Setting timing on a 225??
- Thread starter zcook13
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Have fun getting to the bolt. I used a 1/4 swivel on an extension from the bottom. My dist wrench was just a hair short!
nm9stheham
Well-Known Member
When you move that slot under the distributor body, do it a little at a time. Keep in mind that 10 degrees movement under there is 20 degrees of crank timing change. I've overdone it without thinking and had to go back a take some the change out 'cuz I went too far.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Yeah, I figured that out too, which is why I just snugged the bolt down just enough to make the initial setting, then pulled it back out for final tightening. Its just too frustrating to try and do it all down there, with bigarse hands.
Sarge
Power timing. This is very important.
Inside the dizzy is a mechanism that automatically advances the timing beyond what you initially set it to. This amount can be in the range of about 28 to 36 degrees, in oem units.It takes some 2400 rpm or more above idle,to achieve this full rpm. This timing has to be kept at a safe value so that your engine isnt damaged under full load/ full power timing, due to detonation. Detonation wreaks stuff. Important stuff like bearings and pistons. This safe full-power timing is usually around 36*. The factory units have this built in. But when the end user starts adding timing at idle, the same amount gets added to the other end. NOT good. So whatever you add at idle, you have to subtract at the top.
-The safest way to do this is to determine beforehand what your dizzy is doing. What I do is simply check the idle timing( at 0 to 10*BTDC), and then rev er up until it stops advancing, and record the numbers. Supposing your idle-timing is currently set a 5*BTDC, and it stops advancing at 35*. Doing the math means ; 35 - 5 = 30* in the dizzy. Thats about right for a stocker( 35* being less than the safe limit of 36*).
-Now you might want to increase the idle timing to 16*. Well 36 - 16 = 20* would be the new limit in the dizzy. You would have to modify the automatic advance mechanism to do this before you apply full-load/full-rpm to the engine, to prevent internal damage. At light-load/lower rpms the engine might happily accept the extra timing. And it seems there is a wide range of acceptable timings at those load settings. However, at full-load/full-rpm, there is no such variation. 36* is pretty much it, no matter what the engine combo. There is a bit of wiggle room in this number depending on the fuel used.
-Now the thing you really want to know is how to limit that automatic advancing feature, right? well 1st lets call that feature; centrifugal advance. Once you have the dizzy out, you will see there are 2 flyweights in there, that fly out with rising rpm and return with falling rpm. The amount of motion is governed by a slots and pins arrangement. The length of the slot determines the amount of travel. So all you have to do is limit the slot length and you are in business.
-So measure the slot length, and the pin od.Subtract the two and you are left with a number that represents the effective slot length and the advance that you previously measured by revving it up and idling and doing the math. I dont recall the pin size, so Im gonna guess at the following example. Say the slot is 4/10 of an inch; thats .400, and the pin is 5/32;thats .150. The math says; .400 - .150 = .250 is the effective slot length. And your centrifugal was 30*, as previously measured. again the math says; .250/30 = .008 inch per degree. Now you want to try 12* idle timing, and want to limit power-timing to 32* to allow up to 4 more degrees of initial idle timing to play with. So the math for that would be 32 - 12 = 20* centrifugal. and the effective slot math would be; 20* x .008 = .160 , now dont forget to add back the pin size (.150). So; 160 + .150 = .310, the new total slot length.
-So in this example you would have to shorten the slot from .400 to .310. This is usually done by welding. Or brazing.I like brazing cause its a bit easier to hand file. I also like to put a bit of extra material in there for two reasons. Firstly,its easier to file some more out than braze some back in and refile, and 2) It allows me to make a pin-matching cradle in the brass to prevent the pounding out of the brass over time.
-It sounds like a lot of work for very little gain, like you said. But it was really worth it on my slanty. The engine really woke up, and the torque/mpgs were really noticeable.
-Theres a bit more bad news. To gain access to those slots, the cam will have to come off the top. And thats often a battle with that stupid little spring that Chrysler put in there, to do the holding down. Its not bad getting it off, but back on is often a challenge. After I get it apart I drill and tap the top of the shaft for a tiny machine screw. Problem solved.Well not quite; You have to figure out a retaining system under that nice new screw. A bushing and properly sized washer and a lock washer for the screw did it for me.
-If this is a daily driver, it would be best to obtain a spare dizzy to be modded beforehand, as this modding can really chew up some hours.
-Looking back, this is one of those mods that Im really glad I did, despite all the work and hours. Your results may vary. All the best to you.
Sarge
Power timing. This is very important.
Inside the dizzy is a mechanism that automatically advances the timing beyond what you initially set it to. This amount can be in the range of about 28 to 36 degrees, in oem units.It takes some 2400 rpm or more above idle,to achieve this full rpm. This timing has to be kept at a safe value so that your engine isnt damaged under full load/ full power timing, due to detonation. Detonation wreaks stuff. Important stuff like bearings and pistons. This safe full-power timing is usually around 36*. The factory units have this built in. But when the end user starts adding timing at idle, the same amount gets added to the other end. NOT good. So whatever you add at idle, you have to subtract at the top.
