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1966 Mustang coupe/HCI 5.0/ TKO-600/ 3.80:1 Trac-Loc
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Discussion Starter · #21 ·
I stuck a rubber bushing on the stop pin with the size of .050" and with the .150" of the pin and the .384" 9L slot. I calculated 14 degrees of advance as opposed to 18. After adjusting the timing back to 24 degrees I was left with 38 total timing. I drove to school this morning (120 mile round-trip) and the top end seems to be a lot smoother feeling than before and I believe that I might have even gotten a smidge more fuel mileage.

One side note, is it normal for the exhaust to smell almost burnt like? It smells like this when cruising but most notably when I go WOT to 6500 rpm through the gears. I don't believe its running rich because my plugs aren't fouled or covered in carbon and I've noticed the porcelain stays almost completely clean. There is no glaring signs on the plug that they're running lean.

But could I be running too lean? Is this a normal smell? I just finished jetting the carb down to the stock 66 primaries and 134-39 metering plate. First it had 71 Jets and the 134-21 plate and it stunk like gas all the time.
 

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Sorry, can’t help with the carb tuning. Reading plugs is tricky, you really need to run at WOT and then shut engine off, then pull plugs and look down the insulator to see what’s really going on. Anyway, having run (and melted) engines that I thought were ok but turned out to be lean, “fat & happy” is the way…
 

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1966 Mustang coupe/HCI 5.0/ TKO-600/ 3.80:1 Trac-Loc
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107 Posts
Discussion Starter · #23 · (Edited)
@LSG So I went ahead ripped off the timing cover, confirmed I was Dot to Dot, and advanced the cam to the 4A position on the sprocket. I kept it at 22 Degrees of timing and drove it around. No pinging while going thru the gears at WOT and definitely felt so much stronger and still pulled to 6500. It will ping once I the rpms drop while still in high gear ( 4th/5th <1600) Lowest I 've realistically gone previously is 1400 with no pinging when cruising down the highway as well as no pinging when mashing the pedal at said rpm.

Anyways, I decided to pull some timing to 18 degrees check if it solved the pinging in that specific scenario, which almost fully did, but once I pulled into the driveway and idled for 10-15 mins I noticed the temp gauge was at the P in TEMP where it usually sits between the E & M. I know that means the timing is too retarded so I bumped it up to 24 and the temps came down. Then tried to drive and at around 2000 rpm in 1st the engine began to load up bad and backfire very loudly (not sure which end it came from). Turned around and set the timing to 21 and now there's some light stumbles now with the occasional backfire out the exhaust when accelerating and passing that rpm area. The stumbles clean up with more throttle but I haven't gotten to drive it much since yesterday.

I found that the vacuum advance diaphragm is leaking and will not hold vacuum. I have a new one on order. Could this be causing the part throttle acceleration stumbling due to the increased vacuum which sucks in air thru the leak? Could I test by plugging the ported vac line and driving without vacuum advance or will that also cause drivability issues further complicating the diagnosis?

Ill fiddle around with it for a few days and drive it to school on Monday and see how it goes. The timing/Temp stuff keeps giving me issues I'll tear it down again and set it back to how it was once I'm out for winter break.
 

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1966 Mustang coupe/HCI 5.0/ TKO-600/ 3.80:1 Trac-Loc
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107 Posts
Discussion Starter · #24 ·
I tested it this morning. Plugged the ported vacuum port and drove it around. No more stumbles and I was able to advance it to 28 degrees so I drove it to the parts store and picked up the vacuum advance and hooked it up and achieved the same drivability as before. More power down under for sure. But what gives? I thought it would need less timing than it did before but now it just overheats at 22-24? I will also lower the total timing because the engine seems to start to misfire and vibrate like crazy when in 4th gear high rpm around the 56-6000 rpm mark
 
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