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Timing 305 Chevy


consec3's Avatar
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08-16-03, 04:35 PM   #1  
consec3
Timing 305 Chevy

I'm trying to check the timing on my 1986 Chevy C-10 truck. The
harmonic balancer is rusted and the only thing I can see is a groove which I think is the timing mark, right? Anyway it is so cramped up that I can barely see the little timing teeth mounted above the balancer. Any idea which one of those little teeth is the 4 degree mark. I tried to brush them off but still can't see any marks on them.
The timing check is because my truck idles great, but with a little gas given to it, it bogs down and sputters. Burns gas like there is no tomorrow and has little power on the take off. This happens only after it warms up, runs great cold.
I have changed the plugs, plug wires, dist. cap, rotor and
rebuilt the carb. Old truck cranks up within 1 second of turning the key. I'm stumped so any idea will be appreciated.

Thanks in adavnce.

 
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08-16-03, 06:50 PM   #2  
your deep v mark is o and the first point of the deep v is 4 degrees.
might check the egr valve to see if it is causing your stumble also might have the catylitic convertor tested for a restriction which any exhaust shop can check for you.

 
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08-17-03, 12:29 AM   #3  
I know you said you rebuilt the carb, but have you made sure the choke isn't sticking shut, or maybe the pulloff isn't working, etc...


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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08-17-03, 04:53 AM   #4  
Joe_F
If the truck doesn't have a vacuum advance like an old time distributor---forget about adjusting the timing, it's futile---the computer will uncompensate for what you do. And the problem is not likely here as others have stated.

 
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08-17-03, 09:33 AM   #5  
consec3
Timing mark moves

Thanks to all who took the time to reply to me. I set the timing to 4 degrees with vacuum advance hose off and plugged as the sticker under the hood states to do. After reconnecting the vacuum advance hose the timing mark (groove) moves to the left
past all the timing marks (about 1 inch past them). Is this normal ? The stumble is still there too. The EGR is closed at idle and as RPM is incresed it rises, at approximately (no tach) 1500-2000 RPM it stumbles as though it has lost the fuel supply. If pushed past that RPM it acts like it has restored fuel supply but runs like it is in a bind (bogged down or pulling a heavy load).

Again thank's to all who replied.

 
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08-17-03, 09:40 AM   #6  
consec3
Answer to choke question

I set the choke using a drill bit as a guide for the opening. It opens all the way at operating temp. However, I did pull the EGR
vacuum hose off and drove it and it was ok for awhile but after ten miles the choke closed all the way down. I have restored the vacuum hose to it and am at square one again. Thanks for your reply and I am not real sure if I have it set right except for a 1/8 opening at cold and open all the way at operating temp.

 
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08-17-03, 10:56 AM   #7  
As far as the timing yes that is ok, when you hook the vacuum advance lines up it will move to the left. This also tells you that your vacuum advance is working.

 
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08-17-03, 11:18 AM   #8  
From what you have described, you need to replace the EGR valve. If your stumble is at or above 45 mph with the EGR connected and it does not stumble below that, and then you said that you disconnected the EGR valve and it ran fine except for the choke plate problem. It sounds like you may have just had it adjusted incorrectly to start with or it wasnt tight. Whatever the case may be, replace the EGR valve and readjust the throttle plate and you should be fine.
Hope this helps ya,
Billy

 
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08-17-03, 12:57 PM   #9  
Joe_F
I agree. Take off the valve and I'll bet it's stuffed with carbon. You can try to clean it, but it sounds wasted.

The drill bit method to set carburetors has not been "valid" since 1978 when Rochester Products developed the BT7704 Borroughs/Delco choke angle gauge. THAT is the correct way to set a choke .

Also, you may wish to check the ported vacuum switch for proper operation if that is where your EGR vacuum line originates from as well.

