Can you help diagnose an ignition or fuel problem?
jim larson said
Jun 5, 2018
The issue just showed up last Friday and Sunday. As you probably know I have a stock ignition and fuel set up in my 396. Friday night I went to Rochester and car ran fine. When I went to start the car to go home, it kind of didn't want to start, added some fuel at the first gas station, along the way when I pulled up to a stop sign it stopped, started right up, stopped at the next stop sign, started right up. Going down the road it started missing. At next stop sign as I was pulling though the intersection it stopped, though I was in for it. Started and drove the last 30 miles home with no issues. Thought issue had resolved itself.
Sunday morning I drove the the all GM show with no issues. Went to go home and kind of didn't want to start. Went down Larpenter to the east and car was missing periodically, This kept up down to hastings and south. Engine kept quitting and then starting as I left it in gear, then going down a big hill by the cannon river the engine quit, big backfire, then engine started, a little further along the way on a level road engine quite and car came to a stop. Thought I was doomed. But engine started and I drove the last 15 miles home. Evidently Rachael's prayers were answered.
Yesterday I replaced points which had been in the car for 5-8 years and they were somewhat burnt. Wanted to replace bronze carb filter; but none in town. Started car, set dwell to 29* and took car for a drive. Ran great.
What else could be the problem? Thinking some kind of fuel or electrical problem. Car always started right away after dying, so thinking it is more likely electrical. Rotor and distributor cap look good. Should I carry a spare cap, rotor, coil, and fuel filter in the car?
Bobs_Place said
Jun 5, 2018
Intermittent problems are tuft to find, so put a low current light on the + side of the coil, with the key on the light should be on, when the engine acts up watch the light, if light goes out your losing the feed to the coil. If the light stays on when the engine kills than check the wire between the coil and points for shorting or opens, be sure to check it inside the dist. as the wire bends every time the vacuum advance changes timing. More then likely NOT the coil, just have not seen many failed coils, however if they were to fail intermittently I would think they would act up more so when hot. So don't go buy one as I have one you can use for testing.
Also it doesn't sound like fuel problem but don't overlook it. When it acts up and if your at a place were you can pull the sight level plugs on the carb, that can tell you if it starving for fuel or flooding.
Lost in the 60s said
Jun 5, 2018
My first recommendation was going to be to replace the points and condenser. You already did that and it's back running.
Everything you've described is electrical, to me, and with points, they are the usual culprit.
Enganeer said
Jun 5, 2018
My 64 did something like that were it would run fine then stone cold quit, even while driving, then turn back on again. Turned out electrical connectors at the junction box that goes between the firewall were going bad and cutting the power to the ignition. Limped it home with one foot pressing on the interior wire harness at the firewall. Got a new wire harness, no issues.
Bobs_Place said
Jun 5, 2018
Also you said the car backfired one time that sound like ignition.
Larry Lucast said
Jun 5, 2018
I was thinking it might be passing little bits of water in the gas. A cheap test would be to add a can of HEET.
jim larson said
Jun 5, 2018
Enganeer wrote:
My 64 did something like that were it would run fine then stone cold quit, even while driving, then turn back on again. Turned out electrical connectors at the junction box that goes between the firewall were going bad and cutting the power to the ignition. Limped it home with one foot pressing on the interior wire harness at the firewall. Got a new wire harness, no issues.
Hope it’s not that; but wiring harness is origional.
Plan is points & condenser (Done). Hope that solvers the problem. Then coil and wire to dist from coil. Then fuel filter and heat. If problem not solved then I will have to look at wiring harness.
