Runs great UNTIL vacuum advance line is connected
07-09-2018, 10:19 AM
#21
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[QUOTE=big block ken;1597560427
It ran perfect, with the timing at factory spec 4* at 600 rpm and dwell at 28-30. But as soon as I unplug the vacuum advance line and connect it to the diaphragm, it sputters and runs terrible. [/QUOTE]
Based on this limited information, I would suspect you have an ignition problem. I.E., no problem until the breaker plate moves/rotates under vacuum.
Check all the wires in the distributor for damage, fraying, loose, broken, etc.
It ran perfect, with the timing at factory spec 4* at 600 rpm and dwell at 28-30. But as soon as I unplug the vacuum advance line and connect it to the diaphragm, it sputters and runs terrible. [/QUOTE]
Based on this limited information, I would suspect you have an ignition problem. I.E., no problem until the breaker plate moves/rotates under vacuum.
Check all the wires in the distributor for damage, fraying, loose, broken, etc.
Last edited by MikeM; 07-09-2018 at 10:22 AM.
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big block ken (07-09-2018)
07-09-2018, 12:39 PM
#22
Pro
The factory spec of 4* BTC at 600 rpm just seems so low, especially since using Lars theory of setting it at peak street rpm of 2800-3000 (I assume big blocks would be the same as small blocks, but he doesn't say), I had timing set at @ 34* total then. And then it just fell wherever it was at idle
So you have the light, how much does the timing change when you hook up the can? Suck on the hose and look at the marks. I had to limit mine, due to some trailer hitching at cruise (not your problem it seems). Usually the idle would pick up when you plug in the can.
Last edited by Tiros; 07-09-2018 at 12:54 PM.
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big block ken (07-09-2018)
07-09-2018, 01:00 PM
#23
Safety Car
The breaker plate ground wire brazed on, UNDER the breaker plate is very susceptible to breaking and causing intermittent ground when breaker plate is moved.
Open the points adjustment door and run a temporary ground using wire with clips on both ends.
Open the points adjustment door and run a temporary ground using wire with clips on both ends.
Last edited by 65tripleblack; 07-09-2018 at 01:02 PM.
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big block ken (07-09-2018)
07-09-2018, 08:38 PM
#24
Burning Brakes
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If you set initial timing at 4* BTDC and can't get the engine to run with the vacuum advance connected something is wrong. Could the TDC mark on the damper have slipped on the rubber or something amiss inside the distributor.
....Even with timing advanced to 12-14* at idle, it still misses and backfires when the vacuum line is connected to the distributor. So I'm leaning toward a distributor problem.
That carburetor # does not sound right to me, I thought the Holley # was 3811.
....Even with timing advanced to 12-14* at idle, it still misses and backfires when the vacuum line is connected to the distributor. So I'm leaning toward a distributor problem.
That carburetor # does not sound right to me, I thought the Holley # was 3811.
07-09-2018, 08:44 PM
#25
Burning Brakes
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Ported vacuum on a Holley is taken from the metering block via a port just above the idle mixture screw on one side. To your point, if you look at the 3370 metering block, you will see an unmilled boss where the ported vacuum nipple would be installed. It is not included on this carb as Holley considers this a performance carb, not an economy or emission carb.
07-09-2018, 08:54 PM
#26
Burning Brakes
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I can't make any sense out of your statement. The VAC signal line must be removed from the VAC and plugged with a golf tee to set initial timing.
Yes, it is plugged with a golf tee during initial timing. The vacuum and centrifugal advance specs are in your CSM. I think the max centrifugal is 30 @ 5000, which is very lazy, and maximum vacuum advance is 16 @ 12" and the VAC is stamped 360 12. So you need to check both. VACs eventually fail due to seizing up or a ruptured diaphragm,which will cause a significant vacuum leak. See Frankie's post above. I pulled the entire vacuum line and sucked the diaphragm, which held for at least 5 seconds on my tongue.
