Starting to understand why building engines may be best left to the professional

[Yellow Truck]

Ross - I hear you. My plan is just to get the idle where I need it, the I planned to swap the distributor and get the timing where I want it. I don't want to swap the distributor until I have it running and staying lit.

I agree it is probably something I did - I ran over the wires twice yesterday. I have a thought last night in bed that I will run over this morning. If it isn't that I'll start with a systemic approach to finding the fault.

[Yellow Truck]

Had to get the motor home ready to put away until I need it in late December, so only had a few minutes for the truck today. Everything takes longer when you can't use your dominant hand.

In any case demonstrated again my limitations as a mechanic. Turned out it was what popped into my head late last night. I forgot to attach the + to the electric choke. Attached it and the fuel pump ran for a few minutes. I'll try to get under the hood tomorrow but it is supposed to rain.

[Drew Pojedinec]

Mmmm yeah, good thing us "professional" mechanics never forget anything like that  ;-)

[Yellow Truck]

This is a head scratcher, and frankly it is scaring me. I got it started, had to open the primary a little to get it to stay lit, and with it running around 500-600 RPM it was showing 5 inches of vacuum. I tried turning the mixture screws IN 1/4 from the 3/4 out where they were. It ran much worse, so I took them back 1/4, then out another 1/4 (so they are now one full turn out). It idled a little more smoothly but vacuum stayed around 5.

At this point I put my timing light on it and it was showing around 16 degrees (actually shows 18 but I know the balancer is 1.5 degrees advanced). Now my light has a dial where you can retard the light so 15 degrees advance will show as zero, so I tried that to see if I could get a clean read on how many degrees it was advanced - instead I got the timing jumping around like crazy.

Took the light back to zero and the timing was showing 16. Backed of the clamp and moved it back to 16 and it ran worse, advanced it as far as 30 degrees advanced and the vacuum came up to 8, and the idle picked up.

I can't believe this engine likes 30 degrees initial advance at idle. I've asked a my buddy with the old school Snap-On light if he is around because I'd like to check it with his, but the last time I did this I got the same answer with both lights.

I'm afraid to drive this with that much advance, but it idles like crap at 16-18.

Last, I'm about to wire up the Duraspark, the wires are all the same (black with a red stripe). I called Faron and he told me that if I look at the end of the plug, with the ground at the bottom, the spade on the left is the trigger and it should have been the orange wire. Going to try that, but the distributor won't change what the timing light is telling me, so this is not a distributor problem.

[Yellow Truck]

In addition to wanting to know what to do when the engine seems to like 30 degrees of initial advance, I have a question about the MSD wiring for the Duraspark.

It is currently wired for a Pertronix:

Screen Shot 2017-09-30 at 2.26.34 PM by Fred Snoyd, on Flickr

Note that the red wire from the MSD goes to both the red wire on the Pertronix AND the ignition wire.

Here is what MSD calls for with a Duraspark:

Screen Shot 2017-09-30 at 2.29.44 PM by Fred Snoyd, on Flickr

There are a few differences:

• The white wire is not used
• The violet and green wires are used (magnetic pickup), and,
• The red wire seems to connect to the positive on the coil

The last one is what I don't understand. Now (with the Pertronix) the red wire is connected to the Pertronix AND the ignition. In the Duraspark instructions there is no ignition wire. I don't have that "Ford Coil Connector", so I assume the red wire just connects to the + on the coil. There is a green wire in the diagram that comes off the Ford Coil Connector, but since I don't have one, I have no idea where it goes.

Since something needs to turn this on, I assume deleting the ignition wire is a non-starter.

[Drew Pojedinec]

I like to use that 8869 harness.  It's like $18 and keeps you from hacking up factory wiring.

random thoughts:
You keep working on a cold engine.... don't tune a cold engine.
Until oil and water are up to temp, don't expect the engine to idle well.  If it in fact idles well cold that is because it is stupidly rich (or the choke is engaged)  Adjusting the idle screws at this point is a mistake.  This is why the initial idle screw setting is 1.5 turns out, even tho that is almost never the final setting..... it's a rich setting so you can get the engine started the first time.
This is why there is a choke on street carburetors.

Ok, now.... you live in Canadia (which is cold), with an Edelbrock performer rpm intake and BBM heads, both of which are aluminum and wick away heat rapidly and neither have an exhaust crossover.  Couple this with a performance cam and an overly large carburetor, which although usable, both lend themselves toward a lesser signal..... which leads to worse atomization.... which is the path to the dark side.
Imagine being inside the intake manifold on a cold start.  You don't have atomization, you don't have perfect clouds or air and fuel mixed.... you have liquid fuel running down the sides and floor of the intake while the engine is trying to stay running.
Until oil and water are up to temp and the intake and carburetor are up to temp that fuel is staying dang near liquid.  Once everything is up to temp, you will have proper atomization and thus a decent idling engine.

So when you say "The engine runs best with 30 degrees of advance while cold."  So?

[Yellow Truck]

Drew,

First, on the wiring of the Duraspark, thanks for the suggestion. Cheapest I can find in Canada is $30, so I'm ok with cutting the wire. At $18 I'd buy the harness. Still doesn't answer what to do with the ignition wire.

