Timing/Ignition questions.

[Fredensborg]

Looking over all my vac lines and I'm not sure what this is, and if it needs something hooked up to it or not.

 

[jbojo]

Looking over all my vac lines and I'm not sure what this is, and if it needs something hooked up to it or not.

Expansion valve for the AC.

 

[Fredensborg]

Ok, so that has nothing to do with my issues then....thanks.

 

[Mister 4x4]

Looks like a heater control valve for the heater core to me (that's probably not the official terminology for it, but you get the gist).  Should have the hoses from the water pump going to it (inlet and outlet).

 

[jbojo]

Looks like a heater control valve for the heater core to me (that's probably not the official terminology for it, but you get the gist).  Should have the hoses from the water pump going to it (inlet and outlet).

Eric,

The two inlets are threaded, this is an AC expansion valve.  I just looked at my pics from my 73 during my build and I have the same one.

 

[Mister 4x4]

Oh crap - you're right.   :shootself: 

Hey - cut me some slack... mine was an original 'No A/C' car (I added mine via Classic Auto Air).    :whistling:

 

[Fredensborg]

I worked on this again today, and didn't make much progress.

I set the idle for 3000 rpm, then shot the timing and set it around 30 BTC. (my harmonic balancer hash marks only go to 30) I did this while the vac advance was disconnected and plugged, however the timing did not move at all even after I hooked the vac advance line back up. Is this part of the problem? it seemed to make no difference at all at any rpm weather the vac line to the distributor was hooked up or not, the timing stayed wherever it was at that rpm.

I can get the car to run as low as 1000 rpm if I stay in the drivers seat and gently feather the gas....the idle set screw doesn't seem to be helping me much. when it is at the point where it wont stay running and I have to screw it in to increase idle speed, I have to turn it in at least 1 whole turn to get to the point it will stay running. By then we are in 2000-2500 rpm territory.

I also don't think the idle mixture screws are doing much for me either. I start out with them at 1 1/2 turns out...with the idle set screw set for 1000ish rpm (where it wont stay running) I screw them out 1/2 turn at a time thinking maybe the motor is dying because its not getting enough gas...but I've backed them out as far a 5 whole turns (1/2 at a time) and it doesn't help, still wont idle below 1500ish. I pulled them completely out and squirted some carb cleaner in the holes and blew some compressed air in there too, made no difference.

I pulled the vac line to the break booster and plugged it. made no difference.

I put a vac gauge on the lower port on the front of the carb. pulls 20" vac when the motor is in the 2000 rpm area. when it approaches lower idle and starts to die, its at 10".

I sprayed starter fluid around the base of the carb, nothing.

 

[Fredensborg]

Sorry to bump this, but anyone have any ideas?

 

[Stanglover]

I worked on this again today, and didn't make much progress.

I set the idle for 3000 rpm, then shot the timing and set it around 30 BTC. (my harmonic balancer hash marks only go to 30) I did this while the vac advance was disconnected and plugged, however the timing did not move at all even after I hooked the vac advance line back up. Is this part of the problem? it seemed to make no difference at all at any rpm weather the vac line to the distributor was hooked up or not, the timing stayed wherever it was at that rpm.

I can get the car to run as low as 1000 rpm if I stay in the drivers seat and gently feather the gas....the idle set screw doesn't seem to be helping me much. when it is at the point where it won't stay running and I have to screw it in to increase idle speed, I have to turn it in at least 1 whole turn to get to the point it will stay running. By then we are in 2000-2500 rpm territory.

I also don't think the idle mixture screws are doing much for me either. I start out with them at 1 1/2 turns out...with the idle set screw set for 1000ish rpm (where it won't stay running) I screw them out 1/2 turn at a time thinking maybe the motor is dying because its not getting enough gas...but I've backed them out as far a 5 whole turns (1/2 at a time) and it doesn't help, still won't idle below 1500ish. I pulled them completely out and squirted some carb cleaner in the holes and blew some compressed air in there too, made no difference.

I pulled the vac line to the break booster and plugged it. made no difference.

I put a vac gauge on the lower port on the front of the carb. pulls 20" vac when the motor is in the 2000 rpm area. when it approaches lower idle and starts to die, its at 10".

I sprayed starter fluid around the base of the carb, nothing.

 Fred, I'm not really qualified to answer your questions, but I may be able to help a bit from what I learned on my 351C 4V with a new Holley Street Avenger 670.

It does seem odd that it runs too fast and you can't get the idle set at 800 or so. I have not read all of this post, but from what I see, you did not say what carb you have on the car. That is important info the more qualified will need.

My question is, what happens if you screw the idle mixture screws IN all the way? It should kill the engine. If it doesn't, then you may have the same issue I had on mine. The mixture screws are not working because the transfer slots are open way too far so fuel is pouring in, literally and there is not enough air to balance it out. In my case, it was more of it running over rich, black smoke and black plugs rather than an idle issue. I tried different jets, but ended up back with the original Holley #65 main jets. In frustration, I took my car to a local tuning specialist. What he told me and did was a bit baffling, but he drilled a small hole 3/32" diam. in each of the primary plates, reset the curb idle screw to the ABSOLUTE minimum to make sure the transfer slots were "square" as he called it, i.e. visually open the same height as the width. The result blew me away. It runs almost perfectly now. I'm NOT saying this is you issue, but it does seem like your carb needs a rebuild by an expert tuner. My experience taught me that an amateur can only p*ss around so much before loosing it completely!