Total WOT advance should be in the range of 36-40, as high as you can go in that range without detonation, and with lighter springs you can set it a few hundred revs above the point of maximum advance. With 30 centrifugal, initial should be in the range of 6-10, and total idle advance with the VAC connected should be in the range of 22-26 and stable.
Duke
Yes, it is plugged with a golf tee during initial timing. The vacuum and centrifugal advance specs are in your CSM. I think the max centrifugal is 30 @ 5000, which is very lazy, and maximum vacuum advance is 16 @ 12" and the VAC is stamped 360 12. So you need to check both. VACs eventually fail due to seizing up or a ruptured diaphragm,which will cause a significant vacuum leak. See Frankie's post above. I pulled the entire vacuum line and sucked the diaphragm, which held for at least 5 seconds on my tongue.
Total WOT advance should be in the range of 36-40, as high as you can go in that range without detonation, and with lighter springs you can set it a few hundred revs above the point of maximum advance. With 30 centrifugal, initial should be in the range of 6-10, and total idle advance with the VAC connected should be in the range of 22-26 and stable.
Duke
07-09-2018, 09:37 PM
#27
Burning Brakes
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I did pull the vacuum line off of the manifold port on the carb, which has a very strong vacuum, and sucked on it hard while connected to the distributor diaphragm. But nothing changed. It didn't cause a backfire, until I reconnected it to the carb manifold port.
But I have to say that it does run steady and is totally responsive. It just bothers me to leave that vacuum line disconnected, which has been connected to that distributor since it was brand new. But who can complain after 52 years, and 90k miles with only one broken valve spring.
07-10-2018, 01:45 AM
#28
Melting Slicks
The whole point of vacuum advance is to gain economy and maybe a hint of drivability.
We traditionally run 10-15* of idle advance in awide range of applications.
So using vacuum advance to add 10-15* at idle to already 10-15* is not the normal method because it will result with 30* of total idle advance.
Instead the traditional method is to use the alternative ports on throttlebody/carb that only provide vacuum when the butterfly valve is open beyond a specific point, such that a total vacuum advance is applied only while the owner is on the throttle.
Total advance varies, typically 30-40* during cruise is acceptable with gasoline, even 87 octane in a majority of 8.5 and 9:1 compression ratio is quite common i.e. truck engines with low octane maps
We traditionally run 10-15* of idle advance in awide range of applications.
So using vacuum advance to add 10-15* at idle to already 10-15* is not the normal method because it will result with 30* of total idle advance.
Instead the traditional method is to use the alternative ports on throttlebody/carb that only provide vacuum when the butterfly valve is open beyond a specific point, such that a total vacuum advance is applied only while the owner is on the throttle.
Total advance varies, typically 30-40* during cruise is acceptable with gasoline, even 87 octane in a majority of 8.5 and 9:1 compression ratio is quite common i.e. truck engines with low octane maps
07-10-2018, 02:43 AM
#29
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The symptoms read like either the distributors internal ground wire is disconnecting or the negative side coil wire is shorting inside as the breaker plate is rotated by the vacuum can.
07-10-2018, 07:39 AM
#30
Burning Brakes
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I'll pull the cap, rotor, points, and ignition shielding to get a good look at the distributor base plate. Is it possible to see that internal ground wire? If so, I could check it for continuity. And what would cause the coil to short out internally as the breaker plate rotates? Would that be due to a loose ground on the plate also?
07-10-2018, 08:08 AM
#31
Race Director
I don't think they mean the coil is shorting internally. I think they are suggesting that maybe when the vacuum advance is connected and it rotates the breaker plate to advance timing - it's shorting the negative wire connection to the plate. When the vacuum advance is disconnected the plate resumes position and the weak connection isn't shorting again.
Sounds very possible since as Mr. Spock would say - it's illogical that the engine would run worse with manifold vacuum advance connected at idle.
Edit : Instead of "shorting" I guess it would be more correct to say it's breaking connection or losing connectivity.
Sounds very possible since as Mr. Spock would say - it's illogical that the engine would run worse with manifold vacuum advance connected at idle.
Edit : Instead of "shorting" I guess it would be more correct to say it's breaking connection or losing connectivity.
