[Starsky95]

I have a 408w that I recently installed a ready to run msd distributor into. My old cheap hei style distributor did alright but it was time to upgrade. The guy I bought the engine from said timing should be set at 12° at 1000rpm and 36° at 3000rpm. So I changed the advance bushing and springs to get me a total of 35° when idle is set at 12° at 1k. I checked the idle with vacuum advance disconnected and capped off but the car runs rough when driving. It idles alright and has a stumble when revving but can't be driven without issues. Where should I start? Should I return the distributor back to the stock setup? I'm assuming the 12° at 1000rpm means that the curb idle should be set at 1k? That seems kinda high to me. I could really use some help.

 

[Action]

Welcome to the FFO!

What is a 408w?

On a stock engine of the period the base ignition timing was likely something like 8 to12 degrees BTDC at curb idle which would be less than 1000 RPM, (Vacuum advance disconnected)
Total advance would be in the 35 degree area at 3000 RPM which is what the PO said.

I do not understand your statement of, "I checked the idle with vacuum advance disconnected and capped off but the car runs rough when driving. You drove the car with the vacuum advance disconnected?

Action

 

[Starsky95]

Welcome to the FFO!

What is a 408w?

On a stock engine of the period the base ignition timing was likely something like 8 to12 degrees BTDC at curb idle which would be less than 1000 RPM, (Vacuum advance disconnected)
Total advance would be in the 35 degree area at 3000 RPM which is what the PO said.

I do not understand your statement of, "Dexter recall!? - Airstream Forums (airforums.com) ". You drove the car with the vacuum advance disconnected?

Action

It's a stroker motor built from a 351 Windsor. It's not stock anymore but the builder said 12° at 1000rpm. Any idea why he would want the idle so high? If I go by the chart in the msd manual for the advance adjustments the curve starts just after 1k. I'm not sure if there's too much timing or what the issue is. When I first installed and drove the car it drove alright once moving but ran rough when taking off from a low speed/stop but I ended up blowing a head gasket after driving it for a few miles. I'm not sure if that was due to bad timing or not.

 

[Action]

Head gasket "blown" is typically due to installation error on a newly built engine
Rough running can also be due to camshaft events
Why don't you ask the builder?

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[SteveH21]

Do you know the specs of the cam? 1000 is really high unless it's a radical cam. Tell us more about the engine. What heads, carb, comp ratio and manifold do you have? And what duration at .050".

I have a decent cam in mine (228I/234E @ .050") and I can idle at 650-700 with 18 degrees at idle. I have it set to 35 total full in at 2800 rpm. That stumble could be the carb. I would back the idle off to 750 and put a vacuum gauge on it and see what vacuum you get by advancing it between 12 and 20. If you have aluminum heads and not crazy compression you can run a base around 18-20.

Steve