Timing Dance ! Vacume Advance ?

-
If it is pinging at 32 and 34 degrees it will still ping at 36.
Are you sure it's pinging???
Set your timing at 30 and test drive.
See if it go's away.

If your having this much detination ,you will hurt the motor drag racing it that way.
What plug are you running ????(company and part #)
 
T67POWER said:
If it is pinging at 32 and 34 degrees it will still ping at 36.
Are you sure it's pinging???
Set your timing at 30 and test drive.
See if it go's away.

If your having this much detination ,you will hurt the motor drag racing it that way.
What plug are you running ????(company and part #)
Click to expand...

I will mess with the timing in the morning. I will start at 30.I just put in the champion plugs. new 8mm accel wires and runs the same as before when I had autolite and 7mm wires.The new plugs are the same as the autolite 65 cool plug. It might be header ping .This is all about the darn throttle lag. My carb may be bad from the start. Thanks for taking all this time. I have had this lag for a year. to me its always felt like the timing was retarded or carb problem.
 
T67POWER said:
I don't take the chance of being in the wrong situation and having the motor pay the price.
FOR EXAMPLE: HOT DAY\\BIG HILL \\ THREE QUARTERS THROTTLE.
REMEMBER (((( YOU CAN'T ALWAYS HERE DETINATION))))

If it's all about drag racing then it gives you no benifit, and you will not have any detination problems creep up on you.
Click to expand...

T67,
The vacuum advance only operates at light load situations where the manifold vacuum is high. In your example; up hill with the throttle 3/4 open the manifold vacuum will be low and there won't be any (or very little) vacuum avance and at WOT acceleration there won't be any vacuum advance at all. The vacuum advance does not react to rpm changes it reacts to changes in manifold vacuum. When the throttle is just cracked open you have maximum manifold vacuum and maximum vacuum advance. When the throttle is fully open you have minimum manifold vacuum and no vacuum advance.

With any modified motor the initial timing, total mechanical advance, rate and vacuum advance have to be dialed in for the combo. The total amount of advance the vacuum pod can add is fixed by the stop built into the arm of the pod. There is a number stamped on the arm which represents the number of degrees the pod can add in cam degrees (double this number when talking about crank degrees). But the vacuum required to get it to start moving and the amount of vacuum to reach full advance is adjustable with an allen wrench through the vacuum nipple. If you had a situation where you had detonation under a light load situation or under light acceleration then you would adjust the pod so the advance starts coming in at a higher vacuum level. If you had the same situation with the vacuum advance disconnected then the timing is coming in to fast and you need stiffer springs in the distributor.

pilotsf,
I don't think you have said what distributor you have but with 17/18 initial and 34/36 mechanical it sounds like you have the mopar perfromance distributor. These come through with very light springs (likely the pink ones) which may have your timing coming in too fast. You may need to go to stiffer springs. These distributors have a Mallory advance mechanism in them and there is a tuning kit #29014 that you can get from Summit or Jegs that has a wide assortment of springs and a chart that shows you which springs or combinations give which timing curves. Remember as you reduce the amount of mechanical advance built into the distributor with the stops you have to go to stiffer springs to have it still be all in at the same rpm.

On my 360 I needed 17 initial and with the magnum heads I have, I run 33 total mechanical. With the light pink springs it would be all in around 1800 rpm. To get it back up the 2600 rpm range I need to go to the next to stiffest brown springs.
 
dgc333 said:
T67,
The vacuum advance only operates at light load situations where the manifold vacuum is high. In your example; up hill with the throttle 3/4 open the manifold vacuum will be low and there won't be any (or very little) vacuum avance and at WOT acceleration there won't be any vacuum advance at all. The vacuum advance does not react to rpm changes it reacts to changes in manifold vacuum. When the throttle is just cracked open you have maximum manifold vacuum and maximum vacuum advance. When the throttle is fully open you have minimum manifold vacuum and no vacuum advance.

With any modified motor the initial timing, total mechanical advance, rate and vacuum advance have to be dialed in for the combo. The total amount of advance the vacuum pod can add is fixed by the stop built into the arm of the pod. There is a number stamped on the arm which represents the number of degrees the pod can add in cam degrees (double this number when talking about crank degrees). But the vacuum required to get it to start moving and the amount of vacuum to reach full advance is adjustable with an allen wrench through the vacuum nipple. If you had a situation where you had detonation under a light load situation or under light acceleration then you would adjust the pod so the advance starts coming in at a higher vacuum level. If you had the same situation with the vacuum advance disconnected then the timing is coming in to fast and you need stiffer springs in the distributor.

pilotsf,
I don't think you have said what distributor you have but with 17/18 initial and 34/36 mechanical it sounds like you have the mopar perfromance distributor. These come through with very light springs (likely the pink ones) which may have your timing coming in too fast. You may need to go to stiffer springs. These distributors have a Mallory advance mechanism in them and there is a tuning kit #29014 that you can get from Summit or Jegs that has a wide assortment of springs and a chart that shows you which springs or combinations give which timing curves. Remember as you reduce the amount of mechanical advance built into the distributor with the stops you have to go to stiffer springs to have it still be all in at the same rpm.

