Dead Cylinder Questions
Thread Starter
Racer
Joined: Jul 2007
Posts: 348
Likes: 12
From: Ocala, Florida
Dead Cylinder Questions
On a 383 stroker I have a dead cylinder #2. With a heat sensing gun each header reads between 4 & 5 hundred degrees #2 reads 160 to 190. I have checked the spark plug, fires in another cylinder, moved the spark wire to another cylinder, fires, changed the distributor cap and rotor, cylinder still dead, ran a compression test on #2 cylinder, 150 lbs, checked valves on #2 appear to be moving the same on cylinders 4,6,8. I am baffled. HELP JAY
Le Mans Master
Joined: Jan 2000
Posts: 8,918
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From: New Hill NC
On a 383 stroker I have a dead cylinder #2. With a heat sensing gun each header reads between 4 & 5 hundred degrees #2 reads 160 to 190. I have checked the spark plug, fires in another cylinder, moved the spark wire to another cylinder, fires, changed the distributor cap and rotor, cylinder still dead, ran a compression test on #2 cylinder, 150 lbs, checked valves on #2 appear to be moving the same on cylinders 4,6,8. I am baffled. HELP JAY
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
Only two ways for it to not get fuel to #2 cylinder: 1) the intake valve is not opening; 2) there is a blockage in the #2 port on the intake manifold.
If it's not 'hot', it can't be firing. If it's not the plug, wire, cap or rotor, it must be getting spark. Getting spark but no fire = no fuel mixture in cylinder.
I would think that any blockage in the intake manifold would clear itself under the suction of the intake cycle. ???? More likely that the intake valve is not opening.
If it's not 'hot', it can't be firing. If it's not the plug, wire, cap or rotor, it must be getting spark. Getting spark but no fire = no fuel mixture in cylinder.
I would think that any blockage in the intake manifold would clear itself under the suction of the intake cycle. ???? More likely that the intake valve is not opening.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
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From: Seattle WA
St. Jude Donor '14
I know you moved and checked the plug and wire, but check the ignition where it is by just hooking your inductive timing light to it - just fire it up, connect the light to the #2 wire and point it at your hand...if the light is flashing, the plug is firing and we move on. If it's not flashing, or flashing consistently, then we need to check the path: rotor->cap->wire->plug.
Next, pull the valve cover - easiest thing to check for is a pulled rocker stud, not at all uncommon in this vintage. If nothing's obvious, then pull the coil wire, have someone crank the engine, and watch the rockers on #2...and compare them to #4 - are they moving about the same amount?
If nothing comes from either of these, circle back and we'll look at other stuff
Next, pull the valve cover - easiest thing to check for is a pulled rocker stud, not at all uncommon in this vintage. If nothing's obvious, then pull the coil wire, have someone crank the engine, and watch the rockers on #2...and compare them to #4 - are they moving about the same amount?
If nothing comes from either of these, circle back and we'll look at other stuff
Burning Brakes
Joined: Sep 2012
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From: coon rapids mn
pull the valve cover and remove the spark plugs .have some one turn the crank over with a big ratchet .you will watch the push rods on #2 to see if they are moving the same as other cylinders .
Team Owner
Joined: Jan 2006
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From: Crossville TN
No. The distributor doesn't care which cylinder is getting the spark. That is determined by the distributor cap. The distributor cap contact could be bad, but you stated that it did the same thing with two different caps.
Last edited by 7T1vette; Dec 11, 2013 at 10:08 AM.
Safety Car
Joined: Mar 2007
Posts: 3,652
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From: Bridgewater nj
I wiped out a cam a few years ago and the valve was still moving but I didn't figure it out until a week later and 50 miles before it got real bad. Then another cylinder dropped out and then I could see the difference in the rocker movement.
Either way, if the cam is wiped the damage is done! Catching it early will most likely save your bottom end. So you might want to get a micrometer with the magnet block to get a good reading on your valve lift.
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From: New Or-leens Loo-z-anna
You can get a "cheap" dial indicator ( a device that measures the amount of movement) -----you only need a cheap one unless you're going to be doing some serious engine rebuilding)------and set it on the top of the intake rocker arm--use a tool to rotate the engine by hand to check the total movement of the intake & then the exhaust valve---then compare those measurements to the spec. chart for your engine to determine if the cam lobes are wearing out.
Simple/easy to do after removing the valve cover---other cylinders can be checked also----write down the findings for future reference!
Simple/easy to do after removing the valve cover---other cylinders can be checked also----write down the findings for future reference!
