Re: Vacuum advance diaphragm question/part number request 340-6
[Re: John_Kunkel]
#1948733
11/10/15 02:22 PM
11/10/15 02:22 PM
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f2502011
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If I have to replace it I'll need to replace it with an original. Anyone know what part number I need to look for? Manual Trans 3514265 Auto Trans 3620704 Anyone know what the difference is between these two? Mine is an automatic and I haven't been able to find a 3620704 but have found a 3514265.
1970 EK2 T/A 727
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Re: Vacuum advance diaphragm question/part number request 340-6
[Re: f2502011]
#1948738
11/10/15 02:29 PM
11/10/15 02:29 PM
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RapidRobert
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Anyone know what the difference is between these two? The only difference will be the amt of (total) adv the can offers (& it'll be stamped on the arm). You might be able to lookup the two different numbers (amounts of adv) & likely can live with/use either one and depending on if the number of the one you get is more or less than your orig bad one you can alter the amt of adv. decreasing it is easy, increasing it is hard(er) but can be done. this is a seperate mod than adjusting the tip in with the 3/32" allen wrench. EDIT What number is on yours and have them check what number is on the one that they do have (& post em)
Last edited by RapidRobert; 11/10/15 02:59 PM.
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Re: Vacuum advance diaphragm question/part number request 340-6
[Re: f2502011]
#1948806
11/10/15 04:01 PM
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As I try to get this thing tuned, another question is where is the best place to get a good intake manifold vacuum reading? I've tried the port on the carb for the vacuum advance and there is little if any vacuum there which could also be part of the problem unless that is normal? What should it be? Stock car, stock carbs stock cam etc.
1970 EK2 T/A 727
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Re: Vacuum advance diaphragm question/part number request 340-6
[Re: 62maxwgn]
#1949461
11/11/15 04:31 PM
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The vacuum advance port on the carb is ported vacuum,you won't get a reading there at idle,Take it off the PCV port on the carb or directly off the intake.If "nothing" has been modified you should have at least 17" or more. Also,
Incidentally,the Prestolite advance you posted above is for a big block,this is the correct small block advance. What are the differences?
1970 EK2 T/A 727
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Re: Vacuum advance diaphragm question/part number request 340-6
[Re: f2502011]
#1949899
11/12/15 11:47 AM
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Pulled my cap to take a look and used vacuum pump to help see what's going on. The VA doesn't do anything until about 8 and doesn't move anymore after 15. It's kinda jerky too and not smooth in its operation.
1970 EK2 T/A 727
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Re: Vacuum advance diaphragm question/part number request 340-6
[Re: f2502011]
#1949985
11/12/15 02:53 PM
11/12/15 02:53 PM
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RapidRobert
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The VA doesn't do anything until about 8 and doesn't move anymore after 15. It's kinda jerky too and not smooth in its operation. that is normal, you're in good shape (on this)
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Re: Vacuum advance diaphragm question/part number request 340-6
[Re: f2502011]
#1950040
11/12/15 04:43 PM
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I would like to see what number is stamped on the arm but I can't see it with it together. I've never taken one of these apart before how does it come apart so I can see the arm, springs etc.? Is there anything special about it as far as disassembly? Is there a way to know how much advance the distributor has other than figuring it out with a timing light? I've set my initial timing to 10 btdc and I've revved it up to 2000-2500 rpm and it seems the timing wants to keep climbing beyond 36 so I didn't go any higher to see where it would stop going up. I'm used to GM distributors they don't look like this.
1970 EK2 T/A 727
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Re: Vacuum advance diaphragm question/part number request 340-6
[Re: f2502011]
#1984180
01/05/16 03:09 PM
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Finally getting around to replacing the vacuum advance. I was unable to find an NOS canister for the automatic but got an NOS 3514265. They look the same but the arm on my original is an 8 and the one on the new one is 8.5. What do I need to do to set up the 3514265 to work as it should for my car?
1970 EK2 T/A 727
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Re: Vacuum advance diaphragm question/part number request 340-6
[Re: f2502011]
#1984189
01/05/16 03:22 PM
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RapidRobert
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I doubt you will notice any pinging from the addit'l (1) degree you'd see on the crank (8.5-8=.5 x 2 = (1) deg. You can JB weld shims on either side of the notch in the arm on the case itself to limit the arms' travel & experiment with thickness till you see 16 addit'l on the crank when you plug in the can (you'd have it idling & plug the can into manifold just for this situation) assuming the chain and intergear slot/dist notch is tight so the mark ain't dancing around at idle so you can see exactly if the can is giving you exactly 16 (8x2)
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Re: Vacuum advance diaphragm question/part number request 340-6
[Re: RapidRobert]
#1984253
01/05/16 04:41 PM
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I doubt you will notice any pinging from the addit'l (1) degree you'd see on the crank (8.5-8=.5 x 2 = (1) deg. You can JB weld shims on either side of the notch in the arm on the case itself to limit the arms' travel & experiment with thickness till you see 16 addit'l on the crank when you plug in the can (you'd have it idling & plug the can into manifold just for this situation) assuming the chain and intergear slot/dist notch is tight so the mark ain't dancing around at idle so you can see exactly if the can is giving you exactly 16 (8x2) By chance does the diaphragm adjust with an Allen wrench to limit advance?
1970 EK2 T/A 727
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Re: Vacuum advance diaphragm question/part number request 340-6
[Re: f2502011]
#1984286
01/05/16 05:28 PM
01/05/16 05:28 PM
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RapidRobert
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CCW with a 3/32" allen wrench slows when (in hg amt) the curve amt (8x2=16 degrees) starts by tightening the spring so it takes more vac to overcome that tension & there fore at what amt (in hg) the curve ends so in effect once you are in the curve by tightening the spring (CCW) you have less adv at any given in hg amt so likely that would quell any pinging if it did ping exp cuz we are very close on the amt. you would monitor this in eveyday driving under varying RPM/throttle (load) positions
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