Hot Big Block

I'm at my wits end.  I purchased a '65 Chevelle three years ago.  At that time it was a 454 .030 over and it ran warm.  I have since rebuilt it, now .060 over and added .25 to the stroke, now a 496.  All of the internals, upper and lower, and I mean all, are new. The block is casting 361959, heads 353049. Running SRP 18cc domes for about 10:1, producing 543HP @ 5,800 and 548TQ @ 4,300. Block was sonic tested after boring with nothing found out of acceptable range. Running two 1,360 cfm electric fans, full time, behind a new Griffin two row (1-1/4" tubes) aluminum radiator, and a stock GM water pump. The car is equipped with a 4" cowl induction hood, not sealed to air cleaner/intake.  This is essentially a street legal drag car, no heater or bypass, no A/C.  I have never had this car get hot at idle from a cold start.  Take it down the road and within 15 minutes both eyes are on the temp gage as it goes to 210 and beyond, I've seen 240+. I have done every tried and true trick in the book to stop this phenomenon; three different water pumps, different thermostats, no thermostat, outlet restriction plates, pusher fans, puller fans. I can back the timing off from inside the car without results, so that's not the problem.  I've got in my head that this is an air flow problem, so yesterday I fabbed up a 6" deep shroud for the upper half of the fans/radiator, and made a filler for the area between the top of the grille and core support to make sure air was going through the radiator and not over the top it while driving down the road, all to no avail.  Granted, it was 95+ outside air temp but I don't have this problem with any of my other three cars in the same conditions. Once I get the car back in, I can cool it down in a matter of minutes by shutting it down, letting the fans run for a couple of minutes, starting it back up to cycle the coolant and within 10-15 seconds, the gage is back down to 180. I've had numerous knowledgeable people look at this thing, leaving them shaking their heads.  I know this issue has been beat to death in every forum out there,  but anything and everything mentioned does not help with this one.  By the way, on the dyno, 179 degrees.  Is it possible that the  volume of air entering the engine bay off the windshield through the back of the hood is great enough to stop airflow through the radiator at highway speeds?  Haven't tried running with the hood off, but only because that seem too far fetched.  Anyone?  

Have you replaced the temp gauge and sending unit?  

Yes, the whole panel is all new Autometer SportComps and sending units.  This motor definitely gets HOT.  

Just helped a buddy of mine fix a similar problem with his '65 Corvette with a bored out 402 big block. The bock is a passenger car unit that didn't have to bottom, center water jacket holes drilled at the factory (But the heads did have the corresponding holes). It was a serious coolant restriction that caused the motor to heat up. We drilled the holes, no more heating problems.

What's strange is it runs at normal temp sitting at idle, but when you're driving and have airflow through the engine, it heats up.  

Yes, 55, you're essentially turning a "series flow" block into a "parallel flow" block. I know the block was originally a no-holes series flow, and we (the engine builder and I) talked about drilling the holes, but can't recall if it was done or not, the heads were in place the last time it was going back together by the time I saw it.  I'm trying to get a hold of him now.  What I'm really trying to find out here is does anyone have any thoughts on if it's possible, because of the amount of air being brought forward by the cowl induction hood, to build a high pressure area in the engine bay behind the radiator, preventing air from passing through the radiator at boulevard and highway speeds.  I know it sounds crazy but where is all this air going since its not ducted/sealed to the air cleaner?  

I have the same to the t problem with same engine combo you have.I have been building big blocks a long time and never had my butt kicked like this.I have done everything possible to keep it cool nothing works.I did notice the extra holes some big blocks have in the block.The first time i rebuilt it witch was last month the block i used was a gen 4 2 piece rear main it had those holes in it and the head gaskets also had them,well turns out on a test drive watching the temp gauge climb to 230 again i smelled coolant pulled into my shop and saw steam coming from valve cover breathers.Anyway i pulled it and tore it down to discover a crack in the block i hade another block at the shop and had all the goodies fitted to the new block,now i noticed when installing the heads that this block didnot have the extra holes in it like the other block but the heads do have holes in them.Well felpro sells both style head gaskets with or without holes,without holes is stock.i chose the gasket that fit the block without the two lower holes.This engine still runs hot,do you mean i have two drill two holes in the block to cure it? man iam fustrated,on top of that it tends to drop off fuel pressure the longer it runs,everyting is new 2 times over.Holley blue and you know the rest.Any sugestions will be greatly apreciated!  

