
Accell high output coil
Mid America True Dual Kit and Flowmasters
I finally got the carb to where it seemed to be doing really good. Had great throttle response, decent on the upper end as well. This morning after taking the slow drive home from work, it backfired and died on me while pulling into the driveway. Idle in Park or Neutral is about 700 rpm and in gear, it is about 500 rpm. At times if you hit the gas too hard from a stop, it will stumble really hard. Other times, it will go without missing a beat. When driving, sometimes if I do a heavy take off, it will try to die on me like it is starving for fuel. have a brand new mechanical pump and new fuel filter on there. I am going to try to mess with the timing some more today. Does this sound like a timing issue or more like a carb issue? Any help at all will be apprecated. I am leavng for the sand box soon and just wat to be able to enjoy my Baby for a little while before I go.
Thanks,
Glen.....
Heel & Toe
Joined: Mar 2006
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From: Pace Florida
Sounds like a carb issue to me. I had similar issues until I had my carb rebuilt. The choke was the main culprit.
What is your timing set to? Does it wander at idle, or stay where it's supposed to be?
What is your timing set to? Does it wander at idle, or stay where it's supposed to be?
Melting Slicks
Joined: Mar 2006
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From: Orange Park Fl
Sound like typical Holley / Accell issues to me, I usually avoid them. Last Holley product I bought was defective, and as the dealer and I tried to explain the problem to one of their tech guys, he told me "The product is fine, I guess we just don't make things for YOUR car." I took that statement to heart. Sensei
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From: Ft Hood TEXAS
Originally Posted by KMB
Sounds like a carb issue to me. I had similar issues until I had my carb rebuilt. The choke was the main culprit.
What is your timing set to? Does it wander at idle, or stay where it's supposed to be?
What is your timing set to? Does it wander at idle, or stay where it's supposed to be?
The carb s brand new, out of the box. So if it needs to be rebult, it's going back. As far as timing, it is set at 7 degrees BTDC at idle. Stll tryng to understand the concept of the "total" timing. The engine is not wandering at idle at all. Smooth idle and the tach sits pretty steady.
Melting Slicks
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From: Madison Ms
Originally Posted by hotwater
The carb s brand new, out of the box. So if it needs to be rebult, it's going back. As far as timing, it is set at 7 degrees BTDC at idle. Stll tryng to understand the concept of the "total" timing. The engine is not wandering at idle at all. Smooth idle and the tach sits pretty steady.
Man....wind that toy up!! Get that thing up to a least 12 and try her out. You could probably get even more out of her. Listen carefully to your engine for pings/knocks from running to much timing however. If you hear any pinging, knock it back a couple of degrees, and try again.
Read Lars paper to fine tune it, but for starters, advance that timing!! https://www.corvetteforum.com/techti...=109&TopicID=3
Last edited by MsVetteMan; Apr 4, 2006 at 04:48 PM.
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From: Ft Hood TEXAS
Originally Posted by MsVetteMan
7???
Man....wind that toy up!! Get that thing up to a least 12 and try her out. You could probably get even more out of her. Listen carefully to your engine for pings/knocks from running to much timing however. If you hear any pinging, knock it back a couple of degrees, and try again.
Read Lars paper to fine tune it, but for starters, advance that timing!! https://www.corvetteforum.com/techti...=109&TopicID=3
Man....wind that toy up!! Get that thing up to a least 12 and try her out. You could probably get even more out of her. Listen carefully to your engine for pings/knocks from running to much timing however. If you hear any pinging, knock it back a couple of degrees, and try again.
Read Lars paper to fine tune it, but for starters, advance that timing!! https://www.corvetteforum.com/techti...=109&TopicID=3
that you need to time it correctly before messing around with the carb.
Melting Slicks
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From: Madison Ms
Before, and without vac advance hooked up. Setting timing a idle is just a basic quick way to get you in the ball park and running okay.
