455 overheating issues at intake , not the block

wskirvin

wskirvin

Master Mechanic
May 22, 2017
252
63
Indianapolis, In
Okay so i'm kinda lost at the moment. Finally fired up the 455 tonight...... runs great, no smoke, weird noises or anything..... until its ran a bit then it starts over heating, i've checked the block, radiator, hoses, water pump, everything i can think of. even tried running it without a thermostat just incase it was stuck or the block was vapor locked. going to do a cooling system pressure test tomorrow as well as a compression test on all the cylinders... i've got no oil in the coolant, and no coolant in the oil so i'm kind of lost. Its an Edelbrock 2151 RPM intake and E heads. Now if the exhaust crossover plugs havent been installed, would that cause the coolant to boil? when t starts to overheat i have checked it twice with a laser thermometer and both times, the block and heads have been around 180 but the intake along the front by the thermostat housing, as well as the back passenger side coolant outlet are well over 230. i've been running the engine on a test stand with a 3 row aluminum radiator with dual 12" electric fans and shroud. The radiator and fans seem to be working right. on at 185* The temperature at the Radiator outlet going to the water pump inlet stayed around 140-150 until the temperature spikes at the intake and then next thing you know, you are looking at 230* and a geyser out of the radiator and overflow, but before the temperature spikes, there are no signs of compression in the coolant or any aeration like there was head gasket issue. Has anyone ran into this before? possibly a cracked intake or i just need to plug the exhaust crossovers?
 
TURNA

TURNA

Geezer
Jul 24, 2009
8,234
113
Socialist NY
Does the top rad hose get super hard?

A cracked head could be the issue with exhaust gases getting into the coolant.


Oil water in either fluid is not always the case with a head gasket/cracked head.
 
Canon_Mutant

Canon_Mutant

Royal Smart Person
Aug 15, 2015
1,088
113
Sounds like the coolant is not circulating. Are both radiator hoses getting hot? Had a friend that (mistakenly) put silicone on his head gaskets on his small block Chevy which just squished out into all the water passages plugging them. Or, possibly use silicone on your intake gaskets beyond just the ends? Also, did you get the right head gaskets, did they have water passages for a big block, and/or did they have cutouts for water passages that you failed to cut out?


Lastly, the crossover is worthwhile to block off for performance reasons if (of course) you are not running a heat choke? But should not be affecting this problem.
 
565bbchevy

565bbchevy

Geezer
Aug 8, 2011
6,384
113
Michigan
Though I don't have answer I just want to say I appreciate your post with the info you have given, what is happening and what you have checked etc.
instead of the typical "my motor is overheating what's wrong".
 
pontiacgp

pontiacgp

Canadian Prime Minister
Mar 31, 2006
25,143
113
Kitchener, Ontario
I agree with TURNA, at 230 degrees you should not be getting gysers from the rad and overflow. Sounds like exhause gases getting into the coolant by a cracked head or a head gasket
 
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olds307 and 403

olds307 and 403

Comic Book Super Hero
Oct 14, 2008
4,776
113
Melville,Saskatchewan
As said you may plugged the coolant ports at the intake, it can happen. As said the top rad hose will super pressurize and actually become oversized with a cracked head or blown head gasket. Had that happen on my Dakota, blown head gasket then cracked head on a 5.9 and on the head gasket on the Olds 350 in my Z71. Same thing, coolant, violently leaving the rad cap. I probably wouldn't hurt to have the plugs in the heads, can eventually crack the intake. But it will not cause you motor to overheat. I am running the SB RPM with no plugs on my Olds 350, many hours drive with a 2 core copper brass recored never above 195 for temp. A pressure tester is a good idea at this point.
 
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airboatgreg

airboatgreg

Royal Smart Person
Oct 2, 2016
1,599
113
Warm it up, shut off for ten minutes or so. Start up and see if you have a skip. If you do most likely head or gasket
 
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wskirvin

wskirvin

Master Mechanic
May 22, 2017
252
63
Indianapolis, In
Thanks for the info everyone. I double checked when i put the heads on that the gaskets had all the coolant passages. They are the cometic mls gaskets so possibly they are leaking? I have a set of felpros i could put on it, but it runs was too smooth and that why i wasnt sure on the head gasket being bad or a cracked head. The water pump is a high volume milodon that Summit Racing sells. Definitely going to go out shortly and do a cooling system pressure test and a compression check


Sent from my iPhone using Tapatalk
 
wskirvin

wskirvin

Master Mechanic
May 22, 2017
252
63
Indianapolis, In
Sounds like the coolant is not circulating. Are both radiator hoses getting hot? Had a friend that (mistakenly) put silicone on his head gaskets on his small block Chevy which just squished out into all the water passages plugging them. Or, possibly use silicone on your intake gaskets beyond just the ends? Also, did you get the right head gaskets, did they have water passages for a big block, and/or did they have cutouts for water passages that you failed to cut out?


Lastly, the crossover is worthwhile to block off for performance reasons if (of course) you are not running a heat choke? But should not be affecting this problem.
Both rad hoses are getting hot, but the lower isnt getting about around 150. Thats whats throwing me off. They are both hard but thats due to the fact that i have the gates universal hoses with springs in them


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