continuing carb issues

[homer]

I thought I had fixed my carb problem with a good amount of carb cleaner -- the engine ran fine last weekend -- however during a nice drive tonight the engine would barely move with modest to heavy throttle from a standing start after peforming just fine for a couple of miles. The engine revs just fine standing still in the driveway and has a full tank of fresh gas -- having read through the holley book I found on amazon ("Holley Rebuilding & Modifying")my guess is the power value may be bad -- any one had a similar problem and found a simple solution?

[gasman]

Rick and Brent are the guys to weigh in here. It is my understanding from reading your previous thread that carburetor cleaner fixed your problem previously. If you had power valve problems, I would think you would be having problems with your secondaries and not primary's. There are several threads within the last month on this issue. The problem I had was finding a mechanic that could rebuild my carburetor. I finally gave up and took the easy way out by replacing the carburetor. Our own "Eliminator" called Quick Fuel Technology and speced a carburetor that I'm very happy with. What a world of difference. Anyway, Rick and Brent will certainly read this and respond. Both will give you great advice.

Steve Foushee

[homer]

something must be wrong -- with 400hp I cannot come close to spinning the rear wheels -- pulled the a plug tonight and it was not too dirty with soot makes me think I may not be running too rich -- perhaps it is the secondaries?? very frustrating

[Brent]

Homer,

Have you checked the mechanical things? Timing,valves,plugs?

Spraying carb cleaner down from the top can only do two things. Clean the inside of the booster or clean an idle air bleed opening. Neither of which sounds like your problem.

Check valves,timing and plugs
Check fuel pressure
Check float levels

In other words, start at the fuel pump and make sure everything is OK working your way to the center of the carburator. If you narrow it down to that then it is time to disassemble and clean.

Check these things and post again.

Brent

[Brent]

If you want to call me during the week to discuss stuff.

1-800-365-9220

Brent

[homer]

Thanks -- the engine has 200 miles on it after rebuild and run in -- checked the plugs and are ok -- have not had a chance to check the timing (need to get myself a timing light) or the valves -- tried choking out the engine by removing the air cleaner revving to about 3000 rpm and quickly dropping a towel over the carb -- did this a couple of times with carb cleaner in between and the problem has seemed to go away -- I dumped some of the "clean your fuel system" stuff into the gas tank with a fresh amount of gas and drove for a while and now everything seems to be running ok -- will try a run tomorrow and see what happens --

[Jim Harding]

quote:Originally posted by homer

-- tried choking out the engine by removing the air cleaner revving to about 3000 rpm and quickly dropping a towel over the carb -- did this a couple of times with carb cleaner in between and the problem has seemed to go away --

I've heard a lot of tricks to fixes, but this one escapes me.[?] I can't seem to come up with a reason to even try this.... except maybe out of pure frustration... but the consequences seem to over ride any chance of cure. The fact that the problem went away is more reason to discover just what the problem was rather than taking any satisfaction in the result. I'm happy for you that the car now runs better, and equally happy that you didn't burn down the barn in the process[}:)]

- Jim -

Jim Harding
La Plata, Maryland

1982 #3004
http://www.capitalareacobraclub.com/albums/album26/1aLeftside.thumb.jpg

[bittentoo]

I don't know what exactly are your carb problems? Please be more specific; does it idle ok, stumble or die when you take off, just no power when you accelerate, so on.

I would start by replacing the fuel filter and go from there.

Lets hear more and good luck!

[homer]

tried another run today -- car was fine for the first couple of miles and heavy acceleration, idled fine, fired right up -- but out of the blue the car would backfire under acceleration or going up hill -- once it starts these episodes standing still and giving it a shot of throttle causes a popping backfire as well -- came home in second gear at about 2500 rpms engine hit 230 deg as I pulled into the driveway and shut it down to cool off -- seems to be getting enough fuel -- engine is a SA406 with holley double pumper 750 -- so much for the simple solution -- engine has less than 200 miles on it -- looks like I be quickly learing how to check timing, values etc --will be calling southern for help as well

[homer]

Finally got my self a timing light -- at 2500 rpm was at 26 deg -- spoke to southern automotive and the proper setting is 36 deg at 2500 rpm -- I think I adjusted the timing correctly -- I loosened the bolt at the base of the distributor that holds it to the manifold and rotated the dist until I hit the proper timing -- hopefully this is correct -- the dist cap has a bit of play back and forth about 1/8-1/4inch -- is this normal?

