Overheating Big Block
 

Now after finishing my 67 Chevelle, I took it for a test drive and it seems to have a overheating problem. It is a stroked 454 crate motor. Has aluminum heads, bored .060 has 10.5 forged pistons... I have a three core aluminum radiator, two electric fans, running a single belt march system with reverse flow water pump. tried 195 and 180 thermostat and nothing changed. When I took it down the highway and would reach 190 hang there a short time then up to 200 to 205+ I would get it back to the garage and it would blow water in the overflow and eventually on the floor. I tried it just sitting and at 190 it would start to flow water into the overflow tank which seems odd to me. It has a 16lb cap and I have tried two. The outside temp was 85 on several test runs. But the other day we had a front come through and at 75 I drove it and it stayed at 190, which I thought it should have ran cooler. the fans are working fine, I do not know how to proceed in what could be the problem. I have never ran a reverse flow pump. But we have run out of things to check... any ideas???

It should definitely not be puking coolant at 190 degrees.

I would normally think you need a new cap but you mentioned trying two. Have you verified your temps with either an infrared gun or different temp gauge? You can pick up a cheap temp gauge at your local part store pretty cheap, or Summit has a variety of gauges you can order for not much $$.

Before anyone tries to convince you otherwise, you can absolutely cool a big block motor with electric fans. Many will want you to swap to mechanical clutch fans but that is traditional, I'd rather use points for ignition because it came that way 50 years ago, thought process. I look at that the same way I do those who say electric fuel pumps are no good on an old car. This too is bogus, but you can't just slap some cheap part on and expect it to work as well as something that was carefully engineered by a multitude of well-paid GM employees. You do need to CAREFULLY and thoughtfully plan out your cooling system while making sure to not skip any area. You need quality fans with good relays and wiring. These fans need to be mounted with some kind of shroud - this I suspect you lack. Many fans come built-in with a plastic shroud that mounts to the radiator and/or core support. They often have flaps to allow air to flow through at highway speed but close at idle so that you pull as much air across the radiator as possible. If you have two fans just quick-tied through the radiator and no shroud, you will very likely have problems.

Also, how do you have your fans programmed to turn on? Is there any type of relay/controller or is it simply a switch?

Again, I do not think at 190 degrees you should be seeing any coolant bypass the radiator cap. This still seems wrong to me as 190 is normal operating temperature, even 205 is not really overheating but is certainly warm (or warmer than I like to see my car get.)

Post some photos of your set up and maybe something will jump out.

When your fans come on, how hard do they blow? If you held a piece of paper either in front of the radiator (not as easy to do) or behind the fans, how hard does it pull/blow air?

EDIT - Why do you have a reverse flow pump? Is this a serpentine system?

Yes it is a serpentine single belt. The water pump came in the kit. The fans are not flat against radiator. there is a flat aluminum plate that the fans mount to that holds them about 1/2in from the radiator. The fans are on thermostat control, and come on at 180deg, or when the air is on. the plate is solid there is no rubber flaps. I had those on my previous car but this one does not. The fans seem to move air across the radiator fine but nothing to brag about. I put in a new temp gauge to make sure it was correct. I might suspect it could be in the fans, being no flaps it would not allow good air flow going down the road. I sent a pic to check out and see what you think. I tried to spare no expense on my cooling system. The fans came as an assembly with the radiator....

Well that set up is certainly better than what I had in my mind. The flaps can certainly play a role going down the road but the car should be able to maintain normal operating temperatures while idling. There was a thread on Team Chevelle by Brandon from ATK Engines with a similar looking shroud and he was having very similar issues with his electric fans. I only briefly paid attention to his issues but I do remember him taking a hole saw and making holes in his shroud so air could freely flow through the shroud at highway speed. I'm not sure that was his entire issue but when the shroud is solid like that it basically creates back pressure and does not allow the air to move across the radiator like it should. You would think it would just tunnel it through the fans but that is apparently not the case....

