Head gasket replacement success, but engine running really choppy (1980, 20r)
12-28-2016, 06:39 PM
#1
Registered User
Thread Starter
Join Date: Jun 2015
Posts: 22
Likes: 0
Received 0 Likes
on
0 Posts
Head gasket replacement success, but engine running really choppy (1980, 20r)
Last night the exhaust on my 1980 pickup notified me that the head gasket has finally left this mortal coil. Fortunately for me I had an extra brand new gasket on-hand along with a FSM so I followed the instructions and took my time; this evening after finishing up I (to my own amazement) started it up, and at 1k idle it lopes a bit but taking it on a drive the choppiness gets worse as the RPMs increase. Right now I'm pretty beat and have other chores to finish before waking up for work tomorrow; and hoping maybe one of you know exactly what is causing this.
Details:
1.) 20r, Weber 32/36 carb (with fuel pressure regulator, 2.5PSI)
2.) I followed the FSM head removal/reinstall instructions faithfully; including the method to reinstall the distributor. It starts and runs so I'm pretty sure I got that part correct.
3.) Possibly a vacuum leak, I'm not exactly sure; I'm very certain that I reconnected every hose -- this includes the one that goes to the vacuum advance on the distributor. I don't have a tool to measure vacuum at the moment, however.
4.) Oil and coolant was replaced.
5.) Using my timing light, I checked each spark plug wire. There's a spark going to each plug.
6.) Timing was set to 8' as per FSM spec. I know that with Webers it's usually preferred to set it around 12' as a minor tweak but the choppiness of my engine is far beyond what that can help at the moment.
7.) During the head gasket change, the timing sprocket stayed where it was so the teeth are where they should be. I painted the chain as per the FSM suggestion and when I was all said and done it aligned with TDC.
Thanks!
Details:
1.) 20r, Weber 32/36 carb (with fuel pressure regulator, 2.5PSI)
2.) I followed the FSM head removal/reinstall instructions faithfully; including the method to reinstall the distributor. It starts and runs so I'm pretty sure I got that part correct.
3.) Possibly a vacuum leak, I'm not exactly sure; I'm very certain that I reconnected every hose -- this includes the one that goes to the vacuum advance on the distributor. I don't have a tool to measure vacuum at the moment, however.
4.) Oil and coolant was replaced.
5.) Using my timing light, I checked each spark plug wire. There's a spark going to each plug.
6.) Timing was set to 8' as per FSM spec. I know that with Webers it's usually preferred to set it around 12' as a minor tweak but the choppiness of my engine is far beyond what that can help at the moment.
7.) During the head gasket change, the timing sprocket stayed where it was so the teeth are where they should be. I painted the chain as per the FSM suggestion and when I was all said and done it aligned with TDC.
Thanks!
12-29-2016, 06:21 AM
#2
Registered User
Several questions:
Is it running rough from idle to top end?
Is the 8 degree timing where it was before this?
Have you tried ether (or similar spray) to check vacuum lines and connections?
How old are the vac lines?
How many vac connections are there on an 80?
Is it running rough from idle to top end?
Is the 8 degree timing where it was before this?
Have you tried ether (or similar spray) to check vacuum lines and connections?
How old are the vac lines?
How many vac connections are there on an 80?
12-29-2016, 06:24 AM
#3
Registered User
Easiest most common mistake is having the distributer stuck in a tooth off. If it only seems to just start to run right at one extreme end or the other of how far you have it turned, then that's probably what happened. If not, then you'll have to dig deeper into other ideas.
Other than that, it's just the obvious stuff that we can't know from over here on the internet and have to take your word for, since there are so many little things anybody can mess up. When I did my head gasket, my engine was running rough. I was really scared that it was leaking and I messed up something major. I turned out I had actually bent the metal connection inside one of the spark plug wires, at the spark plug, so it wasn't actually connected to the plug end. Any little thing like that can cause it to run rough.
But check to see if turning the distributer all the way one way or the other gets it close to running right. I've had the distributer on my different trucks out maybe 6 times. Probably 3 or 4 of those times it took me more than one try to get it in just right.
Other than that, it's just the obvious stuff that we can't know from over here on the internet and have to take your word for, since there are so many little things anybody can mess up. When I did my head gasket, my engine was running rough. I was really scared that it was leaking and I messed up something major. I turned out I had actually bent the metal connection inside one of the spark plug wires, at the spark plug, so it wasn't actually connected to the plug end. Any little thing like that can cause it to run rough.
But check to see if turning the distributer all the way one way or the other gets it close to running right. I've had the distributer on my different trucks out maybe 6 times. Probably 3 or 4 of those times it took me more than one try to get it in just right.
Last edited by 83; 12-29-2016 at 06:25 AM.
12-29-2016, 09:05 AM
#4
Registered User
Thread Starter
Join Date: Jun 2015
Posts: 22
Likes: 0
Received 0 Likes
on
0 Posts
This was exactly the problem. I pulled the distributor out and set it a bit to the left and re-inserted and this cleared the problem right up. Ran down the interstate pretty well. Thanks!