Lost in the 60s said
Jun 5, 2018
If you think it's starving for gas, I would do the fuel filter and heet before coil and wire. Like Bob said, a coil just quits and doesn't come back. The wire could have a bare spot and is bouncing on a metal part, causing the miss and erratic ignition, but it would be a rare case and you should be able to see that with a good visual check.
jim larson said
Jul 28, 2018
Well I was going to NSP last night, got as far as the intersection of 10 and 61 north of Hastings. Same problem surfaced, I thought the change of points fixed it. Car began to miss on 61 north to Cottage Grove, got off on the first tar road to the right and headed to 95. Car stopped about 6 times, I thought I was going to have to call Mitch. Got to 95 and headed to Hastings. Got the Beerstube parking lot with the car stopping about half a dozen time.
Preparing for a beer and burger and a guy asked if I need help as the hood was open. He call an old retired mechanic, whose first car was a 66 Impala 427. He first thought float sticking or fuel; but ruled that around, then he messed with the dwell, he had a neat tool about 2' long with a dial at one end that he rotated, then he tried air/fuel mixture screws. Finally after about 30 min, car idled fine and ran at ideal for about 5 Min. Headed home toward home. Car stopped about a half dozen time on the way towards Meiseville. Then stopped dead. Waited for 10 Min, car started and I headed for the Meiseville church parking lot. Church closed so prayers wouldn't help. Had a burger and a beer, after an hour headed home. Car stopped just into Red Wing, stopped 3 more time, then I droved the backroads towards Lake City, after about 10 Miles, I ran it though the gears twice and made it home.
Put in a new condenser this morning along with a new coil. Started car and took it for a 20 mile drive. Going through the gears 1-3 up to 5000rpm three time. Got home and car sat idling fine for 5 minutes before I shut it off.
Afraid to go more then 10 miles from Lake City. It may have been an electrical issue with a coil or a condenser or another issue to surface it ugly face again. Plan to drive it for about 2 hrs on Monday around the tarred back roads pm Monday. Should I put in a new bonze fuel filter in the Holly or pull the fuel bowel to check the float, even though I think it is not a fuel issue?
Could there be a wiring issue? Should I changed rotor, it looked OK? What about the distributor cap, could that be an issue, it looked OK. I looked at the wire from the distributor to the coil and it looked OK and the grommet in the distributor looked OK. the other wire and resister wire to the Coil looked ok; but they were wrapped in tape, so I could not see if there was a brake in insulation if that would cause any issue? Rachael's night out on her 71's birthday was memorable.
-- Edited by jim larson on Saturday 28th of July 2018 02:05:00 PM
-- Edited by jim larson on Saturday 28th of July 2018 02:06:09 PM
jim larson said
Jul 28, 2018
Bobs_Place wrote:
Intermittent problems are tuft to find, so put a low current light on the + side of the coil, with the key on the light should be on, when the engine acts up watch the light, if light goes out your losing the feed to the coil. If the light stays on when the engine kills than check the wire between the coil and points for shorting or opens, be sure to check it inside the dist. as the wire bends every time the vacuum advance changes timing. More then likely NOT the coil, just have not seen many failed coils, however if they were to fail intermittently I would think they would act up more so when hot. So don't go buy one as I have one you can use for testing.
Also it doesn't sound like fuel problem but don't overlook it. When it acts up and if your at a place were you can pull the sight level plugs on the carb, that can tell you if it starving for fuel or flooding.
Just reading back though your post Bob. Could you explain a little what you mean by "put a low current light on the + side of the coil". How do you do that? Do I just put a light with two wires, one to the + side of coil and the other wire to ground. Then drive the car and the light should stay on, if it goes out there the coil is not getting power and the alternator is doing something odd? For some reason the coil was installed so it touched the intake (do think it is suppose to ). Engine failure was after driving about a 1 hr or so, would this heat the coil up and cause it go fail?
dashboard said
Jul 28, 2018
Jim, have you been able to check the fuel level in the carb bowl when it stalls yet?
jim larson said
Jul 28, 2018
dashboard wrote:
Jim, have you been able to check the fuel level in the carb bowl when it stalls yet?