[Jim Harding]

Homer,

If your estimates are accurate, that seems like too much slop to me.
Don't know what dizzy you're using, but the "notch" in the casting and the "key" on the cap usually make for a tight fit.

- Jim -

Jim Harding
La Plata, Maryland

1982 #3004
http://www.capitalareacobraclub.com/albums/album26/1aLeftside.thumb.jpg

[homer]

ignition is msd 8al, electronic distributor fairly non-descript black -- the play is in relation to the twisting motion where the dist cap is held down by the metal clips -- what is the "nothc" and "key" -- sorry for the rookie question but I am new to this

[Jim Harding]

I guess each dizzy has it's own way of securing the cap..... On my stock dizzy, there is a notch in the edge of that cap that fits over a boss used to mount the vacuum advance unit. Only can go on one way, but there is a slight bit of twist play, but not as much as you mentioned with yours. I believe the Mallory unit I had had a notch on the edge of the dizzy casting that mated with a key on the cap. Having no knowledge of the MSD stuff to offer any suggestions, I'd still think there is something to locate the cap (other than the mounting clip detents) that would prohibit mounting the thing 180 degrees out of phase, and holding the thing more securly to prevent any twisting movement.
All in all, maybe even with the slop in the cap that you have, there is still little chance of the cap moving while in operation and altering the timing.
Getting back to you total advance..... you said you have adjusted it for 36 degrees at 2500 RPM. Does it increase anymore if you bump the RPM up to say 4000? Just wondering how quick the total mechanical/centrifugal advance comes in. Does this dizzy also have vacuum advance? And finally, after setting the total advance at 36 degrees, what does the (static) advance look like at idle?
Keep plugging away Homer, this gremlin is bound to turn up. Wish I were closer to observe what it's doing so I could offer some better advice.` Good luck Bud!

Oh, one more thing. Does the carb have a choke? Just wondering.... since it seems to run OK until it warms up than goes to pot. Thinking the choke might not opening all the way and causing an over rich condition.

Jim Harding
La Plata, Maryland

1982 #3004
http://www.capitalareacobraclub.com/albums/album26/1aLeftside.thumb.jpg

[pgermond]

Jim has a good point that gets overlooked. I have an SA also, and the Holley has an electrical choke if it's like mine. You need to get 12v to the carb - on the passenger there is a tab that will mate-up to a slip on connector. The car engine will start fine, probably idle a little high, backfire, and will load up after some time on the road. You will also notice it's running very rich (it stinks!)

Good luck.

Phil

427 Roadster, #4279436
Southern Automotive FE
3:31 and Toploader

Roseville (N.Cal)

[Brent]

I have a MSD billet dist. and the cap has a notch to locate it in place. My dist. cap might have 1/16 of play from side to side if you really twist on it.
When you have the timing light on the balancer does the mark bounce around or stay in one place?

Brent

[homer]

the mark holds steady at constant rpm -- the play in the cap is simply the space on either side of the hold down clips -- did I correctly adjust the timing by loosening the bolt at the base of the dist that holds the dist to the manifold? At higher rpm the timing climbs above 36deg but haven't had a chance to measure yet -- as I raise the rpm from idle the timing climbs with rpm increase -- I presume this is normal

[pgermond]

Bill Parham use the "power timing" method. For an FE, that is 36-38 degrees at 3000-3200 RPM (that's on 93 octane fuel). Your engine should idle at 900 - 1000 RPM. If you send me you e-mail address I'll copy the page and send it to you.

Phil

427 Roadster, #4279436
Southern Automotive FE
3:31 and Toploader

Roseville (N.Cal)

[Jim Harding]

quote:Originally posted by homer

the mark holds steady at constant rpm -- the play in the cap is simply the space on either side of the hold down clips -- did I correctly adjust the timing by loosening the bolt at the base of the dist that holds the dist to the manifold? At higher rpm the timing climbs above 36deg but haven't had a chance to measure yet -- as I raise the rpm from idle the timing climbs with rpm increase -- I presume this is normal


Homer,

Yes, you are correctly setting the timing by moving the distributor around after loosening the base hold down bolt.