On the timing thing, you are saying I chickened out too soon? At the time I did wait for it to get warm enough that it would hold idle, I planned to make just enough adjustments to stay running, then I was going to let it run long enough to hit full temp. When I saw the timing behaviour it kind of freaked me out. Wasn't cold today, but the engine was just warm.

BTW I do have the heat cross over in the intake - I'm running a Holley Street Dominator intake. I had not realized the BBM heads do not have the heat cross over. Silly me. This does explain why this engine runs better when REALLY hot.

If I can get the wiring figured out I'll stuff in the new distributor and let it hit full temp before I mess with it.

[Drew Pojedinec]

Nope, no crossover.
It's typical even when the water temps at 180 that the engine isn't "really" up to temp yet.
Pretty common to have where you pull up to a redlight and it'll start to idle a lil rougher.  By the time the light turns green you get a little shudder that is quickly remedied with a little throttle.
It's an annoying tuning issue, I deal with it a lot as I get folks that have all the "race car parts" but aren't willing to deal with the "race car issues" and want me to tune it out. 

[Yellow Truck]

I appreciate you pointing that out, I think I noticed that there was no heat cross over when I assembled it but it had slipped my mind. I don't mind letting it get really hot before I drive it, it isn't a commuter vehicle so I'm not jumping in and trying to go someplace. I had noticed that I needed to drive it a couple of miles to get the idle to settle down, and it snaps a lot harder when really hot.

Now, all I need is to be told what to do with that ignition wire.

UPDATE: Think I figured out the wiring - I need to run the MSD red wire that goes to the Pertronix and ignition switch now just to the ignition switch. The "Ford Coil Connector" threw me for a loop.

[comet2]

im pretty sure you use it just as the pertronics did i cut off the dura spark plug and substituted the small square msd plug  but otherwise wired as shown . if you want i will come over tomorrow and help nothing else to do im dying to hear this thing run!!!

[My427stang]

Sorry I haven't been around, did a couple of long runs with the Mustang this week.  Most notably was a cruise to Speedway Motors twice LOL thought I lost my military ID and made the 54 mile drive a second time and hyper speed before the museum closed.  Approx 198 miles by 1 PM good for the car to get the miles on and get this...ID card was home the whole time 

So, first, the vacuum, I have an odd concern that keeps ringing in my head when you thought the advance slots for the cam were backwards in operation.  Not sure I can say anything about that but it nags in my mind as I type.

Regardless, Drew brought up a very valid point, you cannot tune cold.  Fuel is falling out of suspension, bores are tight, valves aren't sitting exactly as they would, no heat in intake or exhaust, that's why any engine needs a choke.  To believe it, realize how much a choke starves an engine of air, yet it still runs, but it only does it when cold

Second, one good thing is your carb is pretty close. If the idle screws kill the motor when turned in, and level off somewhere else, it's on the idle circuit, so sleep easy with tha

I don't have any more to add on low vacuum until we hear how it runs, but get the distributor in, set the timing, get it good and warm, set the idle a/f and idle speed and see what it does.

The carb adjusting normally, makes me think everything is normal in terms of intake leaks and overall setup, but if you advance a big cam, vacuum has to come up.  So let's see what happens after the distributor

BTW, have you tried a second vacuum gauge?  I have had them read incorrectly.  Another option would be hook yours to another vehicle

[Yellow Truck]

Good on you for getting it out for a work out. I'm jealous, even in good trim the truck is not a highway cruiser!

I did install a vacuum gauge under the dash, and it gives more or less the same reading as the one under the hood, so I think the numbers are correct.

I wouldn't worry about my mistake about the timing slots - I'm sure what happened was I took some measurements that suggested the cam was installed at the degree called for by Comp, but when I decided to advance it as per your recommendation and I measured again, The A4 slot was actually slightly retarded to where it had been before I took off the timing set. I think all I was seeing was that my first measurements were bad. I did improve my technique and am confident that the cam is now about 4 degrees advanced even though I had to use the A8 mark.

Drew made a good point about it being cold, it wasn't cold, but it was just barely warm enough to hold an idle. I'm not willing to pay $30 for the harness so I'll make up a connection later today and get the new distributor in and start it again.

[My427stang]

Let us know

FYI a cold engine is lean because of fuel not staying atomized, lean engines need more advance. 

Hopefully you are good to go after the distributor.  Also, don't idle it lower than you have to.  Not sure where you idle, but that could be a 900 rpm idle for your setup.

[turbohunter]

Hey Paul, do I remember waaay back that Jay installed a plug in the rear PCV on the manifold or was that left open?

Edit:
OMG I think I brain farted to a whole other thread.

[Yellow Truck]

Marc, currently the PVC is closed off as are all the vacuum ports.

Ross, I have been setting idle around 8-900, and it drifts up to 1,000 when it is hot. I don't run a choke at the moment - I plan to install a manual choke at some point - but I hadn't set the idle when hot, had been leaving it a little high.

BTW I was encouraged that the engine responded to the mixture screws, when I first ran it it would idle with the screw turned all the way in, so it had been pulling fuel from somewhere other than the idle circuit. I'd say the carb is closer to where it needs to be than it has in a while.