| Author |
Message |
Bill Sebestyen (Bill308)
Member
Username: Bill308
Post Number: 328
Registered: 5-2001
| | Posted on Friday, August 23, 2002 - 1:16 pm: | |
Mitchell,
The inter relationship between ignition advance and idle speed is kind of like a catch-22 if the advace mechanism isn't right.
If the springs are weak, and say you are at 2500 rpm, the ignition will be advanced from where it should be. The advanced timing supports the high idle speed. If the engine were to be put under load, the drop in rpm may allow the timing to back off sufficiently to allow a normal idle speed of 800-1200 rpm when the load is removed. At a high idle, air velocity through the carbs raise the emulsified fuel in the main system and if the fuel level is already high due to float valves that are no sealing, emulsified fuel could begin to flw through the main system. |
Mitchell Minh Le (Yelcab1)
Member
Username: Yelcab1
Post Number: 317
Registered: 11-2001
| | Posted on Friday, August 23, 2002 - 9:56 am: | |
My choke (starter) is totally disconnected and not used. That is one reason why the car will idle cold at 500 rpm, warms up to 1000 rpm. THis is fine, but if I take it for a 1 mile drive, it will idle at 2000-3000 rpm and will not drop down to 1000 rpm where it is supposed to be. That is what everyone here is trying to figure out |
George Daina (Oof_n_goof)
Junior Member
Username: Oof_n_goof
Post Number: 113
Registered: 7-2002
| | Posted on Friday, August 23, 2002 - 9:04 am: | |
This is strange, the the cold idle is lower than the hot idle, normally it's the other way around. When cold, your idle is higher, and drops as the engine warms. |
Mitchell Minh Le (Yelcab1)
Member
Username: Yelcab1
Post Number: 316
Registered: 11-2001
| | Posted on Thursday, August 22, 2002 - 11:42 pm: | |
When the car idles at 1000 RPM, then there does not seem to have any dumping of fuel. The dumping of fuel seems to cause the car to idle high at 2000 or 3000 RPM, and then back fires (loud pop out the exhaust) when the engine shuts off.
I did clean the distributors and saw 4 springs for each distributors, 4 weights and more spacers (shims). I had no way of knowing and measuring the advance mechanism, and or the strengths of the springs. All I did was cleaned them and grease them and put them back.
The shop near where I live Modena Motors I think, refused to check the distributors for me.
A thought, if I have a way of checking the timing while the idle was high and incorrect, would the timing still be at 7 BTDC, or more advanced because the distributors now spin faster due to the higher idle. And, will that tell me anything about the causes? |
Bill Sebestyen (Bill308)
Member
Username: Bill308
Post Number: 326
Registered: 5-2001
| | Posted on Thursday, August 22, 2002 - 9:17 pm: | |
OK Mitchell, the high idle device was removed and the carbs are returning to their stops.
I agree, you need to attend to the fuel dumping from the mains. Does this occur when the idle is at 1000 rpm also?
Are the carbs synched off idle, at say 1500 rpm, as well as when on the stops?
Another possibility is the advance springs in one or both of your distributors is weak and not allowing the ignition timing to back off reliably.
|
Mitchell Minh Le (Yelcab1)
Member
Username: Yelcab1
Post Number: 314
Registered: 11-2001
| | Posted on Thursday, August 22, 2002 - 8:06 pm: | |
On my car, there is no bi-metalic hi-idle device. If you are talking about the thing attached to the top of the intake manifold cross member, then it is gone. All I have is a cable connected to an arm that is connected through 2 links to the left carburetors (2). The left carbs are connected to the two right carbs through intertwining arms.
When it is high idle, finger pressure will not get the carbs to return to the fully closed position because it is already there. What I am trying to say is that I do not think it is in the linkages or stuck movements or things of that nature.
It seems to be one or more carbs is dumping raw fuel down the throats. Maybe it is the needlevalves, maybe it is the floats, maybe it is some other causes within the carburetors that I am not familiar with. I did pull out the starter valves attached to the chokes and they all seem fine. They move up and down and stay down all the way because the choke cable is not even attached. |
Bill Sebestyen (Bill308)
Member
Username: Bill308
Post Number: 323
Registered: 5-2001
| | Posted on Thursday, August 22, 2002 - 7:40 pm: | |
Mitchell,
Again, a good plan of action. Changing the contaminated oil was a good move. Usually break-in oil is a little thinner than you would normally use, maybe 10-40, unless it really hot out.
A couple of things to check:
Is the bi-metallic, high idle divice moving into a position to prevent the carb linkage from returning all the way to the close position?
