Strange carb problems

[fmahannah]

Edelbrock 800 on a torker II, sitting on a 413 bored 60 over, 440 ported heads, adjustable drivetrain. Only thing I know about the cam is it is mopar, purple shaft?, and lumpy.

This is on a recently purchased 63 polara 500, pushbutton auto, AC.

Previous owner did not drive it hardly at all the last 2 years. Runs, idles, and drives .... but exhaust will burn your eyes.

Idle mixture screws have no effect. Idle is at 750 even with them screwed all the way in. Removed and shot air in there, no difference.

No obvious signs of flooding other than fumes. Hooked up vacuum guage and only getting 4-5 lbs at idle. Picks up normally at all throttle levels.
Knew this was too low at idle even for a lumpy cam, contacted owner and when he had the carb tuned he had 7-9 lbs and added a summit vacuum pump
to run the brake booster, which works well.

Step down spring was already yellow, tried blue made no difference in idle. Changed back to yellow.

Even stranger, timed vacuum port on carb reads identical to the full manifold vacuum port 4-5 lbs. I thought the timed port should read
zero until throttle is open? Is it possible that a vacuum leak would do this? I always thought a vacuum leak at the carb would increase idle
speed because of extra air drawn in, but that is not happening. I can idle down to 500 and it keeps running and does not stall in neutral.

Before I tear the carb down for a rebuild and new gaskets, has anyone ever run into this before or are there anythings outside the carb that I can check first.

Previous owner has vac advance disconnected and all in at 34-36. Never saw this done before.

Thanks for any help or ideas. Want to take car to a cruise in on Saturday but don't want to fumigate everyone there

 

[BIGSHCLUNK]

Cant say I know jack about eddy carbs BUT I had a holley issue where the fumes would burn your eyes out. Leaky power valve...

 

[Garys1969RR]

May not be a carb problem. What is your ignition timing set at? Stock specs are usually too conservative in my opinion. Try as much advance as it will take. I run 18 to 20 initial advance and 38 total. This is without the vac advance hooked up. Try experimenting with more timing and see if that helps. The eye burning fumes sound like unburned fuel coming out the exhaust. Late (retarded) ignition timing has had the same effect on my engine.

 

[nm9stheham]

Based on the symptoms of:
- the idle screws and idle mixture screws being all the way closed and having no effect
- the very low idle vacuum and the presence of port vacuum at idle.....
It is pretty clear that the throttle butterflies are not properly closed and you are idling on the transition circuits. The open butterflies will mess up your manifold vacuum and make it low, and that is also causing the ported vacuum.

Disconnect the throttle linkage/cable and see if it changes just in case the linkage/cable is holding the throttles open. If not, then remove the carb and work on the throttle butterfly stops to get them to close properly on both primary and secondary. They should be almost all the way closed with their edges just not touching the bores. Then you need to start fresh on a carb tune, starting with setting up the idle.

 

[lewtot184]

vacuum is very low due to camshaft and improper ignition advance curve. use lighter step up springs for the metering rods and get the distributor re-curved. I've found that the calibration on the 800's is fairly fat. jetting them down seems to help. the 800avs is calibrated richer than the eps carb. I can't think of any reason for the edelbrock 750's and 800's to be jetted so fat. try .107's in front and .104's or even .101's in the back either the 71x47 rod or the 68x47 rod. try some blue or yellow step springs and definitely recurve the distributor.

 

[fmahannah]

I was thinking something like that because of the vacuum at the port, but what could cause the throttle issue on a carb that was running fine before and did not have any changes made to it? I will try to check the butterflies tomorrow and see what is going on there

 

[SlinktRR]

4-5" vacuum is really low. I get 9-10" with same carb, probably same or similar cam (MP hydraulic). Is that reading while in gear? The metering rods are probably bouncing around and dumping fuel in. Start with basics and set timing, then idle mixture/speed. Try to set your curb idle to around 900-1000 and then tune your idle mixture for max vacuum while maintaining RPM. Also I've found that I need to have the throttle cracked open slightly (idle speed adjustment screwed in) at idle for it to behave when letting off the throttle. 750rpm is too low to operate with 4".

 

[snakeoil24]

NM9 is really right on for the off idle circuit, this is independent of any thing. If the butterflies are not closed properly everything is going to be off and not easily addressed. Settle this and then the timing issues. Rich carb will also be addressed partially once throttle plates are seated.

 

[fmahannah]

OK I completely cleaned and rebuilt the carb, set everything to specs. Set the idle speed screw so that when off the fast idle stop from the choke it had the correct amount of transfer slot exposed. Did not find anything binding or keeping the plates open when I tore it down. Put it on the car, started right up, warmed until the choke opened all the way. The minute it dropped off the fast idle cam it stalled. Had to go at least two more full turns on the idle screw to get it to idle around 750. Idle mixtures still have no effect.

Manifold vacuum is still 4-5 lbs max at idle. I am pretty sure it is the transfer slots being exposed making it run off the transition and too rich.

Honestly I have never heard of vacuum that low from a non radical cam, and previous owner had twice that vacuum reading when he had the carb tuned (so he said).

Not sure what my next step should be. Could the brake booster he has installed be losing my vacuum? It has a summit vacuum pump to let the brakes work, but still hooks to manifold vacuum port directly on the torker intake.

The only other option I have found is to drill the throttle plates to get more idle speed without having to adjust idle so fast that it opens up the transfer slot, not sure if that really works or not.

Any ideas really appreciated, thought I was buying a running driving nice old car that I would not have to mess with right away.

