Cold Exhaust from Driver’s Side
Thread Starter
8th Gear
Joined: Sep 2020
Posts: 8
Likes: 9
From: Charleston, SC
Cold Exhaust from Driver’s Side
Hello! I’m new here! I just finished putting a bunch of new parts on my 1980’s engine (Top end kit, carb, fuel pump, headers, spark plugs, spark plug wires, rocker arms). When doing the cam break in my buddy noticed that the driver side exhaust was cold. It felt like it was puffing out ambient temperature air, and the exhaust piping was much cooler than the other side. We both recognized that it sounded different from the passenger side as well. Our first thought was that there was something wrong with the ignition system (currently still running the original distributor, with new wires and plugs). Using an inductive timing light we saw that all 4 wires were sending current. Next, we took out the spark plugs, and when we took them out 2 looked normal, one snapped in half but looked fine, and the last had a significant amount of soot for only running for 1/2 an hour. I replaced the spark plugs and no change. I’ve been trying to find possible issues but I’m stumped. Thanks in advance!
Last edited by John Minnehan; Sep 18, 2020 at 06:13 AM.
Thread Starter
8th Gear
Joined: Sep 2020
Posts: 8
Likes: 9
From: Charleston, SC
Race Director
Joined: Oct 2019
Posts: 10,735
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From: Deep in the Pisgah National Forest
It's very easy to mix up the spark plug wires on cylinder pairs. For instance 1 and 3, or 5 and 7. Doing that will spark the cylinders on the wrong stroke and they won't fire at all. This happened to me the other day on cylinders 2 and 4.
Check the firing order of the wires on the distributor and label each. The routing of the wires makes it impossible to visually trace so use an ohm meter on each wire, one at a time.
Check the firing order of the wires on the distributor and label each. The routing of the wires makes it impossible to visually trace so use an ohm meter on each wire, one at a time.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
If fuel is flowing to all eight but two are spot fouled then it is in the ignition.
Jebby
Le Mans Master
Joined: Jun 2019
Posts: 7,658
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From: Indiana
i think he said only one was fouled? One cracked but ok
Le Mans Master
Joined: Aug 2017
Posts: 8,336
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From: Cool Northern Michigan
You say you and your buddy. Did one of you set the valve-lash on one head? Somebody else did the other side?
A quick compression test might tell us a story between the two heads also.
A quick compression test might tell us a story between the two heads also.
Last edited by HeadsU.P.; Sep 26, 2020 at 10:29 AM.
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Thread Starter
8th Gear
Joined: Sep 2020
Posts: 8
Likes: 9
From: Charleston, SC
Update: I purchased new spark plugs, the ones recommended by Edelbrock for these heads. I also replaced all the spark plug wires. I double checked each spark plug wire going to the correct cylinder. After starting her up and letting her run we don’t think the ignition is the problem. Only about 30 seconds of running and it was apparent that the passenger side was running way richer than the driver side. The inside of the exhaust was coated in soot where as the drivers side was spotless. After checking the carb again, it still doesn’t look like that is the issue. I plan on double checking the lash and then going from there. I am also waiting for a cylinder compression gauge to come in the mail.
Last edited by John Minnehan; Sep 18, 2020 at 02:54 PM.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Update: I purchased new spark plugs, the ones recommended by Edelbrock for these heads. I also replaced all the spark plug wires. I double checked each spark plug wire going to the correct cylinder. After starting her up and letting her run we don’t think the ignition is the problem. Only about 30 seconds of running and it was apparent that the passenger side was running way richer than the driver side. The inside of the exhaust was coated in soot where as the drivers side was spotless. After checking the carb again, it still doesn’t look like that is the issue. I plan on double checking the lash and then going from there. I am also waiting for a cylinder compression gauge to come in the mail.
Jebby
Le Mans Master
Joined: Apr 2011
Posts: 6,284
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From: Hermosa
Check the valve lash while you wait. Could be some valves are just cranked down too hard. 1/2 to 3/4 turn after lash is taken up. Use the jiggle up and down method vs the spin method on the pushrods to accurately judge when lash is gone.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
At this point, you don't know 100% for sure one bank is running richer. Sooty plugs could also be poor firing of those cylinders from low cylinder pressure, known as incomplete burning.
Why would just one bank of cyl have low cyl pressure? That gets back to compression test: head gasket or valve lash.
Dual plane Intakes do not feed all the drivers side cylinders from the drivers side Intake plenum. Nor does the passenger side. This makes me think your issue is not Intake or carb related. There is no correlation. But valve lash or head gasket on one bank does have a correlation.
Why would just one bank of cyl have low cyl pressure? That gets back to compression test: head gasket or valve lash.
Dual plane Intakes do not feed all the drivers side cylinders from the drivers side Intake plenum. Nor does the passenger side. This makes me think your issue is not Intake or carb related. There is no correlation. But valve lash or head gasket on one bank does have a correlation.
Last edited by HeadsU.P.; Sep 19, 2020 at 06:15 PM.
Instructor
Joined: Nov 2016
Posts: 169
Likes: 43
From: Stockholm Sweden
I actually had the same problem recently !
Thought it was the ignition that was the culprit. Changed plugs, wires and distributor. Still same problem. Turned out to be valve lash. Had to redo all my valves ,preload + 1/2 turn (hydraulic) Now runs like a champ
Thought it was the ignition that was the culprit. Changed plugs, wires and distributor. Still same problem. Turned out to be valve lash. Had to redo all my valves ,preload + 1/2 turn (hydraulic) Now runs like a champ
Thread Starter
8th Gear
Joined: Sep 2020
Posts: 8
Likes: 9
From: Charleston, SC
I will definitely reset the lash on the passenger side and see what happens, I’m hoping that is the only issue. For those following along, I won’t be able to work on the car until next weekend but I will post an update as soon as I can!
Thread Starter
8th Gear
Joined: Sep 2020
Posts: 8
Likes: 9
From: Charleston, SC
To anyone who is still following along, I did the compression test today and got some interesting results.1 : 155
3: 145
5: 140
7 : 160
8: 142.5 (150)
6: 75 (155)
4: 0 (152.5)
2: 145 (145)
The drivers side did not have any issues but 6 was low and 4 had 0 psig! I reset the lash on both sides, (I did the divers side last weekend) and the passenger side today. After resetting the drivers side I got the numbers in the parentheses, so all were as expected. I’m hoping to start her up tomorrow and see how it goes. Thanks for everyone’s help so far!
3: 145
5: 140
7 : 160
8: 142.5 (150)
6: 75 (155)
4: 0 (152.5)
2: 145 (145)
The drivers side did not have any issues but 6 was low and 4 had 0 psig! I reset the lash on both sides, (I did the divers side last weekend) and the passenger side today. After resetting the drivers side I got the numbers in the parentheses, so all were as expected. I’m hoping to start her up tomorrow and see how it goes. Thanks for everyone’s help so far!
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Looks like your onto something! Good luck.