Mystery problem with Cougar timing solved - probably

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4,006
Location
Chicago, IL
Thread starter
A couple of weeks back I posted that our car suddenly started missing, running poorly, lacked power. Of course, adding to the confusion were the following facts: - my son swapped out the MSD 6AL for a 6+, preparing to setup nitrous injection and wanting to use the timing retard feature available in the 6+ - he actually drove the car home from storage; I had not driven it yet this year when it was running properly; so while it seemed that the problem started when he switched the MSD box, I could not be sure Further symptoms were confusing: the initial timing was around 30-35. Yes, initial timing. (probably should have been in the 15-20 range) and it was fighting itself when cranking, which it never had done. To try to diagnose the problem, we swapped in the original 6AL MSD ignition box, with little to no improvement. Did the following: initially a compression test on 7 of the 8 cylinders. the last one was too difficult to access. since then we did a leak-down test on all 8. all were between 2-4% leak-down when cold. good there. Pulled the timing cover. there was 1/2 - 3/4" deflection in a previously tight double roller chain. ok. a little odd for a 2000 mile engine. put in a new chain. Then we found this - which I'm 99% sure was the real problem: the + and - were reversed between the magnetic pickup on the distributor and the MSD ignition box. Certainly my son modified that wiring when he swapped the boxes. I know that it was correct originally; I even told him to be careful to get those correct. verifying with the tech info available at MSD, they state that definitely swapping those wires will cause timing issues by approx 20 degrees. sigh. I wasted a lot of time tracking this down and I suppose that I should have caught that sooner. oh well. at least we have a new timing chain.
 
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4,006
Location
Chicago, IL
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Dart SHP block bored/honed to 4.030 with torque plate. block was square decked, line-bored. Currently using Valvoline Racing synthetic. the pretty blue color matches the car.
 
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21,068
Location
Apple Valley, California
Line boring will move the crank slightly closer to the cam. Making for a loose chain in short order. Plus add on machining tolerances in both the bock and chain and you can have parts that do not play well together.
 
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4,006
Location
Chicago, IL
Thread starter
ah!!! I missed that point! I could not figure out why timing sets were available with reduced crank to camshaft center distances! I figured it was not because of crank grinds, because the bearings are oversized. line boring!!! thanks!!
 

CT8

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15,409
Location
Idaho
When diagnosing a problem like you mentioned , Start at where work or modification was done .For example the engine ran good until I replaced the ignition parts. you look and the ignition work done not the timing chain.
 
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