On my 360 I needed 17 initial and with the magnum heads I have, I run 33 total mechanical. With the light pink springs it would be all in around 1800 rpm. To get it back up the 2600 rpm range I need to go to the next to stiffest brown springs.
Click to expand...

Thanks for all the info again.
 
If you lag is 1/2-3/4 throttle, it is carb related. As previously mentioned, vacuum advance is light throttle only. For now I would cap the vacuum advance at the carb (no need to cap at dist) and set the timing just below the point where you start to get ping using the gas you typically run. This will have your ignition in a stable condition so you can focus on the carb.

The Owners Manual that came with you carb has some pretty good tuning advice. Read and heed. First make sure your float levels are correct. Then, if the jetting is basically close it may be as simple as going 1/4 turn tighter on the secondary air door.

Then, once the base timing and carb are where you want them, you can connect the vacuum advance and set it up. (Timed port is on the passenger side of the carb).
 
C130 Chief said:
If you lag is 1/2-3/4 throttle, it is carb related. As previously mentioned, vacuum advance is light throttle only. For now I would cap the vacuum advance at the carb (no need to cap at dist) and set the timing just below the point where you start to get ping using the gas you typically run. This will have your ignition in a stable condition so you can focus on the carb.

The Owners Manual that came with you carb has some pretty good tuning advice. Read and heed. First make sure your float levels are correct. Then, if the jetting is basically close it may be as simple as going 1/4 turn tighter on the secondary air door.

Then, once the base timing and carb are where you want them, you can connect the vacuum advance and set it up. (Timed port is on the passenger side of the carb).
Click to expand...

Thats good advice ! I got the timing all set per fishy68 and t67. 34* at 3000 rpm. Awesome ! As far as the carb I have the edelbrock 800 and have the manual and had it dyno a/f and it has a lean spot in it. I have the stiffest step up springs and still have 3/4 throttle lag(just for a second,but enough). So what is the 1/4 turn on the air door. can you help me more? By the way floats are at 7/16 with air horn upside down and 1 inch drop per manual. 120 gph holly fuel pump New. Im sure my prob is carb related.
THANKS
 
If you had a holley,i could help you, i don't know anything about your carb.
Maby someone else will be able to give you some advice.
I only run 750 holley's in the 4150 double pumper series.
I think you have to change the metering rod's to richen or lean out the carb.Good luck.
 
Installing bigger jets and/or smaller diameter metering rods will enrichen the carb fuel/air mixture. Sounds like that's what you need. The adjustment for the air door is just to tailor how fast the secondaries open. If you loosen it the stumble could be worse since it's already running lean. Get the jetting correct and then adjust the door so it opens as quick as possible without any stumble.

If you look in the tuning manual it will show which jets and metering rods were installed in the carb and will have a chart that you can follow to jet it up. Of course you'll need a jet/tuning kit to do this with. Jetting it up 2-3 notches and the stumble will probably go away. Remember to jet the secondaries up the same amount as you do the primaries to keep it balanced. In other words if you jet up the primaries 3 sizes jet up the secondaries 2 sizes also.
 
fishy68 said:
Installing bigger jets and/or smaller diameter metering rods will enrichen the carb fuel/air mixture. Sounds like that's what you need. The adjustment for the air door is just to tailor how fast the secondaries open. If you loosen it the stumble could be worse since it's already running lean. Get the jetting correct and then adjust the door so it opens as quick as possible without any stumble.

If you look in the tuning manual it will show which jets and metering rods were installed in the carb and will have a chart that you can follow to jet it up. Of course you'll need a jet/tuning kit to do this with. Jetting it up 2-3 notches and the stumble will probably go away. Remember to jet the secondaries up the same amount as you do the primaries to keep it balanced. In other words if you jet up the primaries 3 sizes jet up the secondaries 2 sizes also.
Click to expand...

OK. at W.O.T. Im a little rich. (a/f reading 12.10 @5300rpm) Still change secondaries ? I have stiff springs(and a extra kit) but no metering rods so that's easy to get and can try a smaller rod. Now is the air door the secondary butterfly ? Because I have that wired wide open at all times. I removed all manual choke parts. California warm. Thanks guys.
 
