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Discussion Starter #1
Picked up the 68 today, after getting a new front end alignment. Drove the car home, and the brakes were kind of sticky. Not a big deal, as everything is painted, new and tight! The engine however, was a different story. Now it is popping back through the carburetor. And, it has a case of either/ or idle. It will either idle at 1800, or stall out and want to die.
Could the fact that I put the lightweight springs in the distributor have a negative affect on my timing somehow? The car idled and revved just fine sitting in the garage, no problem at all. Put a load on the engine, and now she's popping and *****ing about going 40 miles an hour. Performer RPM heads, recent valve job, new plugs properly adjusted throttle linkage for the primary and secondary carbs. I was all set for a 5K run home, (if ya know what I mean) and that did not happen...It was an intermittent backfiring too, not as constant as you would think...
Running out of time and idea's before the next trip, I really don't want to leave her like this for 6 months....
 

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I'm dealing with much the same issues with mine. Put a new MSD in it and couldn't get it to run. I changed the springs from the slowest to the fastest and back again. Moved the timing all over the place. Got it to run fair, but it lacked the power it had before the new dizzy. Yesterday drove it about 20 miles and had to stop 5 different times because I couldn't keep it running. This gave me time to think and I began wondering if there was a fuel blockage. Turned out that the filter was black with debris. I'm certain that the problem is fuel now, but, I do have to finish the carb cleaning before I can be 100% sure. I did order a new gas tank this morning though. These cars are amazing, I put power steering and brakes on it, destroyed my old distributor, (by accident, a well intended helper), purchased one that was bad out of the box, installed another and now have fuel isses. I don't care how hard you try, you can't draw a line to fuel problems that started with power steering, or can you?
 

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What distributor are you using?
Points or Pertronix?


Grab another distributor and see if the problem is still there. Lightweight springs might be giving you too much advance

If it still exists swap out the coil
 

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Discussion Starter #4
It's the same Ford duraspark distributor that the car had before the engine mods. I also installed an MSD coil.
 

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Sounds like the timing is way off.
 

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+1 - firing on the intake stroke --- or you got a plug wire crossed. Since you had the dizzy out - I'd double check that you aren't off a tooth first.
 

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From your description, meaning the car was running fine after you put the distributor in, and it will at times run smoothly, I'm still betting on it being fuel starved.
 

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Discussion Starter #8
Well, here is an audio clip of the car. I did not change anything between this clip, and driving the car to the alignment shop. I will take a look for a loose wire, but it sure sounds good for having a wire out of order...
http://s819.photobucket.com/albums/zz114/woodsnake4462838/?action=view&current=9ac4c5e0.mp4

I did not change the fuel filter in the car, but I drove it to the shop, and it was fine. I will try and change the filter this weekend, if it breaks 40 degree's outside..
 

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I would put the springs back and see what happens.
After that, double check the timing. After that, pull the distributor and see if you've developed a problem with the bushing/bearing on the distributor shaft.
Check the filter too. Never know.
 

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Are you running a vacuum advance. Doesn't look like it is connected in the VID. Is it connected to ported vacuum


If you changed the springs in the distributor the car will behave differently when it is not under load (revving it in the garage) to when it is under load (on the street) as the vacuum levels and therefor the amount and rate of advance changes.

First step is to put the spring back as that appears to be the only change made.

Are you sure the secondaries aren't opening too early and dropping in too much fuel. This also needs to be fine tuned under load
 

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Discussion Starter #11
Yes, it does have a vacuum advance, that is hooked up. Initial timing is 14 degrees, timing was set with the advance disconnected. I still have the stock springs that came out of the distributor, I can try and put them back in, and see how she does. I will work on that this weekend. I am out processing all this week, getting my computer training and 'stuff' done.....
After the grueling 14~ mile trip home, the car was popping in the drive way, with no load and just throttle. Do you think the springs may be responsible for the strange idle condition as well?
 

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If your running to light of a spring it could be advancing under idle - if putting the stockers back in doesn't make any diff, check that you haven't developed a vac leak somewhere too.
 

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Discussion Starter #14
"If your running to light of a spring it could be advancing under idle"
I only installed the 'lightweight' spring set that is available. I feel a new thread coming on....
 

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Discussion Starter #15

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Woodsnake, I listened to the video and it sounds like the cam is wiped out, or a lobe, or there's an exhaust valve stuck/busted spring..something. If you had a crossed wire it probably would idle ok but pop when you advance the throttle. If the firing order has been changed from 302 to 351 it more than likely wouldn't run.
Questions though..did you change the cam in this when all these parts got changed? How about lifters?
It sounds to me like the distributor springs are a coincidence, as you could put 25 initial in it and would still run, when you put it under load you'd then get ping/detonation. So I'd check some stuff: pull the valve covers and crank (not start) it and watch the valvetrain to see if all the rockers are actuating the same amount. They should all be moving about 1/2 inch roughly. Next make sure the valves are adjusted correctly, maybe one is cranked down so tight it's holding an exhaust valve open....let us know
 

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Discussion Starter #17
The engine only has about two and a half thousand miles since it was built. When we put the new heads on it, we followed the Comp Cams method exactly, I.E. starting with number one cylinder, when the exhaust valve starts to move, adjust the intake to zero lash, plus 1/2 turn. Continue to rotate the engine until the intake reaches max lift, and is almost all the way down, and then set the exhaust to zero lash plus a half turn.
 

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Sounds about right on the methods. I imagine you have double checked it to death by now on that - which still kinda leads back to thinking timing still? Going back to where it was running good to be sure you introduced the trouble and not something else sounds like the best course of action. Especially if you want to get it going before you leave...you can fight this battle when you get back/settled.
 

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Yup sounds valve train related to me also. What does it sound like if you go WOT for a split second? If its an exhaust valve not opening far enough it will pop through the carbs like a SOB. You can also try hooking up a vacuum gauge and see it the needle fluctuates aka bounces at idle and cruise, if so definite valve train problem. Wiped exhaust cam lobe, rocker arm, lifter etc. A bad intake valve guide, valve, or valve seat are also possible.

Bill
 

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Discussion Starter #20
I guess I will try and get through the valve train adjustment one more time.....The heads are fresh, really, there should be no surprises here...
 
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