part throttle surge problem

[HP2]

Well, checking the vacuum canister was easy enough, so I started with that and had no change.

So out came the vacuum gauge and I started tinkering with adjustments until I got the highest possible vacuum readings. That smoothed things out some, but the surge was still there. Out came the step up springs and I replaced them with a lower tension. Yet another improvement, but still kind of rough. Seemed more like a miss now than a surge. By now the sun was behind the garage and as I'm standing there wonder what to do next, I notice a small arc by a header tube. So I throw a tarp over the front end and watch the light show. Two boots were consistently arcing with a third intermittently arcing. So  I replaced a bunch of boots and finally everything smoothed out. Double checked the timing, 12 initial, 28 mechanical, 38 with vacuum. 

[Bullitt-]

 

[Chryco Psycho]

 

[dodge freak 2]

Yep the old header burns the plug boot problem.

I had a small tear in a plug boot were my MSD 7 al box would be strong enough to cause the spark to jump to the header but when switching to an old MSD 6  box the spark was  weaker and motor ran fine.

But I thought the 7 box went bad and shipped it back to MSD. 3 weeks later I get it back--"no problems found". I hooked it back up and the misfire came back.

Thankfully I got a nice MSD tech guy who was able to clam me down as I was yelling how come you guys did not fix my box and he explain to me the box has to be ok and worked with me to find the problem.

The longer the motor rans the worst the misfire got. Heat must make the spark easier to misfire.   

[71chally416]

Double checked the timing, 12 initial, 28 mechanical, 38 with vacuum.

That's 28 + 12 = 40? What is the timing when you hold the throttle to the max advance with the vac unhooked?

[HP2]

12 at idle. 28 total at max advance without vacuum. 38 total with vacuum.

[71chally416]

Now I see how you can run it without detonation 

[ntstlgl1970]

Might want to swap back to the original step up spring since it was an ignition problem, I like it when solutions are just simple stuff...

[HP2]

Glad I was able to amuse you...

So I take it in your opinion I'm leaving performance on the table because of my timing.

[71chally416]

 

[HP2]

So I guess this really begs the question at what point does ignition advance trump compression ratio or vice-versa. Currently my cam is installed 4* advanced to further increase cylinder pressure. This has me wondering if I return it to a straight up position and crank in more timing, what the results will be. Maybe I'll try that this summer and see what the results are...if I don't sell it first.