Home » Public Forums » GMCnet » Crossover Intake Manifold Temps
| Crossover Intake Manifold Temps [message #61913] |
Tue, 27 October 2009 09:14  |
larry.whisler
Messages: 356
Registered: August 2005
Karma: 8
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Senior Member |
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I was just reading the thread on the use of block off plates on the intake manifold and I have a question.
Shortly after returning home after a recent trip, we were unloading the coach and my wife made a comment about gasoline fumes in the coach.
I removed the hatch cover and top of the air filter to find that the carb was boiling out fuel.
I have headers and a new stainless steel exhaust system so I know the exhaust is not causing back pressure.
Is it normal for the manifold to run this hot?
larry whisler
76 glenbrook
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| Re: Crossover Intake Manifold Temps [message #61929 is a reply to message #61913] |
Tue, 27 October 2009 11:18  |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Yes, it is normal but not desirable. This is exactly why we put in the blocking plates. The engine with that large crossover worked OK in a Toronado but in a GMC where it works harder and burns more gasoline per mile it runs the manifold much hotter.
As Jim K points out, what can exacerbate the problem is if you have a muffler with some restriction in it. Then some or most of the exhaust from one side of the engine flows through the crossover to the other less restricted side. Blocking Plates will prevent that cross flow.
I went to the single rear muffler as designed by Emery and sold by Jim K. The pair of mufflers up front work OK as long as they are the same and have not come apart internally. Even with good mufflers, blocking plates are the way to go in my opinion.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Crossover Intake Manifold Temps [message #62036 is a reply to message #62025] |
Tue, 27 October 2009 22:25 |
GMCNUSA
Messages: 283
Registered: August 2006
Location: Indianapolis, IN
Karma: 0
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Senior Member |
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Has anyone ever shot the crossover section of the intake manifold with a
temperature gun?
============================================================
Larry
I have stainless block off plates and using a digital infrared gun shot my intake just after shutting down the engine and the crossover area was within the same temperature varibles of the other intake runners. My plates have been on the Dick Paterson rebuit engine about 53000 miles and the paint on the cross over looks like the other parts of the intake.
Larry Dilk
Indianapolis, IN
76 Eleganza II
Patterson 455,Turbo City TBI,
Just LOVE It!
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| Re: [GMCnet] Crossover Intake Manifold Temps [message #62049 is a reply to message #62036] |
Wed, 28 October 2009 06:57 |
fred v
Messages: 999
Registered: April 2006
Location: pensacola, fl.
Karma: 0
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Senior Member |
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| GMCNUSA wrote on Tue, 27 October 2009 22:25 |
Has anyone ever shot the crossover section of the intake manifold with a
temperature gun?
============================================================
Larry
I have stainless block off plates and using a digital infrared gun shot my intake just after shutting down the engine and the crossover area was within the same temperature varibles of the other intake runners. My plates have been on the Dick Paterson rebuit engine about 53000 miles and the paint on the cross over looks like the other parts of the intake.
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i would expect that but what does one read without block off plates?
Fred V
'77 Royale RB 455
P'cola, Fl
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| Re: [GMCnet] Crossover Intake Manifold Temps [message #62069 is a reply to message #62025] |
Wed, 28 October 2009 09:45 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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| Robert Mueller wrote on Tue, 27 October 2009 22:28 |
Larry,
The following statement was copied from a website that sells exhaust gas temperature gages:
"most engines average 1400 - 1600 F @ Wide Open Throttle"
Regards,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
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That may be what they say, but I don't agree.
When they say most engines, they must be including production passcar motors. If any that I ever had on my dynos ever got that hot they would be shut down and re-calibration ordered.
Even the 1200*F that is relatively common, exhaust valves in cast iron heads will recede at an alarming rate. If it has good valves and seats then you better have the techs build a 316/321SS pipes for it or it will be shut down before you finish the first set of power curves. Only if the engine is running way rich and retarded are you likely to have that level of exhaust heat, and that will do damage in short order.
What difference does this make to normal humans?
None.
Thermocouples types J or K that are used in engine laboratories will be effective at those temperatures.