If the mixture is rich at WOT don't install bigger jets. I don't remember you saying it was rich at WOT. Put in metering rods that'll enrichen the cruise. The small diameter of the rod should be the same but the larger diameter will need to be smaller. In other words if their .070/.049 rods now install .065/.049 rods. If it's still lean at part throttle install .058/.049 rods. Those are just generic numbers I pulled up but they illustrate what change you need to make.

You should not have the secondary air door wired open because that'll cause a huge stumble when you floor it. Wiring the choke open is ok in a warm climate like yours but never wire open the secondary air door.
 
Like Fishy said... you can change the fuel curve on an Edelbrock by changing the rod to get more or less fuel in on each step of the rod. This is one of those areas where Holley simply isnt as flexible or as good IMO... The old Carter AVS rods had 3 steps... Edelbrock AVSs have two. The lower end of the rod is the power step, the upper section the cruise step. By matching the jet and rod combo you should have no trouble tuning the primaries. The vacuum level will tell you which step up spring you need. Simply going with the heaviest spring can also hurt you. Read the tuning manual and it has the idle vacuum amounts and corresponding spring. On top of the primaries is the choke plate... Which you say you dont need and wire open/remove parts. The secondary has jets only (no metering rods) because the air door controls the part throttle airflow and therefore the fuel flow. The air door is NOT a choke. It's to allow the air speed in the secondaries to increase in a steady manner so you don't have bogs. Liek was said.. more preload (tighter spring tension holding it closed) is better than too little as it will bog and there's nothing you can do about it until the air speed picks up with rpm.
 
Secondary air door wired open. That's your problem.

And you gain nothing by removing the choke.
 
Do you have a fuel pressure regulator... From what I know, Edelbrock performer's do not like more than about 5.5 lbs per square inch.. I have the same fuel pump and carb and added a mr gasket regulator in line..

my 2 cts
 
fishy68 said:
If the mixture is rich at WOT don't install bigger jets. I don't remember you saying it was rich at WOT. Put in metering rods that'll enrichen the cruise. The small diameter of the rod should be the same but the larger diameter will need to be smaller. In other words if their .070/.049 rods now install .065/.049 rods. If it's still lean at part throttle install .058/.049 rods. Those are just generic numbers I pulled up but they illustrate what change you need to make.

You should not have the secondary air door wired open because that'll cause a huge stumble when you floor it. Wiring the choke open is ok in a warm climate like yours but never wire open the secondary air door.
Click to expand...

Sorry for bad info. I have the choke door open. only one air door on carb. I have 1412 performer. I ordered metering rods per the manual. In the carb now I have .071/.047 . The next two step to rich rods are .068/.047 , .065/.047 , .070/.042 and .070/.037 without changing the jets. Thanks for that info. when I read the manual I didnt get it until you spelled it out. After I get all this worked out then I will hook up the vacuum advance and tune it back counter clockwise if needed. THANK s
Dale
 
If your timing dances around with the vacuum advance hooked up then I think you should try re-phasing the toothed magnetic rotor in your distributor. If you look it should have two slots to fit on the dist. shaft pin located roughly 180* from each other; they are actually about 170-175* apart and depending on the one you slip over the pin your rotor-to-cap phasing will be off. This causes the distributor rotor to be too far away from the cap contacts when the distributor is at FULL advance (mechanical+vacuum) and makes the engine misfire at very light throttle.

You know I just looked up the part number for your carb and it is the 800 cfm version; this carb is TOO BIG for your 360, plain and simple. Swap a 650 cfm Performer on there and it will run much better.
 
The 800 is a little big. The secondaries do still have an air door. But it's counterweighted instead of preloaded with a spring. I would try a couple things.. First, for the primaries try leaning the power step of the rod, while going richer on the cruise step. You may need to play with rod and jet to get that. Second, try a larger squirtor, or try moving the link rod on the accerator pump arm to the hole closest to the pivot... It should be in the middle from the factory. Last, you can try to jet up a couple steps on the secondary. I run 750s on 360s normally and my feeling is you want to fool the engine into thinking the carb is smaller.
 
moper said:
The 800 is a little big. The secondaries do still have an air door. But it's counterweighted instead of preloaded with a spring. I would try a couple things.. First, for the primaries try leaning the power step of the rod, while going richer on the cruise step. You may need to play with rod and jet to get that. Second, try a larger squirtor, or try moving the link rod on the accerator pump arm to the hole closest to the pivot... It should be in the middle from the factory. Last, you can try to jet up a couple steps on the secondary. I run 750s on 360s normally and my feeling is you want to fool the engine into thinking the carb is smaller.
Click to expand...