Well Dave, I'm going to add fuel to the fire so to speak.  I talked to my builder this morning and he did indeed punch the holes during the last go around, so it evidently is not a cure all; helps most but not all situations.  It's a no-brainer operation, just a big hassle if that's the only reason to take things apart.  I'm curious, what intake and carb are you running?  I'm grasping at straws; about all I have left.  

I started with a 60 over block old 1972,eagle crank h beam rods mahle forged pistons it is a 496 stroker kit.10.5 to 1 compression it has square port heads big bracket cam now the intake is a single plane high rise it looks like a team G.And i bought a brand new 750 quickfuel double pumper,nice looking expensive like everthing i put in this motor,it sure runs hot new w pump high flow edelbrok new radiator new dual flexolite fans best of everthing.it runs hot and the valve train is noisy.It will run 190 sitting but when you drive it runs 220 and 230 till it shuts off never boils over but fuel boils in carb bowls causing the engine to die.under hood temp unreal.make sure your water pump is turning the correct way,do you have a serp belt set up or v belt.I have a serp belt spinning a high flow pump reverse rotation,check lower hose for collapsing under load do you have a sprig in yours?  

We're running more similar than you know.  I'm running a QuickFuel 830SS on a Team-G, but fed by a GM Performance mechanical. Serp belt, RH mid-mount alt, long pump. No one makes a reversed long for BBC so it better be right. I know what you mean about under hood temps when you come in- makes you wonder where the fire is and when is stuff going melt.  Can't touch a thing.  No spring on the lower hose. I find it interesting that you're running a Team-G.  You don't suppose there are flow issues there do you?  They've stopped producing it... hmmmm.  

hot rod,if you have a standard w pump you best make sure it is spinning the corret way,you say you are running a serp set up most i have seen spin the pump reverse.I I installed a reverse flow long nose pump on my engine.witch way does your pump spin? did you look at your lower hose when you crack your throttle does it close or is it kinked?  

rod,i have used team g intakes on drag motors for years and they work good,never used one on a street motor,today i took mine for a spin for the first time,left shop it was 190 soon 210 and 30 min into the test drive 220 at times it looked like it wanted to go to 230 but would come back down to 220 when i pulled back into shop and shut it off it didnt puke any coolant and would start right back up,funny you mension you can run your fans for a few and crank it up and all is well,same here.I installed the bypass hose that goes from intake to the back of the pump a desperation move but i dont know what else to do.i will drive it tomorrow and see it is only a water pump bypass but who knows.it runs much better at 190.  

Dave, pump has no choice but to rotate same direction as crank on my setup; I may have misled you; its not a full serp system, I'm running a serp belt pulleys on a conventional layout, only have balancer, pump, and alt. to run. This pump was on a  '74 Gen4 before and was fine so I know it's not reversed. I've run mine with and without the bypass hose, made no difference, right now it's without.  I'm going to pull the hood off this weekend and take it out and see what happens.  I'll let you know.  

rod fixed my overheating problem,want to know how?  

Dave, sorry havent' been on here for a few,  sure, what's up???  

I changed the crank pulley to a 5 3/4 diameter this slows the flow through the rad down,also installed a restrictor in place of the t stat the kit came with 3 of them.But iam sure the biggest problem is the fan,YOU CANT RUN ELECTRIC FAN ASSEMBLIES ON THE STREET.I put a 6 bladed steel fan on with a fan clutch off a 94 chev pickup made a shroud that looked factory and now i run 180 all day in florida in the summer with a/c!I also changed the cam to a more radical sollid roller but i dont think that helped my running hot issue,although cured my accessive valve train noise i had.Spoke to a car bud of mine he gave me the idea about the fans he had the same problem with his 70 chevelle.He has the best of everthing his car is BAD TO THE BONE ,he chased his running hot issue for 2 years and finally took his top of the line twin flexolites off and installed the 6 bladed fan and proper shroud and fixed his also.