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| chl_carlin |
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can some one help me to decrease the amount of mechanical advance on the dizzy. as i need to do this so i can bring the ignition timing to 12 -15" without ping. plz help. some pics could be great too.
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| The Dog |
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Isn't std ignition timing on a 250 8 deg?
If you really wanna crank the timing up, try putting a t piece in the vaccuum line that runs to your dizzy. Hook this extra line to a windscreen washer bottle. This sucks a relative amount of water into the carby thus reducing detonation. the advantage I found with this method over using any sort of pump is that, to a certain extent it sucks in the water ( thus creating water injection) at a relative rate ie. the harder you rev it the more water it draws. This sounds "agricultural" but it works as good as any I've heard of in regards to setup costs and ease of installation 
_________________ You'll ride a black tornado across the western sky
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| fastleno |
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BAHHHHHA you for real funny stuff.
i am guessing you after 12_15 at idle and full at revs swing out to 35-38 here is a quick guide first you have to pull ya dissy apart and adjust the stoppers where the weights swing out to, just use the pliers and bend em in a bit, (few mm inward to the center of the dissy) put the dissy at 12-15 fire it up and check it with a timing light make sure its at 12-15 the spin the motor up to say 4000 rpm the weights should be at full advance and check timing to see if you have the full advance you want, easy as that, you might have to pull it down and muck about to get it right a few times but thats ho its done but also the strength or the springs on the weights also plays a big role, lighter and heavier springs will depict when the advancing ramp starts, a heavier spring might not advance the timing untill 4000rpm whereas a light one could get you full advance at 3000rpm, thats basically how to graph a dissy, easy to do but put aside a few hours cos you might have to pull the dissy down and adjust springs and stoppers a few times. |
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| cjh |
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The proper way to do dizzy's is to pull it apart, total strip done, clean, check the bush for wear, make sure everything is free to move.
With the weights out, add a small bit of weld to the slot where the poles stick through, this is where the weights are at rest, so as to take up the advance for when at idle, then file it with a chainsaw file. When partly assembled spread out the outer spring mountings, just lightly. Depending on how much weld you add, and how much you file out will determine where you can have the dizzy set at. It is trial & error, but when you have done as many as I have over the years, you can get it right first go, good luck with it. Anyway, you get your 12 to 15 at idle, recommend no more than 14 BTDC at idle, and no more than 32 to 36 at revs. I have had success with this method using a comp ratio as high as 10.6:1 on pump fuel and no pinging.
_________________ http://youtu.be/jJTh9F3Vgg0 |
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| fastleno |
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either either same s**t diffrent bucket, there is a few difrent ways to graph a dissy, both the ways above are a backyard fix, the PROPER way is to spin the dissy up in the proper machine and change the size of the weights, springs, base plate and so on, so shut the f**k up and go play with C**k sum more.
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| chl_carlin |
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sounds great, ill have a look at one of the worn out ones in the shed. cheers guys
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| chl_carlin |
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fastleno wrote: either either same s**t diffrent bucket, there is a few difrent ways to graph a dissy, both the ways above are a backyard fix, the PROPER way is to spin the dissy up in the proper machine and change the size of the weights, springs, base plate and so on, so shut the f**k up and go play with C**k sum more.
you are right but no need to be an a**hole |
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| fastleno |
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chl_carlin wrote: fastleno wrote: either either same s**t diffrent bucket, there is a few difrent ways to graph a dissy, both the ways above are a backyard fix, the PROPER way is to spin the dissy up in the proper machine and change the size of the weights, springs, base plate and so on, so shut the f**k up and go play with C**k sum more. you are right but no need to be an a**hole |
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| chl_carlin |
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yeh i desided to get it done properly when i get it jetted on the dyno, cos the 500 holley i put on it has got the same jets in it from when it was on a 350 chev.
has any one ever made a custom bush with a needle roller bearing. i have the skills to do this but would it get enough oil
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| tickford_6 |
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Posts: 6449 Joined: 11th Nov 2004 |
a 500 seem overly lagre for that engine. what jets are in there now? pretty sure the factory jetting is 71s or 72s
95% of the time the factory jetting is spot on or only needs change one up or down. |
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| ebfairmont3.9 |
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i dont no about the old dizzys but why couldnt ya throw it to 15deg. and block the vacuum advance off???
_________________ 1994 ED Fairmont Champaign Gold - AU Series II Intech 4.0L - EL EFI - Thermo Fans - 4.11 LSD - Pacemaker 4480 Into Custom 3" Exhaust - Shift Kit |
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| cjh |
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ebfairmont3.9 wrote: i dont no about the old dizzys but why couldnt ya throw it to 15deg. and block the vacuum advance off???
Because the Mechanical advance would still take it up there. A 600 Holley works well on a 250 Xflow, with the right headwork and cam, and exhaust with the dizzy done right.
_________________ http://youtu.be/jJTh9F3Vgg0 |
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| The Dog |
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That thing of yours is kinda warm tho cjh
. We used a 465 on a more wild than mild 250 in a cortina and it was damn quick and never had any issues. By the same token I used a 500 on what was basically the same engine and it always underperformed. I always blamed this on the fact it was a 2 barrel 
_________________ You'll ride a black tornado across the western sky
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| tickford_6 |
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Posts: 6449 Joined: 11th Nov 2004 |
cjh wrote: Because the Mechanical advance would still take it up there. A 600 Holley works well on a 250 Xflow, with the right headwork and cam, and exhaust with the dizzy done right. it's not realy the best setup. 600cfm is far to much. a 450 or if you want a vac second a 465 would be better. but even at %100 efficiency the engine doesn't need that much carburation. you might loose a few hp up top (like 3 or 4) witht he smaller carb but the midrange and low rpm manners will be far improved. |
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| cjh |
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tickford_6 wrote: cjh wrote: Because the Mechanical advance would still take it up there. A 600 Holley works well on a 250 Xflow, with the right headwork and cam, and exhaust with the dizzy done right. it's not realy the best setup. 600cfm is far to much. a 450 or if you want a vac second a 465 would be better. but even at %100 efficiency the engine doesn't need that much carburation. you might loose a few hp up top (like 3 or 4) witht he smaller carb but the midrange and low rpm manners will be far improved. It was making over 170 RWHP with a 2.92 LSD & single rail and needed a bit more tuning to achieve more. Low down torque was not a problem, it would smoke 265/70 15's. Also raced a BA XR8 Auto, twice, and won.
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