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 Posted: Jan 19, 2019 11:50AM
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Quote:
Originally Posted by h_lankford
 
If your ignition system had those badly corroded connectors, were you getting intermittent lousy spark and therefore poor combustion, therefore unburned fuel, and therefore your gas in oil finding?
Yes, except that my mass O2 meter is spot on and my plugs are a nice golden brown. So, I'm leaning toward static pressure in the fuel line. We'll see in a couple of months when I submit another oil sample for analysis.

 

Michael, Santa Barbara, CA

. . . the sled, not the flower

      Poser MotorSports

 Posted: Jan 19, 2019 10:57AM
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Quote:
I checked the plugs and discovered I wasn't getting any spark. After polking around a bit, I found that 2 bayonet connectors on the 2 wires leading to the distributor were badly corroded.

I replace the connectors and will try starting 'Rosebud' again this morning. Will advise.

If your ignition system had those badly corroded connectors, were you getting intermittent lousy spark and therefore poor combustion, therefore unburned fuel, and therefore your gas in oil finding?

 Posted: Jan 19, 2019 10:32AM
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Quote:
Originally Posted by Rosebud
 
I was hoping the problem was related to low fuel pressure, in which case I'd simply dial in an extra psi or two. So now I'm thinking the cut-out is more of an electrical issue and not related to fuel pressure. Coil? Distributor?
[UPDATE] The cut-out problem wasn't related to the fuel pressure after all. When I couldn't get 'Rosebud' to start last night, I checked the plugs and discovered I wasn't getting any spark. After polking around a bit, I found that 2 bayonet connectors on the 2 wires leading to the distributor were badly corroded. I replace the connectors and will try starting 'Rosebud' again this morning. Will advise.

Re: Fuel pressure. A couple of weeks ago I began switching off the fuel pump 30 seconds before shutting the engine down to avoid static pressure in the fuel line bleeding into the carbs. Some thought that was the source of the gas in my oil sump. Turns out 30 seconds is way too long; caused a fuel starvation sputter after a minute or two of driving. That's what led me to think the cut-out problem was related to low fuel pressure. I'm now switching off the pump 5-10 seconds before shut down. The next oil analysis will determine if I've solved the gas-in-the-oil problem.



 

 





 

Michael, Santa Barbara, CA

. . . the sled, not the flower

      Poser MotorSports

 Posted: Jan 19, 2019 10:01AM
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Quote:
Originally Posted by 1963SV2
Never worked ..or didn't work properly???

The original Smiths tachos were prone to interference in the trigger line.  Mine always wandered a bit until a mate made me a filter which was placed in the line just before the tacho to clean up the signal.

Cheers, Ian
Actually, it did work for a month or two—the needle bounced around a bit and it wasn't very accurate; +/- 10%. Now the needle is all over the place. I seem to recall seeing something about installing a filter on Smith tachs. Would you have a link to the info?

 

Michael, Santa Barbara, CA

. . . the sled, not the flower

      Poser MotorSports

 Posted: Jan 18, 2019 04:40PM
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Never worked ..or didn't work properly???

The original Smiths tachos were prone to interference in the trigger line.  Mine always wandered a bit until a mate made me a filter which was placed in the line just before the tacho to clean up the signal.

Cheers, Ian

 Posted: Jan 18, 2019 02:42PM
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Quote:
Originally Posted by malsal
See if you notice the tachometer needle jumping when the hesitation occurs.
That would be a good tip… if the tach worked. New Smith's tach never worked right out of the box. Three different auto-electric shops looked at it, confirmed it was wired correctly, scratched their heads and said there must be something wrong with the tach. Warranty period has since expired.

It's always something…

 

Michael, Santa Barbara, CA

. . . the sled, not the flower

      Poser MotorSports

 Posted: Jan 18, 2019 01:37PM
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See if you notice the tachometer needle jumping when the hesitation occurs.

If in doubt, flat out. Colin Mc Rae MBE 1968-2007.

Give a car more power and it goes faster on the straights,
make a car lighter and it's faster everywhere. Colin Chapman.

 Posted: Jan 18, 2019 12:50PM
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Quote:
Originally Posted by Rosebud
 
I had originally set my fuel pressure regulator to 2.5 psi but discovered it had crept up to 4 psi during the past couple of years (although the engine is not running rich). I also noticed that my fuel pressure gauge remained at 4 psi for almost an hour after shutting down the engine. I dialed the pressure back to 2.5 psi, pulled my fuel floats off and drew a vacuum on the check-valves. There doesn't appear to be any leaks, but sitting for an hour w/ 4 psi in the line may have caused fuel to get by the check-valves anyway, as Dan had mentioned.

So, as an added measure I've been switching the fuel pump 
off about 30 seconds before shutting the engine down which brings the residual line pressure to zero. I'll put a couple thousand miles on the oil and send another sample in for testing. Will post the results here. Thanks all.
[UPDATE] Since I've dialed back my fuel pressure to 2.5 psi I've experienced an intermittent but serious issue. The engine has cut-out momentarily (≤1 sec.) several times this past week. Yesterday it wouldn't start at all, today it starts and runs fine. I was hoping the problem was related to low fuel pressure, in which case I'd simply dial in an extra psi or two. But now that I think about it, it seems to me that a low fuel condition would cause more of a sputter than a momentary cut-out. It was as if I had turned the ignition off for a second. So now I'm thinking the cut-out is more of an electrical issue and not related to fuel pressure. Coil? Distributor?

