408, Small or Big Block? Need EGT Info

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70DusterBob

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I have a 408, I've been told that the Small Block Category is the correct place for this post.

I have edited this original post because there was too much confusion as to what I am looking for with EGT readings. I understand that there are a lot of variables that affect the EGT "Normal" reading for each tuned motor.

I am trying to find out how hot is too hot for the EGT reading. What temperature do I need to make sure the reading stays under to know that I will not burn a valve.

Please do not tell me I cannot tune a motor with an EGT gauge. I am not trying to tune my motor, I am simply trying to find out what temp is not safe for the valves.

Thanks
 
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Small block pictures below...
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Screw EGT temp readings and pay attention to your spark plugs. Add an 02 sensor if need be. also pay attention to your distributor curve.
 
I know the 360 block makes it a small block, but the 408 insides make it a big block. I didn't know which category to post this question in.

I got the EGT to keep an eye on the temps. I am making modifications to the engine and need to see if the engine runs any hotter with the mods or not. I don't know how I am supposed to keep an eye on my dizzy curve. But I have an AFR Gauge. I know reading plugs is important but they don't tell you what your EGT is when you accelerate vs cruise. Cruise at 40 vs cruise at 70, know what I mean? I keep an eye on the plugs for back up, to verify that my instruments are not way off, but I need to get a feel for what the engine temps are running at at various speeds.

I have an MSD dizzy, I put a 14 bump stop in it per advice. If I run with the medium silver and blue spring, it is very spicy, so I went with two medium silver springs and it still runs great, but not so spicy on acceleration. I'm not drag racing, but I do step on it and will be making chassis dyno runs. With that said, I am not looking for 5hp differences, I am looking for big ones, once I get significant bumps in hp, then I can fine tune, but I am experimenting and don't want to burn my motor up. So basically, what is a normal EGT Temp and what is too hot, what is dangerously hot?
 
Again, screw the EGT readings. The state of tune is what your after. If you’d tune is right, the EGT will be where there supposed to be, in a safe zone. Chasing EGT is a sure way to not get the most out the engine.

Your not keeping an eye on the distributor tune but know what it is and how to improve it.
 
Again, screw your chunking the gauge, I'm gonna use it. I have someone working with me on the dist tune, you apparently don't know that but seem to think you know I'm not keeping an eye on it.

It would be nice if you wouldn't try to tell me what to do, suggestions are appreciated, that's what I'm here for, not to be treated like an ignorant child. And I suggest that if you can't tell me what the EGT readings should be, don't reply.
 
Rob is correct..EGT readings are pretty much worthless, and completely worthless when the engine isnt under load.
You would need to have the motor on an engine dyno or chassis dyno to get any temp reading that would be of tuning value.
At idle, temps are going to be all over the map off the carb idle circuits. You aren't going to get any data at all worth looking at.
Sometimes... hearing what you seem to not want to hear...isn't a bad thing... your barking up the wrong tree with that EGT probe
 
EGT 12.5 ish 15 spike
I researched this as I will be running nitrous which can quickly spike egt
Keep a close eye on timing
 
EGT 12.5 ish 15 spike
I researched this as I will be running nitrous which can quickly spike egt
Keep a close eye on timing

What? Are you actually reading your EGT?

To the OP, as others have mentioned EGT is not the ideal way to tune. The only guys I've seen that used egt's were running alcohol or gas and a LOT of nitrous on very fast drag cars.
 
Rob is correct..EGT readings are pretty much worthless, and completely worthless when the engine isnt under load.
You would need to have the motor on an engine dyno or chassis dyno to get any temp reading that would be of tuning value.
At idle, temps are going to be all over the map off the carb idle circuits. You aren't going to get any data at all worth looking at.
Sometimes... hearing what you seem to not want to hear...isn't a bad thing... your barking up the wrong tree with that EGT probe