Last edited by DansYellow66; 07-10-2018 at 08:11 AM.
07-10-2018, 08:10 AM
#32
Safety Car
I'll pull the cap, rotor, points, and ignition shielding to get a good look at the distributor base plate. Is it possible to see that internal ground wire? If so, I could check it for continuity. And what would cause the coil to short out internally as the breaker plate rotates? Would that be due to a loose ground on the plate also?
If the ground is not the issue then check for a short as 63 340 suggests.
Last edited by 65tripleblack; 07-10-2018 at 08:11 AM.
07-10-2018, 08:13 AM
#33
Safety Car
The whole point of vacuum advance is to gain economy and maybe a hint of drivability.
We traditionally run 10-15* of idle advance in awide range of applications.
So using vacuum advance to add 10-15* at idle to already 10-15* is not the normal method because it will result with 30* of total idle advance.
Instead the traditional method is to use the alternative ports on throttlebody/carb that only provide vacuum when the butterfly valve is open beyond a specific point, such that a total vacuum advance is applied only while the owner is on the throttle.
Total advance varies, typically 30-40* during cruise is acceptable with gasoline, even 87 octane in a majority of 8.5 and 9:1 compression ratio is quite common i.e. truck engines with low octane maps
We traditionally run 10-15* of idle advance in awide range of applications.
So using vacuum advance to add 10-15* at idle to already 10-15* is not the normal method because it will result with 30* of total idle advance.
Instead the traditional method is to use the alternative ports on throttlebody/carb that only provide vacuum when the butterfly valve is open beyond a specific point, such that a total vacuum advance is applied only while the owner is on the throttle.
Total advance varies, typically 30-40* during cruise is acceptable with gasoline, even 87 octane in a majority of 8.5 and 9:1 compression ratio is quite common i.e. truck engines with low octane maps
07-10-2018, 09:00 AM
#34
Team Owner
I ran my 61 at 38* initial + centrifugal and 50* with vac advance and I was on the bitter edge.
Last edited by Frankie the Fink; 07-10-2018 at 09:03 AM.
07-10-2018, 09:49 AM
#35
Melting Slicks
Original engines from 1960's are no longer typical. The old, sloppy, terrible engine style is long gone. if you still have one of those I am sorry for you. they don't make them like that anymore though. Any engine made in Japan after 1989 and any V8 made by chevy after 1998 is not going to tolerate much more than 44* of timing at cruise, and most want 37-42*.
the more advance an engine needs in general, the less efficient it is typically found to be. Really ancient 60's engines needed much more advance because chamber tech in the 60's sucked in America. Nowadays you find 40-45* for cruise situations max. Nobody uses 50* anymore with engines made after 1998. Which is what everybody should have in their cars by now, Sequential EFI, excellent fuel efficiency engines from 99+ cost $300-$500 for ~5.3L and support 500-800rwhp depending on the year (gen4 internals in some 2004 gen3 blocks). Almost double the NA power potential of a big block from the 70's
get with the program dudes ;D
Last edited by Kingtal0n; 07-10-2018 at 09:53 AM.
07-10-2018, 09:50 AM
#36
After trying everything else, I thought this was simple enough. So I went back into the garage and used a pointed test lead to ground on the plate and points screw, but no change. I also tightened up the carb base and bowl screws a little, but no change.
I did pull the vacuum line off of the manifold port on the carb, which has a very strong vacuum, and sucked on it hard while connected to the distributor diaphragm. But nothing changed. It didn't cause a backfire, until I reconnected it to the carb manifold port.
But I have to say that it does run steady and is totally responsive. It just bothers me to leave that vacuum line disconnected, which has been connected to that distributor since it was brand new. But who can complain after 52 years, and 90k miles with only one broken valve spring.
I did pull the vacuum line off of the manifold port on the carb, which has a very strong vacuum, and sucked on it hard while connected to the distributor diaphragm. But nothing changed. It didn't cause a backfire, until I reconnected it to the carb manifold port.
