Okay, so I've been looking and almost all the info I can find is for a large cap ignition. I'm running Megasquirt II on a 383 with basically a stock HEI system. I put a 369 HEI module in instead of the 048 and I'm not seeing a lot of difference. I've got Accell stubby plugs due to my headers and I'm running 8mm silicone jacket wires. I'm getting a miss at higher RPM while accelerating and I think I'm probably missing some at idle.

I'm thinking I'm probably due at least an ignition coil. I'm thinking about the MSD Blaster SS or the Mallory equivalent instead of a stock style coil; The connectors are kind of annoying honestly. If there's a good stock style coil I'm still receptive to that as well.

Any thoughts? Just trying to get this thing running best as I can.

 

I used a stock small cap with new fresh cap and rotor, mallory plug wires, ngk resistor plugs, some time of aftermarket coil but cant remember what it was, and a mallory hyfire ignition box on my nitrous 383. 7000 rpm 600 ish hp no problem. Used the same on my first turbo build to 6200 rpm and 800 hp.

Whats your plug gap? Using a resistor style plug?

 

How does the cap/ rotor look? Tested the pickup coil? Have you ohm checked the wires? No burn through or arc out to ground? Pulled the plugs to look at them? Are they Cracked ? Ohm checked the coil?
Even if they are new, they could be bad and worth a double check b4 buying a coil

 

I used a Davis Unified Module and coil with a fresh cap & rotor and 8mm wires. Misfire free to 6,500 rpm on my TBI'd single plane intake Vortec 350.

Check to be sure the distributor vent screen is clear and clean. The small cap can build up ionized air inside rather quickly and that can cause misfiring via spark scatter. It helps to set your initial distributor timing to around 16-20° as it positions the rotor closer to the terminals on the cap for the cylinder that is firing. Less energy is required to jump the gap in the distributor leaving more to fire the plugs. I drilled a hole in an old cap to properly phase the rotor.

 

Gap wise I Went with stock which I believe is .045. May be too big.

Plugs themselves are Accel 576S.

Wires are 8mm I believe Accel Super Stocks but I'd have to go look.

I'll check the cap and rotor. All the distributor bits except the above are stock components. The cap is aluminum terminal if that makes a difference although I'd think it minimal.

I do have a Pertronix Second Strike box around here somewhere I could install. May have to look into that.

 

Try .032-.035 gap and see what happens

 

Yeah that's too much gap for a high performance application. We generally just gap everything at 0.025 since we tend to have so many cars that hit the dyno and blow the spark out under boost. It's less destructive to ignition components too - less voltage required to push the spark. We really don't see any issues with a .025 gap.

I get all my distributors and coils from Davis Unified Ignition. I second that recommendation.

I didn't like the Accel plugs I used. The NGK plugs are almost as short and 1/3 the price.

GD

 

Gap tightening is on the list still.

I did however install the CDI system since it was simpler and easier in inclement weather we're having right now. My AFRs are now way lean. Based on a bit of reading this seems normal. What are the chances I'm on the right track here?

 

Most likely showing lean because more fuel is burning.

 

I don't know if this applies to your situation, but if your rotor is the same one as the one used in my 1995 GMC truck (TBI), then there is an issue with some brands of rotors arcing out to the center mounting post, right through the plastic. You would need a strong eye loupe to even see it. Your first indication of this happening would be in moist weather in situations where the ignition system's demands are heavier. I keep a new, spare rotor in the truck, just in case.

 

Do you guys have a preferred cap/rotor brand? I know the Astro guys like "brass contact" ones. Any thoughts welcome.

I'm probably going to end up with a coil at this point anyways as well. From what I've read ohming a coil can be kind of sketchy in terms of a checking methodology.

Today's nice, if I get a chance I'm going to start pulling plugs too. I want to see what my plugs look like and be sure my WB output is trusthworthy and that I'm getting fuel everywhere evenly and obviously regapping.

ED:Also on the NGKs, I have a set sitting on the dash right now that were previously installed. A few of the cylinders have about 1/8" between the header and the plug. Not really workable regrettably. Maybe I should see if I can find/make some spacers for the headers.

 

You might want to use this rotor. Accel makes a nice cap.

https://www.thirdgen.org/forums/tech...-minimize.html

 

The quick & easy way to space the headers out would be to stack multiple gaskets. But then, your y-pipe might have trouble bolting up.
You could just run the shorty plugs in the cylinders with the tight clearance issues.

 

I don't really like the idea of mixing plugs. I would think having them consistently good/bad would be better than having them mixed with bad plugs.

Here's pics of the plugs I extracted today. Interesting results. #3 seems like it's real rich compared to the others. I may pull the valve cover on that side and check the push rods. This is an HSR equipped engine so I'm not sure if the fuel pattern looks consistent. Based on what I've read it seems off compared to the usual air distribution.

The plugs are certainly good enough to reuse so I'll be tossing them back in. I checked gap and they were at .032 so no work was required on them. Interesting. They are 576S plugs.

 

Pulled pushrods. Found a few that seem about .020 shorter than the rest. Thinking about just ordering a set of pushrods up. What are the opinions of the BTRs vs the Comps? I think the Comps are standard steel and the BTRs are 4130. I'm guessing they're probably a vastly superior product.

https://www.summitracing.com/parts/btc-pr7275312-16

vs

https://www.summitracing.com/parts/cca-7809-16

 

What you said about the two is correct. Plus look at the ends. BTR is formed, Comp is welded. Formed is better.

If you suspect that two pushrods are worn shorter, than you can expect that the two rockers pushrod cups are worn also. Inspect those.

 

Thankfully the rockers look good esp since they're Comp Aluminum rollers w/poly locks. I improvised a measuring system to check the pushrods. .011 to .031 off in length! Glad I caught that early. I want to check and see how the alignment looks and then order new pushrods. Wasn't my install and although I certainly made it worse I'm convinced it was at least started when I got the engine.

 

Just a quick update since I got these changed out, realized I had a massive exhaust problem that was causing my O2s to be off and then had to redo my exhaust which took forever to accomplish. All seems pretty well now, she definitely revs to about 6K no problem I just need to keep tuning at it. I was having idle issues due to previous fueling alterations but I think I'm going to be near a point I can check. I have a Second Strike box w/rev limiter that I can get to without the break up happening. I have one of the "369" modules and a stockish coil. Hopefully I'll be able to keep tuning it out. I may put in the aftermarket coil eventually but I don't think I'm to needing it yet and it may wind up being because I keep having the wire at the coil connector break off which is aggravating.