Thank you for your reply. Sometimes people say things in a way that rubs me wrong and I can't understand what they are trying to say. But!! I am NOT trying to tune the engine to the EGT gauge. Like I said earlier, I am making modifications to the engine and need to see if the engine runs any hotter with the mods or not. I am not trying to tune my engine, I have it tuned rather well. What I am doing is, and I hate to say it because everyone things anyone who tries to vaporize fuel is a nut, but I am vaporizing fuel. Rather well. I need to make sure that the engine temps are within normal range at cruise, then under acceleration in steps so I don't burn up my motor on the floor on the dyno. It "is" unlikely that I will be vaporizing fuel so well that under acceleration it would burn up, but cruising at 70mph, I probably could. I have to adjust the A/F ratio at the carb via jetting, acc pumps, cams and shooters, to adjust the carb for the modification, but it super helps to know the normal EGT Range, as stated below. I apologize to Rob if I came across harsh, but he apparently did not understand that I am not tying to tune the engine. It is helpful to know I can adjust the timing, probably 1-3 degrees would make a big difference in temps, but I if I didn't know what the temp is supposed to be or where it is at without the mod, how could I know how much it needs to be adjusted? How do you keep and eye on timing curve without having something to base the curve/timing advance on?? What instrument do you use to keep an eye on your timing? Plugs are a good indicator, but they are not real time. I know pings are bad, but you couldn't hear a ping with the mufflers I have and the decibels of my exhaust if your life depended on it. I met someone with experience racing who told me how to set up my dist, so I went with that, adjusted it to run best, start well when hot, but I started with the range set by the MFG, adjusted it according to a race expert who has a 408, and tweaked it to run at it's best. What else is there to do?

Thank you, and does this help you to understand why I need to know them?
 
EGT 12.5 ish 15 spike
I researched this as I will be running nitrous which can quickly spike egt
Keep a close eye on timing

Thanks!!!! I think you may have understood what I was asking and why. I appreciate it. I need to know what normal is, or the range, so I will know if "IT" is too high, not my tune. I am making mods, not trying to tune the engine. If the mod makes it hotter, I can then adjust the carb, maybe retard a little timing, but if I don't know what normal is, how am I supposed to watch my timing? It would make sense that I could, with a good tune, see what it is without the mod, make them mod and see what it is, but if I don't know the normal range, and danger range, it wouldn't help.
 
What? Are you actually reading your EGT?

To the OP, as others have mentioned EGT is not the ideal way to tune. The only guys I've seen that used egt's were running alcohol or gas and a LOT of nitrous on very fast drag cars.

I appreciate that he at least answered the question. But that sounds like AFR to me. Any idea of the normal, and too hot range for the EGT is, at the primary tube 2-1/2 inches away from the head?
 
What? Are you actually reading your EGT?

To the OP, as others have mentioned EGT is not the ideal way to tune. The only guys I've seen that used egt's were running alcohol or gas and a LOT of nitrous on very fast drag cars.
I didn’t say ideal. With egt. 02 sensor, plug reading, the right timing etc. as tools to tune , in this case more tools are mo better
better
Forgot ; MSD 8680 adjustable dash timing controller. Set up in the middle of 1-15
Degrees, you will have 7 1/2 degrees advance AND retard for a total of 15 degrees adjustment, that is my ideal
 
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I didn’t say ideal. With egt. 02 sensor, plug reading, the right timing etc. as tools to tune , in this case more tools are mo better
better

That makes sense to me. I will use all of these as indicators.

Thank you
 
Again, screw your chunking the gauge, I'm gonna use it. I have someone working with me on the dist tune, you apparently don't know that but seem to think you know I'm not keeping an eye on it.

It would be nice if you wouldn't try to tell me what to do, suggestions are appreciated, that's what I'm here for, not to be treated like an ignorant child. And I suggest that if you can't tell me what the EGT readings should be, don't reply.
I didn’t treat you like an ignorant child but I can if you want. It would be pointless since you want to be hard headed and stick to your guns on what your doing which would be *** backwards. If your EGT’s sky rocket to the point of burning up an engine, you sure did something wrong that you could have avoided with ether an 02 or spark plug readings.

Well, have fun then. I’m out.
 
I didn’t treat you like an ignorant child but I can if you want. It would be pointless since you want to be hard headed and stick to your guns on what your doing which would be *** backwards. If your EGT’s sky rocket to the point of burning up an engine, you sure did something wrong that you could have avoided with ether an 02 or spark plug readings.

Well, have fun then. I’m out.
Maybe out but it’s not over. LOL
 
I didn’t treat you like an ignorant child but I can if you want. It would be pointless since you want to be hard headed and stick to your guns on what your doing which would be *** backwards. If your EGT’s sky rocket to the point of burning up an engine, you sure did something wrong that you could have avoided with ether an 02 or spark plug readings.

