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Engine warm up
- Thread starter AUSMHLY
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WALTER
Jedi Hopeful
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I used to have to wait till it was up to 190 degrees before it would run smoothly. If it didn't it would backfire and sputter terribly. I did a few things before it(BJ8) stopped acting up. So I'm not sure what the cure was. I set the timing with a timing light, replaced my plug wires and started using "real" dashpot oil instead of mystery oil.
Good luck,
Walter
Good luck,
Walter
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I have read the proper warm up procedure for British Cars, in what world can you drive at a constant 30 MPH on top gear until the engine warms up???
Sorry, but back in the day practicality required the motor to sit and idle until warm on really cold days.
These days with our collector cars unless you run ice rallies or live in a very cold part of the world the cars pretty much are only driven when it is nice out, and warming up is not much of an issue, a few seconds to let the oil circulate and you should be good to go.
If my car sputtered etc. until fully warm in moderate to warm weather I would assume the carbs were too lean and richen them up.
Greg
Sorry, but back in the day practicality required the motor to sit and idle until warm on really cold days.
These days with our collector cars unless you run ice rallies or live in a very cold part of the world the cars pretty much are only driven when it is nice out, and warming up is not much of an issue, a few seconds to let the oil circulate and you should be good to go.
If my car sputtered etc. until fully warm in moderate to warm weather I would assume the carbs were too lean and richen them up.
Greg
anthony7777
Yoda
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oh boy greg looks like youve really gone and done it this time! /bcforum/images/%%GRAEMLIN_URL%%/devilgrin.gif /bcforum/images/%%GRAEMLIN_URL%%/cry.gifKeoke said:
My car has the thermal choke which works well. The only thing I do different when it is cold is NOT back up. The car runs so rich while it is on If I back up too fast I will get raw fuel on my dash board.
I have it adjusted down as far as it will go to limit the amount of extra fuel the choke is suppliying.
Kevin R
I have it adjusted down as far as it will go to limit the amount of extra fuel the choke is suppliying.
Kevin R
anthony7777
Yoda
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and no need for the "third tail light" /bcforum/images/%%GRAEMLIN_URL%%/lol.gif
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Marvel Mystery Oil actually lubes the upper cylinder stuff better than dashpot oil.
Hi Cyra,
Marvel Mystery Oil is a type of “Snake Oil” IMMHO. According to the manufacturer, you add it to whatever system you are having problems with: fuel tank to keep spark plugs sparking, transmissions to keep them turning. One guy even took some to relieve constipation! I believe that the Marvel Mystery Oil is thinner than dashpot oil. "Real" dashpot oil is 20W oil.
The SU carburetor was designed as a constant-velocity carburetor. The dashpot pistons lift and drop in response to vacuum changes (usually) due to the butterfly changing positions. This keeps the velocity (not quantity) of the air through the carb constant. If the dashpot piston lifting lags the butterfly opening, then you increase the air velocity momentarily and draw more fuel than normal for the air quantity. This richens the air mixture and prevents engine hesitation just as an accelerator pump does on other American carbs. The dashpot oil works as a dampener. It slows the lifting of the pistons, but not the dropping. The thinner the oil, the faster the dashpot pistons lift in response to acceleration which opens up the carburetor throats. This translates into a leaner fuel mixture upon initial acceleration: less air velocity draws less fuel pass the needles. A heavier oil will slow down the pistons and give you a richer mixture initially: higher air velocity (because of restricted throat) draws more fuel.
Some people use automatic transmission fluid (ATF), which I believe is close to the same weight as MMO. This is thinner than 20W oil and lets the pistons rise faster. This may cause your engine to hesitate on acceleration. Some people use 30W or 20W-50 which might make it sluggish on acceleration. It all depends on your setup. If everything is stock and set to original settings, then you may want to start with 20W dashpot oil. You can try different weights of oil and see what you get.
Remember of course, you mileage may vary!
Mark
Marvel Mystery Oil is a type of “Snake Oil” IMMHO. According to the manufacturer, you add it to whatever system you are having problems with: fuel tank to keep spark plugs sparking, transmissions to keep them turning. One guy even took some to relieve constipation! I believe that the Marvel Mystery Oil is thinner than dashpot oil. "Real" dashpot oil is 20W oil.
The SU carburetor was designed as a constant-velocity carburetor. The dashpot pistons lift and drop in response to vacuum changes (usually) due to the butterfly changing positions. This keeps the velocity (not quantity) of the air through the carb constant. If the dashpot piston lifting lags the butterfly opening, then you increase the air velocity momentarily and draw more fuel than normal for the air quantity. This richens the air mixture and prevents engine hesitation just as an accelerator pump does on other American carbs. The dashpot oil works as a dampener. It slows the lifting of the pistons, but not the dropping. The thinner the oil, the faster the dashpot pistons lift in response to acceleration which opens up the carburetor throats. This translates into a leaner fuel mixture upon initial acceleration: less air velocity draws less fuel pass the needles. A heavier oil will slow down the pistons and give you a richer mixture initially: higher air velocity (because of restricted throat) draws more fuel.
Some people use automatic transmission fluid (ATF), which I believe is close to the same weight as MMO. This is thinner than 20W oil and lets the pistons rise faster. This may cause your engine to hesitate on acceleration. Some people use 30W or 20W-50 which might make it sluggish on acceleration. It all depends on your setup. If everything is stock and set to original settings, then you may want to start with 20W dashpot oil. You can try different weights of oil and see what you get.
Remember of course, you mileage may vary!
Mark
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Actually I think Marvel Mystery oil is akin to gas additives that were recommended back in the day, upper cylinder lubricant.
But I wouldn't put it in my dashpots and have no idea if it makes things better, but have heard some say it helps with sticky valves.
Keoke--I havere-read, don't know the problem, maybe I am dense, I did say 30 MPH instead of 20, but don't see that as real relevant.
But I wouldn't put it in my dashpots and have no idea if it makes things better, but have heard some say it helps with sticky valves.
Keoke--I havere-read, don't know the problem, maybe I am dense, I did say 30 MPH instead of 20, but don't see that as real relevant.
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MarkA said:
With H6's on a modified BN2 running four oz. springs, I actually get better throttle response with NO dash pot oil. Just the slightest bit of ATF for lubrication of the parts. No flat spots or hesitation. As you say, it all depends.
D