ok, so the other day i figured out that my optic eye in the distributor for my xr700 was set too far clockwise making the timing extremely retarded.. go ahead...

tonite i decided to set the timing, but found if i set it to the stock setting, the car was detonating and idle was very poor as well as performance. I set it back to where it idled best, had best throttle response and stopped detonating, and it is...according to the timing light-yes w/ hose off at 3500rpm- about 20degrees advanced. Im thinking maybe the timing is advanced but the optic is still off making up for the difference, anyone had this problem? This is a real pain in the ass since my timing marks are useless now.

sorry can't help you....but damn i envy you. I just blew my P-unit. i'm back to points.

You've got to get the "optic eye" at the leading edge of a slot...any slot..as long as the engine is at TDC #1 or there abouts..if the dizzy is in the correct orientation for the required swing (vac can in correct position), you can set any timing you want.

Are you disconnecting and plugging both advance and retard vacuum hoses?

its a 74 motor, only has the retard hose. DOesnt seem to effect the timing process a whole lot anyways. First i had the eye set to the latest setting on the shutter, but she was not liking it. She really likes it on the earliest setting, but where do i put it and still get the timing back to 27 degrees or do i ? Im just trying to get it to run the way it does now, w/ the timing back almost to stock- mild cam needs slight advance to idle correct.

If you have stock injection with a stock cam, you want stock timing. Regardless of what points/electronic ignition you're using. I've never set up a crane, so I can't help. But if you can get 27 degrees full advance you should be set.

Your retard hose is connected to the retard connection on the vacuum canister correct? If you connect it to the wrong port it will advance the timing. Set the Crane to 27 and leave the retard hose plugged. Does it still detonate?

i went off this routing diagram. Vac is run from the intake to the retard portion of the dist., i dont think i have a vac canister...

The red hose is retard, the light blue hose is advance. Set it to 27 and leave the retard off for testing. The retard is for emission mostly anyway.

QUOTE (xsboost90 @ Jun 21 2005, 09:52 PM)

i went off this routing diagram. Vac is run from the intake to the retard portion of the dist., i dont think i have a vac canister...

i think thats what he was referring to.

QUOTE (xsboost90 @ Jun 21 2005, 11:15 PM)

...my timing marks are useless now.

No, they're NOT.

i don't want to go the all-caps route, but this is *Really Important*. so read carefully, hear me now, believe me later... you time your engine in *EXACTLY THE SAME WAY* you did before. the points replacement module does *not* change the timing, and you don't dink with them to *change* the timing !

ALL the XR700 does is replace the points. that's it.
but (as you've discovered) they change the place in the distributor rotation when the ignition event occurs -- unless you somehow managed to install them so that the shutterwheel slit hits the sensor at *exactly* the same place as the cam opened the points before. not only is this unlikely, everything you've posted indicates this is not so.

in your earlier discussion i was witing for the part when you mentioned retiming the engine after installing the XR70, and i don't think you did. you MUST - just as you have to check (and possibly adjust) the timing after replacing *any* points.

bit of background to bring everyone up to where this is headed.

"timing" the engine means: setting the place in the distributor rotation where the ignition event occurs. this is done by moving the fixed reference (distributor body) so that the moving element (distributor shaft) makes the ignition event happen at the proper angular measurement from the fixed reference.

all that shutterwheel alignment crap is *ONLY* to get your static (engine not running) timing "close enough" so that the engine will start and you can use the normal, correct, standard timing procedure. (and for completeness, location of the sensor block also affects "spark index" - because you want to make sure that the rotor is pointing at a plugwire tower at the ignition event under all spark advance conditions.)

if your engine starts, you are *done* screwing around in the distributor. let it warm up, and us the STANDARD, PUBLISHED timing procedure.

your timing marks HAVE NOT CHANGED!

i have tried very hard to make this as straightforward but explanitory as possible. IT'S IMPORTANT that you understand this stuff. PLEASE ASK if there is any part of it that needs to be explained better -- BEFORE you go tinkering with your engine again.

the thing is...ive built my fair share of engines. Im not stupid when it comes to timing a car and how to do it. The dist. timing still works the same as far as when the rotor is passing the cap etc etc. The xr700 DOEs effect when it sparks though. If the eye is set in the wrong spot, then the rotor sends spark at the last millisecond of its passing by the cap, or at the very first millisecond yadda yadda. You want it to spark right in the middle of the electrode on the cap. Crane has a procedure where you drill a hole in a rotor cap and set the timing while watching the rotor through the hole to make sure its sparking in the middle of the electrode, however they dont explain how to fix it if its not. You turn the dist and the timing is off. you mess w/ the eye and the timing moves as well.

it is possible however that this distributor gear has been messed w/ by the PO of the motor-who built it- and while i trust his building skills, i believe that as long as it ran right he wouldnt worry about if the timing marks were right or not.

