EGT for a Sonny Leonard 632

[ch85us2001]

Hi all,


What should the EGT be hovering around for a 632? It's pretty aggressive (1320 Hp all motor), with no spray. Were running in about 4000' Corrected conditions, and it's going around 1575 to 1600 degree F. Water temp is 160 pulling into the box, something like 180 or 190 at the top end, I believe (fuzzy on that one). Its in a 2500 lb doorcar. We have two Holley 1150's, with .108 jets in 'em.

Does it need to be fattened? Leaned?

Thanks in advance.

[John_Heard]

If the plugs are showing lean then I would think that EGT is a bit on the hot side. If the plugs are fat, then you're probably burning some in the headers driving the EGT up. What's the plugs look like?

[nj]

Here's a couple things to think about when dealing with egt's. First egt readings are like weather stations, you can not compair your readings with someone else and expect to get the same results. We have tested a couple different egt gauges and sensor manufactures. They all read slightly different. Your egt reading is unique to your engine due to the gauge and sensor your using. Your reading of 1500 may work fine in your car but will melt the pistons in someone else car. Gas and alcohol engines also have different readings. With that being said, You can use your reading as a starting point just keep in mind that just because its reading 1500 degrees doesnt mean that the real world temp in that cylinder is 1500.

Things that effect egt air/fuel ratio, engine timing, and sensor placement. Did you change the jetting from Sonny's tune up? The more timing you take out of an engine the higher your exhaust temps will be. If Sonny dyno your motor what timing did he come up with and did you change from this point? Sensor placement, it should be about 1 13/4 to two inches away from the header flange. If you get the sensor to close to the head your temps will go up and give you a false reading. Your highest egt reading should be at the end of your run. if it occurs early on in the run and stays that way chance are your to lean.

Heres what i would do,
Put a new set of plugs in it. Check your timing
Make a pass and figure out where in the run the highest egt is.
Then pull the plugs and get a good reading the old fashion way.
You can go to the articles section on this sight and read the nos plug reading article for some good info.
Take note, does the plug look lean ( if lean right the egt reading down) or fat. and your mile per hour thru the traps
Go back and fatten the jets up 2 to 3 steps
Make a pass and pull the plugs again. The plugs should look richer than before and your egt readings should have come down. If your mile per hour went up fatten up one more step and make another pass or until the car slows down.
At this point take a egt reading. the plugs should look fat and the car should have slowed down. Write this reading down, Lets say it is 1350 degrees that will be your fat side egt reading. If on your first pass the plugs look lean,the number you wrote down will be your lean egt. lets say it was 1600 degrees.

You now know your tuning window anything close to or below 1350 would be fat and anything above 1600 would be lean. Some where in the middle will be your fast et

Now heres the kicker, that is only good for the timing you started with, if you retard the timing your egt window will move up if you advance the timing your window will move down.

this sounds like alot of screwing around but with some testing it will work. I am a deal for a data logger company. I did some testing on O2 sensors for them. I think the O2 sensor is the better way to go for tuning. I use the egt's to help with the timing and cylinder activity (looking for miss fires, bad plugs ect) and the O2 to tune the fuel. So far it has work out pretty good. We use alot of nitrous in our tune up and these two types of sensors help us make alot of power, with out making alot of junk

hope this helps
nj

[ch85us2001]

The timing was retarded 2 degrees just last week. The jets in it are .108s.


I'm taking it out to Trail's this weekend, so I'll try what was suggested (car's getting a new nose on it now, but thats another story).

Thanks