Big Block too cold

M

mtrhead

Member
Here is what I know of a problem I just got a call on- "big block air boat can't get warmer than 100F since he got it back Saturday!"

A friend had a big block air boat that dropped a valve. He got a new 509" from a shop in Wisconsin that specializes in air boat motors. 600hp/600tq They took the old broken motor in and repaired the head and built a new short block with his parts)

The engine reused his edelbrock heads (weld repair), intake, water pump, etc. can't get it over 100F new motor has a Merlin block with an aftermarket rotating assembly. So they put in a new thermostat (tested it in hot water with flir gun and it opened at 160F like it was marked) and it still wont get over 100F tonight.

My thoughts? is there something different in the Merlin block or head gasket? I dont have anymore info than this tonight. Also, the original motor was GM 454 block and it never had heat issues.
 
if the engines running on all 8 cylinders and the blocks full of coolant and you've got oil in the engine that circulates its a sure bet that it will generate at least that 160F plus in under 10 minutes run time so I'd suspect the temp gauge or connections or the sensors defective, or the t-stats locked in the open position, and the fans and radiator cooling capacity is sufficient to transfer the heat generated to the outside air flow faster than the engine can produce that heat.
engine combustion temps easily produce 450f or higher exhaust temps so its a basic fact that the engine will increase in temps as its run, and the coolant and oil absorb and transfer the heat.
it should be rather obvious that an AIR BOAT with its engine out in the open and a huge propeller moving a great deal of air flow around the engine has the potential to allow that engines cooling system to absorb and dissipate heat at a much faster rate than most cars so youll very likely need to use a 215 F t-stat



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related info
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I'd suggest verifying the ignition timing and looking at the plus as they normally give a good indication of combustion conditions
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BIG BLOCK CHEVY COOLING RELATED INFO

Coolant Routing Mk IV/Gen 5/Gen 6
There are two different ways that coolant can be routed through the engine: series flow and parallel flow. Both ways work just fine. There may be a slight preference for parallel flow, but it is not a big deal. Series flow has the water exiting the water pump, flowing through the block to the rear, it then transfers through the head gasket and into the cylinder head through two large passages on each cylinder bank at the rear of the block. The coolant then travels from the rear of the head, forward to the front of the head, into the intake manifold water passage and out past the thermostat and thermostat housing. The water cools the block first, then it cools the head. The coldest water (coming out of the water pump) is directly below the hottest water (having already picked up the heat of the block and the head) as the hot water transfers into the intake manifold. By contrast, parallel flow has the water exiting from the water pump into the block, where a portion "geysers" up into the head between the first and second cylinder, another portion "geysers" up to the head between the second and third cylinders, another portion geysers up to the head between the third and fourth cylinder, and the remainder transfers to the head at the rear of the block. The coolant temperature inside the engine is more even that way. The differences in coolant routing is having (or not having) the three additional coolant transfer holes in each block deck, and three matching holes in the head gasket. The heads have passages for either system, and are not different based on coolant flow.

Be aware that gaskets that DO have the three extra holes between the cylinders often have restricted coolant flow at the rear--instead of having two large coolant transfer holes at the rear, there is only one, and it's the smaller of the two holes that remains. This is important because if you use a parallel flow head gasket on a series flow block, you can have massive overheating and there's NOTHING that will cure the problem except to replace the head gaskets with ones that don't restrict flow at the rear of the block, or to drill the block decks to allow the coolant to flow into the head between the cylinders. Here's why they can overheat: A series-flow block doesn't have the openings between the cylinders, no coolant can flow up to the head there. The gasket may only have the single, smaller opening at the rear, so the amount of water that gets through that opening is greatly reduced from what the block designers intended. The result is that the coolant flow through the engine is only a fraction of what is needed.

Most, but NOT all Mk IV engines are Series Flow. ALL Gen 5 and Gen 6 engines are Parallel Flow. A series flow block can be converted to parallel flow by drilling 3 holes in each deck surface, and then use parallel flow head gaskets. You can use the parallel flow gaskets as templates for locating the additional holes. It's really easy: Put the parallel flow gaskets on the block, mark the location and size of the three extra holes. Remove the gasket. Grab a 1/2" drill and a drill bit of the correct size, and pop the extra holes in the block. There is NO modification needed on the head castings. Some blocks have one of the holes already, but it needs to be ground oblong to properly match the gasket. Again, very easy with a hand held die grinder and rotary file.
 
