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#1
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Point gap question
What is a good point gap for a distributor using an MSD box. I need gap not dwell. Last question is how do you use a dwell meter? Thanks.
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05 Hemi Magnum R/T (Current) 71 Satellite Custom (Current) 85 Dode Ram /6 (Current) 73 Swinger 76 Ram 3/4 Ton 77 Ram Shortbed 1/2 Ton 74 Duster w/318 92 Sundance 89 LeBarron Convertable Turbo |
#2
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.017
Dennis Jokela |
#3
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point gap should ALWAYS be set by dwell. the gap is given because you wont always have a dwell meter, but you can lose points at any time, and the gap method will get things close enough to run fairly well. the coil doesnt care how far the points open, they can open a mile if they can get closed again before the camshaft has turned 32 degrees. it DOES care how LONG they are open. this is what dwell is... the length of time the points stay open as measured in degrees of camshaft rotation. this is what "charges" the coil for its next firing.
the breaker cam determines dwell in a points type of ignition. things are designed so that .016" of point gap gives the required amount of dwell for a V8 engine. fwiw, .001" of point gap is usually worth about 2* of dwell. to use a dwell meter, you should follow the directions that came with it. as for being any more specific, i cant be. the last time i used a dwell meter was in 1984. i dont own one, and have no plans to ever put myself through the pains that would require the use of one. the electronic distributors are SO much easier to deal with, and they dont wear or burn points. there are no points, so there is no point bounce to worry about. no rubbing blocks to wear, and no lubricant to worry about getting on the contacts causing them to burn. so i guess my question for you would be: why are you using a points system?
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Where are we going?... And why am I in this hand-basket? 84 D250/440/3.54:1 dana 60/16" wheels, 31" tires/A-727trans/3" header mufflers/weighs 5000 lbs/13.22 sec @ 103+ mph. |
#4
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the dwell meter should have two leads to the battery terminals and one to the distributor side of the coil. ( that is the wire leading from the distributor to the coil ) that is if I remember right, it has been a bunch of years for me as well....
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#5
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Thanks for the help, and the info. I haven't used points in a coons age eithier. I have set them before but as of recent is been the peice of cardboard method! My dwell meter only has two leads, it is a Sunpro that I have used for years so I know its a good peice of gear. Anybody remember how to set points using a dwell meter?
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05 Hemi Magnum R/T (Current) 71 Satellite Custom (Current) 85 Dode Ram /6 (Current) 73 Swinger 76 Ram 3/4 Ton 77 Ram Shortbed 1/2 Ton 74 Duster w/318 92 Sundance 89 LeBarron Convertable Turbo |
#6
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more dwell = more gap. so if you are shooting for 32-34*, you set the gap at .016", button the dist back up, and check the dwell. IF all is well, you will be real damned close. if you have 30*, you need to open the gap about .001-.002". if you have 36*, you should close the gap about the same amount, .001-.002".
each adjustment requires removal of the dist cap, which means that you cant set the dwell with the cap on, because the engine must be idling or at least cranking to measure the dwell. only GM addressed this issue by putting a sliding "window" in the cap, allowing the dwell to be adjusted while the engine is running. now... if you can get the use of a distributor machine, you CAN adjust things with the dist cap off. except for the GM dist's, this is the way to set dwell. as for connecting the dwell meter, i cant say about yours. one lead will certainly connect to the points side of the coil. this wire should be marked with a green boot or green insulation. the other wire i havent a clue, unless it is a ground, in which case it should be black. i suppose it could be connected to the other side of the coil, but this is just guessing. i wouldnt think it would be connected to the + side of the battery, but who knows. one last thing, and it is important: the timing is set AFTER setting the dwell, ALWAYS! the opening of the points is what determines timing, adjusting the dwell after setting the timing throws the timing off by the same amount the dwell changes.
__________________
Where are we going?... And why am I in this hand-basket? 84 D250/440/3.54:1 dana 60/16" wheels, 31" tires/A-727trans/3" header mufflers/weighs 5000 lbs/13.22 sec @ 103+ mph. |
#7
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Good advice, the points are set at .017 and it runs and starts great. The engine is a slant 6 with MSD box. I had points on my Satellite but man that got old really quick. Creative what is your opinion of those petronix upgrades for points ignitions? I have an MSD 5 box which limits what I can do as far as points and electronics but it will run the amplifier.
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05 Hemi Magnum R/T (Current) 71 Satellite Custom (Current) 85 Dode Ram /6 (Current) 73 Swinger 76 Ram 3/4 Ton 77 Ram Shortbed 1/2 Ton 74 Duster w/318 92 Sundance 89 LeBarron Convertable Turbo |
#8
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ok... except I made a mistake here. i used the dwell for a V8 engine as the example, not a 6 cylinder. i guess i wasnt clear about that. sorry.