What you will want to do after is check to make sure you are getting 36* of timing all in before 3000 rpm. If you are not, you will need to change to some softer springs in the distributor. But for now, adjust your idle timing for 12 to 15* BTDC. After you get it set, tighten down the distributor, hook up the vac, and set your idle rpm between 800 and 900 rpm with the idle adjustment screw. You have to play with that a little. Some cars want more, and some less.
See what kind of difference it makes, but listen carefully for pinging or knocking.
What you will want to do after is check to make sure you are getting 36* of timing all in before 3000 rpm. If you are not, you will need to change to some softer springs in the distributor. But for now, adjust your idle timing for 12 to 15* BTDC. After you get it set, tighten down the distributor, hook up the vac, and set your idle rpm between 800 and 900 rpm with the idle adjustment screw. You have to play with that a little. Some cars want more, and some less.
See what kind of difference it makes, but listen carefully for pinging or knocking.
Last edited by MsVetteMan; Apr 4, 2006 at 05:23 PM.
Melting Slicks
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From: Madison Ms
Originally Posted by hotwater
According to the chilton manual, it says 6 degrees BTDC.
Chilton is for a stock setup and strictly for economy, and is very conservative. You won't hurt anything, just start a 10 if that makes you feel better, and then work your way up.
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From: Ft Hood TEXAS
Originally Posted by MsVetteMan
Lars, or Chilton? Trust us.......
Chilton is for a stock setup and strictly for economy, and is very conservative. You won't hurt anything, just start a 10 if that makes you feel better, and then work your way up.
Chilton is for a stock setup and strictly for economy, and is very conservative. You won't hurt anything, just start a 10 if that makes you feel better, and then work your way up.
BTDC right?
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From: Ft Hood TEXAS
Originally Posted by MsVetteMan
Yep.......
^^^^^^^^^^^^taking advice from a man who blew his motor up last week
^^^^^^^^^^^^taking advice from a man who blew his motor up last week
I will give it a try. I trust you guys more than the chilton manual when it comes to the performance related stuff. How far up will the factory timing tab go to?
Melting Slicks
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From: Madison Ms
You do have a timing light, right?
Easiest way to do it is loosen the distrib. bolt (not to loose), crank her up, unplug vac at carb (you may have to raise the idle at this point), and start nudging the distrib. counter clockwise a little at a time, then checking timing light, and so on. Just work slowly. A little turn means a lot, so don't get carried away. You can tell by ear how it's doing as you turn the distributor. Take it up to 12 and test drive. You can readjust if necessary.
DO NOT ADVANCE IT TO MUCH!! BACK IT DOWN IF YOU HEAR ANYTHING FUNNY. TEST DRIVE IT AND MAKE SURE IT'S NOT PINGING. RUNNING TO MUCH ADVANCED TIMING CAN CAUSE YOU TO OVERHEAT, or Worse.
There, I feel better now.
Take the time to read some articles of setting timing. (google). Buy a spring set for your distrib. and nail it later!!
Easiest way to do it is loosen the distrib. bolt (not to loose), crank her up, unplug vac at carb (you may have to raise the idle at this point), and start nudging the distrib. counter clockwise a little at a time, then checking timing light, and so on. Just work slowly. A little turn means a lot, so don't get carried away. You can tell by ear how it's doing as you turn the distributor. Take it up to 12 and test drive. You can readjust if necessary.
DO NOT ADVANCE IT TO MUCH!! BACK IT DOWN IF YOU HEAR ANYTHING FUNNY. TEST DRIVE IT AND MAKE SURE IT'S NOT PINGING. RUNNING TO MUCH ADVANCED TIMING CAN CAUSE YOU TO OVERHEAT, or Worse.
There, I feel better now.
Take the time to read some articles of setting timing. (google). Buy a spring set for your distrib. and nail it later!!
Last edited by MsVetteMan; Apr 4, 2006 at 05:41 PM.