-The safest way to do this is to determine beforehand what your dizzy is doing. What I do is simply check the idle timing( at 0 to 10*BTDC), and then rev er up until it stops advancing, and record the numbers. Supposing your idle-timing is currently set a 5*BTDC, and it stops advancing at 35*. Doing the math means ; 35 - 5 = 30* in the dizzy. Thats about right for a stocker( 35* being less than the safe limit of 36*).
-Now you might want to increase the idle timing to 16*. Well 36 - 16 = 20* would be the new limit in the dizzy. You would have to modify the automatic advance mechanism to do this before you apply full-load/full-rpm to the engine, to prevent internal damage. At light-load/lower rpms the engine might happily accept the extra timing. And it seems there is a wide range of acceptable timings at those load settings. However, at full-load/full-rpm, there is no such variation. 36* is pretty much it, no matter what the engine combo. There is a bit of wiggle room in this number depending on the fuel used.
-Now the thing you really want to know is how to limit that automatic advancing feature, right? well 1st lets call that feature; centrifugal advance. Once you have the dizzy out, you will see there are 2 flyweights in there, that fly out with rising rpm and return with falling rpm. The amount of motion is governed by a slots and pins arrangement. The length of the slot determines the amount of travel. So all you have to do is limit the slot length and you are in business.
-So measure the slot length, and the pin od.Subtract the two and you are left with a number that represents the effective slot length and the advance that you previously measured by revving it up and idling and doing the math. I dont recall the pin size, so Im gonna guess at the following example. Say the slot is 4/10 of an inch; thats .400, and the pin is 5/32;thats .150. The math says; .400 - .150 = .250 is the effective slot length. And your centrifugal was 30*, as previously measured. again the math says; .250/30 = .008 inch per degree. Now you want to try 12* idle timing, and want to limit power-timing to 32* to allow up to 4 more degrees of initial idle timing to play with. So the math for that would be 32 - 12 = 20* centrifugal. and the effective slot math would be; 20* x .008 = .160 , now dont forget to add back the pin size (.150). So; 160 + .150 = .310, the new total slot length.
-So in this example you would have to shorten the slot from .400 to .310. This is usually done by welding. Or brazing.I like brazing cause its a bit easier to hand file. I also like to put a bit of extra material in there for two reasons. Firstly,its easier to file some more out than braze some back in and refile, and 2) It allows me to make a pin-matching cradle in the brass to prevent the pounding out of the brass over time.
-It sounds like a lot of work for very little gain, like you said. But it was really worth it on my slanty. The engine really woke up, and the torque/mpgs were really noticeable.
-Theres a bit more bad news. To gain access to those slots, the cam will have to come off the top. And thats often a battle with that stupid little spring that Chrysler put in there, to do the holding down. Its not bad getting it off, but back on is often a challenge. After I get it apart I drill and tap the top of the shaft for a tiny machine screw. Problem solved.Well not quite; You have to figure out a retaining system under that nice new screw. A bushing and properly sized washer and a lock washer for the screw did it for me.
-If this is a daily driver, it would be best to obtain a spare dizzy to be modded beforehand, as this modding can really chew up some hours.
-Looking back, this is one of those mods that Im really glad I did, despite all the work and hours. Your results may vary. All the best to you.
cuda dad
Well-Known Member
Much easier to remove the oil filter to access the bolt on the bottom of the distributor. I set my 67 at 5 degrees Before TDC as prescribed and it runs great. No pinging at all, plenty of power. Of course it's completely stock.
Thanks for heads up, nm9stheham!
Another good tip! Thanks, cuda dad!
Thanks, AJ! I don't know what's worse, you being able to explain that so well or the fact that I completely understand it! Lol. I generally always set my timing to max (36*-38*) on my Ford's and let the initial fall where it wants to. Great explanation above. I've messed with the springs and such and have have heard of putting a rubber cap on the tab to limit the advance slotting. Not sure I really want to tackle all of that. And if I did, I'd definitely get another distributor to tinker with first. For now, she has other issues, loose timing chain and valve adjustment, and my tranny just took a dump on me last Friday, so it'll be this spring before I tinker with anything. Any thoughts on using an aftermarket distributor with the adjustable advance mechanism? Other than the outrageous cost compared to a stock distributor of course.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Oh boy, on the aftermarket ones! If you can find one for the slanty, you will save a ton of time. I had mine in and out so often, I just kinda threw it in the general direction of the hole and it would practically find its own way home! For me, because I already know my way around, and know what the sbms I work on around here need, its hard to justify the money. If I was a newbe it would be money well spent. And if I was working in a shop that charges the big bucks, its no-contest, cheaper for the customer in the long run.
Thanks for the help, AJ! Lot to think about now. First gotta just get her back on the road.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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I hear ya.