Yes it was at the correct height.
dashboard said
Jul 28, 2018
You might try running the engine for a bit to warm things up than try playing with the ignition switch itself. Just move it around, wiggle it to the off and start direction (don’t engage the starter) and see if you can duplicate the failure.
jim larson said
Jul 28, 2018
dashboard wrote:
You might try running the engine for a bit to warm things up than try playing with the ignition switch itself. Just move it around, wiggle it to the off and start direction (don’t engage the starter) and see if you can duplicate the failure.
I am planning to hook up a low voltage light to the positive side of the coil. If car stops and light is on, then ignition switch should be OK. If light is off then power is somehow interrupted, at least that’s my thinking as Bob suggested to do that.
if engine stop while going down a hill or car has a little speed if I leave it in gear it will start back up and run a while then for no reason the engine will kill. So I am thinking the switch is not a problem And there will still be power to the coil. So some thing regarding coil or distributor or fuel. Thinking ignition most likley. Hope changing coil and condenser will help.
-- Edited by jim larson on Saturday 28th of July 2018 08:58:14 PM
Bobs_Place said
Jul 28, 2018
I think your on the right track with the light.
When you checked the wire from the coil to the distributor did you check the wire inside the distributor? just give it a little tug, it will stretch if it is bad, that wire bends each time the vacuum advance moves the point.
From your latest post, the condition dose sound more like electrical/ignition, if the problem was fuel the engine would not restart without a lot of cranking. Sometimes electrical components will act up only when hot, when the bad part cools the car will start and run normally.
jim larson said
Jul 29, 2018
Bob, wondering if you could just check power to the coil with a test light when the engine stops if you leave the ignition on? Will that do the same thing as a light
In doing a little reading on the coils it seem resistance can change when they get hot and cause an engine failure. Well it was so nice today so I took the car for a drive. Drove it twice on Saturday, about 20 miles each time after the coil/condenser change with no issues.
Well I drove it about 2 hrs and 100miles. various speed. Not a single issue, acceleration excellent, cruise excellent, when stopping for a turn or light, idled down and sat at about 750 rpm. Filled the car up and will drive about 3 hr or about 150 miles on Tuesday. At least with the car always starting again I am not to nervous and will be able to find a good spot to pull off the road and let the car cool, if it stops. No interstate driving for a while, especially in the metro area, I get nervous when I am in my silverado with air bags and shoulder belts when on 494/694 or 35.
Bobs_Place said
Jul 29, 2018
Yes, the test light will tell you the if there is voltage at the coil, and it is hooked up the same way as the light that I was recommending you hook up, but with the test light you have to get out and hook it up to find out if there is voltage, than you would need to have someone crank the engine with the test light on the coil. But, it dose sound like you have narrowed it down to the condenser or the coil.
dashboard said
Jul 29, 2018
Wire up the light in such a way that you can zip tie the bulb to the drivers wiper. That way if it is intermittent you’ll see it right away.
jim larson said
Jul 29, 2018
Bobs_Place wrote:
Yes, the test light will tell you the if there is voltage at the coil, and it is hooked up the same way as the light that I was recommending you hook up, but with the test light you have to get out and hook it up to find out if there is voltage, than you would need to have someone crank the engine with the test light on the coil. But, it dose sound like you have narrowed it down to the condenser or the coil.
I hope it is the condenser or coil
jim larson said
Jul 31, 2018
Well drove the car 126miles without a glitch. So I think the issue was condenser or coil.
Car seemed kind of hard to start the last three days, so checked the timing. Looks like the shade tree mechanic messed with distributor, I was in the car starting it so couldn't see what he was doing. Well the base timing was at 4, I previously had it at 14 since the distributor was recurved and mechanical changed from 15 to 11 so to add only 22 instead of stock 30 at the crank. so a total timing of 36.
Looks like my VC is adding about 14 at idle, since timing goes to 28 at idle when I hook up the VC I will have to look the VC specs up to see if that is what it is suppose to do; but I am thinking It is suppose to add 7 at the distributor at idle and go up from there to 14, so adding 14 and 28 at the crank. So at cruise at about 50mph I should have about 54 degrees advance. Does this all sound about right?