If it's NOT the carb, then maybe your distributor is shot. Been there, done that too.

Let us know if you have any progress.

 

[Don C]

Vacuum leak or carburetor.

Perform an engine condition cranking vacuum test.

Warm up engine

Plug all vacuum ports on manifold and carburetor

Turn idle mixture screws all the way in

Turn idle speed screws, including choke fast idle, all the way out to make sure both the primary and secondary throttle plates are fully closed

Disable ignition so engine doesn't try to start

Connect vacuum gauge to intake manifold

Crank engine until vacuum reading stabilizes and record vacuum readings.

There will probably be some needle bounce while cranking, but not wild fluctuations. For a stock or lightly modified engine you should get at least 10 inches of vacuum. Heavily modified engines may be as low as 4 inches with more needle bounce.

Edit: The best way to perform this test is with the carburetor removed and intake blocked, but requires a block-off plate that seals well.

Typing this made me think of another possibility. If you have a 4-barrel carburetor and the secondary throttle plate isn't closed, to specs, at idle you will have the problem you describe.

 

[Stanglover]

Good post Don, I always learn from you.

However, when you said  "turn the idle screw including choke fast idle screw" did you mean the curb idle screw? That is not the same as the idle mixture screw, so I found that confusing.

Please clarify.

Geoff.

 

[Don C]

Thanks Geoff, that's why I never present a report without a knowledgeable proof reader taking a look. What seems clear to a writer may not be.

I added speed after idle to differentiate from idle mixture.

 

[Stanglover]

Thanks Geoff, that's why I never present a report without a knowledgeable proof reader taking a look. What seems clear to a writer may not be.

I added speed after idle to differentiate from idle mixture.

 Don, as I thought. Thanks for clarification. "Knowledgeable" is a bit of a stretch though!

Also, I seemed to have missed that we are dealing with an Edelbrock carb. I re-read the whole thread and why I didn't remember is a sign of old age I guess!! What I don't think I saw was the cfm of the Eddy carb. I guess no matter what cfm it is, it should still run and idle, but performance will be off if it is too small for the engine.

I think I would be pulling the last of my hair out by now if I were 'fredensborg'!

 

[Don C]

I didn't remember what carburetor it was, either, and didn't feel like going back through all the posts

 

[Mister 4x4]

I thought he said 600cfm w/electric choke (Edelbrock 1406).  Based on the rest of his engine's appointments, I'm pretty sure it's not too small.

I don't recall if it's a used carb, came with the car, or new out of the box.  If it's not new out of the box (I suspect), I'd be willing to bet that there might be a float-level issue and/or issues with the jets, if the vacuum checks out.

 

[Twins]

I thought he said 600cfm w/electric choke (Edelbrock 1406).  Based on the rest of his engine's appointments, I'm pretty sure it's not too small.

I don't recall if it's a used carb, came with the car, or new out of the box.  If it's not new out of the box (I suspect), I'd be willing to bet that there might be a float-level issue and/or issues with the jets, if the vacuum checks out.

It is a 1406.  It came off my car and it was working well when I removed it although I mentioned to him he might want to rebuild it as it sat on a shelf for a while when I went with another brand.  It was not exhibiting the symptoms he has been experiencing.  I am wondering if he has a vacuum leak. 

Also, the carb was shipped and I'm sure tossed around a bit and perhaps that might cause a float to be knocked out of whack?

 

[Mister 4x4]

Knowing that, the first thing I would do is pull the top cover and check the float level, along with functionality of the needle valve.  Pulling the jets for cleaning would be a good idea as well.

My pal's Jeep (CJ-5 w/AMC 304 - Edelbrock 1406) has similar issues after it's sat for months on-end between car shows.  But, it's more of an 'all or nothing' deal, which is why I'm thinking the jets might be partially clogged (more vacuum will help suck more fuel through the jets, where as when it reaches a certain low-point, it might struggle to pull enough fuel through).

 

[Stanglover]

Well, I'm out of ideas. I'd love to know what it turns out to be, something stupidly simple probably.

I might learn something as well from it.

 

[Twins]

Well, I'm out of ideas. I'd love to know what it turns out to be, something stupidly simple probably.

I might learn something as well from it.

I sent Jason a message. I just realized I had a similar issue with a different carb and the problem was the high speed idle and choke were not set up correctly. I could not get the car to run without staying on the gas petal -of course until it was warmed up.

Might be too simple but maybe he doesn't have the initial highbspeed idle and choke set right. I'm sure I'm not describing this right. Also I didn't read the whole thread again and this was probably mentioned already!

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[Stanglover]

Well, I'm out of ideas. I'd love to know what it turns out to be, something stupidly simple probably.

I might learn something as well from it.

I sent Jason a message.  I just realized I had a similar issue with a different carb and the problem was the high speed idle and choke were not set up correctly.  I could not get the car to run without staying on the gas petal -of course until it was warmed up.  

Might be too simple but maybe he doesn't have the initial  highbspeed idle and choke set right.  I'm sure I'm not describing this right.   Also I didn't read the whole thread again and this was probably mentioned already!

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 Could be. I also think he is not letting the engine reach FULL operating temp and one can't do much until it has, especially where the choke is concerned. Am I right?