distrubutor identify and gap/dwell set

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Lorna c
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distrubutor identify and gap/dwell set

Post by Lorna c »

I've been reading about these Distributors and I believe I have the smog one ,but there are no numbers stamped on it I believe the total advancement is past 35 degrees could someone tell me for sure. Also being self-taught mechanic that I am does the dwell have more to do with the timing set, rather then necessarily the distributor do I understand the works of all this correctly or am I way off.. pls if someone on super bowl Sunday is looking here , pls help me .. lol .. thx
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Re: distrubutor identify and gap/dwell set

Post by jrusso07 »

Waiting for game to start..drinking beer, trying to stay warm....

You need to remove the points and point plate to see the markings on the distributor cam. They are marked on the wings where spring pivots attach. See this pic https://farm3.staticflickr.com/2900/146 ... 2fbb_o.jpg

7.5 is non-smog.

Dwell is the angle that the points remain open. It is directly related to point gap. Set the gap right and dwell will be right. You need a dwell meter to measure the dwell angle
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Re: distrubutor identify and gap/dwell set

Post by notoptoy »

Dwell can be thought of as a measure of the points setting, if the points are set right your dwell should be darn close. Timing does not affect Dwell. As far as your distributor, you have to remove the breaker plate and read the number on the points Cam.
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Lorna c
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Re: distrubutor identify and gap/dwell set

Post by Lorna c »

no I mean the setting of the points kinda dictate when and how much fire is built up before ignition right ? too soon not good too late too much built up and pool , (?) if so then a tweak here and there,, example= my timing is set to fire at 5-7° btdc... so it's not too low on the idol end to send things backwards inside on excelertion (not sure of the jargon) if I do have the smog distrubutor , then fiddling with the timing is not so textbook exact with my mix of things . the gaps are quite different between the different distrubutors ,, sorry for long question but this is what makes me not commit to a gap/dwell. and things .. is it wrong to kinda fiddle and see how the car responds to different sets -? not textbook , but close to textbook ? because basically the # s in the book I've used and the car doesnt run as well as some settings in the middle of txt . soooo , my point , if my timing is different than text book should the gap change a touch too ? my valves are at the .17 as far as I know . haven't been in there in a few months ,but they were when I did them . . but this stuff seems pretty intricate so it brings the question , ... if ones off from textbook should they all follow ? the 3 main measurements . valves, dwell , and timing ? not so much sparkplug . anyway , is that too much thinking for this or is it something that's right / better way to do a motor timing kinda thing ? do I understand things circling this or not ?
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Lorna c
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Re: distrubutor identify and gap/dwell set

Post by Lorna c »

jrusso07 wrote:Waiting for game to start..drinking beer, trying to stay warm....

You need to remove the points and point plate to see the markings on the distributor cam. They are marked on the wings where spring pivots attach. See this pic https://farm3.staticflickr.com/2900/146 ... 2fbb_o.jpg

7.5 is non-smog.

Dwell is the angle that the points remain open. It is directly related to point gap. Set the gap right and dwell will be right. You need a dwell meter to measure the dwell angle


yes I have a dwell meter .. I was told that that's the correct way to measure points . if the dwell is correct the points will be . now why is one way considered better ? or is it his opinion and there like a coin flip ? as I learned this timing stuff I understood it as I heard it all come together for the first time . perfect timing I think they call it ,. well it all made sense when that happens . it all works together and individual . the cam rotates the distrubutor spins throwing the spark to the plugs like a quarterback throws along pass timing it just right at max compression . the valves then open to vent , spark fires sending piston down (horsepower on timing for that ) then vacuum and centrifical force sucks piston back up , and timing( turning distrubutor thing for whatever ° btdc , is the base rythum to match all the others to ?... is that the idea of timing ? so one changes they all change ?
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Re: distrubutor identify and gap/dwell set

Post by AidanDawn2000 »

I don't 100% follow you but this is what I have hard on the subject:

Dwell is just a "truer" measurement of point gap, as uneven wear can through off a feeler gauge.

You really need to confirm which dizzy weights you have. Either remove breaker plate and check stamping or, if you have a timing light, just see how much mechanical advance is being added (make sure to plug vacuum line and make your initial measurement below ~900rpm)

I don't think the valves will have changed in a few months.
Oil a little low? Time to get a longer dipstick:)
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Re: distrubutor identify and gap/dwell set

Post by AidanDawn2000 »

If you want a visual there are manny YouTube videos showing the whole process.
Oil a little low? Time to get a longer dipstick:)
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Re: distrubutor identify and gap/dwell set

Post by Lorna c »

OK thank you
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Re: distrubutor identify and gap/dwell set

Post by Gregs672000 »

Dwell is another way of measuring point gap. The points act as an off/on switch, telling the coil when to fire. Set the gap with a feeler Guage when the lobe on the shaft that the points ride on is causing the points to be fully open.

As noted , remove the top plate that the points attach to in oder to be able to see the numbers that tell you what distributor curve you have.

Since you are just learning, might suggest some utube or other resources (basic car manual) to understand some main systems and how they work and why.