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Latest from this AM based on some of the information:

"Header temp is 400 +. After an hour of running you can still touch the intake and head. My infrared temp gauge reads just over 100"
 
I find it hard to believe that the air flowing around the engine that's feeding the prop is flowing over and drawing that much heat out of the engine,
especially if the previous engine did not have a similar problem retaining heat,Id suspect the t-stats locked open at least par way.
whats the engines oil temp in the oil pan?
are you running an oil cooler?
do you see coolant flow in the radiator?
have you tried installing a 200F t-stat?
 
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Update: They changed the fluid, the thermostat, the sending unit, the gage, and blew the system out and Everything returned to normal? Still don't understand how it could be cold to the hand on the intake after one hour but all is well now.
 
great! thanks for getting back and posting, so few people do that and its usually a P.I.T.A. to find out what happened in unfinished threads

I think it is 80 & up mark IV big block engines that has the later improved cooling with the three extra holes.
(look at the gasket info below)
ITS Real easy to drill the holes in the earlier blocks if you don,t have then with a 3/8" drill , using the gasket as a pattern as it was found to increase cooling.

BTW fritz1990 posted this info

Top gasket pic is one with the extra cooling holes. Can use this gasket as a template to drill these 1/2" holes in the deck of the block. All heads already have these holes just some blocks don't.

The holes are the three on the bottom side of the gasket right below the ones between the cyls. The ends of the gasket are also different.

Just don't use the top gasket on your block without drilling the holes. I have to run to work and I can explain the difference later. The top setup is suppose to give you a lil' better cooling but there are many like yours running around, not a real big issue, just better to do it now.

If you have the three holes in the block you can run either gasket.

The bottom gasket is the one you will need to use if you don't drill the holes.

fel8523.jpg

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BBC HEAD GASKETS READ THIS LINK
http://www.cartechbooks.com/vstore/show ... apter=7174

Three types of gasket materials are generally available, steel shim, composition and copper gaskets. Cast iron heads can use all three types of gasket materials. Aluminum cylinder heads require the use of composition or copper gaskets. Various compressed gasket thicknesses are offered. Remember that you should have a minimum clearance of .035"-.040" between the top of the piston deck and the deck of the cylinder head when using steel rods. Aluminum connecting rods typically require a larger clearance.
Fel-Pro composition head gasket (PN-8180-PT) for 4.250" bore Mark IV engines. It has two additional holes for head bolts that go into the lifter valley found on some high performance Bowtie and aftermarket blocks.

Different head gasket bore sizes are offered. Mark IV head gaskets have different coolant core hole passages than gaskets for Gen.V engines, blocking some passages and opening other coolant passages. Some block deck coolant core holes are round, while on Gen.V production blocks the holes are irregularly shaped on the block deck. Mark IV heads and head gaskets should be used on Mark IV blocks. Likewise Gen.V style cylinder heads and gaskets should be used on Gen.V blocks. There are exceptions. Mark IV heads can be used on Gen.V "Bowtie" and on Gen.VI HO blocks because the core holes in these block decks will seal the water core holes found on Mark IV heads. If you build this combination then use a Mark IV style head gasket and plug the core hole in the Gen.V "Bowtie" block deck located near the front head dowel pin location (see photo). Otherwise coolant entering the front of the block can bypass the rest of the block and exit out thru the head and intake manifold.

Steel shim gaskets and copper gaskets require the use of head gasket sealant. Composition gaskets do not require sealant.

Head bolts should be completely cleaned and then torqued down in the proper sequence and to the correct torque values. Head bolts or studs, used on aluminum heads, need to have a hardened steel flat washer (PN-3899696) under each bolt head or nut, to prevent damage to the aluminum head surface. Head bolt threads going into water passages should be coated with sealant and head bolts going into blocks with "blind" holes should be coated with moly lube or oil. Some head gaskets do not need retorquing, but it is a good practice to retorque all of the head bolts after the motor has been heated up the first time and allowed to cool down. Remember, do not try to put Mark IV heads on a production Gen.V block and visa versa. You can use Mark IV heads on the new Gen.VI 454 and 502 HO blocks or on "Bowtie" blocks.
 
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