FWIW, I rebuilt my first 904 in 75 at the ripe young age of 22. I got forced into it, like most of us at that age, due to lack of funds. I think as far as A/Ts go, that unit is pretty simple. Even the valve body isnt too complicated. I was a little apprehensive, but it worked out perfect. I was freshly married and living in an 8th floor apartment.Tore that puppy apart up there, and rebuilt it (now cleaned at the car wash), on the dining room table. Hers no less. She came with her new furniture.And a brandy new mattress set I might add. I had nothing.
What was my point again? Oh yeah, I remember. Trannies. If you got a circlip pliers, and a feeler gauge and know how to read, its a piece of cake. Be sure to airtest it before the VB goes back on. Oops, you will need a custom spring compressor to change out the lip seals in the clutches.I made one up.Its not complicated. A big bolt, about 5/8 x 6 with a nut and a stack of washers 1 in high, 2 flat bars about 1/2x1x6 and centerdrilled for the bolt, and a ring about 4"dia.x 1 hi. You will have to finalize the sizing when you get there as Ima guessing here. Honestly its easy. At least until you get to the VB.Heh-heh. If you get a shift kit, they have pretty good pics. At least the TransGo kits do/did.A camera can be a good friend. As ever; all the best 2U
FWIW, I rebuilt my first 904 in 75 at the ripe young age of 22. I got forced into it, like most of us at that age, due to lack of funds. I think as far as A/Ts go, that unit is pretty simple. Even the valve body isnt too complicated. I was a little apprehensive, but it worked out perfect. I was freshly married and living in an 8th floor apartment.Tore that puppy apart up there, and rebuilt it (now cleaned at the car wash), on the dining room table. Hers no less. She came with her new furniture.And a brandy new mattress set I might add. I had nothing.
What was my point again? Oh yeah, I remember. Trannies. If you got a circlip pliers, and a feeler gauge and know how to read, its a piece of cake. Be sure to airtest it before the VB goes back on. Oops, you will need a custom spring compressor to change out the lip seals in the clutches.I made one up.Its not complicated. A big bolt, about 5/8 x 6 with a nut and a stack of washers 1 in high, 2 flat bars about 1/2x1x6 and centerdrilled for the bolt, and a ring about 4"dia.x 1 hi. You will have to finalize the sizing when you get there as Ima guessing here. Honestly its easy. At least until you get to the VB.Heh-heh. If you get a shift kit, they have pretty good pics. At least the TransGo kits do/did.A camera can be a good friend. As ever; all the best 2U
zcook13
Active Member
Wow guys.... That's a lot of great info. I really wasn't expecting all this info and specs. My 225 is all stock so I wont go to crazy with her but I would love to see where she is and mess with the timing a little. Thank you all for your input and specs.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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zcook
Sorry we kinda got off topic there for a bit.
Post 12 is bang on. If youre a newbe, try it. Make sure you know what detonation sounds like, before you get too far into it. Kinda sneak up on it.
Sorry we kinda got off topic there for a bit.
Post 12 is bang on. If youre a newbe, try it. Make sure you know what detonation sounds like, before you get too far into it. Kinda sneak up on it.
That's one of my concerns. I don't believe I do know what detonation sounds like. I see a lot of people refer to it and I sit here scratching my .... head.
nm9stheham
Well-Known Member
You'll know 'pinging' when you hear it; it is an irregular, light rattly sound. The best conditions to first hear it are low RPM's and accelerating with mid- to wider open throttle settings. Real detonation is much, much louder, like someone hitting an aluminum piston with a hammer.....reeeeally hard. It is unmistakeable and pretty violent sounding. Usually when you hear light 'pinging', you are approaching detonation and it is time to start backing off.
Some engines have a lot of margin between pinging and heavy detonation. The /6 seems to be one so don't be too afraid of it. My '76 Dart Lite with the lean carb would ping all the time but it rarely seemed to progress to actual detonation, and I had to really bog it badly. Others don't give much warning and just detonate; higher pressure turbo'd engines are a typical example.
Some engines have a lot of margin between pinging and heavy detonation. The /6 seems to be one so don't be too afraid of it. My '76 Dart Lite with the lean carb would ping all the time but it rarely seemed to progress to actual detonation, and I had to really bog it badly. Others don't give much warning and just detonate; higher pressure turbo'd engines are a typical example.
bruceo2011
Still waiting for Y2K
I have a dist wrench from the 60's/70's that is specific to the slantys (7/16) and works on both adjusting bolts. I think you can still find them on e-bay and swap meets.
Cooter
Well-Known Member
To add to Bruces comment, you can get a Harbor Junk 7/16" wrench and apply heat and bend it so it fits around and under the distributor. Be sure to accommodate for the trigger wires so they don't hit the wrench as you tighten or loosen the distributor. Crafty individuals can weld a long extension (again, Harbor Junk) on the end of the wrench.
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