swap running rough
07-20-2011, 07:10 PM
#1
Teching In
Thread Starter
iTrader: (1)
Join Date: Apr 2008
Posts: 19
Likes: 0
Received 0 Likes
on
0 Posts
swap running rough engines a 5.3l bone stock victor jr intake with a holley 750 vacuum secondary carb found no air leaks tried to post video but not sure how to here's YouTube link http://youtu.be/GVWB6bujaTY car starts right up with no problem changed plug wires spark plugs checked ground wires have'nt tuned carb yet, msd box currently has pill#3 but have tried all pills would like opinions of what i should do
07-21-2011, 10:08 AM
#4
TECH Apprentice
Join Date: Feb 2011
Location: Central Florida
Posts: 316
Likes: 0
Received 0 Likes
on
0 Posts
I took my Holley out of the box, bolted it on the car and went. The carbs seem fairly well adjusted from the factory. I have heard other people say the same thing.
I am wracking my brain.....seems like it might be running on seven? Maybe pull the spark plugs and look for a wet one? Is the exhaust smoking? Maybe use a stethoscope or large screwdriver and try to listen for any bumps or knocks in the heads (valvetrain)
Let us know - definitely let us know if it was the carb so everyone can laugh at me
I am wracking my brain.....seems like it might be running on seven? Maybe pull the spark plugs and look for a wet one? Is the exhaust smoking? Maybe use a stethoscope or large screwdriver and try to listen for any bumps or knocks in the heads (valvetrain)
Let us know - definitely let us know if it was the carb so everyone can laugh at me
07-21-2011, 11:35 AM
#5
On The Tree
Join Date: Mar 2010
Location: SpringCity Tn
Posts: 153
Likes: 0
Received 0 Likes
on
0 Posts
If I was you, while its idling, start un-plugging the coils 1 at a time and find the dead cylinder. Then make sure your coil is actually firing, if it is then inspect further, but it sounds like 1 is def dead.
07-22-2011, 11:41 PM
#7
Teching In
Thread Starter
iTrader: (1)
Join Date: Apr 2008
Posts: 19
Likes: 0
Received 0 Likes
on
0 Posts
hey guys so after fixing idle problem thought everything was good engine idles great but stumbles while accelerating either gradually or wot tried tuning carb nothing helps it looks like not enough fuel but i could b wrong dont have much experience tuning read something about 50cc pump not sure what it does or if it would help still using pills that came with msd box tried all heres link to video of car running now thru exhaust http://youtu.be/QR92TfvBZCc once again thanks for any help
Trending Topics
07-23-2011, 08:01 AM
#8
Read the sticky at the top of this section. The stumble is talked about it in there
https://ls1tech.com/forums/carburete...-dist-ls1.html
At a minimum you need to increase the accel pump squirter size and maybe play with the accel pump cams. You gotta make sure you adjust the linkage so even a small throttle movement results in a nice strong shot. I am running a 31 in the primary and 35 secondary with pink cams in both places.
Lots of guys end up going to the 50 cc accel pump on the primary, especially with the single plane intake like you have. I ran that way too for awhile, but then I adjusted the primary idle air bleeds and that allowed me to go back to the 30 cc pump.
Some Holley's seem better suited to LS motors than others. Bolting on an out of the box Holley HP or street avengers doesn't have the stumble problem as bad as the classic double pumpers will. At least that is what I am gathering from reading posts on here. My DP is working good now, just took some trial and error to get right.
https://ls1tech.com/forums/carburete...-dist-ls1.html
At a minimum you need to increase the accel pump squirter size and maybe play with the accel pump cams. You gotta make sure you adjust the linkage so even a small throttle movement results in a nice strong shot. I am running a 31 in the primary and 35 secondary with pink cams in both places.
Lots of guys end up going to the 50 cc accel pump on the primary, especially with the single plane intake like you have. I ran that way too for awhile, but then I adjusted the primary idle air bleeds and that allowed me to go back to the 30 cc pump.
Some Holley's seem better suited to LS motors than others. Bolting on an out of the box Holley HP or street avengers doesn't have the stumble problem as bad as the classic double pumpers will. At least that is what I am gathering from reading posts on here. My DP is working good now, just took some trial and error to get right.
07-28-2011, 12:39 AM
#9
Teching In
Thread Starter
iTrader: (1)
Join Date: Apr 2008
Posts: 19
Likes: 0
Received 0 Likes
on
0 Posts
engines still stumbles when i gradually increase the throttle and tends to backfire from exhaust just changed to 50cc acc pump and changed nozzle to .35 tried tuning carb, unplugged coils plug wires everything seems to b working good found no air leaks car starts and idles fine i just don't know what else to do, what should i b checking? appreciate the responses guys
07-28-2011, 06:05 AM
#10
The accel pump is for hard throttle movements. A stumble with slow movements is a bad mixture in the transition circuits. You need to get the slow movement right before you set the accel pump.
Quick answer is you can cheat a bit on the idle screws and run slightly rich at idle. That will probably help. For my carb I didn't get rid of that slow throttle movement stumble until I made the idle air bleeds a couple sizes smaller and played with the idle feed restrictor size.
There are all sorts of on line guides and info on this site about setting up a carb. Yoiu need to cover the basics first like float level, fuel pressure, leaking gasket surfaces, power valve, ignition timing. Another trick is adjusting primary blades set such that you have just the right amount of the transfer slot visible. You can adjust the secondary blade idle openings or even reduce the idle timing to get the idle speed back down. My motor has a stock cam and pulls 23 inches of vac at idle. I actually have a hard time getting the idle RPM below 950. Think I need a bigger cam.
Quick answer is you can cheat a bit on the idle screws and run slightly rich at idle. That will probably help. For my carb I didn't get rid of that slow throttle movement stumble until I made the idle air bleeds a couple sizes smaller and played with the idle feed restrictor size.
There are all sorts of on line guides and info on this site about setting up a carb. Yoiu need to cover the basics first like float level, fuel pressure, leaking gasket surfaces, power valve, ignition timing. Another trick is adjusting primary blades set such that you have just the right amount of the transfer slot visible. You can adjust the secondary blade idle openings or even reduce the idle timing to get the idle speed back down. My motor has a stock cam and pulls 23 inches of vac at idle. I actually have a hard time getting the idle RPM below 950. Think I need a bigger cam.