Centrifugal advance is the result of increasing the RPM from idle to a maximum RPM point where no more advance takes place. If your static or idle advance is 10 degrees before top dead center for example, the centrifugal advance will increase with RPM to a maximum of 36 degrees BTC at some programmed RPM.

I would think that the 36 degree total advance is maximum that you should get, irregardless of what the RPM is at 2500 or 5000 RPM. What determines when maximum advance is reached is the centrifugal weights and the limiting springs inside the distributor. Lighter springs will cause maximum advance to occur at a lower RPM. If your builder is suggesting 36 degrees at 2500 RPM, I am assumming that he also means that maximum advance should occur at (or just before) 2500 RPM, and that no more centrifugal advance will occur if the RPM is raised above that 2500 figure. If your engine is still advancing past 2500 RPM, put a light on it and chart how much more advance is occurring and at what RPM it stops advancing. Too much lead time can cause preignition and that in itself is power robing and can also distroy an engine.

Get back to your builder and get more infomation on total advance, what RPM that should come in by, and any suggestions he has to get you back within that curve.

Also, it seems that Brent has a dizzy like yours..... check to make sure the cap is on correctly. Like Brent said, his has the key/notch to locate it correctly and his seems to hold more securly than yours.... if the only thing holding yours in place is just the cap latches, you may have a problem.

- Jim -



Jim Harding
La Plata, Maryland

1982 #3004
http://www.capitalareacobraclub.com/albums/album26/1aLeftside.thumb.jpg

[homer]

Thanks everyone for your help-- turns out the carb was not the issue, but the timing. I spoke with SA and they said that sometimes the distributor turns a bit and needs to be adjusted. I am now at 38 deg of maximum advance and the engine runs great.

[J. Phillips]

Homer , poping back thru the carb sounds like a lean condition to me. Since the problem is intermitent , my guess is that you have trash in the bowl that is blocking fuel from flowing through one or both of the main jets .Do you have a fuel filter in the line? Have you checked the fuel pressure? Have you checked for a kinked fuel line ? Usually a blown power valve will cause a rich condition, black smoke , and sluggish especially at low rpm. I hope this is of some help. Jay

JVP

[Alan P.]

Homer, if your not using the choke, wire it open so that it can never close .If it can move at all will your driving it will cause the running problems you've been having

[homer]

Thanks - I do not use the choke and it is wired to remain open -- car runs great now -- just need to figure out why my alternator does not want to put out more than 12V of power

[Alan P.]

Sears Automotive will check your charging system for free but it sounds like your alternator has gone south. Check all your connections and pay special attention to your ground strap from the motor to your frame.

[spd4me]

Homer
Had the same problem your having. Go for a ride and runs great, stop and it starts to stumble. Under acceleration it runs okay. When de-accelerating it seems to pop and backfire. The problem is your fuel bowl adjustment. Mine was not letting enough gas in and causing the motor to spit and stumble. If it does it going up hill, the float valve isn't stopping the gas flow and its flooding the carb. Put a clear view plug in the fuel level sigh hole. That way you can stop and shake the car to see if there is any gas in carb.

[homer]

this is driving me crazy -- adjusted the timing to 38deg max adv at 3500 rpm took the car for ride and it ran great -- had it up on jackstands for a couple of weeks doing some work and took it out today -- ran fine up the street but started to sputter again going up the on-ramp to the highway -- then unfortunately there was a thunderstorm cloud burst with globs of rain hitting me sputtering down the highway -- the car putted home into the garage where I checked the timing again and found that nothing had changed--the engine only has 300 miles on it passed breakin -- the car starts very hard meaning it takes a while for the engine to catch and fire -- is it time to pull the carb which is rebuilt/new?

[spd4me]

homer
You need to check your float adjustment valve. You may not be getting and gas to the carb.

[Brent]

Homer,
On the bottom of the front fuel bowl you will see the acc. pump housing and an arm that rides on a cam on the throttle linkage. With the car not running, If you push down on the arm does fuel squirt out of the front pump squirter ? You should see two steady streams of fuel that spray on the booster housing.

Brent

[homer]

pressed down on the acc pump arm and did get two steady streams of fuel in the bottom of the housing -- sprayed a good amount of carb cleaner into the carb and after revving the engine a couple of times the fuel entering the engine went from large droplets to a firm spray -- have had a backfire through the carb just prior to this problem of sputtering.