GREAT. I ordered the lean power to rich cruise rod today. .065/.047 . I should be good to go. Im going to give this situation a few more weeks to a month and then Im going to get another carb a eddy 750 or a holly. Im for sure getting tired of trying to get this one in tune. Its not awful just not consistent . Drives great at the track so maybe that's all that matters.
 
pilotsf said:
Sorry for bad info. I have the choke door open. only one air door on carb. I have 1412 performer. I ordered metering rods per the manual. In the carb now I have .071/.047 . The next two step to rich rods are .068/.047 , .065/.047 , .070/.042 and .070/.037 without changing the jets. Thanks for that info. when I read the manual I didnt get it until you spelled it out. After I get all this worked out then I will hook up the vacuum advance and tune it back counter clockwise if needed. THANK s
Dale
Click to expand...

Sounds good Dale. One of those rod sets should help. Start with the .068/.047 and test drive it. If it needs more you can go to the .065/.047. Since you said the WOT is rich already the .070/.042 and .070/.037 will only make that worse.
 
If you compare an 800 and 650 cfm Eddy carb side-by-side the main difference is the primary bore/venturi size. This is why it hesitates; the primaries are too big, which is definitely noticeable more when driving on the street because you use only them 95% of the time. pilotsf you should just try (borrow?) a 650 cfm carb on your engine and see if it improves response. IMO even a 750 is too big for street driving; a 650 might lose 10 HP on the very top end but will be more responsive and better on gas on the street. And if you get the AVS version you can tune the secondaries to react as fast or slow as you want.
 
FWIW, I have had 600, 670, 725 and 750 cfm carbs on my 360. The butt dyno can't tell the difference between the 670, 725 or 750 on the top end, there was a noticeable but small difference with the 600 (but the car has run 13.7 @ 102 mph with a very traction limited 2.2 60' using the 600).

But there was a very dramatic improvement in the low and mid range throttle response with the 600 and 670 over the 725 or 750. Plus the 600 and 670 get approx 5 mpg more than the 750.

BTW, don't know if anyone saw HP TV this week end they got over ~420 HP on a sb Chevy 383 with a Holley 600.
 
dgc333 said:
FWIW, I have had 600, 670, 725 and 750 cfm carbs on my 360. The butt dyno can't tell the difference between the 670, 725 or 750 on the top end, there was a noticeable but small difference with the 600 (but the car has run 13.7 @ 102 mph with a very traction limited 2.2 60' using the 600).

But there was a very dramatic improvement in the low and mid range throttle response with the 600 and 670 over the 725 or 750. Plus the 600 and 670 get approx 5 mpg more than the 750.

BTW, don't know if anyone saw HP TV this week end they got over ~420 HP on a sb Chevy 383 with a Holley 600.
Click to expand...

So I installed all the different metering rod combos I could get from the speed shop today and got it a little better but Im over it. Im going to see about a holly 750 my friend has and went to eddelbrock site for a performance 650 or 750. I have to ask one more crazy question and may post it. once I get the carb done , without changing compression is there any way to increase Horse Power. The motor is broke in, 360 cid ,9.5-1 comp, 489 lift cam eddy rpm manifold headman headers and flex fan. I want 300 hp at the wheels and Im at 275hp/300trq at wheels 1/4 mile 13.50 102mph. is that as good as it can get ?
Thanks for all the awesome advice !!!
 
All depends on how well the tune up is, what else you have for a package, etc. What oils do you run? What filter? what is the timing curve? Th eguys that make the most power from a given combo really science it all out...
 
Want more HP to the wheels? Swap in a 4-speed! :-D

Like moper said, tune it up and once it's running as well as possible start looking at things to swap. What heads do you have currently? If they're stock J's you could probably gain another 75 HP with porting or aftermarket ones. What's your exhaust setup too? Might gain 10-15 HP going from H- to X-pipe, or more if you currently have no crossover at all.
 
MOPEkidD-3 said:
Want more HP to the wheels? Swap in a 4-speed! :-D

Like moper said, tune it up and once it's running as well as possible start looking at things to swap. What heads do you have currently? If they're stock J's you could probably gain another 75 HP with porting or aftermarket ones. What's your exhaust setup too? Might gain 10-15 HP going from H- to X-pipe, or more if you currently have no crossover at all.
Click to expand...
The heads are stock 360 rebuilt heavy duty and port and polished with the manifold. exhaust is straight no crossover and low ristricted flow master. Can car be daily driver with after market heads , should I do a new post? getting new carb this week.
 
You must log in or register to reply here.
-

Back
Top