Briefly, regarding ignition timing, the fuel is fired before the piston reaches the very top of its travel in orider to allow the fuel time to burn. The amount of lead time it needs to burn the fuel increases as the speed of the engine (RPM) increases. Thusly, the distributor advances the timing accordingly. However, if you advance it too much the fuel will start to explode too early, causing the engine to fight itself because the piston is too far down in the cylinder and trying to come up but the explosion is pushing it down. Bad.
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Re: distrubutor identify and gap/dwell set

Post by jrusso07 »

To measure dwell the car has to be running so you won't be able to set point gap.

I set gap with feeler gauge (use brass!)

Then I run the engine and see what the dwell is.

Iterate a few times to get it set where it runs best
Joe

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Re: distrubutor identify and gap/dwell set

Post by Lorna c »

Got I I'll take off plate today or tomorrow. I thought some beebee's would come out if I took it off . But either way I need to know so I will .
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Re: distrubutor identify and gap/dwell set

Post by AidanDawn2000 »

I think there is a small gap you can look down through while turning the motor and you can see to see the numbers....if you don't want to take the plate off.
Oil a little low? Time to get a longer dipstick:)
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Re: distrubutor identify and gap/dwell set

Post by Lorna c »

Is turning the front timing belt n motor the same instead of the motor ? I'm going to try that . Something is causing rich . I looked and read the other post on needles and my situation is I believe worn needles . I'm not too sure how they worn so soon but they're shiny up top part of shaft . I thought the entire needle was worn dull but it's the shiny part huh ? I do have other needles in my parts thing but idk how to tell if they're old or new . So I'll be looking into that tomorrow for sure .
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Re: distrubutor identify and gap/dwell set

Post by Gregs672000 »

The needle also slides into a fuel nozzle, and they can wear too. Carefully replacing your needles may help but might not completely solve the issue. How much have you played with the adjustment dial on the bottom of the carbs/fuel nozzle? Tightening it causes the nozzle to raise up, leaning the mixture since it moves the nozzle further up the gradually thickening needle. If the needle is worn (thinner) or the nozzle is wider more fuel gets pulled past the needle/nozzle by the engines vacuum causing a rich mix. Start the car and get her warm, and check your air flow on both carbs to make sure they are balanced and flowing equally (you will need an air flow measuring device, like a unisyn or similar... ask about it if you don't have one) then replace the old plugs with new plugs so you are starting clean. Fully lean out the carbs by Tightening the dial on the fuel nozzle to fully tight, then turn it out say a full turn or two, keeping both equal for each carb (keep track, there is a raised bump on the dial to help you figure out if you went a full turn as I recall). Start the car (if it won't start or stay running then increase the fuel by loosening the dial equally on both carbs until it does), and once warm do the "raise the piston in the carb" test by pushing up the push pin on the underside of the carb... it raises the carb piston a bit, essentially turning off THAT carb and TESTING THE OTHER carb. The engine rpm should go up slightly, then the engine should act like it's running on two cylinders but should keep running. If it does run you know that carb is delivering enough fuel, otherwise richen the mix on the carb you are testing (NOT the one you're pushing up the piston on) by a half turn looser and recheck, adjusting until it does as described. Then move to the other carb and do the same thing, keeping the adjustments the same carb to carb. Now, rev the engine and if it pops or backfires through the carbs then it's too lean. If OK, read your plugs... black too rich, tan just right, white too lean. You only need to check plugs on 1 and 3 or 2 and 4, but you can check all 4 if you like. Adjust your dial accordingly and see if you can get her to idle well and not huff black out the tail pipe at idle, and continue to check your plugs with the goal of getting them tan in color while not backfiring through the carb (always means the fuel mix is too lean). You also want to read the plugs after a bit of a drive, so take it out for a drive and see how she runs... given enough time you will start to feel how the engine runs if it's too lean... it has a "starving" feeling... not just flat but kinda jumpy but hesitates. Too rich will be just flat and boggy. Find a very long straight somewhere where you can drive the car at say 4000rpm for a bit, then quickly but safely pull over and shut the engine off quickly, not allowing it to idle or decelerate for long (I would actually shut off the car as I let off the pedal and coast to the side, but be sure to not lock your steering wheel when you switch off the ignition!), pull your plugs and read them (bring cloth gloves, they're HOT)... that should give you an idea of how it is running while being driven, as your idle mix with worn carb needles can be rich due to worn parts and you can sometimes lean it out and make it right (tan plugs) AT IDLE but be too lean elsewhere which is not good for the engine (safer for the engine to be too rich vs too lean). It may be a compromise, and as parts wear out it will get harder to get it to work properly everywhere until the nozzles and needles are changed out, and hopefully the throttle shafts themselves are not worn so much that they allow too much air past them, causing a lean condition (intake leak). This is a process as you make adjustments, try them out, read plugs, etc over and over until you get the best adjustment.
Hope this Helps! This process is why I LOVE having a wide band Air/Fuel meter for my car, as I don't have to read plugs anymore and just KNOW what the carbs (in my case Dellortos) are doing all the time.
Greg Burrows
'67 2000 #588
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Re: distrubutor identify and gap/dwell set

Post by Gregs672000 »

One other factor to keep in mind is having proper weight oil in the carbs themselves to keep the piston from raising too fast when you stomp on it...marvel mystery oil or ATF works well.
Greg Burrows
'67 2000 #588
Tacoma, WA
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