Well, have fun then. I’m out.
I’m also very hardheaded and love it when people tell me it can’t be done.it makes me even more hardheaded !!
 
I appreciate that he at least answered the question. But that sounds like AFR to me. Any idea of the normal, and too hot range for the EGT is, at the primary tube 2-1/2 inches away from the head?

I've never used EGT's, only afr. My car is a street/strip deal so I used afr to tune the cruise and get close at WOT. Then used the MPH to fine tune it.

I'd be willing to say there are too many variables that affect the egt's for someone to say it needs to be XXXX°. RPMS? Load? WOT? What are you looking to learn from EGT's?
 
Well, when fuel is vaporized better, it tends to burn hotter, or at least that is what everyone I have known tells me. I know the tune of the engine is everything. I know you can't tune to something that varies as much as EGT. I just want to be sure I am not going to burn a valve or anything. I am concerned that if I kept it at cruise and it was burning at 12.5-13 AFR, it could read okay on the AFR but still be burning hot? At WOT we are talking about an extreme condition for any motor. I would like to keep it in normal hot range accelerating from 0-60, then 0-80 maybe, and watching both the AFR and the EGT at the same time. I have a camera in my car that records both gauges simultaneously for me so after my run, I can go home, bring it up on my large desktop monitor and read the gauges. If it is too hot, maybe I could add more fuel, change timing, etc? I was really kind of just hoping there was a range within which the EGT would be considered okay temp, and what tells you to shut off your engine and try again later. I am not sure how much the AFR is going to be affected by my mod. Will a better vapor burn hotter? Will the better vapor keep the same AFR but be more powerful and produce more heat? Or will it change the AFR and the EGT when I really get on it. Isn't there some temp that is too hot for the valves to keep up with? I noticed when I decel the temp goes down, so if it starts getting too hot I could decel to a stop and let 'er cool down, but I have no idea what hot and too hot is. I'm not "Generically" tuning an engine to the EGR, I am looking to see how much heat is produced by a better vaporized mixture, and I don't have a million bucks to do it with. I can make a run, make a pit stop, put the device on in 10 min, and go make the same run, in the same place, on the same day, 15 min apart. That is pretty dang close to the same conditions, so the AFR and EGT should be within 0.3+/- AFR and I guess maybe 500 +/- EGT?
 
I would be trying to keep it fro being too
Well, when fuel is vaporized better, it tends to burn hotter, or at least that is what everyone I have known tells me. I know the tune of the engine is everything. I know you can't tune to something that varies as much as EGT. I just want to be sure I am not going to burn a valve or anything. I am concerned that if I kept it at cruise and it was burning at 12.5-13 AFR, it could read okay on the AFR but still be burning hot? At WOT we are talking about an extreme condition for any motor. I would like to keep it in normal hot range accelerating from 0-60, then 0-80 maybe, and watching both the AFR and the EGT at the same time. I have a camera in my car that records both gauges simultaneously for me so after my run, I can go home, bring it up on my large desktop monitor and read the gauges. If it is too hot, maybe I could add more fuel, change timing, etc? I was really kind of just hoping there was a range within which the EGT would be considered okay temp, and what tells you to shut off your engine and try again later. I am not sure how much the AFR is going to be affected by my mod. Will a better vapor burn hotter? Will the better vapor keep the same AFR but be more powerful and produce more heat? Or will it change the AFR and the EGT when I really get on it. Isn't there some temp that is too hot for the valves to keep up with? I noticed when I decel the temp goes down, so if it starts getting too hot I could decel to a stop and let 'er cool down, but I have no idea what hot and too hot is. I'm not "Generically" tuning an engine to the EGR, I am looking to see how much heat is produced by a better vaporized mixture, and I don't have a million bucks to do it with. I can make a run, make a pit stop, put the device on in 10 min, and go make the same run, in the same place, on the same day, 15 min apart. That is pretty dang close to the same conditions, so the AFR and EGT should be within 0.3+/- AFR and I guess maybe 500 +/- EGT?
dang man , you’re definitely on it !!
 
I would be trying to keep it fro being too

dang man , you’re definitely on it !!

Thanks, I've got the hammer down; the pedal to the metal, I've got every available brain cell on it and I am very close. I don't give up so it won't be long.
 
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