Just leaving for a short trip to see how the car rums with the change in timing.
Bobs_Place said
Jul 31, 2018
54 deg is acceptable under light loud cruise, no more. If the engine misses,runs ruff or bucks, back the timing down 2-4 deg.
However if I read the numbers right your only getting a 50deg maximum, 14 base timing, 14 vacuum and 22 centrifugal. I don't think you'll see much difference, but as test you could go up 4deg just to see if the engine responds well to the change at 50mph cruise speed, Idle would then be 32, probable won't like that and no full throttle as that will be 40 deg at speed. Even 28 at idle might be high, just have to see what the engine likes.
jim larson said
Aug 1, 2018
I checked the spec on my VC and it is suppose to add 8 dist or 16 crank degrees with all in at 8", so I backed off the base to 12 plus the 16 from the VC and the 22(I think of mechanical adv) that would give me 28 at idle, 34 total and 50 at cruise.
Interesting that with base at 4 and vac at 16 a total at 26 with cruise at 46(thats what it checked out at after the trip yesterday), I had no minor issues when traveling below 1800 rpm in 4th gear at 30 mph in town.
I can't find my spec sheet that the guy from Competition Engines gave me when he re-curved my distributor, so I am going kind of off a suspect memory. But I think he had the mechanical start at 12 and all in at 2500 with 22 degrees added and to set base timing at ?(12-14). He based that off what my cam numbers were. Does that sound reasonable.
Bobs_Place said
Aug 1, 2018
If the base timing is 12 and vacuum advance ADDs 16 crank degs, that should be 18 at idle, there should be no centrifugal advance at idle and vacuum adv. should be all in. At WOT there is no vacuum adv. therefor 12 base and 22 centrifugal gives you 34. Part throttle cruise you get both vac and centrifical advance, the amount of adv is dependent on RPM and throttle opening. In your case sounds like centif is all in early say 2500 and vac adv. is also all in above 8in vac. That could give you 50 deg at 2500 rpm, at that speed you will not back off timing until you get down to 8 in vac. That is probable about a 40 to 60% throttle setting. When the timing was retarded to 4 base, that's about 8 less over all so your looking at maybe 11 centrif and still close to 16 vac that's 31at 1800rpm, still seems high
So, what is your vac at idle, what is the vac at your typical cruise speed, what's the cam duration.
I think the centrif. adv dose not need to be in so quick, the difference between all in at 2500 and 3500 is not going to be noticeable to your set to the pants dino. If your at full throttle and pounding gears your not going to be at 1800 to 3000, your going to be above 3 to 3500 or more. Now even with that less aggressive curve when you tip the throttle in the vac. adv. won't cut back the timing until 8in vac, at 3500 that's about 60 to 80% throttle. That would rattle the engine until vac adv is gone.
I would go to stiffer springs in the centrif adv. that will move the curve up and go to a vac can that is all in just under idle vac or one that starts just after idle vac. Nether centrif or vac should be parochially in at idle, this will cause an inconsistent idle speed.
jim larson said
Aug 1, 2018
Checked my manifold vacuum today, at cruise on a flat surface at 50 mph the manifold gauge reads 17"Hg.
When just idling the gauge flutters between 10Hg and 12"Hg.
The VC1765 is suppose to start at 5-7Hg with 8* of advance @ 11-13HG.
Would this mean that all the advance could be in at Idle, so it could add 16* at the crank at idle?
I dropped the base timing back to about 10* with VC disconnected. When I connected the VC up the advance went to about 26*.
I am not sure about how much the distributor adds or when it is all in, as I have a hard time to increasing the rpm and reading the advance at various rpm; but I am thinking it looks like it is all in by about 2700 rpm and the total looks to be about 34*. So think the distributor adds about 24*.
So think at cruise I have about 50* advance (10+16+24). I will have to look for the spec sheet from Competition Engines: but that was 12 yrs ago.