Last edited by doorgunner; Dec 12, 2013 at 07:54 AM.
Thread Starter
Racer
Joined: Jul 2007
Posts: 348
Likes: 12
From: Ocala, Florida
OK here is the progress. Valve cover pulled intake valves opening the same on pass side bank. Put in a different distributor. Removed carb a holley 4150 650 cfm, blew out all passages on carb. Today a friend loaned me a boriscope I will examine the the intake passage. I will report my findings. JAY
Thread Starter
Racer
Joined: Jul 2007
Posts: 348
Likes: 12
From: Ocala, Florida
The motor does not pop thru the carb. It runs smooth on the road. When I raise the RPM's the header for that cyl Heats up but runs cold at idle. I have rebuilt the carb, replaced the dist, verified the intake andexhaust valves for that cyl move the same as the other cylinders on that bank. A friend loaned me a boroscope but have not checked the intake passages yet. Will update on progress.JAY
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
OK. Here's one from "left field":
Is it possible that the spark plug threaded hole for that cylinder has been repaired with a Heli-Coil sometime in the past? If so...and if the mechanic decided to put epoxy on the Heli-Coil to assure that it stayed put...the spark plug would have little [or no] ground circuit with which to fire. The plug is grounded via the threads in that hole. If there was epoxy on the Heli-Coil threads, it would insulate them and prevent firing.
Is it possible that the spark plug threaded hole for that cylinder has been repaired with a Heli-Coil sometime in the past? If so...and if the mechanic decided to put epoxy on the Heli-Coil to assure that it stayed put...the spark plug would have little [or no] ground circuit with which to fire. The plug is grounded via the threads in that hole. If there was epoxy on the Heli-Coil threads, it would insulate them and prevent firing.
Safety Car
Joined: Jan 2009
Posts: 4,000
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From: New York
How does one think blockage with no adverse running conditions ? When you built the motor did you leave a rag in the intake ? Or had it tapped off ? If it is a blockage it must have been done when it was built and missed....
OR......Are you losing coolant ? Cause it sounds like it is at water temp.. So head gasket ? Which as i think about it makes a lot more sense then a blockage that causes no driving issue.
OR......Are you losing coolant ? Cause it sounds like it is at water temp.. So head gasket ? Which as i think about it makes a lot more sense then a blockage that causes no driving issue.
Safety Car
Joined: Jan 2009
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From: anchorage ak
OK. Here's one from "left field":
Is it possible that the spark plug threaded hole for that cylinder has been repaired with a Heli-Coil sometime in the past? If so...and if the mechanic decided to put epoxy on the Heli-Coil to assure that it stayed put...the spark plug would have little [or no] ground circuit with which to fire. The plug is grounded via the threads in that hole. If there was epoxy on the Heli-Coil threads, it would insulate them and prevent firing.
Is it possible that the spark plug threaded hole for that cylinder has been repaired with a Heli-Coil sometime in the past? If so...and if the mechanic decided to put epoxy on the Heli-Coil to assure that it stayed put...the spark plug would have little [or no] ground circuit with which to fire. The plug is grounded via the threads in that hole. If there was epoxy on the Heli-Coil threads, it would insulate them and prevent firing.
Team Owner
Joined: Apr 1999
Posts: 21,953
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Clamp your timing light to that cylinder. It will tell you if the wire is getting spark. cheap wires can get holes blown in them and they arc to the block instead of jumping the resistance of the plug. Fire the motor in a dark room and if it looks like a light show under your hood you are screwed.
Pull that plug out and lay it across the intake manifold and have your buddy crank the motor over in a darker setting. If the motor fires up it is fine. Just watch for the plug firing
You said the valves are opening so it only leaves one thing lack of spark or lack of spark at the correct time.
If you have the wires in the wrong order the plug could be firing on other than the compression stroke never heating the primary tube.
Pull that plug out and lay it across the intake manifold and have your buddy crank the motor over in a darker setting. If the motor fires up it is fine. Just watch for the plug firing
You said the valves are opening so it only leaves one thing lack of spark or lack of spark at the correct time.
If you have the wires in the wrong order the plug could be firing on other than the compression stroke never heating the primary tube.
Le Mans Master
Joined: Jan 2000
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From: New Hill NC
Safety Car
Joined: Jan 2009
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From: anchorage ak
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
the helicoil has to be touching the metal on metal in the threads somewhere. The spark from a plug can arc more than a 1/2 inch when you have bad wires. So the tiny width of epoxy is nothing