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Old 06-14-2016, 06:38 PM
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Hot heads, cold block

383 SBC 350 block 327 heads. cylinder heads are very hot. Block runs cool 170.
If you drive thru a drive-in ...the poor person at the pass out window gets cooked!
Are the 327 and 350 head gaskets different.
Fuel mixture ok
Ignition timing ok
Will borrow a heat gun and take some measurements
Got to be water flow problem of some kind or steam pockets
Help

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Old 06-14-2016, 07:07 PM
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what temp are the heads? The castings are more than 45 years old
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Old 06-14-2016, 08:09 PM
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Put the aprons back into the engine bay to keep hot air off the cashier at the drive-in.
Yes, you can use the same head gaskets on a 327 and a 350.
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Old 06-15-2016, 05:08 AM
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when you get the infrared and find out the block and heads are the same temp within a few degrees and the hot air is coming off the radiator and some off the headers. do you have a belt driven radiator fan..or an electric radiator cooling fan.

the air off most radiators is crazy hot.. aim at the fins of the radiator. the top will be hotter than the bottom as some of the heat has been lost if the radiator is working properly..
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Old 06-15-2016, 07:02 PM
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Hello:
Having trouble using the site. Posted yesterday for the first time and see a few replies. Don't know how to reply to them. SBC ,383, very hot cylinder heads. Have not barrowed a heat gun yet. I know the block is running cool at 170 because of the temp gage and the fan switch turning the fan at 180. Look forward to using the site. NOTE: I have a lot of SBC experience, but this problem is getting to me.
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Old 06-15-2016, 08:38 PM
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You can reply to individual messages by hitting 'quote' button... or use general form at bottom of page... You can also edit the quote to include only what you want to address...
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Old 06-15-2016, 08:47 PM
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Quote:
Originally Posted by gary1929 View Post
Hello:
Having trouble using the site. Posted yesterday for the first time and see a few replies. Don't know how to reply to them. SBC ,383, very hot cylinder heads. Have not barrowed a heat gun yet. I know the block is running cool at 170 because of the temp gage and the fan switch turning the fan at 180. Look forward to using the site. NOTE: I have a lot of SBC experience, but this problem is getting to me.
So what leads you to think the heads are hotter than the block??

There are no water temp ports in the block, only in the head or the intake manifold....and the hot water from the block has to go through the heads to get to the temp sender and the water neck to go out to the radiator.....so if temp gauge reads fine heads can't be any hotter than the block by more than 5-10.

Where do you have the water temp sender located??

What actual proof do you have the heads are really hotter??
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Old 06-16-2016, 02:41 PM
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The sending unit is in the intake. the fan switch is in the radiator lower tank and it is an electric fan and shroud assembly covering all of the radiator core. The heads will burn you if you touch them! No retarded timing ...14 at idle and 34 total at 3,000
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Old 06-16-2016, 03:18 PM
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Quote:
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The heads will burn you if you touch them!
.. 160+ degrees F will burn you...
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Old 06-16-2016, 03:24 PM
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Quote:
Originally Posted by gary1929 View Post
. ..... The heads will burn you if you touch them!
This is completely normal. Once up to temp virtually any parts of the engine will burn you....head, block, valvecover, intake, waterneck, even the carb if the engine has run for an hour. Only takes 150 to feel burning hot to the skin.

Engine water flow is from radiator to water pump, from water pump into block, from block up into heads, forward through heads to intake crossover, and out the waterneck and back to the radiator.

Unless you are showing a high temp at the intake crossover the heads are no hotter than any other part.

You need something more scientific than "it will burn your hand"....like the engine is actually overheating and experiencing spark knock(detonation) or boiling over, laser temp gun readings, temp probe in rear of intake reading a lot different than front.

Otherwise, the head area will seem hotter due to header or manifold heat and hot oil splash on the underside of the valvecovers will make the surrounding area seem hotter than other areas.
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Old 06-16-2016, 03:30 PM
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X 2... Only get concerned if the coolant is boiling over...
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Old 06-16-2016, 08:39 PM
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Results with infared gun
Rad lower tank 170
upper tank 170


Block front 178
rear 240


LH head front 203
rear 258


RH head front 204
rear 220
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Old 06-16-2016, 08:59 PM
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Some intake manifolds have provision for pulling coolant from the rear of them/from rear of heads... and/or a coolant crossover there...
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Old 06-16-2016, 09:08 PM
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Quote:
Originally Posted by gary1929 View Post
Results with infared gun
Rad lower tank 170
upper tank 170


Block front 178
rear 240


LH head front 203
rear 258


RH head front 204
rear 220
Completely normal, rear is always hotter than the front due to distance from the pump...... and the heads are always a bit hotter than the block because the water is pumped into the block first, then up to the heads.

The front to rear difference is why a lot of the newer performance intake manifolds have water ports in the rear as well as the front, so the rear can be connected by separate water lines to a spacer under the front water neck or to the two front corner water crossover ports.
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Old 06-17-2016, 08:21 AM
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Quote:
Originally Posted by gary1929 View Post
Results with infared gun
Rad lower tank 170
upper tank 170


Block front 178
rear 240


LH head front 203
rear 258


RH head front 204
rear 220
Except for the radiator tank temperature this looks pretty typical.

The return tank should be hotter as it is receiving the heated coolant, the tank on the inlet side of the pump should be cooler shown the core has removed heat.

The front side of the engine is cooler because this is where the pump is putting the cooled coolant is introduced here. The coolant gets hotter as it flows to the back of the block and as it flows through the heads.

The heads are hotter than the block this is where most of the combustion heat is. Chevy picks up the temp off the left head for the gauge, this is the hotter head because the pump rotation when driven clockwise with V-belts favors flow to the passenger side by a small amount. Heads running hot on the rear is always a problem with built up engines. As ericnova72 points out it is a good idea to use or to modify an intake manifold so there is an external return from the rear of the manifold for both sides. This can be incorporated into the bypass which usually goes through the heater core or it can be routed to an adapter at the water neck. Some more recent design manifolds have dual return bosses on the front crossover for this purpose. If you were to run L31 Vortec heads the intakes for those route rear head coolant returns under the manifold connecting with the front return as part of the casting. This is, also, common on the much less desirable LO5 Swirl Port heads.

Bogie
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