Is your issue isolated to while driving or can you sit at idle for an extended period without overheating? I'm still not sure about your overflow at 190 issue. The only logical thing there is the cap. I would definitely put either a 180 or 160 degree stat in the car with a bypass or a small hole drilled.

The temps are coming down so it makes troubleshooting these issues a bit more difficult as these cars will run cooler by default. Let me know if the car can idle without overheating. Also, how is the timing set? Do you have vacuum advanced and if so is it on full manifold vacuum or ported?

Well I'll go in a different direction. What's your ignition timing set at, initial and full advance? Are you running a vacuum advance? Manifold or ported?


Oops! Missed Eric's last post, he already asked these questions.

First thing that jumps to mind is the reverse flow pump.
Have you re torqued your head bolts.

Ok I have just finished running it for 25 minutes in the garage, paid close attention to the temp when it pushed fluid into the overflow tank. At 185 deg it filled fluid into the tank but less than half way, really weird why its doing that. The next thing it never got above about 185, but if you put your hand on the top part of the radiator it will fry your hand, and I have stainless water hoses, if you touch the top one same thing you cannot hold on to it. BUT I can reach down and grab the bottom hose and keep my hand on it with no problem seems less than half the temp of the top section... what the heck is going on. Right after I started it maybe less than three or four minutes I was just going to watch and see if the water was flowing after the thermostat opened up , it blew water everwhere like it was under severe pressure......... Im still going to check the timing, but I think if it sits and runs a good temp it should not be that....It is a vacuum advance, at the carb.timed at 10deg... the temp outside is at 70deg so I decided to go for another drive, temp climbed to 190, then in a few minutes it climbed to 205 so I decided to take er back before it got too hot... let it run in the garage with a big fan running in front of it to see if it would cool down, it would not, sucks I cannot even drive the car after all that work. It does have a 180 stat in it and there are a couple of holes drilled in it....

You should keep the cap off until the thermostat opens up and water starts flowing through the tubes. You might have a big air pocket in there.

I had some issues with my mild 350 too.
Two things solved it:
a) correct the timming advance;
b) change the cheap electric sensor for a good (AutoMeter) mecanical one.

Solved!

Of course the "b" alternative have nothing about really cooling the engine, but several people talked to me about bad temperature sensors.
Check it!!!

Do you have your old pump and V belt pulleys.???
Just a thought.

Well still having the same old problem. The latest thing I have found out is the pressure in the radiator is really high, while watching the temp gauge
, I noticed that at 160 even before the thermostat opens up it is blowing water out the overflow and into the tank, cannot understand where so much pressure is coming from. I put a cap tester on and watched how high it would go and it topped out at 25lbs. But when the temp reached 160 the pressure on the cap was at 20lbs. There is no water in oil and none in exhaust pipes... what else could cause such a pressure increase.... and such an overheating problem... I did call the march company and they said that was not a reverse flow pump, its arranged so the water still flows the right direction as factory.... driving me nuts,, getting to the point of taking it to a mechanic or someone that is a lot smarter than me...

Over heating and high radiator pressure is sounding like a head gasket problem.

That was my thought too but if it is that and you would think it would be more noticeable

Don't they make a sensor you can detect the exhaust gas in the radiator. It acts like a head gasket but water is not getting into the oil or cylinders, pulled plugs and all look normal. I have heard to do a compression test and the one that is blown will read low... but still water in the cylinder would be quite obvious. When I was shining a light in the overflow and watching the water come in from the bottom it was blowing air bubbles for a couple of minutes still that is weird to me also....

You would think with a blown head gasket one or more cylinders would fill with fluid during cool down, causing a hydro-lock when you try to start it up. Not every time, just depends on where the pistons are sitting in the cylinder when you shut it off.

Don't think this is the real problem but 10 degrees base timing is not nearly enough for a big block. It will run cooler if you up the timing.

I'm still leaning something is going on with a head gasket if you are getting bubbles in the coolant. But I'm not an expert on the subject only what has happened to me in the past.

