I "think" intake type "might" have something with fuel distribution.

 

Intake is the old RPM. Not a air gap. You saying that runner is not getting as much fuel?

 

If it's not getting enough, it'll be hotter - lean runs much hotter than fat.

 

What engine and how much is the temperature differences? All cylinders don't get the same amount of fuel/air flow, so there will be slight differences.

 

Its a small block. 383. Im unsure of the temp difference, didnt have a infrared gun.

 

What were the temp differences? I didn't check before tearing my motor down but I did notice that the front spark plugs 1&3, 2&4 were "cleaner" than 5&7, 6&8 which had a black, sooty appearance, not fouled but black.

 

Not sure of the tempature difference at this time.

 

Two or four idle mixture screws? What carb?

 

Holley 3310 with a rear block added.

 

I would start out with testing the compression first.

 

Please clarify what is "not equally" hot. How much temperature difference are you talking? Did you use a pyrometer or just your little brother's hands? I've never seen all 8 being dead on equal

 

The spray bottle with water tester!

 

Buy this and check your temps.

https://www.harborfreight.com/infrared-thermometer-93984.html

 

And I was just at HF.
We just need temps from every tube about 2" from the flange.
I don't think any carb can deliver 100% equal fuel.
Ignition condition and remember that type of plug wires will carry voltage differently.
Compare #1 & 7 spark plugs. Never run 5 & 7 wires in parallel. I cover both of mine in that corrugated electrical conduit.
That is why we now have multi port injection.
Rick

 

On my LS using a IR temp gun at idle the temps are all over the place. As long as they all have heat I don't worry much. Just changing the placement of the temp gun makes a pretty big difference sometimes.

 

Before temp tools the wet rag was a tool. We all likely did it.

 

Not me. What would be the point in doing that? If the heat difference from one tube to the next had to do with a tuning issue, how would you correct it and then check the difference or the change with a wet rag?

IMO anything short of one tube being so much colder than the others that you can actually touch it with your bare hand and keep it there, I don't see any point in attempting to determine if all the tubes are the same temperature. Anyway I was just messing with Aaron. No offense was intended.

 

I saw this thread this morning and checked mine today. After driving the car (ceramic coated headers) 2” from head on header tubes ranged between 220 and 190 30 sec after shutting the car off. Cylinders 1 & 2 were around 190. The rest were pretty close around 220. Possibly the fuel distribution (single plane intake) or maybe the fans cool them more. Although I doubt it.

 

Aaron. Not always but don’t trust infrared for reading temps on shinny surfaces. Not sure if your headers are dull but. The slightest angle or distance from the flange and temps drift a lot. I use a type k thermal coupler made for contact readings. We use it in refrigeration to read temps on suction lines sweating and shinny lines, where infrared don’t work reliably.

I also like using it on my bikes, after sync carbs, I read each exh pipe,,if reading are off, and carbs won’t sync there’s a valve clearance issue with an exh or intake valve.

on cars almost the same. if you have a dual plane manifold with out the cut out there could be some temp differences related to that. You could follow intake runners to see if you spot a pattern.
you could have a intake or exh valve staying open. Compression test or leak down could spot this. Spark plug, or wire, distributor cap, rotor. Hope you find it

 

Aaron. Not always but don’t trust infrared for reading temps on shinny surfaces. Not sure if your headers are dull but. The slightest angle or distance from the flange and temps drift a lot.

That's^^^^ a very good point. I've seen as much as a 50 degree temp difference on my ceramic coated header tubes, using a pyrometer gun. But I also noticed the lack of repeatability of the readings. It wasn't easy to get the same temperature reading on the same header tube even with merely 10 seconds apart of the readings.

 

I used the wet rag test looking for faulty plugs. Worked good for me. Then I took 3 different spark plugs of the same range to work and tested them. Found that all 3 leaked at the porcaline at different times under the same pressure. Switched to Autolite then. NGK was not available then.
Rick

 

Yes. As do cylinder heads also. But I believe that's been said already.