But - most steel softens at 1k*F and is really wilty at 1200*.
If one is going to run spark ignition engine at WOT for extended periods, an exhaust system that is made of better stuff is a requirement.
Aircraft (ask KenB) watch EGT like a hawk. Cracks in the exhaust system are still relatively common.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Crossover Intake Manifold Temps [message #62108 is a reply to message #62069] |
Wed, 28 October 2009 12:49 |
Gary Casey
Messages: 448
Registered: September 2009
Karma: 0
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Senior Member |
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Just a few comments about EGT. Yes, we airplane drivers watch EGT's carefully, usually with a readout for each cylinder, but partly because the fuel system isn't capable of correctly adjusting the mixture by itself. Cruise conditions (naturally aspirated) are usually at full throttle, but at the higher altitudes this might be 20 inches MAP, about the same as a motorhome would be at sea level cruise. Best power mixture is richer than peak by about 150 degrees. Best economy mixture would be just a touch leaner than peak EGT. Pass car engines run at stoic, something like 50 degrees rich of peak. I would guess most car engines (including ours) will be running at least 1400F at a steady cruise. Full throttle will (or should) be 1250 to 1350F. All aircraft exhaust systems are stainless, but I forgot what alloy. 304? 309? And it makes some difference how the temperature is measured: How far from the valve, what direction from the valve, how close to
other cylinder ports, etc. Matt is right, 1600 in a pass car engine at WOT probably indicates the mixture is leaner than best power or the spark is retarded. Things that influence EGT: Spark timing - retard raises EGT. Mixture - peaks at near best economy, lower on either side. Compression ratio - higher lowers EGT. Dual plugs lower EGT. Higher coolant temperatures raise EGT, but not by a lot. Higher inlet air temperature raises EGT, but not by a lot. Higher manifold pressures raise EGT. Regardless, it's hot.
Regarding the strength of steel - I don't think the typical stainless is very soft at 1,000F, but over 1600 it will not have a lot of its original strength. Aircraft engines have exhaust systems that typically survive for more than 2,000 hours, and most of that is at high load. Turbo engines can run turbine inlet temperatures up to 1600 continuously. Exhaust systems cracks (aircraft engines) are not "common", but they are something to watch out for.
Just some random thoughts,
Gary
________________________________
From: Matt Colie <mcolie@chartermi.net>
To: gmclist@temp.gmcnet.org
Sent: Wed, October 28, 2009 8:45:12 AM
Subject: Re: [GMCnet] Crossover Intake Manifold Temps
Robert Mueller wrote on Tue, 27 October 2009 22:28
> Larry,
>
> The following statement was copied from a website that sells exhaust gas temperature gages:
> "most engines average 1400 - 1600 F @ Wide Open Throttle"
>
> Regards,
> Rob Mueller
> Sydney, Australia
> AUS '75 Avion-The Blue Streak TZE365V100428
> USA '75 Avion-Double Trouble TZE365V100426
That may be what they say, but I don't agree.
When they say most engines, they must be including production passcar motors. If any that I ever had on my dynos ever got that hot they would be shut down and re-calibration ordered.
Even the 1200*F that is relatively common, exhaust valves in cast iron heads will recede at an alarming rate. If it has good valves and seats then you better have the techs build a 316/321SS pipes for it or it will be shut down before you finish the first set of power curves. Only if the engine is running way rich and retarded are you likely to have that level of exhaust heat, and that will do damage in short order.
What difference does this make to normal humans?
None.
Thermocouples types J or K that are used in engine laboratories will be effective at those temperatures.
But - most steel softens at 1k*F and is really wilty at 1200*.
If one is going to run spark ignition engine at WOT for extended periods, an exhaust system that is made of better stuff is a requirement.
Aircraft (ask KenB) watch EGT like a hawk. Cracks in the exhaust system are still relatively common.
