Team Camaro Tech banner

1 - 18 of 18 Posts

·
Registered
Joined
·
6,106 Posts
Discussion Starter #1
We'll not cold but cooler than the other 7. My 327 in my 68 has been running funny, kinda sounds like I'm running on 7 cylinders. So when I started it up yesterday I felt the header tubes to see if I'm firing on all 8. Well the number 7 was cooler than the others. I'm gonna bring a laser thermometer home from work and check it Monday to see what I really have. My question to you all is what do you think I have wrong here before I start to panic.
 

·
Registered
Joined
·
406 Posts
You don't need a "laser"... sounds like you have a "dead" cylinder. You'll need to determine why the cylinder is not firing. I would check if the cylinder is getting spark first, check the plug wire and spark plug on that cylinder. Then if you have a"good" spark, you'll need to check compression on that cylinder and go from there.
 

·
Registered
Joined
·
8,108 Posts
What Maurice said. There is a dead cylinder almost certainly. Check for a good spark (sometimes a plug will crap out, so make sure the spark is strong) and then move on to compression or check valve train motion out first, it could be valve train related also.
 

·
Registered
Joined
·
406 Posts
What Maurice said. There is a dead cylinder almost certainly. Check for a good spark (sometimes a plug will crap out, so make sure the spark is strong) and then move on to compression or check valve train motion out first, it could be valve train related also.
Yes, make sure the valves are actuating on that cylinder, I guess I took that for granted. You could have a rocker arm issue, broken valve spring or a cam lobe wiped out as well. Like we said, check the spark first. Hopefully you're lucky and it's just a plug wire or a spark plug.
 

·
Registered
Joined
·
406 Posts
Well Im getting a strong spark. The rocker and spring look good the push-rod doesn't feel loose. The plug was a little black and cruddy.
Make sure your rocker arms on that cylinder are traveling the same distance as all the others when you crank the engine.. It's not 100% accurate but it's a quick visual check for a wiped cam lobe.

was the spark plug oily? I assume it was at least wet with fuel, since that cylinder has not been firing.

Now if it was me, I'd get a NEW spark plug and install it in that cylinder and see if the "miss" goes away. Be advised, spark plugs can fire, and the spark can look pretty good "outside" of the engine. This does not mean they are exactly good. There is a lot of pressure in a cylinder, due to compression, and a weak spark plug may misfire when it otherwise looks good. My "guess" is the cylinder will still probably be dead, but lets hope not. Also, don't just clean the old spark plug. Once a spark plug is "fouled" it's no good and cant be trusted. despite what anybody else tells you...get a NEW spark plug to test the cylinder.

Now, if the engine still misses, you need to do a compression test. Good luck !
 

·
Super Moderator
Joined
·
32,518 Posts
You can use water drops on the header tube.
Replace spark plug as suggested.
 

·
Registered
Joined
·
8,349 Posts
Swap the wire too with another cylinder. Then if both do good you'll know it was the plug. If the other cylinder goes cold then you'll know it was the wire.
 

·
Registered
Joined
·
6,106 Posts
Discussion Starter #10
Spark is strong but it was kind of nasty when i took it out as well as the others. I just got done taking temps on all 8 header tubes at the first bend coming out of the head. They all warmed up about the same temp. In no time they were in the low 200's and in maybe 2 minutes they were all in the mid 300's. The way I read the temps the other day is with a wet shop rag. (not very accurate)
I think I'm sucking up some oil through my PCV valve, it has no baffle. Probably squirting from one of the pushrods. So that may be fouling my plugs. What do you think?

forgot to mention this last temp test was after I installed the new plug
 

·
Registered
Joined
·
8,108 Posts
Spark is strong but it was kind of nasty when i took it out as well as the others. I just got done taking temps on all 8 header tubes at the first bend coming out of the head. They all warmed up about the same temp. In no time they were in the low 200's and in maybe 2 minutes they were all in the mid 300's. The way I read the temps the other day is with a wet shop rag. (not very accurate)
I think I'm sucking up some oil through my PCV valve, it has no baffle. Probably squirting from one of the pushrods. So that may be fouling my plugs. What do you think?

forgot to mention this last temp test was after I installed the new plug
It may have just been a simply fouled plug, every now and then my old 406 would kill a plug from idling around a lot, it ran like crap then a new plug with take care of it for a long time.

Did it look oily? Or just dry black carbon or soot?

Can't hurt to do a compression test, if it's good it could be a valve stem seal or just a fouled plug. If it happens again with no obviously oily deposits you may need a heat range warmer.
 

·
Registered
Joined
·
406 Posts
Spark is strong but it was kind of nasty when i took it out as well as the others. I just got done taking temps on all 8 header tubes at the first bend coming out of the head. They all warmed up about the same temp. In no time they were in the low 200's and in maybe 2 minutes they were all in the mid 300's. The way I read the temps the other day is with a wet shop rag. (not very accurate)
I think I'm sucking up some oil through my PCV valve, it has no baffle. Probably squirting from one of the pushrods. So that may be fouling my plugs. What do you think?

forgot to mention this last temp test was after I installed the new plug
So did you replace the spark plug(s)? Is the engine still misfiring?

Either way, you can probably stop checking the hedder tube temps now.

And yes, do fix the PCV/baffle issue, it does foul plugs...
 

·
Registered
Joined
·
6,106 Posts
Discussion Starter #14
So did you replace the spark plug(s)? Is the engine still misfiring?

Either way, you can probably stop checking the hedder tube temps now.

And yes, do fix the PCV/baffle issue, it does foul plugs...
changed the #7 plug only (for now) then checked header temp. As far as misfiring I didnt drive it tonight its raining. Test drive tomorrow.
 

·
Registered
Joined
·
406 Posts
changed the #7 plug only (for now) then checked header temp. As far as misfiring I didnt drive it tonight its raining. Test drive tomorrow.
How was the test drive ?
 

·
Registered
Joined
·
6,106 Posts
Discussion Starter #16
How was the test drive ?
I bead blasted the rest of the plugs with my tiny bead blaster. Drove it the next day and it ran amazing with no backfiring at all. btw all the plugs were black and crusty. I need to find a baffle for my pcv.
 

·
Registered
Joined
·
406 Posts
I bead blasted the rest of the plugs with my tiny bead blaster. Drove it the next day and it ran amazing with no backfiring at all. btw all the plugs were black and crusty. I need to find a baffle for my pcv.
Yup. I'd Fix your PCV issue and then replace all the plugs.
 
1 - 18 of 18 Posts
Top