For some reason the engine is hard to start after it sits for a day or more ( that use to be true; but only after 3 or more days), I have to crank it quite a bit. What could be possible causes?
Bobs_Place said
Aug 2, 2018
As I recall you have a 3.08 gear? And with a 2.52 1st gear that makes start-ability a bit tricky at times. The correct timing at idle will help, so I would try some quick test drives from stop to just enough to get the car rolling, start at 10deg . add 4 or 6deg retest, if better, repeat. Do this with the vacuum to the dist. removed and plugged. The goal is to get the car rolling with the least amount throttle and minimal clutch slippage. You may need to drive the car more than just 3 or4 starts to find what the engine likes, when there no improvement or the engine pings go back. From that point we adjust the advance curve to hit the 34-36 deg on the top end. Than the vacuum advance maybe go to a VC1760 ,It's all in at 14-18 in vac with 24 crank deg which we well limit on the low end to get 12-16 deg.
I know this could be time consuming, but some experimenting to find out what the engine likes might be worth it. Drive it for a few days if you need to. Remember this is to help find the best base timing so do low speed driving, stop and go type driving.
jim larson said
Aug 2, 2018
I wasn't clear; by start I meant starting the engine. Car has good manners starting in 1st gear. Taking the car for a short drive today to check if it pings.
Lost in the 60s said
Aug 3, 2018
I have the same problem with the fuel draining back out of the carb and needing long crank times to prime.
I just ordered 1 of these to see if it really works to keep the gas in the carb.
Your right, I wasn't thinking engine starting as I got sidetracked on your questions/concerns on timing.
I would pull the bowel level plugs before starting the engine to check fuel level, check and snug bowel screws, I suspect you have an internal leak, maybe replace metering block gasket. I don't believe the fuel can drain back as the inlet to the fuel bowels is above the fuel level on a Holley.
The issue just showed up last Friday and Sunday. As you probably know I have a stock ignition and fuel set up in my 396. Friday night I went to Rochester and car ran fine. When I went to start the car to go home, it kind of didn't want to start, added some fuel at the first gas station, along the way when I pulled up to a stop sign it stopped, started right up, stopped at the next stop sign, started right up. Going down the road it started missing. At next stop sign as I was pulling though the intersection it stopped, though I was in for it. Started and drove the last 30 miles home with no issues. Thought issue had resolved itself.
Sunday morning I drove the the all GM show with no issues. Went to go home and kind of didn't want to start. Went down Larpenter to the east and car was missing periodically, This kept up down to hastings and south. Engine kept quitting and then starting as I left it in gear, then going down a big hill by the cannon river the engine quit, big backfire, then engine started, a little further along the way on a level road engine quite and car came to a stop. Thought I was doomed. But engine started and I drove the last 15 miles home. Evidently Rachael's prayers were answered.
Yesterday I replaced points which had been in the car for 5-8 years and they were somewhat burnt. Wanted to replace bronze carb filter; but none in town. Started car, set dwell to 29* and took car for a drive. Ran great.
What else could be the problem? Thinking some kind of fuel or electrical problem. Car always started right away after dying, so thinking it is more likely electrical. Rotor and distributor cap look good. Should I carry a spare cap, rotor, coil, and fuel filter in the car?
Intermittent problems are tuft to find, so put a low current light on the + side of the coil, with the key on the light should be on, when the engine acts up watch the light, if light goes out your losing the feed to the coil. If the light stays on when the engine kills than check the wire between the coil and points for shorting or opens, be sure to check it inside the dist. as the wire bends every time the vacuum advance changes timing. More then likely NOT the coil, just have not seen many failed coils, however if they were to fail intermittently I would think they would act up more so when hot. So don't go buy one as I have one you can use for testing.
Also it doesn't sound like fuel problem but don't overlook it. When it acts up and if your at a place were you can pull the sight level plugs on the carb, that can tell you if it starving for fuel or flooding.
