del91_305

Well, here i am still trying to get rid of this problem. Over the summer i converted my TBI over to carb, along with 081 heads and bigger cam and edelbrock RPM intake, oh and the carb is an edelbrock 1406 model. Well, the car runs pretty good, mechanically everything seems to be in great shape, only thing is,
When i am at a dead stop, and i all the sudden mash the gas, it does not take off like it should, it doesnt bog or anything, just acts like it doesnt have the *****, it wont even break the tires loose. Ive fooled and fooled with the carb and ive finally got it where im gonna leave it. Timing is set at 18 degrees with a total of 36. Somethings gotta give, i cant figure it out for the life of me. Whether is still cold or at running temp, still the same. Anyone have any suggestions? Anything for me to try would be great. I still suspect timing, but im not too sure.

dimented24x7

iTrader: (2)

Sounds like its going lean when you hit the gas. How does it do if you roll into the throttle rather then slam it down?

84z28350

Ive got the exact same problem with my 1406 carb....

It does pick up very nicely above 2kRPMs and isnt too bad if i roll into the throttle from dead stop.

I had a thread a while back and most people came to the conclusion my cam timing was out.

del91_305

Yea if i am at a roll then stomp it, it does fine

84z28350

Damn these edelbrock carbs, Ive got a buddy that has a 1406 on his truck right now doing the same thing too...

You ever try some new metering rods or springs? Neither of us have yet, we plan on getting rid of these and going back to holley double pumpers soon.

del91_305

Yes i have tried that and also tried changing the pump stroke on the accelerator pump. It makes it run different, just doesnt get rid of the problem. Actually though i have tried changing any jets yet

84z28350

Both of us have also tried the accelerator pump with no avail.

SSC

It's most likely timing, advance the timing a tad bit and see if it helps if not try a tad more.

88_Import_Slaye

check your thottle cable, it might be stretched, it might be too long to work with the carb, what ever. Check your vacuum hoses and actual vacuum, if you have an ECM, then try resetting it by disconnecting the battery and and backup fuses and drain the power. Check fuel pressure, run some fuel system cleaner, see if that helps. Are you running too high octane? Is your carb brand new or used? is your A/F ratio off? Do you smell gas when you try to take off but it doesnt go anywhere?

My mom's pontiac did that same thing, it turned out that her throttle cable came out of the bracket, so it wasnt pulling the linkage like it should of, I fixed it and it ran much better.

Make sure you are getting WOT on your carb, have some one mash the pedal and then you try to rotate the linkage, if you can rotate it at all, you need to adjust or replace your thorttle cable.

just some things to try.

Edit: Also, I had similar issue with my V6, I replaced EGR and PCV and that helped a ton, I also had a very clogged catalytic converter, I gutted it and it ran much better with double the gas milage.

del91_305

Well the timing is already at 18 degrees, will it hurt to advance it more?

I have check the cable and it is fine and the vacuum. i have the ECM but i dont think it serves any function anymore. fuel pressure runs constant at about 6 PSI. I run 93 octane all the time and i have pulled the plugs to check the color and they look just like they should

84z28350

No smog equipment to go bad on either one of our engines. We checked for WOT, yes it opens all the way till it hits the stop.

No ECM on either of our vehicles.

On my engine i run a locked out 30-40*(cant tell for sure but the timing mark is @ about 11:00) and that seems to work the best for it, im not sure what timing my buddy is using though.

I run straight pipes off of my headers that dump by the rear tire and he runs headers stright out the back of the truck with bottles about mid way. I highly doubt its our ehaust systems.

The only things i run from vacume are the brake booster and the modulator, both are new lines that i replaced when i put the motor in a few months ago. i did check them with a can of ether and concluded no vacume leaks.

We bought both our carbs brand new, we both run a mix of 91 octane and AvGas which helps with the botom end and i think thats what allows me to run so much advance.

Were both ready to smash the living $h!t out of our carbs...

88_Import_Slaye

check your coil and dizzy? Getting enough when you need it? Maybe it's failing.

Do you run auto and manual? If auto, then have you chekced the TV cable and pressures? If manual have youi checked the clutch cable?

del91_305

well i have replaced the cap but i havent replaced the button or coil

Oh and mines an auto

84z28350

My buddy runs a almost new MSD system on his truck (a couple months old) and i still run a good old GM HEI, A few things have been replaced on it but i dont know if its actually the problem as the new MSD unit on my buddys truck doesnt help him.

We both run Autos, no TV cable here as be both run TH-350s.

