V8 running on 7 cylinders, bad?

[OilyWater]

I have a carbed 7.4L engine in my Blazer. There is something wrong with one of the cylinders, not sure exactly what, but when it's spark plug wire is hooked up it backfires through the carb. When that cylinder's wire is unhooked, it runs fine.

Is it bad to drive around like this? (on only 7 cylinders) Will the unburned fuel wash the oil off the cylinder?

I don't really want to fix it until the weather warms up. I don't drive this truck very often so the loss of power/mileage isn't really a problem.

 

[eljefino]

you bet it's bad. All that gas will wind up in your catalytic convertor and could burn your truck down.

 

[Crashbox]

Is it either number 5 or number 7 cylinder? If so there's a slight possibility of crossfire from the adjacent wire... Just a thought.

 

[cousincletus]

Could be a stuck or burnt valve.

 

[Rickey]

Crashbox has a good point. Also you may overheat the catalytic converter if it has one. The engine may have a burned, sticking or bent intake valve on the affected cylinder. I personaly wouldn't operate an engine for long in this condition as more damage could occur. How many miles and any other symptoms would be useful. Valve troubles can sometimes be diagnosed by removing the rocker cover on the affected cylinder. A broken valve spring or stuck lifter can also cause this symptom. Has the engine been overreved? Good luck. Rickey.

 

[Master ACiD]

i bought an old ford in north georgia and drove it down to south florida on 6 cylinders. it has a burned head gasket between 2 cylinder.

i did 100 mph the whole way home, with the throttle floored. after i got home and replaced the headgasket, the 2 dead cylinders looked fine with the head off. could still seencross hatching. that engine ran great after i changes the head gasket.

 

[Gary Allan]

I'd go with Crashbox for the best hope for cheap and easy.

Check your cap and wires. I had an engine that ran smoother on 7 then on 8. The carbon track fired both cylinders when either sparked ...caused all kinds of havoc when hooked up to all 8. Take either off ..smoother.

I know it's rare for an HEI cap to have issues (I never had any problems with them) ..but it's worth checking into

 

[mechtech]

Sounds like 5 and 7 plug wires are crossed, or maybe a cracked cap.

 

[BlazerLT]

How about actually pulling the plug instead of being lazy and running around on 7 cylinders.

The time it took to type your message could have been used checking the cap and rotor or the plug itself.

Sorry for being rough, but you have to see how ridiculous the question is.

 

[GeaugaFletcher]

quote:

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I don't really want to fix it until the weather warms up.

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Whoa, it's at least 55 today here in Tulsa and I know you're farther south than me. Suck it up, man, it's not cold at all.

 

[OilyWater]

Thanks for the suggestions guys, but this simply is not going to get fixed until at least late spring. I am not in Texas right now and it's about 40 degrees and raining. I've already replaced most of the ignition system, there's most likely a problem with the intake valve not closing for whatever reason.

I just don't want to do any further damage to the engine before I fix it. If that means not driving it until spring, then that's what will happen. This truck hasn't had a cat since about 1982 when the stock 305 was yanked.

I seem to remember people unhooking 4 cylinders on a V8 during the 80s gas problems, but they weren't pumping unburned fuel through their engine either. It runs surprising well missing 1 cylinder...

 

[andyd]

fine, you're gonna side line a truck for a problem that will prollly take about an hr to fix. 40f is is great car crawling weather in these parts, keeps the skeeters flying slow enough to catch easily.

If you havent replaced the cap/wires/ plugs in this decade, thats what I would try 1st.

 

[pmwalter]

Wouldn't you be shaking back and forth with a cylinder out? A cylinder stopped working on one of our 7.3L Powerstrokes and the whole rig shaked like a martini being mixed.

Rough ride.

 

[Chris142]

This is typical of a flat cam lobe. And typical for a BB Chevy. Dont run the engine till it's fixed or you will run all that cast iron cam stuff through the soft bearings.

 

[BlazerLT]

I am unsubscribing to this thread, this guy is just being lazy and there are plenty of other people that need help that will actually do the work.

 

[OilyWater]

Good *** there's a lot of ******** on this forum. It was a very simple question. I don't need your high and mighty opionion of what I should be doing with my truck. Unlike some of you guys I have more important things to do than work on an old truck I rarely drive in the rain. You people have no idea what the problem is, or what my situation is.

 

[Gary Allan]

Well, at least you have the full spectrum of advice and opinion on the rest of your life as well as this problem.

You'll figure out that most of us here are, basically, geezers. You know the type ...they forget a few selective parts of their own history in the formation of their opinion on how others should do things. If you can't be miserable and treat others like dirt in your golden years ..well ..that's your own fault.

It's an evolutionary process. You'll go through it too some day.

 

[Drew99GT]

I could say something about a certain poster (as this kind of stuff is routine), but I'll just zip my lips.

 

[Rickey]

Hey OilyWater, something I had forgotten: find a magnet, pull the dipstick and drag the oily part across the magnet. If there are any appreciable metal shavings in ihe oil they will stick to the magnet like little wkiskers. If this happens then suspect a cam lobe worn down as suggested above. I also suggest running it briefly before testing to stir things up a little as metal will tend to settle out of the oil. Good luck. Rickey.