Everything you've described is electrical, to me, and with points, they are the usual culprit.
Also you said the car backfired one time that sound like ignition.
Hope it’s not that; but wiring harness is origional.
Plan is points & condenser (Done). Hope that solvers the problem. Then coil and wire to dist from coil. Then fuel filter and heat. If problem not solved then I will have to look at wiring harness.
Well I was going to NSP last night, got as far as the intersection of 10 and 61 north of Hastings. Same problem surfaced, I thought the change of points fixed it. Car began to miss on 61 north to Cottage Grove, got off on the first tar road to the right and headed to 95. Car stopped about 6 times, I thought I was going to have to call Mitch. Got to 95 and headed to Hastings. Got the Beerstube parking lot with the car stopping about half a dozen time.
Preparing for a beer and burger and a guy asked if I need help as the hood was open. He call an old retired mechanic, whose first car was a 66 Impala 427. He first thought float sticking or fuel; but ruled that around, then he messed with the dwell, he had a neat tool about 2' long with a dial at one end that he rotated, then he tried air/fuel mixture screws. Finally after about 30 min, car idled fine and ran at ideal for about 5 Min.
Headed home toward home. Car stopped about a half dozen time on the way towards Meiseville. Then stopped dead. Waited for 10 Min, car started and I headed for the Meiseville church parking lot. Church closed so prayers wouldn't help. Had a burger and a beer, after an hour headed home. Car stopped just into Red Wing, stopped 3 more time, then I droved the backroads towards Lake City, after about 10 Miles, I ran it though the gears twice and made it home.
Put in a new condenser this morning along with a new coil. Started car and took it for a 20 mile drive. Going through the gears 1-3 up to 5000rpm three time. Got home and car sat idling fine for 5 minutes before I shut it off.
Afraid to go more then 10 miles from Lake City. It may have been an electrical issue with a coil or a condenser or another issue to surface it ugly face again. Plan to drive it for about 2 hrs on Monday around the tarred back roads pm Monday. Should I put in a new bonze fuel filter in the Holly or pull the fuel bowel to check the float, even though I think it is not a fuel issue?
Could there be a wiring issue? Should I changed rotor, it looked OK? What about the distributor cap, could that be an issue, it looked OK. I looked at the wire from the distributor to the coil and it looked OK and the grommet in the distributor looked OK. the other wire and resister wire to the Coil looked ok; but they were wrapped in tape, so I could not see if there was a brake in insulation if that would cause any issue? Rachael's night out on her 71's birthday was memorable.
-- Edited by jim larson on Saturday 28th of July 2018 02:05:00 PM
-- Edited by jim larson on Saturday 28th of July 2018 02:06:09 PM
Just reading back though your post Bob. Could you explain a little what you mean by "put a low current light on the + side of the coil". How do you do that? Do I just put a light with two wires, one to the + side of coil and the other wire to ground. Then drive the car and the light should stay on, if it goes out there the coil is not getting power and the alternator is doing something odd? For some reason the coil was installed so it touched the intake (do think it is suppose to ). Engine failure was after driving about a 1 hr or so, would this heat the coil up and cause it go fail?
Yes it was at the correct height.
I am planning to hook up a low voltage light to the positive side of the coil. If car stops and light is on, then ignition switch should be OK. If light is off then power is somehow interrupted, at least that’s my thinking as Bob suggested to do that.
if engine stop while going down a hill or car has a little speed if I leave it in gear it will start back up and run a while then for no reason the engine will kill. So I am thinking the switch is not a problem And there will still be power to the coil. So some thing regarding coil or distributor or fuel. Thinking ignition most likley. Hope changing coil and condenser will help.
-- Edited by jim larson on Saturday 28th of July 2018 08:58:14 PM
I think your on the right track with the light.
When you checked the wire from the coil to the distributor did you check the wire inside the distributor? just give it a little tug, it will stretch if it is bad, that wire bends each time the vacuum advance moves the point.
