| Exhaust Crossover confusion [message #351584] |
Sun, 26 January 2020 16:07  |
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Tom Lins
Messages: 372
Registered: February 2004
Location: St Augustine, FL
Karma: 1
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I am confused over the temp readings I get using a non-contact temp gauge on the intake manifold.
I drove from the storage facility we keep our GMC at to my house (about 10 miles at 70 mph)
When I got into my driveway I opened the engine cover and measured the following temps.
End of left exhaust manifold 450 deg F
Top of choke stove 277 deg F
Top of runner to next cylinder fore or aft 225 deg F
Top of end of manifold fore and aft 217 deg
I was expecting the temp on the top of the choke stove to be higher if the crossover was not blocked.
The reason I was measuring the temps is to attempt to determine if my crossover is blocked short of pulling the manifold.
I guess another question I wonder about is if the factory choke would work at all if the crossover was blocked.
This all feeds into why I had 2 FI-Tech units fail after very short periods of time.
The first after about 800-900 miles and the second after 250 miles.
The engine runs fine now with the carb back on it.
Tom Lins
St Augustine, FL
77 GM Rear Twin, Dry Bath, 455, Aluminum Radiator Quad-Bag Suspension Solar Panel
Manuals on DVD
YOUTUBE Channel: GMC Dealer Training Tapes
http://www.bdub.net/tomlins/
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| Re: Exhaust Crossover confusion [message #351591 is a reply to message #351584] |
Mon, 27 January 2020 08:44  |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Another permutation other that open or blocked would be restrictors. That's the Cinnabar practice as it retains some warm up benefit and the factory choke works fine. If they have worked on it they can probably look up service history
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Exhaust Crossover confusion [message #351597 is a reply to message #351591] |
Mon, 27 January 2020 15:46 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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JohnL455 wrote on Mon, 27 January 2020 09:44Another permutation other that open or blocked would be restrictors. That's the Cinnabar practice as it retains some warm up benefit and the factory choke works fine. If they have worked on it they can probably look up service history
Thanks John,
That was what I was going to add.
From experience, those intake temperatures are about what I would expect. The exhaust you saw was maybe a little low, but I measured it with a thermocouple on the exhaust flange.
This is memories from when I was McCord's (RIP) aftermarket we were supplying OE to the Chrysler (RIP) V-engine line. I was also using those tools for aftermarket parts. While it was not an issue with the port fuel versions both the RPD groups FI and Carb were complaining about heat burning the paint off the intake passage. So, I got a carburetor engine and did some dyno time. We changed aftermarket to a restrictor on one side only. The other side remained a steel flange insert.
The OE parts just had flanges at both sides, but it also had a far smaller cross port than the 455 does.
Matt - the dynoland refugee
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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