the point gap/dwell for a 6 cyl is different... and a 225 is different from a 251 BUT... i didnt screw up as bad as i might have. the book i have gives the point gap for both engines as .017-.023" with a dwell angle of 40*-45* for the 225 and 36*-42* for the 251. this means that you are set at the tight side. not bad, but not good. as the rubbing block wears, the points slowly close (they wont open as far), so you really should gap them to the larger side. as for the dist, i dont use a "performance" dist, other than my original distributors arent "stock". well, better clarify that... i have several BB dists, one of them has been modified. it has been phased and curved for the 440 in my truck. it has the stock vacuum adv and the stock internals. the other 2 of them are stock. my 360 dist, which is currently in use, appears to have had the strong spring removed from it, as all the timing appears to be in by 1500 rpm. i am cheap... unless someone gives me a good reason for doing something as expensive as buying a distributor (the parts stores here want something like $200 for a replacement--- meaning rebuilt unit), i am going to run the original. this does NOT mean that i am above correcting (or having someone correct) known problems with them. where the pertronix, mallory, MSD, jacobs, or MP distributors are concerned... in MY opinion, they arent worth the money, unless you are going for all-out, race only applications. a good stock dist can and will handle any demand you put on it as long as you maintain it. if you need performance from it, that is inexpensively done, too. FBO phased and curved my dist to my 440 for $100... and it IS my original dist. the originality doesnt really matter to me, after all, the 1978 440 is in a 1984 D250, but it MIGHT matter to those of us that insist on having a "numbers matching" car. if you want to upgrade to an electronic system, i would recommend a visit to the local salvage yard. get the dist, ballast resistor, ecu and wiring harness from any /6 vehicle. shouldnt cost more than $25 or so. you dont need the ecu anyhow, because even i (being the "king of cheapness") wouldnt use it, i would buy a new one. you DO, need the plug that connects to it, and the wiring that goes to the dist from it. the rest you can make up as you install it. of course, the MSD you have will replace the ecu, so all you may really need is the dist. get the other stuff anyway if you do this conversion... it could save you some money and walking if something goes sour. my truck is set up so that i can replace my hi-perf ignition system with a stock system in the length of time it takes to change ecu's. the ecu i am currently running is a hi-perf stock replacement thing from FBO Systems. it is literally a straight bolt on. and with coil, dist cap, ballast resistor, and rotor, it cost me $117, including shipping. it does, however, deliver enough spark to make you 'sing for joy' (or something) should you upset it... lol. for a daily driver, it is good enough. and it is a vast improvement over the stock ecu. as for the MSD 5, go ahead and run it. i have nothing against MSD, and will someday probably own one (or something similar), but i need OTHER things first. i would be a LOT better off if i spent the $250 or so for the MSD 6AL on a set of taylor extreme service plug wires. the MSD doesnt do much good when the headers burn the ends off of my wires.
__________________
Where are we going?... And why am I in this hand-basket? 84 D250/440/3.54:1 dana 60/16" wheels, 31" tires/A-727trans/3" header mufflers/weighs 5000 lbs/13.22 sec @ 103+ mph. |
#9
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Long time but as I remember............
Hook the dwell meter up with the coil wire off and the distributer cap removed. Loosen the screw that holds the points, then turn on the ignition and have someone crank the engine. Inserting a flat screwdriver into the slot between the dist plate and points, set the dwell to 30. Put the cap and wire back on and start the car checking the dwell. Do this till dwell is at 30.
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#10
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I use to have single point dist i'm driving pow pow pow switched to mp with crome box no problems yet over four years
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#11
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Quote:
__________________
Where are we going?... And why am I in this hand-basket? 84 D250/440/3.54:1 dana 60/16" wheels, 31" tires/A-727trans/3" header mufflers/weighs 5000 lbs/13.22 sec @ 103+ mph. |
#12
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Thanks fellas, I will dwell it up tomorrow. One last questions is where does the meter hook up to? I have a positive and negative connection?
__________________
05 Hemi Magnum R/T (Current) 71 Satellite Custom (Current) 85 Dode Ram /6 (Current) 73 Swinger 76 Ram 3/4 Ton 77 Ram Shortbed 1/2 Ton 74 Duster w/318 92 Sundance 89 LeBarron Convertable Turbo |
#13
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More dwell = less gap
Not trying to be argumentative, but as the dwell angle increases, the point gap decreases. This is because dwell angle is the number of degrees the distributor cam turns from the time the points close until they open again. A larger point gap will cause the points to open sooner and close later, thus decreasing dwell.
For a six lobe breaker point cam, 38 degrees of dwell is common and for an eight lobe cam, 30 degrees is common. The point gap depends on the roundness of the lobe. A new sharp lobe will have less gap than an old worn or modified lobe with the same dwell measurement. Years ago, "hot rodders" rounded the breaker cam lobes in order to lessen point float at higher rpms. With the rounded lobes, the gap was smaller with the same dwell measurement. Reading the contact points in order to use the correct condenser became an art also. Rember to adjust the ignition timing after tinkering with the dwell angle. Increasing dwell angle advances the ignition timing while decreasing dwell retards the timing. This point gap thing came up just a few days ago at a friends shop. A dealership mechanic with several years experience came by to shoot the bull and conversation lead to him saying he had "heard of points, but never seen them." What year did point type ignition fade away in production cars? My lawn mower still has them! |
#14
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I think the point thing faded out in the mid 70's. My 77 Ram had an electronic set up and it was a slant also. Its tough to find someone who really knows points. I know back in the day guys could really whip up some black magic with these things and really make them bump!
__________________
05 Hemi Magnum R/T (Current) 71 Satellite Custom (Current) 85 Dode Ram /6 (Current) 73 Swinger 76 Ram 3/4 Ton 77 Ram Shortbed 1/2 Ton 74 Duster w/318 92 Sundance 89 LeBarron Convertable Turbo |
#15
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This was the end result, using a sun meter attach the black to a ground, attach the red to the wire going to the distributor and turn it on. Check the dwell and ten cut it off and adjust. I was only 10 or so out on the dwell but man did it make a difference. If anyone is interested there is a good article on distributors in hot rod mag this month!
__________________
05 Hemi Magnum R/T (Current) 71 Satellite Custom (Current) 85 Dode Ram /6 (Current) 73 Swinger 76 Ram 3/4 Ton 77 Ram Shortbed 1/2 Ton 74 Duster w/318 92 Sundance 89 LeBarron Convertable Turbo |
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