Plug reading...

[HwyStarJoe]

Hi all,

Anyone care to read these plugs and give me your opinions?
They look strangely clean to me.

(Forum will only let me post 5 pics... so I picked random ones but all 7 I took look just like these)

It's an old 305 that has a miss when I've been driving it for a while. Starts out pretty smooth but once it's warmed up the miss gets worse and worse.
The reason I'm not showing Plug #1 is because it's brand new.... It's an Autolite AR135, while the rest are new AC R45TS's. The header pipe is in the way of #1 so I have to run a shorty there.
2 thru 8 have about 50-60 mixed highway\around town miles on them.
1406 carb is freshly rebuilt.

After looking at these, I was hoping the plugs could point me in the right direction but there's no smoking gun, UNLESS one of these is just not firing at all. I haven't dug into the wires or HEI distributor yet.

Maybe it's not ignition, but I was hoping the plugs would at least be that nice tan color like plugs #6 and #8. Too lean? It was extremely rich before I got my hands in there and rebuilt/tuned the carb and put these plugs in.

Thanks

[geezer#99]

Have you checked the rockers are all moving the same amount?

Oil on the plug threads shows your guides are leaking. Maybe bad seals.

And it’s running a tad rich. You might want to lower your float levels a bit or check for a leaky booster.

[HwyStarJoe]

Hey Geezer, I haven't run it with the covers off or done a lash yet, but I did do a cursory check of the rockers and springs. So it could be lash, pushrods or lifters.
And I'm sure the valve seals are trash. This thing is tired to say the least.

I set the floats lower than the spec to .5" as opposed to what Edelbrock states.

[Ironangel]

Those plugs look extremely lean to me...The miss could be a lean bog or stumble because it's either getting to much air and/or not enough fuel. There may be a vacuum leak as well...The dirty threads are likely from leaky valve cover gaskets and crap built up outside the plug holes...Not to contradict Geezer, jus sayin wut I'm seein...

[HwyStarJoe]

Yeah, I'm not worried about the oily threads. She's a leaker. ��

As for being lean, like I said it was HUGELY rich when I got it and I took care of that. I can't find a vacuum leak so it's probably more a fuel issue.
I adjusted the carb again but it may be jetting.
I gotta replace the fuel pump gasket anyway so I may throw a pump on as well.

The 'miss' is still there but now it's just constant and doesn't get any worse as I drive it. That leads me to believe it's a carb\fuel issue. And I need too replace the cap/rotor and wires still.


Thanks

[kwmech]

How many miles are on these plugs?

[HwyStarJoe]

Maybe 60-70

[vince1]

I'd make sure the valves are not set too tight for one and secondly that they have enough travel by not having a worn cam lobe.

[HwyStarJoe]

That too...need to do a lash for sure. Prolly find bent pushrods and lug nuts holding the rockers on.

[Dead Parrot]

Replace the cap/rotor/wires first. Miss could be one bad wire or crack in the cap.

If the miss is still there after replacing the cap etc., pull plug wires one at a time and see if you can ID the cylinder that is missing. That can tell you which pair of rockers to inspect.

[HwyStarJoe]

Right.
Well, since the fish ain't bitin', might as well play with the truck
😉

[HwyStarJoe]

Alright...played with it this weekend... I believe I found the source of the 'miss'.

It's definitely on the right (pass) side.
I did a valve lash, so that's right on. No probs on the top end or pushrods. So cam is OK too. Plug wires and cap are good.

I believe there's a piston with bad rings. It smokes on that side, and holding my hand in front of the exhaust pipe, it's got an inconsistent pulse on the pass. side, where it's very consistent on the driver's side. Dead cylinder.
My guess is a broken compression ring...that's why I don't have fouled plugs.
��

Time for an LS swap I guess.