Vortec Thermostat Experiment

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0xDEADBEEF

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Theoretically, the greater the delta between the heat source and the heat sink the more efficient a heat engine is.
 

L31MaxExpress

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Theoretically, the greater the delta between the heat source and the heat sink the more efficient a heat engine is.
Efficient not powerful. Cold air is more dense and at 11:1 compression I can run more timing with cooler combustion chamber temps. The air intake on an Express van will easily heat soak 140-170F or more at slow speeds.
 

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Efficient not powerful. Cold air is more dense and at 11:1 compression I can run more timing with cooler combustion chamber temps. The air intake on an Express van will easily heat soak 140-170F or more at slow speeds.

In this case efficiency and power are the same thing.
 

L31MaxExpress

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In this case efficiency and power are the same thing.
Maybe on a dyno with an infinite cool water and cool air ducted directly to the engines air intake. Put an engine in the engine compartment of a vehicle, run it on a warm day and the hotter operating temperature will cost power. The denser the air entering the engine the more power it will make. The negligible difference in friction and improved heat retention in the chamber from 180*F to say 210*F will be more offset by the 30-40*F high air inlet temps.
 

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Maybe on a dyno with an infinite cool water and cool air ducted directly to the engines air intake. Put an engine in the engine compartment of a vehicle, run it on a warm day and the hotter operating temperature will cost power. The denser the air entering the engine the more power it will make. The negligible difference in friction and improved heat retention in the chamber from 180*F to say 210*F will be more offset by the 30-40*F high air inlet temps.

It's the physics of heat engines, of which I am not an expert, but know just enough to be dangerous.

Denser air allows for a larger combustion event which is our heat source. If the heat sink doesn't warm up an equal or larger amount, then you have enlarged the delta and make more power.
 

Schurkey

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Hot block.

Cool intake manifold/cylinder head.

Thus all the effort to make "reverse cooling" work on the old "Gusher" Pontiac V8s from '55 to '59 or '60; and the LT1 SBC of the '90s. The supposed benefit was to keep the head cool using the water fresh out of the radiator; and then warmed by the cylinder head, the pre-heated coolant goes into the block.

Unfortunately, there's other factors at play, including trying to get any air or steam pockets to go "down" with the liquid coolant flow instead of rising to the top via gravity.

Harley popped some brain cells with liquid-cooled cylinder heads and air-cooled cylinder barrels for the same reason--keeping the heads cool and the cylinder hot.
 
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L31MaxExpress

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Hot block.

Cool intake manifold/cylinder head.

Thus all the effort to make "reverse cooling" work on the old "Gusher" Pontiac V8s from '55 to '59 or '60; and the LT1 SBC of the '90s. The supposed benefit was to keep the head cool using the water fresh out of the radiator; and then warmed by the cylinder head, the pre-heated coolant goes into the block.

Unfortunately, there's other factors at play, including trying to get any air or steam pockets to go "down" with the liquid coolant flow instead of rising to the top via gravity.

Harley popped some brain cells with liquid-cooled cylinder heads and air-cooled cylinder barrels for the same reason--keeping the heads cool and the cylinder hot.
Knowing what I now know about the LT1, I would have built a 396 off the clean 4-bolt LT1 block I have. I also had a set of Lloyd Elliot ported LT4 heads and a ported LT4 intake. I was going to build the LT4 top end LT1 for my 1980 Corvette when I owned it. I sold the LT4 stuff off when I was buying parts for the 383. I could have built a 12:1 396 cubic inch reverse cooled LT4 for less than the 383. The Vortec accessories will physically mount to the LT1. The LT1 can use a SBC balancer. The LT1 can also run on an 0411 without using a cam sensor. To be honest the LT1/LT4 architecture would fix several problems that the L31 has in an Express van, especially with headers. Plug wires would be far easier to access with the LT1. The LT1 intakes forward facing throttle body also fixes the 90* turn at the throttle body to the air intake that is so horribly restrictive on the vans. The only problem with the LT1 architecture is that mounting a mechanical fan would involve some interesting fabrication, but it has been done. The mechanical fan probably would have amounted to a B-car LT1 mechanical fan setup in a universal fan shroud on one side of the radiator and a 16" electric fan on the other. Hindsight is 20/20 though. I still have the LT1 block at the shop and it may someday find its way into the van if the 383 ever gives up the ghost.

The LT1 block architecture has a steam pipe that vents air and steam out of the rear of the cylinder heads. It works very similarly to the 4-corner cooling upgrades on performance small blocks. Like the LS engines, the LT1s steam pipe outlet heats the throttle body.
 

L31MaxExpress

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I have some data on what the higher coolant temperature did to performance. When tuning the spark MAP for best acceleration I made numerous datalogs in the same spot of road. repeated those runs today. 30 mph is 3,400 RPM and 50 MPH is 5,200 RPM, shifter in 1st from a 25 MPH roll. 40-70 MPH starts at 2,950 rpm and ends at 4,600 starting in 2nd gear from 35 mph. I see why it feels like it has less power, it does. 4* less timing with the 195*F at WOT due to Coolant and IAT compensation. I will definitely be picking up a cooler high flow thermostat before the weather heats up again next summer.

180*F Thermostat
30-50 MPH = 2.76s
181*F Coolant @ Start
183*F Coolant @ End
106*F IAT @ Start
104*F IAT @ End

40-70 MPH = 6.74s
185*F Coolant @ Start
183*F Coolant @ End
108*F IAT @ Start
99*F IAT @ End

195*F Thermostat
30-50 MPH = 3.09s
196*F Coolant @ Start and End
122*F IAT @ Start
118*F IAT @ End

40-70 MPH = 7.36s
198*F Coolant @ Start
201*F Coolant @ End
116*F IAT @ Start
108*F IAT @ End
 
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