If the high idle cam is not preventing a full return, does the carb linkage allow the carbs to fully close? During a high idle condition, see if finger pressure will fully close the carbs. You should be in the 3-4 range on each barrel, using a BK Synchrometer at idle. This should give you about 1000 rpm. |
Mitchell Minh Le (Yelcab1)
Member
Username: Yelcab1
Post Number: 312
Registered: 11-2001
| | Posted on Thursday, August 22, 2002 - 6:13 pm: | |
I already changed the oil once before the drive today. The oil that came out flushed out all the gunk and whatever else is collected in the engine during the assembly process. It was a bit black from the running in, and from the gas that went unburnt in the carbs. As soon as the problem is resolved, I will change it again with fresh 20-50 oil. |
Edward Gault (Irfgt)
Intermediate Member
Username: Irfgt
Post Number: 1862
Registered: 2-2001
| | Posted on Thursday, August 22, 2002 - 5:19 pm: | |
It seems that you are puking raw fuel into the cylinders which is a bad thing especially on a newly rebuilt engine. I would change my oil immediately after the flooding issue is resolved. |
Mitchell Minh Le (Yelcab1)
Member
Username: Yelcab1
Post Number: 311
Registered: 11-2001
| | Posted on Thursday, August 22, 2002 - 4:39 pm: | |
OK,
Test drove it today for the first time in months, and the first time after the rebuild. It runs well enough, smooth, sounds good, and shifts well. Two miles into the drive and the high idle comes back. Stopped at the gas station to gas up and talk to some mechanics friends and the high idle sounds like it is in one of the carbs, just do not know which one. The pressure regulator is installed and set at 3 psi so that is not an issue. There is a bit of a sipping noise in one of the carbs after the engine has shut off. Our guess is still the needle valves are worn out, which will be changed tomorrow. And this time, i will set the float to shut off the valve a bit earlier (like 2 mm or so). Let's hope that is it, because if it is not, I am out of ideas. The carbs are all synched! |
Mitchell Minh Le (Yelcab1)
Member
Username: Yelcab1
Post Number: 310
Registered: 11-2001
| | Posted on Thursday, August 22, 2002 - 2:55 pm: | |
A leak is a possibility but I have not checked for it. All the gaskets are new, but there may be a bad intake manifold or something like that. Does not explain why there is gas bubbling over the top of the main jets and pooling down over the venturi. Today I installed a pressure regulator, set it to 3 psi, and let it pump for 15 minutes. Saw no gas spilling over the side so let's hope that is the case. Tomorrow when the new needle valves come, I will install them as well and see if the problem persists. Then on to a leak. |
RANDOLPH MADAMBA (Pogibm)
New member
Username: Pogibm
Post Number: 14
Registered: 8-2002
| | Posted on Thursday, August 22, 2002 - 1:39 pm: | |
Mitchell, i'm not sure if your problem with your cars idle is the same thing i had, when my boxer would idle cold it was normal as soon as it warmed up the idle would stick at 2700 or 3000 rpm.Problem was there was a leak between the manifold and the carburator, had a bad gasket.
While the engine is warming up spray some carb cleaner between the manifold and carburator if the idle raises there is a leak. |
Edward Gault (Irfgt)
Intermediate Member
Username: Irfgt
Post Number: 1849
Registered: 2-2001
| | Posted on Thursday, August 22, 2002 - 5:17 am: | |
Get the carbs straightened out first. The oil is probably excess fuel mixing with carbon. |
Mitchell Minh Le (Yelcab1)
Member
Username: Yelcab1
Post Number: 309
Registered: 11-2001
| | Posted on Wednesday, August 21, 2002 - 10:28 pm: | |
Bill
BTW, to spot the oil leak out of the exhaust ports, I just crawled under the car, looked up and saw some oil at the exhaust manifold copper gasket of port 5, 7 and 8. When the engine was cold, I reached up and touched the spots and it felt like oil. Did not remove the header, as that is not quite severe yet.
I remember some similar leaks before the engine rebuild, but more severe. This is not too bad yet. I am tempted to let the engine break in, and then see what it is. Hmm, the thoughts of having to replace some of the viton valve seals with the enging in the car is ... not that palatable. Let sleeping dogs "sleep" for the time being. Any thoughts? |
Mitchell Minh Le (Yelcab1)
Member
Username: Yelcab1
Post Number: 308
Registered: 11-2001
| | Posted on Wednesday, August 21, 2002 - 10:24 pm: | |
Billy bob,
I realized the fast idle speed is a natural occuring phenomenon on carb car, but we are talking idling at 2000-3000 rpm here, after it has been steady at 900 rpm for a good 20 minutes. Plus, the bubbling of the gasoline right over the tops of almost all main jets and pooling down over the venturi is really indicative of something else other than natural phenomenon.
