Hello

I was working on my car this weekend and I noticed that the right side (passenger) seemed hotter than the left side (driver). I took an inferred thermometer and put it on the headers on each side and this is what happened.
The passenger’s side was higher than the maximum temp that the gauge can read which is 500 and the driver’s side was only 320. This was after allowing the car to run for awhile and at coolant temp was at 160.
In addition to that, the car has a backfire-like noise at cruising speeds and it runs very very rich at idle. I thought it was the carb, but I checked all of the settings and they seem okay. It started after I replaced the carb and alternator about 2 weeks ago. (but I never compared the exhaust temp before, so I am not sure if this problem existed in the past.)
Any Suggestions.

I pulled the plugs on the driver’s side and the gap had widened from .035 to about .048 on all of them.

Is it the driver’s side or passenger’s side that has the problem? In other words, is the driver’s side too cool or the passenger’s side too hot???

Thanks,
Joe

I was going to replace all of the plugs and see if that helps? Is that a good starting point, I have a feeling that it will just ruin the plugs???

 

Usually, high temp headers indicates that some combustion is occurring in the exhaust. I'd say that the drivers side is OK but over 500 seems way too high on the other side, and it is probably related to the rich condition. The gap on the drivers side plugs is too wide for a normal ignition. What do the plugs on the other side look like? Are the hot pipes all coming from cylinders connected to the same plenum in the manifold? If so, maybe one side of the carb is out of adjustment...

It could also be a timing issue or valve problem (not much help I know... ).

 

interesting....I would guess to cool is the problem...i guess what i would start doing is measuring individual cylinder readings to see if they are all low or if one of the cylinders is not firing and you just happen to be measuring a cumulative heat reading. i would do this right after start up so you can see a difference before theheat transfer takes place. perhaps it is something simple like some spark plugs not firing. (perhaps crossed wires, or broken plug wires,dead sparkplug)

 

YOu have been a lot of help.
THe timing is set to 18 initial 36 total. I have not have time to pull the plugs on the passengers side yet. I took the carb off and check all of the settings. All four adjustment screws on my demon areat 3/4 of a turn maybe a little less. The car runs very rich at idle. the exhaust makes your nose bleed, seriously. It seemed like the whole headers was hot as opposeed to one section. I have an MSD ignition and the gaps were .035 when I started about 100 miles ago, now they are expanded to almost .048. I will try the new plugs. It may be the float levels on the carb, but they are at 1/2 right now.
Any more suggestions??
Thanks,
Joe

 

How can I test for this. BTW, you helped me with the carb issue and that went great.

Thanks,
Joe

 

My brother, a Wyotech grad, took it for a ride and thought that the backfire lioke noise at cruising speeds was possibly detonation. He was unsure though. It doesn't seem to ping, but it is loud and hard to tell.
I think the compression ratio is in between 10.5-11.0 do you think the timing is too high???
Also, the plugs I pulled out were AC DELCO 2. (I have no idea) I am putting in champion plugs based on a recommendation on this forum.

Thanks,
Joe

 

I'd definately check each cylinder temperature. The pass side shouldn't be that hot, one of those cylinders isn't burning its fuel. You can rule out carburation, each side of the carb feeds two cylinders in each bank. It has to be ignition. Joe
PS, a good carb tune-up woundn't hurt if it's that rich, although it's not the cause of your header temperature problem.

 

HOw do i check the temp of each cylinder on that side? I have an inferred thermometer. Should I just measure the temp at the header by each cylinder? What about spart plugs, can a fouled/damaged/broken spark plug make it run hot?
Thanks,
Joe

 

i would start by picking a spot to aim that the infra red thermoter at that is universal for all cylinders, i would start the engine cold ,get out a clip board and frantically make all my measurements and yell them out to some to write down for about 2-3 minutes then try and sit down and see if there is a pattern that emerges that is different from the rest.

You know if you get really stumped you can take the car to a tune up shop and ask them to run what use to be a $29.95 test and it would tell you everthing you ever wanted to know about your engine from cranking amps to sparkplug effeiciency and a whole lot more....

 

Bob,
I did not know you could have that test done on an older car. Which repair shops will do a test like that. i have brought my car to two shops with bad results. (2) $800 bills and no changes.

What do you think about the plugs? could they be causing the problem?? I haven't pulled the plugs on the passengers side, but if I replace them, could that help? If not, what in the ignition would be causing it???

Thanks,
Joe

 

If it were me I'd be back at those shops complaining that I paid $800 bucks and no changes. Hold them accountable

 

couldn't hurt replacing plugs, many years ago i took a car that i was thinking about buying to a local firestone and asked them to run a diagnostic test on it. it was a precomputer car and they hooked up wies to each of the sparkplugs, tail pipe probe, etc... and ran a simple diagnostic test. I would think this test equipment is still out there why not call a couple of local dealers and see if they can run the test. just ask for the printout they should be willing to give it to you.

 

This is my theory:
The carb had a float stuck all the way down. This caused the car to run rich I think?? Somebody let me know if this is true. The excess gas caused the spark plugs to foul out. What do you think?

I am hoping this is the case.

If it is ignition, what should I look at timing? Plug wires? voltage at the 6AL box??

Thanks,
Joe

 

yes, its a process of diagnosis and elimination, why not plug a timing light on each plug wire to make sure they are all firing, start with number 1 and check youinitial timing setting to start with, somehow you need to check coil voltage, maybe take a plug out and ground it and see if the sprk is jumping suffciently, if thats all right make sure all spark plugs are good if you have no history with them why not replace them.

 

Didn't happen to do some plug wire work did you? 2 plugs out of order on the same bank can give you the symptoms you have.

 

I thought it was lean mixtures that caused real high combustion temperatures, not rich mixtures...

It would seem that the intake may be delivering a lean mixture to one or
more cylinders. I have no idea how to fix this if its the case...

I have a similar problem, though with an 81 electronic carb, cylinders 6 or 8
is very hot compared with the rest...

Good luck.

 

I will double check all of it ASAP.
question about the timing light procedure.
If you put the light on the plug, it will light up if the plug is firing? right?
If they all light the timing light up then all the wires are okay?

Thanks,
Joe

 

Not sure,
I did do plug work but I thought they were all set
I have a diagram of firing order and I will make sure all the plugs are correct.

Thanks,
Joe

 

From what I got in this post and others, it could be either ich or lean that causes high exhaust temp.

Rich because the excess gas gets into the header and then causes combustion not in sync with the engine. Is that right everyone??
Thanks,
Joe

 

Yes that is correct. I would look at two plug wires interchanged. This would explain the popping at cruise. Engine would have a rough idle but may be hard to tell. I would look at the 6 and 8 cylinders interchanged. Good luck