Weird misfire

[-83MONTESS-]

I like it that you are now talking about a small misfire when maintaining a speed, that means you are driving your car...🙂

EXACTLY!!! Lol feels so damn good but the misfire is so damn annoying.

Measure the resistance (ohm) on those spark plug wires. All of them.

It's an easy job and it will help you knock out that part of the equation if further troubleshooting is required..

Dont know much about that holley design so i can judge if the carb could be the sinner here. But it doesnt sound like it.

Thats a good idea. I totally didn't even think of ohm testing them and I was off work all day. Guess I got something to do tomarow!

I pulled a few plugs and I gotta say im surprised. The plugs look really good. Not wet, black or white but a decent tan color. This was the first time I have checked the plugs after driving it so it's nice to know it's not as off as I thought.

 

[-83MONTESS-]

Well I just ohm tested the wires and they all test within MSD's spec of 40-50 ohms per foot.

I did discover that 2 of the spark plug end rubber boots are hardened and cracked from im gonna assume heat. Cylinder #3 and #4 both. I wrapped them up with electrical tape and put an insulating sleeve over them. Do you think this could cause my issue even though the wires are all well within spec? Is it possible for them to arc through still? Im gonna pull all of the plugs tonight and see if the #3 and #4 plugs look any different. It just sucks because MSD doesn't sell wires by themselves so I gotta get a whole new set.

 

[565bbchevy]

I would say if you have two boots that have been burnt and are now cracked one of those (or both) are probably arching through to the header and I would replace them.
On mine #1 and #3 are very close on my header tubes and when I had MSD wires I replaced those two boots with Accel boots because they gave me more clearance to put a 1/2" DEI sleeve on for extra insulation before putting on the spark plug sleeves.
Nothing against MSD but their overly large boots tend to cause clearance issues for BBC engines with headers.

 

[-83MONTESS-]

So im gonna replace the wires, spark plugs and after looking at my plugs maybe bump the primaries up 2 jet sizes. I know I said earlier that it ran rich but that was before I was really able to drive it. Ever since I started driving it the plugs looked better but now im thinking I may be having a lean misfire at cruising rpms. All 8 plugs looked damn near the same so it seems like even though the boots on the 2 cylinders are melted it's still hitting on all 8. Any thoughts? Jets are 77 and 83.

 

[pontiacgp]

it's hard to guess the air/fuel mixture at different rpms. With the wideband gauge it took all the guesswork out for me and I know exactly what the air/fuel mixture is at all times

 

[-83MONTESS-]

it's hard to guess the air/fuel mixture at different rpms. With the wideband gauge it took all the guesswork out for me and I know exactly what the air/fuel mixture is at all times

So that plug doesn't look lean? With the Qjet they were always dark and somewhat wet. It didn't have the miss but it bogged on acceleration.

 

[pontiacgp]

That plug doesn't look lean but that does not mean it isn't running lean at cruise. The main reason I prefer Quadrajets over Holley style carb is with the Quadrajet the metering rods allow fine tuning that you can't do with a Holley

 

[-83MONTESS-]

Well I replaced the plug wires, the plugs, and I jetted the primaries up 2 sizes. It felt a lot better but I still get a random miss here and there will cruising.

I had a buddy bring his timing light over and was surprised to find out that with 10* initial timing it jumps to about 42* at 2,500 rpm. Any ideas why it would do that? And now im having starter heat soak issues yet again.....

 

[pontiacgp]

are you using a digital ignition box?

 

[-83MONTESS-]

are you using a digital ignition box?

Yup the MSD 6al