If all is good, and the carbs are adjusted correctly, I would expect that the car starts out cold at 500-600 rpm, and after it warms up, it would idle at 900-1000 rpm.
This is not that way at all, it would idle cold at 500-600, warms up to 1000 rpm, and then after a good 15-20 minutes speeds up to 3000 rpm. That is very unnormal.
Do you have any other thoughts? |
billy bob (Fatbillybob)
New member
Username: Fatbillybob
Post Number: 16
Registered: 8-2002
| | Posted on Wednesday, August 21, 2002 - 10:10 pm: | |
The idle higher and higher is a natural response to the car coming up to temp. This makes combustion easy. After warm up set the idle speed and check your flows with the linkage in place. Then When you start your car cold the fast idle cam which is temperature dependant will increase the idle on the cold engine. |
Bill Sebestyen (Bill308)
Member
Username: Bill308
Post Number: 322
Registered: 5-2001
| | Posted on Wednesday, August 21, 2002 - 9:49 pm: | |
That a good game plant Mitchell.
How did you observe the oil in the exhaust ports? Did you remove the headers?
How much time on the engine? You really want to run the engine at a fairly fast idle for the first 10-15 minutes or so. This gives the cam and spacers time to establish a good contact area under the best conditions.
Make sure you don't have a lot of gas dilution in your oil. |
Mitchell Minh Le (Yelcab1)
Member
Username: Yelcab1
Post Number: 307
Registered: 11-2001
| | Posted on Wednesday, August 21, 2002 - 6:47 pm: | |
Well, found a suspicious couple of drop leak of oil out the exhaust ports on 5-8. Do not know what that is yet, it is in small amount after about 30 minutes of running in the garage. I am guessing that all the excess lubricant during the reassembly process is oozing its way out. I tightened all the exhaust nuts again and I'll wait to put on some miles on the engine and check again to see if it is still there and what to do about it. At worst, it is one or more of the exhaust valve seals not doing their jobs. One thing at a time, carburettors first. |
magoo (Magoo)
Advanced Member
Username: Magoo
Post Number: 3065
Registered: 2-2001
| | Posted on Wednesday, August 21, 2002 - 5:42 pm: | |
I love em, Varoooooom!!!! |
Edward Gault (Irfgt)
Intermediate Member
Username: Irfgt
Post Number: 1848
Registered: 2-2001
| | Posted on Wednesday, August 21, 2002 - 5:20 pm: | |
I hate Carburettors. |
Mitchell Minh Le (Yelcab1)
Member
Username: Yelcab1
Post Number: 306
Registered: 11-2001
| | Posted on Wednesday, August 21, 2002 - 4:34 pm: | |
Back to basics sure helps. Today I pulled the plugs, the distributors, check cam/crank registration, measured the wires, and check the carbs. What I found.
1. point gap was too big on 5-8 dist, reset it
2. static timing again on both distributors to 7 degrees BTDC
3. All wires measured out to 350 ohms to 600 ohms
4. Carburetors were all off in terms of synchronization of their movements. Looked inside and two were totally shut while the two were open too wide (the butterflies). Adjusted them visually for equal open of butterflies as a first order of magnitude guess.
5. checked all idle set screws and set them to 3 turns out. (they were, but did it again anyway)
Fired her up (one coolant leak fixed), and it ran on all cylinders fairly well. The carbs needed to be further synched with a air flow meter. Did that and things smoothed out quite a bit.
Slightly bad news: the old 2 idle speed problem came back (recent posting by others lately). After a 20 minutes warm up, it just idled higher and higher. So I stopped the engine, looked inside the carbs and found:
1. All carbs had significant bubbling over of gasoline out the tops of the main jets, then dripping into the main venturi in vast amount.
I am guessing at this point that there are two potential problems:
1. Too much fuel pressure (unlikely but I will check that)
2. Meter valves are bad and did not shut off the flow of gas into the carbs. I cleaned and adjusted them but did not replace the needle valves during rebuilt. This decision may have come back to bite me on the butt.
3. Floats adjustment off (unlikely because I did them to specs while rebuilding the carbs and did not touch them since)
So, I quit while I had good progress, and tomorrow will order some needle valves from Pierce Manifold.
Any other suggestions???? |