What changes the timing on this truck?

vehicle - 1987 W100, 318, 4 pin connector electronic ignition system, edelbrock 600cfm carb with performer intake and cam.
I just put a new carb, intake maniford, timing gears, and cam in my
truck and checked the timing which was 8 BTDC as list on the label. I increased the throttle gradually up to 4500rpm and the timing never advanced to more the 18 BTDC. There is no vacuum or mechanical advance on the distributor and as far as I can tell there are no sensors connected to the computer, just the ballast resistor. Reading the Haynes repair section on this system gave me no answers. Can someone tell me how the computer adjusts the timing and if the computer might be faulty? I did not check the advance before installing the new carb so it may have always been like that. Truck has always been sluggish but I thought that was from the gearing and 4 wheel drive. Would changing the distributor to one with weights and a vacuum advance give me better economy or performance? I know the vendors selling them say it will but what else would the say. Thanks, George
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george wrote:

Did you degree the camshaft? http://www.cranecams.com/?show=article&id=3
--
Ken



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In article < snipped-for-privacy@e4g2000hsg.googlegroups.com

Trucks with the 318 had electronic ignition with mechanical and vacuum advance distributors. Trucks with 360 and slant 6 engines had a spark control computer.
You mention a computer, is there one attached to the side of the air cleaner or possibly on an inner fender? (you can't miss it, big as a cigar box)
You mention a 4 pin ECU, that is NOT a computer, just an ignition module.
If you measured 18* timing advance, there has to be an advance coming from somewhere. The mechanical advance is below the base plate in the distributor, if you can twist the rotor clockwise an appreciable amount, there is a mechanical advance lurking in the distributor. Vacuum advance should be obvious. Note; of the two advance springs typically installed in the mechanical advance, the lighter ones can and do break, if this happens and the fly weights aren't pulled back fully, you'll see stunted advance.
It's entirely possible that someone put the wrong distributor in the truck, an SCC type distributor from a 360 would certainly fit.
Are you sure the engine is a 318? Was a 318 swapped in in leu of a 360?
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aarcuda69062 wrote:

That's right. If I remember correctly a vacuum hose is connected to the computer module.
JAM
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You're sure of the ignition system? Standard Mopar ECU? Is the distributor hall effect or does it have a pick up coil?

So you do have a computer? That computer will have what looks like a vacuum advance mounted to it, because that's where it is on the computer controlled trucks. Is the computer mounted beside / behind the battery? If you do have a computer, you should NOT have a Mopar ECU, someone's been fooling with it.
It sounds like you can remove the ECU and use it as is or complete what seems to be a conversion that wasn't finished. It'll run MUCH better with the standard Mopar distributor and ECU. BTDT.
This is the complete kit you need, it comes with complete instructions for your truck, including eliminating the computer from the ignition system.
http://moparperformance.carshopinc.com/product_info.php/products_id/36939/P3690426
or
http://www.jegs.com/webapp/wcs/stores/servlet/itemproduct_10001_10002_34258_-1_747043_10679
and I found some instructions, I don't think these are complete?
http://kim_spure.tripod.com/igntion.htm
Use the part number to shop for the best price if you decide to go that way. It sounds like all you really need to complete the conversion is a distributor, ballast resistor and wiring harness though? Check junkyards for the distributor, parts store for the ballast. The harness used to be available as a separate part number or you can cobble something up from the junkyard if you're on a tight budget.
Reading

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Thanks for the responses. Let me try to answer your questions and correct something I said. The truck does not have a computer I was referring to the ignition module or ECU. The distributor has a pickup coil. It is a 318, does not have any advances on the distributor, I double checked under the plate and there is no mechanical advance. It is the original setup, I got the truck from a coworker who was the original owner and he said everything is stock. I did not degree the camshaft, I just followed the instructions from Edelbrock and doublechecked everything I did. Any and all responses are much appreciated.
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In article < snipped-for-privacy@e10g2000prf.googlegroups.co m>,

The ECU has no timing advance capability.
Sounds like somehow somewhere, the wrong distributor got installed in that truck.
The path of least resistance might be to just get a remanufactured distributor for the correct application, install it, set the timing and go.
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George, The later model engines have a crank sensor as the ignition sensor. The sensor is a hall effect sensor which is mounted at the rear top of the passenger side of the block over the flywheel. There are notches on the flywheel that create the trigger pulses. The pulses occur at maximum advance and are delayed depending on the engine speed and vacuum. Rotating the distributor will of course have no effect, as its only job is just to distributed the spark to the appropriate cylinder. There are different flywheels and flexplates depending if the engine is internally balenced or externally balenced. It is possible that the placement of the trigger notches are also different, but I doubt that myself. The placement of the sensor is fixed and also not adjustable. From experience, max advance should be about 37 degrees before TDC. (above 4000 rpm and 0 vacuum) Steve

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George, One other point, your detected 18 degrees is about correct, because your vacuum was still connected. Remember that the computer sees the vacuum from a sensor, not the distributor. Steve

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