Exhaust temperatures

rblong · #1 (**permalink**) 03-26-2005, 09:07 AM

I got a question that I bet someone can help me with. While installing my new pipes I started the car to see how they sounded. I noticed the passenger side discoloring more than the drivers side, I got out my infrared thermometer and the passenger side look like it is runnong 20 or 30 degrees hotter than drivers side. It is hard to get an exact reading since I get some reflection off pipes, but it looks like I amm running like 410+- on pass side and 370+- or so on drivers side. This is at idles with engine warmed up. What do you think?

Bruce Edwards · #2 (**permalink**) 03-26-2005, 02:07 PM

Fuel mix not the same right to left. Are you running a split manifold?

rblong · #3 (**permalink**) 03-26-2005, 04:08 PM

I thought about that also, but did not know there were split intake manifolds. I have a Edelbrock Performer 390 and Speed Demon 750 carb. I suspected I needed to tweak the mixture but wanted to wait till I had my new side pipes on. I will followup after I investigate the split manifold. I appreaciate your help. I see you respond to a lot of peoples engine questions and it is very helpful. May seem basic to you (and probably a lot others) but is reassurance to us not so experienced rodders.

Thanks,
Bruce

Bruce Edwards · #4 (**permalink**) 03-26-2005, 04:40 PM

The Edelbrock RPM is a split style manifold. When you installed the carb you may have noticed a divider in the center of the manifold. Also called a dual plane manifold. It splits the air fuel mix into two sections. to take advantage of longer runners which give better bottom and mid rpm mixing.
Sounds like you just need to work the fuel mix a bit.
That manifold will split 1-4-6-8 on one side and 2-3-5-8 on the other. So if you are going to check with you sensor you will need to compare the correct pipes. Remember that the different length pipes will also change the temp so you want to check it as close to the head side as you can.

rblong · #5 (**permalink**) 03-26-2005, 07:36 PM

Great info! I did find the hotter side with the mix a little leaner - 1/2 tun more CW than cooler side. What is kinda weird is that I started shooting individual cast exhaust ports off head and noticed one on the cooler side running well cooler than all other ports? Now this motor runs smooth as silk, runs like a scalded dog, but the cooler temp makes me wonder about combustion in that one cylinder. If I did not have complete combustion I would think I would have a miss. I have to do more tweaking tomorrow to better understand what is going on. More to come!

misfit41 · #6 (**permalink**) 03-27-2005, 11:44 AM

Im curious if you have checked the header inlet temps near the head ports ,and the temps at the collector,Im curious to know what these are for my own knowledge,thanks,Tim

rblong · #7 (**permalink**) 03-27-2005, 11:52 AM

Yes, I was getting 400 or so at collectors (measured with infrared and I was getting a little bounce cause of the reflection off the steel). I got a good solid reading off cast heads ports and all cylinders were 420-430, except one port was 30 or 40 degrees cooler. I am curious why one was cooler than all the rest. This was at 180 degree engine temp idling at 800.

misfit41 · #8 (**permalink**) 03-27-2005, 11:59 AM

thanks for the info,,I think these guys have it down with the air/fuel ratio ,It is possible valve adjustment on one cylinder may effect exhaust temp if you have solids,but I would think it will have to be out enough you would notice.good luck !,,Tim

Bruce Edwards · #9 (**permalink**) 03-27-2005, 12:21 PM

A tight valve may not show up with out a vac reading until you burn it.
It never hurts to check. If you only have one cylinder at this point that is that far off from the others I would check it just to be sure. It only takes a few moments and can save a valve job down the road. Even no solids need to be adjusted correctly.

rblong · #10 (**permalink**) 03-27-2005, 12:30 PM

I agree on the valve thing and will check. I better go pick up a gasket though in case mine comes apart.

Thanks

ERA Chas · #11 (**permalink**) 03-27-2005, 03:27 PM

rb,
Check the resistance of all plug wires.
The one with cooler temps may have higher resistance reading and less or intermittent spark to the plug.
Good luck,

rblong · #12 (**permalink**) 03-27-2005, 05:43 PM

Great, I have some time till the pipes come back so I have time to "tinker". This is all good stuff. I learn more every day! Maybe someday I'll get to where I can help someone.

Bruce

Excaliber · #13 (**permalink**) 05-12-2005, 05:48 PM

300 t0 400 degrees? You lucky dog, I'm running 900 deg at idle and TRYING to find out WHAT is "normal" for an FE!

rblong · #14 (**permalink**) 05-12-2005, 08:05 PM

WOW - 900 degrees! Once I got my new side pipes with baffles rather than open sidepipes, I retuned the carb the temperature has gone up a little (I am guessing due to a little back pressure now) and is closer to 500 at the heagers at idle. But they all run pretty equal now.