The manuals are hydraulic

dimented24x7

iTrader: (2)

It sounds like a tip-in fuel issue if it does ok when you roll into it. Try rolling all the way to wide open throttle and see how it does. Id say its either overly rich or, more likely, lean. This is a very big issue with any wet flow system, including TBI. Some of the computers have very sophisticated routines to provide infinitly tunable 'pump shot' that can be varied with RPM, manifold pressure, temperature, etc. Those transitions are by far the hardest things to tune. Ive spent many hours tuning out that same problem with my car, and sometimes it takes very large ammounts of fuel to keep the engine from going lean and fizzing out when I stomp on it.

84z28350

It seems all of ours do good if you roll into it but what good does that do a guy. By the time your full into it the guys past you and sitting in his driveway by the time you get moving.

Im thinking maybe fuel pump/pressure issue. I havent checked my pressure yet but both me and my buddy are running stock mechanical pumps.

dimented24x7

iTrader: (2)

Never had the pleasure (or maybe displeasure?) of playing with an Edelbrock carb, but Id imagine youd need to play with the accelerator pump to fix this problem if its a lean condition, which is what it sounds like. There may also be other tricks to fix it.

The easy way to tell which is to look out the back when you step on it. If there is black smoke, then you have too much pump shot. No smoke, too little. The way I tune mine is by giving it so much pump shot via the computer that it blows clouds of black smoke. I then back it off untill theres no more smoke and it doesnt bog. If you have a WB-O2, that can really make it easier to tune.

The problem is that when you go from a dead stop at idle to WOT, the sudden increase in manifold pressure causes the fuel to settle out onto the manifold walls, which causes the engine to go lean. If there was no extra fuel added, the motor would literally just stop running. Ive had this happen. Slam the gas down, and it just stops cold. Have to coast over to the side of the road and restart it. The cure is obviously to add in extra fuel to compensate. My injectors where giving what would have been equivelent to probably a 50+ cc accelerator pump to keep the engine from going lean on tip in.

I think another user here, Pablo, was having similar problems with his edelbrock. Do a search. I think he did some things that helped solve it.

84z28350

We already tried playing with the accelerator pump, is a no go.

dimented24x7

iTrader: (2)

Although you said your car does ok when you roll into it, you said your running locked out timing. That could be the cause there. That may be too much at low RPMs, causing losses in power. As you probably know, locked out timing is mainly for race motors that see high rpm use. If thats what you use the car for, then the loss in low end power may come with the territory.

s for the accelerator pump, what did you do to it? How did the engine react? Ive found that the duration and rate that its delivered at are important. Not only do you need to make sure you have enough, but you have to make sure that you have it long enough as well. This may be more then what you can do with a carb. With the larger TBI I basically have a set of q-jet secondaries on top of my motor. That needs alot of extra gas when I hit it.

84z28350

As i stated up a few posts i have found the locked out to work best. I have screwed around with vacume and mechanical advance for a couple months and the locked out gives me the most bottom end power and good up to 5500RPM then i get some pinging.

Any less advance, when i floor it the motor just flat out dies and is all around gutless.


Both of us have tried moving the are in and out of the accelerator pump, moving it out made it worse and moving it in it still did the same thing as when it was in the center hole.

del91_305

Well im not sure if you all saw my other post or not but, i could hear some valvetrain tick so i went to adjust the lash on the rockers, then i fired it back up and i noticed that i was idleing alot slower, then i put it in gear and everytime it would stall. I noticed that my A/F gauge was maxed out on rich, so i pulled one of the plugs and i was black as cole. So im hopeing that all this time the valves were not opening all the way causing a real lack in performance, not sure if this is whats causing this problem or not, but tommorrow im gonna try and lean it back out and then see how it does, ill keep you all posted

dimented24x7

iTrader: (2)

What are your cam specs? Unless you have a hot cam that idles with like 8 in of vacuum or something you probably should have variable ammounts of advance. Ive found that too much timing at low rpms just makes the motor sluggish and prone to detonation and overheating, which is to be expected. The idea with timing is to give the motor just the right ammount so the mixture is fully burned just after top dead center and ready to do work.

Unless you have a hot combo, all the advance may be just a band-aid fix.

dimented24x7

iTrader: (2)

Edelbrock Performer Cam & Lifters

From your car domain. IF thats the cam you have then you definatly dont need locked out advance. My 350 was the same engine you have before I switched to vortecs and it worked best with around 12 degrees of SA at low RPMs with a total of 34 after 2800 RPM, at WOT. With the vortecs its around 32 degrees of SA total, since the chambers are smaller and better.

84z28350

Im not too concerned of what it should have rather than what works, the locked out works the best.

The car is up on blocks next week anyways so im not concerned about this motor. The new 350 will be going in sometime this winter.