 
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08-17-03, 01:10 PM   #10  
Im betting the operation of the EGR is OK, but the diaphragm is in fact wasted.
Billy

 
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08-17-03, 05:02 PM   #11  
consec3
Any way to test the egr

Thank you for the reply, I have taken the EGR off and the spring
feels strong but I don't know if it is up to par. Is there a way to
test it before I buy a new one ? I ask this as I am on fixed income
and $50 is a lot of money to me. I would also like to say you guys have been great in answering my questions, thanks a million.

 
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08-17-03, 05:38 PM   #12  
The only way to check the operation and the integrity of the diaphragm is to use a vacuum gage. If you were able to move it by hand then the operation part is probably ok. Get a vacuum age and hook it to the port where the vacuum hose goes. Im betting it will not hold vacuum. You might be able to try to suck on it with your mouth, but I dont think most folks will want to do that....LOL.
Billy

 
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08-17-03, 07:10 PM   #13  
Joe_F
I agree. You won't tell much like that.

If you block off the vacuum line and run the truck, does it run any better? If so, the valve is wasted, throw it out and change it with a Delco valve.

 
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08-17-03, 07:33 PM   #14  
consec3
Plugging the vacuum line

You know part of getting old is that your memory some times doesn't work very well. Best as I can recall after plugging it off
(EGR) it seemed to run better but after awhile it bogged down again. I did pull a vacuum on it by mouth and pinched the hose and the egr held in the up position. Does that mean its ok?
Also I found a cracked hose running from the PCV to the carb, it is
right in the crook 90 degree elbow attaching to the carb. Picked up one at the parts house and will try that before going further.
I'll let you guys know if it works out in the morning. Thanks again for being so kind.

 
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08-18-03, 03:44 AM   #15  
Joe_F
Replace every vacuum line there, as they are all old and rotted at this stage of the game. See where that nets you and go from there.

 
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08-18-03, 03:19 PM   #16  
consec3
Vacuum hose repaired

I have just changed out the cracked hoses and the stumble is still there. While engine is running I reached under the EGR and placed my finger on the diaphram. While doing this I applied gas and felt it rise but not all the way up. As I approached the 1500-2000 RPM area it stumbled and the diaphram went down a little.
If I went past 2000RPM it still did not rise all the way, is this normal ? Remember after the stumble it runs ok but feels like it is
under a heavy load. So, change the EGR or try something else ?

Thanks,

 
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08-18-03, 04:15 PM   #17  
The EGR is done. You are creating a vacuum leak when the EGR doesnt open all the way. Thats why it stumbles. Replace the EGR. This should solve your problem.
Billy

 
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08-18-03, 09:52 PM   #18  
Joe_F
I agree. Jot down the numbers stamped on the original valve and find a place that sells AC Delco EGR valves. They will use your original number and cross it over to a new Delco replacement.

The new valve should come with a new gasket, if not, purchase one. Install it, test it out and let us know what you find.

A Delco valve runs about $50 to $75 depending on the source.

 
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08-19-03, 03:05 AM   #19  
I disagree

The more the EGR opens the leaner the mixture gets, it shouldn't open all the way. Exhaust is inert gas and dosen't burn when dumped back into the engine.

I think the underlying cause is a lean condition...suspect is the carb you rebuilt.

With the EGR plugged you said it ran better but still not right. Thats because your richening it up with the EGR plugged. But it still is not enough to over come your lean problem. The further the EGR opens the leaner the mixture gets.

The other clue is you said it runs great cold, thats cause the choke richens it up and compansates the lean condition.

Larry

 
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08-19-03, 09:13 AM   #20  
redneck
What larry said.

 
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08-19-03, 01:14 PM   #21  
consec3
EGR and lean condition

A point well worth taking as a mechanic I had taken it to fiddled
with the mixture using his ear (listing to engine sound) to adjust it. Old billys68ss was right too, I replaced the EGR and so far it
runs great. A little tweaking of the mix and I'll good for another
5 years or so.

Thanks to all of you for all the help, you're a great bunch.

 
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