Blown or deteriorated head gaskets account for one of the most common and obvious causes of coolant bubbling. If the head gasket material blows between a water jacket and the inner area next to the cylinder, compression gases will enter the water jacket and send air through the head and into the cooling system. Blown head gaskets produce profuse bubbling inside the radiator and expansion reservoir. Rapid overheating results

I have been there, Never knew I had a problem.

http://i777.photobucket.com/albums/y...adCylinder.jpg

Try a re torque of all the head bolts..in order.!
See if any are loose...or perhaps pulled a thread in the block.
I had a pulled thread in my block that caused an overheat problem.
my cure was a heicoil...and changing from bolts to studs.

Well after a lot of asking, they do make a combustion leak test kit that lets you know if you head gasket is blown without having to guess. It uses a chemical liquid that changes color if you have exhaust gases in your radiator. It will be here at noon today had to order. At least it will answer one big question... I will update after I do the test...

Well I just finished the test. And it says it does not have a blown head gasket. Shows there are no combustion going into the radiator. That is one big relief and eliminates one big answer but still does not answer why the pressure and overheating. If you want to watch how this is done, go to "how to tell if your head gasket is blown" on the internet and there is a YouTube video you can watch. Now what could be causing the excessive pressure, and overheating????????

I have a similar problem but what I did was to drill and tap the back of the intake and ran braided hoses to my thermostat housing it runs a lot cooler. I had a guy at a car show tell me to put "3" drops of Ivory Dish Washing Soap in the radiator my temp dropped about 3 degrees. One thing you need to remember is you have a big block and they are known for running warm especially if you have a large cam and other goodies. To me 190 to 205 is pretty cool. Good luck

Well I finally got hold of a heat gun to try and see if there was anything I could tell with checking different spots on the engine. Every thing pretty much checks out, but the only thing that stands out is the heads temp. While the right head is at about 185 the left head is around 150, I hope this means something to someone, I hate to think that someone put the head gaskets on wrong. You would think they should be running the same temp or close to each other. Tried running it without a thermostat just to see what would happen.. did not help. Plus it still pushes water in the overflow tank way before the thermostat opens up. Driving me crazy, getting close to tear down time...

Well after trying everything, I finally had no choice but to start tearing stuff down and begin searching for the problem. The last thing I wanted to do was to remove the heads. But after removing one head, there was the problem.... The idiots I purchased this crate engine from installed the wrong head gaskets....Seems as my research tells me, all 454 engines after 85 will have the three lower coolant holes open in the gasket, of course mine were not. You know you would think if it has large coolant holes in the head and the block you would notice a problem especially if you do that for a living...... a relief to finally find it, now a really angry call to the engine people, and putting it back together to be able to drive. Thanks for all the help....

wow that is crazy! i would call and complain about that for sure!! at least you found the problem

Im glad you found the problem.
Now would be a good time to upgrade to head studs.

Well hell just when you think all is well and you have found your overheating problem. Well just before I put my engine back together I decided to call the engine builder to complain, well according to him those head gaskets are correct for that engine and he has built hundreds and those lower three water ports are supposed to be covered. What the hell. Ok someone out there has to have built a 90 model 454 chevy which is a mark iv and the correct head gasket. I am losing my mind. I look at pics of gaskets on the computer for that engine and it shows those lower three holes open. The engine builder says it will cause hot spots in the head and over heat. Well hell its over heating now. He says I have done something wrong on the cooling end of it. Of which I have found nothing wrong. I have built tons of early big block chevy engines, never had a problem on which head gasket to use. Just order the correct one and install it. it should not be this difficult...

Think i would talk to some other builders and get their opinions.

I don't mean to be a wise guy but that block is borderline gen v.

Still trying to solve the head gasket question. Quick question on this 454 block does anyone know about the raised rings above each piston hole on the block deck. I have never seen this before, this in itself looks like it would require a special gasket. If you ever decked this block these would have to be removed in the process.