It's always something, eh?

.

 

Michael, Santa Barbara, CA

. . . the sled, not the flower

      Poser MotorSports

 Posted: Jan 4, 2019 02:23PM
 Edited:  Jan 4, 2019 02:27PM
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Quote:
Originally Posted by Dan Moffet
At excessive pressure, the fuel can force the float valves open and over-fill the bowl (or bowls). If the engine is at higher revs, the mixture will be rich. At lower revs, it may be very rich. If stopped and there is residual pressure, it may pour raw fuel into the carb throat which then can run down into the cylinder, leak past the rings and into the crankcase. 
I had originally set my fuel pressure regulator to 2.5 psi but discovered it had crept up to 4 psi during the past couple of years (although the engine is not running rich). I also noticed that my fuel pressure gauge remained at 4 psi for almost an hour after shutting down the engine. I dialed the pressure back to 2.5 psi, pulled my fuel floats off and drew a vacuum on the check-valves. There doesn't appear to be any leaks, but sitting for an hour w/ 4 psi in the line may have caused fuel to get by the check-valves anyway, as Dan had mentioned.

Fuel pressure is now at 2.5 psi and remains so for up to an hour after shutdown which is still a concern. So, as an added measure I've been switching the fuel pump 
off about 30 seconds before shutting the engine down which brings the residual line pressure to zero. I'll put a couple thousand miles on the oil and send another sample in for testing. Will post the results here. Thanks all.

 

Michael, Santa Barbara, CA

. . . the sled, not the flower

      Poser MotorSports

 Posted: Dec 22, 2018 08:29AM
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CA
At excessive pressure, the fuel can force the float valves open and over-fill the bowl (or bowls). If the engine is at higher revs, the mixture will be rich. At lower revs, it may be very rich. If stopped and there is residual pressure, it may pour raw fuel into the carb throat which then can run down into the cylinder, leak past the rings and into the crankcase.
In a SU carb, the proper fuel level is very close to the top of the carb jet. If too high in the bowl, then it is too high in the jet for proper air/fuel mixture. If the bowl is over-filled, then the level would be higher than the tip of the jet and the carb bridge. At that point it trickles out.

If your bowl float jet/needle is worn or sticky, there is the potential for it to stick open. The top of the fuel tank is higher than the carb. If your tank is full, and you float jet is stuck open, gravity will let the tank drain until the fuel level in the tank is the same as the top of the carb jet. My Mini proved that one winter. I used to winter store the car with a full tank to minimize condensation. The carb float jet stuck open and 2 - 3 litres of fuel drained into my crankcase. Luckily I checked the oil before starting the engine in the spring. Now I leave it with no m ore than half a tank.

.

"Hang on a minute lads....I've got a great idea."

 Posted: Dec 21, 2018 09:22PM
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Quote:
Originally Posted by Rosebud

…Also, boron is as on the high side. Anyone know if boron is used in any critical engine/transmission parts? I use a carbon inhibitor fluid every couple of tank fulls—I'll check the label to see if boron is an additive.

UPDATE: It turns out that boron is an anti-wear additive used in high-quality motor oils. My Amzoil has a significant amount. It's also used as a lubricant in anti-freeze. So, do I have a coolant leak too? Nah… 

 

Michael, Santa Barbara, CA

. . . the sled, not the flower

      Poser MotorSports

 Posted: Dec 21, 2018 08:18PM
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I'd repeat the test first.

 Posted: Dec 21, 2018 06:08PM
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I got the results of my oil analysis the other day and everything looks good except that it shows an excessive amount of fuel in the oil. The testing lab suggests the high gasoline content is a result of 1) piston ring blow-by 2) frequent short trips 3) excessive idling 4) timing/mixture issues. I normally change my synthetic oil @ 3K miles—I stretched it to 5K this time in anticipation of the analysis, so the fuel dilution factor isn't as critical as it appears.

It's a 1275 A+ bored to 1380 w/ 10:1 CR. A compression test shows 195 to 198 psi across the 4 cylinders, so I'm confident I don't have significant blow-by. The car's driven almost every day and always reaches operating temp. My twin SUs are in good order and my mass O2 gauge and spark plugs confirm I'm neither running too lean or too rich. Timing is spot-on.

 

The analysis also shows the oil viscosity is on the low side @ 100°C, but the lab says that's caused by the oil/gas dilution. Also, boron is as on the high side. Anyone know if boron is used in any critical engine/transmission parts? I use a carbon inhibitor fluid every couple of tank fulls—I'll check the label to see if boron is an additive.

Someone suggested that excessive fuel in the oil could be caused by too much fuel pressure and/or a leaky fuel float diaphragm. I have an electric fuel pump that I originally set to 2.5 psi. I checked it the other day and it's reading almost 4 psi. I also noticed that it takes almost 1 hour for the fuel pressure gauge to read zero after I've turned the engine off—plenty of time for fuel to leak past the diaphrams, right?

Questions:

1) Is 4 psi of fuel pressure enough to allow fuel to get past the diaphragm?
2) Is boron used in any critical engine/transmission parts? Bearings, bushings, valves/valve seats perhaps? 

 

Michael, Santa Barbara, CA

. . . the sled, not the flower

      Poser MotorSports