QUOTE (xsboost90 @ Jun 22 2005, 07:47 AM)

Im not stupid when it comes to timing a car...

wasn't suggesting that anyone was stupid, but we do have varying experience levels here (and in the future, when others read this thread) so JUST IN CASE you didn't have the background, i wanted to make sure certain fundamentals had been spelled out. so - moving on...

QUOTE

The xr700 DOEs effect when it sparks though.

which is why you need to retime following installation...

QUOTE

If the eye is set in the wrong spot, then the rotor sends spark at the last millisecond of its passing by the cap, or at the very first millisecond yadda yadda.. You want it to spark right in the middle of the electrode on the cap. Crane has a procedure where you drill a hole in a rotor cap and set the timing while watching the rotor through the hole to make sure its sparking in the middle of the electrode, however they dont explain how to fix it if its not. You turn the dist and the timing is off. you mess w/ the eye and the timing moves as well.

you are correct, as far as that goes.

that was what i referred to as "indexing" the spark.

short version: yes, you move the sensor block in order to get the index right, then you reset the timing to adjust for the change in angular position. done.

(i fought this issue for a couple of weeks, even went off on some wild tangents. believe me, i understand the issue. it's complicated in a /6 because you can't put the block where you want to - it interferes with getting the cap back on. but i digress...)

okay - you don't have to drill any holes in the cap. the cap has a fixed mounting position due to the boss and the notch. use a felt-tip marker to transfer the location of the plugwire bosses onto the distributor body. I *think* you'll find that the #1 index line on the cap mounting face of the body is *already* aligned with the plugwire tower.

so - here's the procedure:

rotate the crankshaft to your initial static time location - perhaps 5-6* BTDC Z1. rotate the distributor so that the rotor points approximately at the plug wire location. make sure that you don't go too far clockwise - give the rotor a little twist CW to see where it will be pointed at full advance.

then - move the sensor block so that the spark is triggered exactly there.

at this position, your rotor is indexed to the cap's plugwire tower and your timing is in the ballpark.

(my problem was that i didn't have the rotor turned far enough at the spark event, trying to optimise for full advance. engine ran like crap under 1500 rpm. re-indexed so the rotor was closer at idle and it was all good.)

so - you're correct - when you move the block to adjust index, it *will* affect the timing - but you just reset the timing (done by rotating the entire distributor body, as you know) and you're done.

i had to install a completely different combination of little brackets and extension arms than i originally thought i was going to need, and i had a grind/file a bit off an edge or two so they could be installed without binding. but you just use whatever combination of parts it takes to get the spark indexed properly. then you set the timing.

I could read techincal stuff all day. You guys are a waterfall.



M

yeah im alittle grumpy in the morning. My rotor turns clockwise. According to the crane instructions it says i need to put the eye on the edge of the shutter late as possible. SHOULD i just put it in the middle then when rotor is pulled to full advance?

QUOTE (xsboost90 @ Jun 22 2005, 10:47 AM)

yeah im alittle grumpy in the morning.... According to the crane instructions it says i need to put the eye on the edge of the shutter late as possible. SHOULD i just put it in the middle then when rotor is pulled to full advance?

de nada.

okay - my take is - it just doesn't matter.

the spark event will occur when it's going to, and while a couple of degrees of camshaft rotation will make a measurable, noticeable effect on timing, the fact is that the shutter wheel and sensor block will decide where to trigger.

the tip of the rotor covers a broad arc just for the purpose of ensuring good spark travel across the full range of advance.

as long as the tip of the rotor points "reasonably at" the plugwire contact across the range of advance, you're cool. if i had it to do now, i'd eyeball the range of advance and make sure that the center of the rotor is pointing directly at the tower halfway through that range. do that and you'll be good to go.

if i had a race car that only operated at very high rpm, i'd probably fudge that index more toward full advance. but it's really splitting hairs at that point.

the ignition event will index around the distributor body in direct porportion to the amount you move the block. so if the rotor doesn't point "far enough" toward the tower, move the block as mugh to the right as you hope to move the rotor.

then retime to align the ignition event with TDC.

This is not a "rocket science" project.

If you bring it to tdc #1, and you have the rotor pointed at any pole on the dizzy cap, that pole becomes #1. If now you set the trigger block to where it aligns with the leading edge (right edge of slot since rotation is clockwise) of a slot in the trigger wheel, you have your intial timing set up.

The only key in this whole thing is having enough swing of the dizzy body to get to 27 degrees advance without the vac can hitting something. Been there did that.

I don't take into account the advance in the dizzy when setting the trigger block.

And yes, sometimes it takes combinations of the brackets supplied, technical bending and filing of the brackets to get the trigger block in a "correct position" so the trigger wheel is not hitting anything.

If you have purchased the lastest version of the Crane\Allison unit, it has an LED on the control box to help you align the trigger block to the trigger wheel slot.

One of the bigger errors is using the wrong timing mark on the impeller for the initial setup....been there and did that too!

And you can also be using a timing light with an "advance" knob on the back, and forget to set it to 0 when using the stock timing marks. Not that I've ever done that ... more than twice in a row...

--DD

Good to see you around DD.