But I have to say that it does run steady and is totally responsive. It just bothers me to leave that vacuum line disconnected, which has been connected to that distributor since it was brand new. But who can complain after 52 years, and 90k miles with only one broken valve spring.
Don't worry you will find the problem and be able to use the vacuum advance, just stay at it until you figure it out because it's done you a favor by presenting the problem in your driveway vs on the road somewhere.
07-10-2018, 10:10 AM
#37
Safety Car
Did you run the test ground wire from the points plate through the window to a good ground on the engine, it does not sound like you did that. Re read post #33, as this will eliminate the ground wire issue.
Don't worry you will find the problem and be able to use the vacuum advance, just stay at it until you figure it out because it's done you a favor by presenting the problem in your driveway vs on the road somewhere.
Don't worry you will find the problem and be able to use the vacuum advance, just stay at it until you figure it out because it's done you a favor by presenting the problem in your driveway vs on the road somewhere.
You meant #23 or #32, right?
07-10-2018, 10:11 AM
#38
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Original engines from 1960's are no longer typical. The old, sloppy, terrible engine style is long gone. if you still have one of those I am sorry for you. they don't make them like that anymore though. Any engine made in Japan after 1989 and any V8 made by chevy after 1998 is not going to tolerate much more than 44* of timing at cruise, and most want 37-42*.
Really ancient 60's engines needed much more advance because chamber tech in the 60's sucked in America.
Nobody uses 50* anymore with engines made after 1998. Which is what everybody should have in their cars by now,
get with the program dudes ;D
You probably didn't notice when you signed up here that this forum is all about cars made in that terrible time frame.
The '50's-'60's.
How do you like that little ole Datsun yer drivin'? Do you have any idea how many of these terribly designed SBC engines have been stuck in Datsuns to make them fast?
07-10-2018, 10:13 AM
#39
Safety Car
My post says "Total advance varies. typically, engines ... 30-40*..."
Original engines from 1960's are no longer typical. The old, sloppy, terrible engine style is long gone. if you still have one of those I am sorry for you. they don't make them like that anymore though. Any engine made in Japan after 1989 and any V8 made by chevy after 1998 is not going to tolerate much more than 44* of timing at cruise, and most want 37-42*.
the more advance an engine needs in general, the less efficient it is typically found to be. Really ancient 60's engines needed much more advance because chamber tech in the 60's sucked in America. Nowadays you find 40-45* for cruise situations max. Nobody uses 50* anymore with engines made after 1998. Which is what everybody should have in their cars by now, Sequential EFI, excellent fuel efficiency engines from 99+ cost $300-$500 for ~5.3L and support 500-800rwhp depending on the year (gen4 internals in some 2004 gen3 blocks). Almost double the NA power potential of a big block from the 70's
get with the program dudes ;D
Original engines from 1960's are no longer typical. The old, sloppy, terrible engine style is long gone. if you still have one of those I am sorry for you. they don't make them like that anymore though. Any engine made in Japan after 1989 and any V8 made by chevy after 1998 is not going to tolerate much more than 44* of timing at cruise, and most want 37-42*.
the more advance an engine needs in general, the less efficient it is typically found to be. Really ancient 60's engines needed much more advance because chamber tech in the 60's sucked in America. Nowadays you find 40-45* for cruise situations max. Nobody uses 50* anymore with engines made after 1998. Which is what everybody should have in their cars by now, Sequential EFI, excellent fuel efficiency engines from 99+ cost $300-$500 for ~5.3L and support 500-800rwhp depending on the year (gen4 internals in some 2004 gen3 blocks). Almost double the NA power potential of a big block from the 70's
get with the program dudes ;D
07-10-2018, 10:51 AM
#40
Race Director
It can vary a little. My open chamber aluminum head BB is limited to 36 (initial + mech advance) and 8 vacuum for a total of 44 deg since any more than that it will miss constantly (or trailer hitch as others call it) at highway cruise speed. But the open chamber heads are really more 70s era technology than 60s. But unless you really set up a modified distributor to allow something like 18 -- 20 degrees initial timing, vacuum advance is definitely your friend on the street.