bad gasoline? (not!)

[JD1964]

Good news! I got it smoothed out, at least tentatively. Rearranging the position of the ignition wires smoothed it out. So, I need to revisit spark plugs and ignition wires and make sure they're all top notch. That includes the parts themselves and the wire routing and securing. I take this as a sigh of relief 😅

Here’s a video of it after fiddling with the ignition wire

 

[JD1964]

I’m going to switch from switch from NGK back to AC Delco spark plugs. The Delco have lower resistance (1500ohms compared to 4000ohms) and may reduce misfire. We’ll see.

Question on plug numbers. What would be the difference between Delco numbers 41-942 and 41-943?

This engine calls for 942’s but I already have a set of 943’s on hand.

 

[JD1964]

Well, I finally decided to study the ignition wires in the dark with engine running. Should have done this earlier the whole diagnostic process. At least I’ve not spent any money yet, except for the alternator connector. I got that all fixed up.

Anyway, here’s a video of number 6 plug boot arcing. Pretty obvious.

 

[Ernest]

You can really hear the miss in that engine when it plug boot arcs... that lQQks bad.

 

[JD1964]

I’m guessing it’s the wire because a plug change didn’t fix it.

 

[JD1964]

Well shame on me for a poor job on the ignition wire routing when I did the engine swap. I thought the header wrap and fiberglass sleeves on the wires would be protective enough. My mistake was the wires were still left too close to header tubes and they burned. Three of them are burned. Time to get busy. In the future I might get a custom set and run them up over the valve covers like the old school sbc, instead of underneath the manifolds like stock LT1. The stock routing works good with stock manifolds and all the stock looms. With aftermarket headers it’s a different story.

Here’s the burned wires.

 

[383_StealthRam]

Good job persevering to ultimately locate the issue...glad you found it and can remedy it.

I'm not sure the feasibility or requirements for converting LT1 to Coil Near Plug (CnP) but I'll tell you I've done this on my SBC using Holley HP EFI and LS3 coils, made my own shorty MSD 8.5mm wires and have never looked back. I have the dual-sync Holley distributor providing crank and cam signals, Angle plug heads (I'm using the GM Fast Burns) does help for keeping the plug boots further away from header tubes. I'm using ARH 1 7/8" and I do use some heat sleeves on the passenger side rear because they tend to be closer because of the primary tube bends on the back two cylinders.

Regards

 

[JD1964]

I'm not sure the feasibility or requirements for converting LT1 to Coil Near Plug (CnP) but I'll tell you I've done this on my SBC using Holley HP EFI and LS3 coils,

Nice setup.

What I meant by modifying ignition wires was to simply route them from the opti, up along the sides of the water pump, then back over the top of valve covers and down to the plugs. So, it’s a modified wire routing but not a modified ignition like yours.

There are options for fully modifying the LT1 ignition system. One is to install a 411 PCM and a crank trigger. Then the opti sensor is bypassed and the opti unit only acts as a distributor but no longer senses crank position. In this option you loose the sequential fuel injection and it convert’s to batch fire. Not an issue for a race car but sequential is probably better for a daily driver.

A better option is Torqhead but it’s expensive.

HOME

TorqHead LTD Home Page

www.torqhead.com

 

[383_StealthRam]

Nice setup.

What I meant by modifying ignition wires was to simply route them from the opti, up along the sides of the water pump, then back over the top of valve covers and down to the plugs. So, it’s a modified wire routing but not a modified ignition like yours.

There are options for fully modifying the LT1 ignition system. One is to install a 411 PCM and a crank trigger. Then the opti sensor is bypassed and the opti unit only acts as a distributor but no longer senses crank position. In this option you loose the sequential fuel injection and it convert’s to batch fire. Not an issue for a race car but sequential is probably better for a daily driver.

A better option is Torqhead but it’s expensive.

HOME

TorqHead LTD Home Page

www.torqhead.com

Wow that's some nice stuff!

 

[Pronto-]

What a mess those wires were. Now you can go back to the NGK plugs. They are WAY better than Delcos.