 

[black64]

OK I completely cleaned and rebuilt the carb, set everything to specs. Set the idle speed screw so that when off the fast idle stop from the choke it had the correct amount of transfer slot exposed. Did not find anything binding or keeping the plates open when I tore it down. Put it on the car, started right up, warmed until the choke opened all the way. The minute it dropped off the fast idle cam it stalled. Had to go at least two more full turns on the idle screw to get it to idle around 750. Idle mixtures still have no effect.

Manifold vacuum is still 4-5 lbs max at idle. I am pretty sure it is the transfer slots being exposed making it run off the transition and too rich.

Honestly I have never heard of vacuum that low from a non radical cam, and previous owner had twice that vacuum reading when he had the carb tuned (so he said).

Not sure what my next step should be. Could the brake booster he has installed be losing my vacuum? It has a summit vacuum pump to let the brakes work, but still hooks to manifold vacuum port directly on the torker intake.

The only other option I have found is to drill the throttle plates to get more idle speed without having to adjust idle so fast that it opens up the transfer slot, not sure if that really works or not.

Any ideas really appreciated, thought I was buying a running driving nice old car that I would not have to mess with right away.

Try plugging the vac to the booster to see if that helps. Usually the brake pedal would be rock hard if the booster is not working. The pedal should drop a little when it first sees vac. Also if you have the vac pump and manifold vacuum tee'd together you would need a directional valve in both of the lines .

 

[fmahannah]

Try plugging the vac to the booster to see if that helps. Usually the brake pedal would be rock hard if the booster is not working. The pedal should drop a little when it first sees vac. Also if you have the vac pump and manifold vacuum tee'd together you would need a directional valve in both of the lines .

Large line goes from port at rear of carb but below it directly from the manifold. That line runs to the vacuum pump, then line runs from pump to booster. Small fitting off booster then runs a line under the dash for the heater/ac I assume. Will try taking the booster completely out of the loop tomorrow and see if vaccum improves.

Just can't figure out why only 4-5 lbs of vacuum at idle. Most vacuum leaks I have had anywhere above the intake have caused the engine to idle too fast and that is not the case here. Just runs really rich and idle mixtures have no effect at all. Will idle all day at 750, lopey and sounds awesome but too many fumes. Also notice some vapors coming out of the oil filler cap in the valve cover.

Previous owner had no issues and twice the vacuum, he might not have thought it was rich. The only thing that happened since he ran it for me and I ran it was enclosed transport on a single truck for 750 miles.

 

[black64]

I have a vacuum pump on my 40 it puts out about 16 inches of vacuum. Your engine is a vacuum pump and also the summit pump so you need vacuum check valve if you have the two plummed together. The plug on the booster is a check valve. Try plugging the vacuum line from the intake to see if that helps.

 

[fmahannah]

Today I checked everywhere for vacuum leaks, disconnected brake booster and vacuum pump from the system, nothing made any difference still idle vaccum at 750 was only 4-5

Timing was fine with plenty of initial advance. Got desperate, pulled the carb, drilled a hole in each primary throttle blade 3/32. Set the idle speed screw so correct amount of slot was exposed, bolted it back on. Fired up, warmed up (ran faster on fast idle than before) and when it dropped off the fast idle I only needed to adjust a little more screw to get 750. Now my mixture screws actually have an effect on rpms and vacuum when adjusted. Vacuum a idle is still 4-5, goes up to 7-8 around 1000 rpms. 750 was a little slow once you dropped it into gear so now have it at about 850. Seems OK

Now not noticing fumes at idle that burned the eyes before, so I think progress has been made. Turns out that the mild cam the previous owner thought was in it is a lot more wild than mild to have vacuum down to 4-5. But the benefit to that is it sounds awesome at idle.

Thanks for the tips guys and I am sure I will be back with others since I am an AMC nut slowly learning my way around this Mopar (and liking it a lot)

 

[The Horvaths]

Have you isolated the brake booster yet? Booster membranes are susceptible to ethanol-induced death if the check-valve fails to close properly. Upon cool down the ethanol fumes can condense onto the membrane and die it will. Sad, but it is all part of Monsanto's business plan. Thus, congress was financially incentivized to force ethanol down our throats. Hey, it's the best government that money can buy! I digress..
4-5" of vacuum is really low.

oh, now I read with eyes open. Yes, you disconnected booster. Glad that you made it work for you. I'll leave my original post because it is possible that somebody may benefit from it in the future. Besides, the rant on ethanol was pure and from the heart!

 

[67 coronet]

to hook up a radical cam and power booster you need to hook up all vac to vac pump only.not to motor at all.if need be,get a vac resevor to hook into that system.only thing hooked to motor,vac wise,would be a vac advance.even then,with that much cam,you should use a non vac advance distributor.

 

[fmahannah]

to hook up a radical cam and power booster you need to hook up all vac to vac pump only.not to motor at all.if need be,get a vac resevor to hook into that system.only thing hooked to motor,vac wise,would be a vac advance.even then,with that much cam,you should use a non vac advance distributor.

Not sure I understand what is being said about not hooking a vacuum pump to the motor? The instructions for the pump from summit tell you to hook one line to manifold vacuum and the other to the booster? If not hooked to engine vacuum how would it sense when it needed to run?

Either way I tested engine vacuum with and without the pump connected and the pump had no effect. Bascially because of my low idle vacuum the pump runs all the time when idling

 

[rumblefish360]

.Sorry guys, he sounds like he is running super rich via the "Burn your eyes out" comment.

To the troubled, you idle adjustment screw is all the way out?
The choke is not on and the choke fast idle screw is all the way out and non effective?

Turning then 2 trim screws with no effect is a classic sign of being overly rich. Or wrong step up springs. You can tune the idle circuit with them out and then take a vacuum reading for the proper spring to install.
If the above two questions I asked are a yes, then it is time to re jet the car leaner.