From your latest post, the condition dose sound more like electrical/ignition, if the problem was fuel the engine would not restart without a lot of cranking. Sometimes electrical components will act up only when hot, when the bad part cools the car will start and run normally.
Bob, wondering if you could just check power to the coil with a test light when the engine stops if you leave the ignition on? Will that do the same thing as a light
In doing a little reading on the coils it seem resistance can change when they get hot and cause an engine failure. Well it was so nice today so I took the car for a drive. Drove it twice on Saturday, about 20 miles each time after the coil/condenser change with no issues.
Well I drove it about 2 hrs and 100miles. various speed. Not a single issue, acceleration excellent, cruise excellent, when stopping for a turn or light, idled down and sat at about 750 rpm. Filled the car up and will drive about 3 hr or about 150 miles on Tuesday. At least with the car always starting again I am not to nervous and will be able to find a good spot to pull off the road and let the car cool, if it stops. No interstate driving for a while, especially in the metro area, I get nervous when I am in my silverado with air bags and shoulder belts when on 494/694 or 35.
Yes, the test light will tell you the if there is voltage at the coil, and it is hooked up the same way as the light that I was recommending you hook up, but with the test light you have to get out and hook it up to find out if there is voltage, than you would need to have someone crank the engine with the test light on the coil. But, it dose sound like you have narrowed it down to the condenser or the coil.
I hope it is the condenser or coil
Well drove the car 126miles without a glitch. So I think the issue was condenser or coil.
Car seemed kind of hard to start the last three days, so checked the timing. Looks like the shade tree mechanic messed with distributor, I was in the car starting it so couldn't see what he was doing. Well the base timing was at 4, I previously had it at 14 since the distributor was recurved and mechanical changed from 15 to 11 so to add only 22 instead of stock 30 at the crank. so a total timing of 36.
Looks like my VC is adding about 14 at idle, since timing goes to 28 at idle when I hook up the VC I will have to look the VC specs up to see if that is what it is suppose to do; but I am thinking It is suppose to add 7 at the distributor at idle and go up from there to 14, so adding 14 and 28 at the crank. So at cruise at about 50mph I should have about 54 degrees advance. Does this all sound about right?
Just leaving for a short trip to see how the car rums with the change in timing.
54 deg is acceptable under light loud cruise, no more. If the engine misses,runs ruff or bucks, back the timing down 2-4 deg.
However if I read the numbers right your only getting a 50deg maximum, 14 base timing, 14 vacuum and 22 centrifugal. I don't think you'll see much difference, but as test you could go up 4deg just to see if the engine responds well to the change at 50mph cruise speed, Idle would then be 32, probable won't like that and no full throttle as that will be 40 deg at speed. Even 28 at idle might be high, just have to see what the engine likes.
I checked the spec on my VC and it is suppose to add 8 dist or 16 crank degrees with all in at 8", so I backed off the base to 12 plus the 16 from the VC and the 22(I think of mechanical adv) that would give me 28 at idle, 34 total and 50 at cruise.
Interesting that with base at 4 and vac at 16 a total at 26 with cruise at 46(thats what it checked out at after the trip yesterday), I had no minor issues when traveling below 1800 rpm in 4th gear at 30 mph in town.
I can't find my spec sheet that the guy from Competition Engines gave me when he re-curved my distributor, so I am going kind of off a suspect memory. But I think he had the mechanical start at 12 and all in at 2500 with 22 degrees added and to set base timing at ?(12-14). He based that off what my cam numbers were. Does that sound reasonable.
