Colder Cylinder... Lifter Failing?

93CalypsoConvert

Active Member
Nov 26, 2020
133
48
38
42
Virginia
After installing aftermarket headers, I noticed all the primaries have a consistent heat pattern except cylinder #2. Checking the temps confirmed cylinder 2 is around 50 degrees cooler at idle. I cannot check the compression because of the stupid GT40p plug location, but I highly doubt its a compression issue. The engine only has a few thousand miles on it and it idles too well. I don't think its a fuel issue since its carbureted. Ignition system was new with the rebuild, and plug wires are in great shape. The spark plug looks great and is gapped appropriately.
Header.jpg

There is a tick near this cylinder so I'm wondering if a lifter is going out, although I am not sure how that would cause a temperature difference. I can't wiggle the rocker and the stud it torqued at 20lb.
 
Last edited:

Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
39,129
15,035
224
Massachusetts
Hows the spark plug look compared to the others? Does it look like it's firing? If you pull a plug (or use a spare) and put the plug on the intake and hook the spark plug wire up, can you see the plug fire if you run the engine?

From the looks of things, i would say that cylinder is not firing. These engines can run on 7 and seems perfectly fine. Really it comes down to air, compression, spark and fuel. SInce it's carbed and running, i'm going to assume airflow and fuel is fine. (unless there is a rag stuffed in the intake port) so really it comes down to checking to se if the spark is firing on that cylinder, and figuring out some way to do a compression test on it.
 

Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
39,129
15,035
224
Massachusetts
I see it now.

I see where you are going with this. Yes, it's possible it failed but not sure if the pushrod and rocker would hold it in place, or if it will be damaged. Unfortunately the lower needed to be pulled to have a look. Not sure a compression test would tell you much as the valve might be hanging open, or might be closed all the time.
 

7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
7,356
3,061
194
Kearney, NE
A header leak can sound like a ticking. 50 degrees difference does not seem like much for a dead cylinder. I’d hate to see you take apart the top end for something simpler.although the lifter cup clip is not right.
 

93CalypsoConvert

Active Member
Nov 26, 2020
133
48
38
42
Virginia
I wonder if the lifter is causing the valve to either bleed compression or prevent it from opening all the way... That would cause a cooler cylinder. I know the valve moves and makes compression to a point. I can't hear an difference in compression while cranking and I can see the rocker moving with the valve cover off. Also no way to do a compression test unless I remove the header... I might go ahead and pull the lifter when I get a chance and see whats up.
 

Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
39,129
15,035
224
Massachusetts
I think at this point, it's your call as to what route to take. I definitely see an issue with that cylinder just based on the appearance of the header alone. As to what to do next, it's all a PITA no matter what. Pull header or pull lower intake.

For me, i need to verify the problem first before fixing it and for me, that means doing the compression test. At least your header hardware looks new, so it wouldn't be too bad to pull that off and check.

Your call though, but I think you have this figured out in terms of what to to next.
 
  • Like
Reactions: 1 users

7991LXnSHO

wanna catch the space herp
10 Year Member
Sep 1, 2010
7,356
3,061
194
Kearney, NE
I think at this point, it's your call as to what route to take. I definitely see an issue with that cylinder just based on the appearance of the header alone. As to what to do next, it's all a PITA no matter what. Pull header or pull lower intake.

For me, i need to verify the problem first before fixing it and for me, that means doing the compression test. At least your header hardware looks new, so it wouldn't be too bad to pull that off and check.

Your call though, but I think you have this figured out in terms of what to to next.
I wonder if the lifter is causing the valve to either bleed compression or prevent it from opening all the way... That would cause a cooler cylinder. I know the valve moves and makes compression to a point. I can't hear an difference in compression while cranking and I can see the rocker moving with the valve cover off. Also no way to do a compression test unless I remove the header... I might go ahead and pull the lifter when I get a chance and see whats up.
Probably will need done soon if it is not already the issue.
 
  • Like
Reactions: 1 user