Well found out what the rings were, this block has had the metal 0-rings cut into it. I have never seen a block with this done, feel kinda stupid. if this is the case to me these have the wrong head gaskets on it. From what I read they are supposed to be copper. The head gasket on there was not correct you could see where the rings made indents in the metal gasket ring but did not touch in places to make a complete circle. Has anyone delt with this type of set up before. the tech guys at summit racing were of no help on my set up.... no help on the cooling what so ever... good lord will this ever end. Said they could not find the part numbers on the pro comp heads so they could not give any info. Pro comp said they are not engine builders so could not be of any help.... and on and on and on.....

Try calling the mfg of copper head gaskets for an Oringed block.
Send them pics if you have too.

Found a company called SCE gaskets.
Watch the video.....give em a call.

MPRAT, try looking at this post from TC about same problem I think.
http://www.chevelles.com/forums/showthread.php?t=549978

Well been awhile since I have been here, still working on the overheating problem with this car. Since I have removed the "O" rings from the block and install back regular head gaskets and got it back running again. While test driving this it began to miss fire so back to the garage and remove the valve covers because of knocking lifter noise to find the engine had ate a quarter inch off the #4 intake lifter and of course ate the cam lobe in the process. So I just decided to pull the engine and start fresh. Took block and heads to local machine shop to have them checked out and ended needing to have the block and heads cut to make em flat again. Checked the cooling system and the block was clean with no blockage. Now after putting all back together again, running great took it out for a test drive to check to see if it still has an overheating problem. After a few miles it got up to 190deg cruising at 50mps then to 195, turned back and headed home, up to 200deg, then 205deg then back home at 210deg, pulled in garage everything working fine, fans running, just a small amount of water in overflow tank. Still this thing overheats for no reason I can find. While apart I checked everything from water pump to radiator everything was fine. I cannot understand what in the hell the problem is. You would think if the engine cooling system is clear that it has to be something up front. I am getting really frustrated with this car. It is not a hot day here, cloudy outside, I would hate to see if I used the air-cond or got caught in any traffic... have tried everything I know and all suggestions... I don't even know a good mechanic shop to give it to and let them have a go at it.... I so hate this car right now....

I had the same problem with my car overheating and just could not figure it out. I had so many people tell me it was the thermostat and last year on the way to the NOCC show I had a problem with it getting to hot again. So when we got to Strongsville I had many people telling me what they thought it was. Ultimately changed the thermostat, AGAIN, and drove it home. My brother, who did alot of the engine work on my car told me that I needed a racing thermostat. He tested it on the stove and even drilled a small hole in it and now my car runs cool. I will ask him what the name of it is if you are interested.

Ms Grumpy ,Im interested in a good thermostat recomendation for my truck ,small block 350 crate motor ,260 HP ,with Vintage Air .I have a 4 core aluminum radiator and a clutch fan on order and should be here soon.

I was pondering this and the same thing Ms Grumpy said hit me last night. I am on a van forum. Same issue with overheating. Todays T-stats must have terrible quality control. It takes several T -stats to find one that works. I went through 4 before I got one that worked. Other members there go through it every spring.

Well I have changed the thermostat several times, even ran it without one, whats strange is not matter what I try or do to this thing it never changes what it does. It does the exact same thing every time. Last night I tried one more time just to see how hot it would go if I kept going. The temp keeps on going up I stopped it at 230, pulling it in the garage and putting a big fan in front to see if it would cool down did not work but only a couple of deg. I have contacted a local mechanic shop as a last result because I give up. It goes in next Thursday and I will hope another set of eyes can see something I cannot. I will give an update and hope its something simple but I doubt it. Then this thing is going on the auction block.......

Just curious but what kind of fuel are you running? A buddy of mine has a built up big block and if he runs any type of pump gas his car overheats. It may be worth a try to use some 100+ octane fuel to see if it helps out.

John sorry it took so long to get back on this. I am pretty sure it was Mr Gasket high flow. I think I bought it at Oreilys.