Matt
--
Matt & Mary Colie
'73 Glacier 23 Chaumiere (say show-me-air)
SE Michigan
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| Re: [GMCnet] Crossover Intake Manifold Temps [message #62249 is a reply to message #62108] |
Thu, 29 October 2009 00:40 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| Gary Casey wrote on Wed, 28 October 2009 12:49 |
Just a few comments about EGT. Yes, we airplane drivers watch EGT's carefully, usually with a readout for each cylinder, but partly because the fuel system isn't capable of correctly adjusting the mixture by itself. Cruise conditions (naturally aspirated) are usually at full throttle, but at the higher altitudes this might be 20 inches MAP, about the same as a motorhome would be at sea level cruise. Best power mixture is richer than peak by about 150 degrees. Best economy mixture would be just a touch leaner than peak EGT. Pass car engines run at stoic, something like 50 degrees rich of peak. I would guess most car engines (including ours) will be running at least 1400F at a steady cruise. Full throttle will (or should) be 1250 to 1350F. All aircraft exhaust systems are stainless, but I forgot what alloy. 304? 309? And it makes some difference how the temperature is measured: How far from the valve, what direction from the valve, how close to
other cylinder ports, etc. Matt is right, 1600 in a pass car engine at WOT probably indicates the mixture is leaner than best power or the spark is retarded. Things that influence EGT: Spark timing - retard raises EGT. Mixture - peaks at near best economy, lower on either side. Compression ratio - higher lowers EGT. Dual plugs lower EGT. Higher coolant temperatures raise EGT, but not by a lot. Higher inlet air temperature raises EGT, but not by a lot. Higher manifold pressures raise EGT. Regardless, it's hot.
Regarding the strength of steel - I don't think the typical stainless is very soft at 1,000F, but over 1600 it will not have a lot of its original strength. Aircraft engines have exhaust systems that typically survive for more than 2,000 hours, and most of that is at high load. Turbo engines can run turbine inlet temperatures up to 1600 continuously. Exhaust systems cracks (aircraft engines) are not "common", but they are something to watch out for.
Just some random thoughts,
Gary
________________________________
From: Matt Colie <mcolie@chartermi.net>
To: gmclist@temp.gmcnet.org
Sent: Wed, October 28, 2009 8:45:12 AM
Subject: Re: [GMCnet] Crossover Intake Manifold Temps
Robert Mueller wrote on Tue, 27 October 2009 22:28
> Larry,
>
> The following statement was copied from a website that sells exhaust gas temperature gages:
> "most engines average 1400 - 1600 F @ Wide Open Throttle"
>
> Regards,
> Rob Mueller
> Sydney, Australia
> AUS '75 Avion-The Blue Streak TZE365V100428
> USA '75 Avion-Double Trouble TZE365V100426
That may be what they say, but I don't agree.
When they say most engines, they must be including production passcar motors. If any that I ever had on my dynos ever got that hot they would be shut down and re-calibration ordered.
Even the 1200*F that is relatively common, exhaust valves in cast iron heads will recede at an alarming rate. If it has good valves and seats then you better have the techs build a 316/321SS pipes for it or it will be shut down before you finish the first set of power curves. Only if the engine is running way rich and retarded are you likely to have that level of exhaust heat, and that will do damage in short order.
What difference does this make to normal humans?
None.
Thermocouples types J or K that are used in engine laboratories will be effective at those temperatures.
But - most steel softens at 1k*F and is really wilty at 1200*.
If one is going to run spark ignition engine at WOT for extended periods, an exhaust system that is made of better stuff is a requirement.
Aircraft (ask KenB) watch EGT like a hawk. Cracks in the exhaust system are still relatively common.
Matt & Mary Colie
'73 Glacier 23 Chaumiere (say show-me-air)
SE Michigan
|
My airplane has a 4 probe EGT (one for each cylinder). The hottest I have ever seen is 1525 F measured about 4" from the cylinder exhaust port. I usually look for peak EGT on the hottest cylinder and then richen the mixture to get about 75 degrees less than than peak. This is only done at altitudes above 5,000 feet. Keep in mind we only run WOT on take off (with a full rich mixture) or over 5,000 feet which is 75% or less of full power due to the thinner air. Turbo charging changes all of this.
Note: My cylinder head temperature usually is 300 to 350. I consider 400 red line but just like my GMC 180 degree thermostat, I am rather conservative on my heat limits. Engine and oil longevity is more important to me than speed.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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