I have noticed little misfire already before, but now when I but rpm-meter, which is connected to sparkplug wire, I found that cyl. 1 and 6 misses quite a much. All wires and plugs are new and ok. Also valve lash is ok.
I also played with idle mix and when leaning it helped some. Any Ideas?
change to different sparks? I'm using now A/C delco sparks.


Joug

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Sorry, my english is not very good

Make sure the gaps are consistent across all plugs

If you are using a electronic dist. check the gap, of the reluctor, with a brass feeler gauge. If using points check the point gap. Also try wiggelint the dist shaft side to side. Too much movement, due to worn bushings, can throw off the dwell.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Pierre, gaps are consistent across all plugs, but they are little bigger than normal. 0.04"

Charlie, I have electronic ignition, that gap is correct and distributor shaft is at excellent state ( is state correct word in this case??)

I have chanced ignition control box and i'm using now accel super coil (Yellow big, liquid cooled). Actually, they made no difference, when I chanced them.

I have a feeling that mixture is not atomizing as well as it should, at those end cylinders. But if it is so, what can I do for it??

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Sorry, my english is not very good

What sort of intake/carb setup are you using? Unless your running mpfi or a 6pack setup its normal for #1/#6 to run leaner then the inner cylinders because of the longer intake runners. Infact if you take a thermometer to the outside of the block in the #3/#4 area youll notice it is hotter then the #1/#6 area. Thats an issue we have to live with unless you want to change intake setups.

Leaning out may have helped because it would have a bigger affect on the inner cylinders then the outer, bringing them closer together but not close enough.

Have you checked your vacuum? It is possible that you have a vacuum leak. If leaning the mixture helped, you may also have a misadjusted choke. What is your timing set at?

Reed

P.S. Your english is better than many "native" english speakers I have met!

I have original -78 supersix with carter bbd. I have rebuilded carb and I also made new throttle axle and metering rod axle. Engine have 130 000 miles behind. Vacuum is @ idle 20 psi. Cylinder pressure is even and about 160 psi. Choke is not the problem, that misfire happened when engine was hot. That meter what i'm using shows if there is no spark at plug. And that time time i checked that, cyl. 1 and 6 misses about every 2 seconds ( this is very difficult to explain). So I try once more. When I connect rpm meter to spark wire 1 it shows correct rpm 750, but drops to zero about every two seconds and comes back to 750. It drops because there is no spark. Meter dont work without spark.

But engine works quite a well at cruise. Only problem is that it aint have that good mileage, that i know is possible. That's why I was thinking if it misses at cruise also, but I cant recognise it. I have Oxygen sensor right after exhaust manifold and I can see mixture fluctuating quite a much at cruise, Maybe that is also normal. I don't know anyone else who has used O2 sensor with carburetor. So I really don't know. That O2 sensor position might also be too far to be hot enough.

And thanks Reed. Writing and explaining in english is not easy for me, But I wont give up. I hope that everyone corrects me if I'm typing somenthing incomprehensible.

Joug

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Sorry, my english is not very good

Heck,
Most of us here don't understand what "incomprehensible" means anyway. You're doing fine. It's kind of fun trying to figure out what you are describing. Kind of like a mental puzzle.

Jerry

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There's a difference between ignorance and stupidity.
Ignorance is not knowing any better.
Stupidity is knowing, yet doing it anyway.

Joug,

Try running a cooler sparkplug in #1 and #6. this will make it look like your mixture isnt as "lean" in those cylenders. Also check the OHM readings on the wires, it should me a minimum of 500 OHMS per inch and a max of 2000OHMS per inch, also wiggle with wire around when testing, if you get fluxuating readings when it means the wire is bad

The compression is good and same with the Vaccum

Justin

P.S. heck you speak better english than me sometimes and i can only speak english I've tried to learn other languages but i cant

Justin, I have tested wires, Just like You suggested, and they are very good (should be with that price). Cooler plugs??, I was thinking hotter. If it is really so, I'll try that. Thanks

Joug

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Sorry, my english is not very good

A hotter plug will make a lean mixture even more lean, however it will make a ritch mixture seem lean. So a colder plug will make a ritch mixture seem even more ritch and a lean mixture seem more ritch (which is what you want in this case)

I'm not sure if you can follow this, but i'd give it a try, plugs arnt all that expensive, and the slantsix has a bad habbit of running lean on #1 and #6 due to the longer runners.

Justin

I'm using now ACDelcos CR45TS plugs. Haynes book says that -76 and later engines use Champion RV17YC and earlier engines RN14YC plugs. I think that those earlier engines have colder plugs. What is the reason for that?

Anyway I'll try colder plugs in cylinders #1 and #6.

Jerry, "incomprehensible" was only word, which I found from my dictionary, that descripes somenthing what is not understandable. And I think, that I am sometimes (read usually) not understandable

Joug

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Sorry, my english is not very good