If the base timing is 12 and vacuum advance ADDs 16 crank degs, that should be 18 at idle, there should be no centrifugal advance at idle and vacuum adv. should be all in. At WOT there is no vacuum adv. therefor 12 base and 22 centrifugal gives you 34. Part throttle cruise you get both vac and centrifical advance, the amount of adv is dependent on RPM and throttle opening. In your case sounds like centif is all in early say 2500 and vac adv. is also all in above 8in vac. That could give you 50 deg at 2500 rpm, at that speed you will not back off timing until you get down to 8 in vac. That is probable about a 40 to 60% throttle setting. When the timing was retarded to 4 base, that's about 8 less over all so your looking at maybe 11 centrif and still close to 16 vac that's 31at 1800rpm, still seems high
So, what is your vac at idle, what is the vac at your typical cruise speed, what's the cam duration.
I think the centrif. adv dose not need to be in so quick, the difference between all in at 2500 and 3500 is not going to be noticeable to your set to the pants dino. If your at full throttle and pounding gears your not going to be at 1800 to 3000, your going to be above 3 to 3500 or more. Now even with that less aggressive curve when you tip the throttle in the vac. adv. won't cut back the timing until 8in vac, at 3500 that's about 60 to 80% throttle. That would rattle the engine until vac adv is gone.
I would go to stiffer springs in the centrif adv. that will move the curve up and go to a vac can that is all in just under idle vac or one that starts just after idle vac. Nether centrif or vac should be parochially in at idle, this will cause an inconsistent idle speed.
Checked my manifold vacuum today, at cruise on a flat surface at 50 mph the manifold gauge reads 17"Hg.
When just idling the gauge flutters between 10Hg and 12"Hg.
The VC1765 is suppose to start at 5-7Hg with 8* of advance @ 11-13HG.
Would this mean that all the advance could be in at Idle, so it could add 16* at the crank at idle?
I dropped the base timing back to about 10* with VC disconnected. When I connected the VC up the advance went to about 26*.
I am not sure about how much the distributor adds or when it is all in, as I have a hard time to increasing the rpm and reading the advance at various rpm; but I am thinking it looks like it is all in by about 2700 rpm and the total looks to be about 34*. So think the distributor adds about 24*.
So think at cruise I have about 50* advance (10+16+24). I will have to look for the spec sheet from Competition Engines: but that was 12 yrs ago.
For some reason the engine is hard to start after it sits for a day or more ( that use to be true; but only after 3 or more days), I have to crank it quite a bit. What could be possible causes?
As I recall you have a 3.08 gear? And with a 2.52 1st gear that makes start-ability a bit tricky at times. The correct timing at idle will help, so I would try some quick test drives from stop to just enough to get the car rolling, start at 10deg . add 4 or 6deg retest, if better, repeat. Do this with the vacuum to the dist. removed and plugged. The goal is to get the car rolling with the least amount throttle and minimal clutch slippage. You may need to drive the car more than just 3 or4 starts to find what the engine likes, when there no improvement or the engine pings go back. From that point we adjust the advance curve to hit the 34-36 deg on the top end. Than the vacuum advance maybe go to a VC1760 ,It's all in at 14-18 in vac with 24 crank deg which we well limit on the low end to get 12-16 deg.
I know this could be time consuming, but some experimenting to find out what the engine likes might be worth it. Drive it for a few days if you need to. Remember this is to help find the best base timing so do low speed driving, stop and go type driving.
I wasn't clear; by start I meant starting the engine. Car has good manners starting in 1st gear. Taking the car for a short drive today to check if it pings.
I have the same problem with the fuel draining back out of the carb and needing long crank times to prime.
I just ordered 1 of these to see if it really works to keep the gas in the carb.
https://www.amazon.com/Farmunion-Return-Petrol-Diesel-Aluminium/dp/B01FSSH7Y0/ref=pd_rhf_sc_p_img_1?_encoding=UTF8&psc=1&refRID=ETZ72VWHNKFM4XADMGGK
Your right, I wasn't thinking engine starting as I got sidetracked on your questions/concerns on timing.
I would pull the bowel level plugs before starting the engine to check fuel level, check and snug bowel screws, I suspect you have an internal leak, maybe replace metering block gasket. I don't believe the fuel can drain back as the inlet to the fuel bowels is above the fuel level on a Holley.