Engine is a stock 1963 Chevy II 194 cubic inch 6 cylinder with a powerglide. It idles around 195 degrees and runs about 210 degrees going down the road. Tried 2 different kinds of gauges and sending units with the same results. Also verified with a hand help IR thermometer. Radiator has been professionally serviced. Pretty much the same results with a 160 degree and two different 180 degree thermostats. Radiator hoses have been replaced. The original lower hose did not have the "don't collapse" spring, but the one that is in there now does. No bubbles in the radiator, plus we have electronically sniffed the radiator looking for hydrocarbons with negative results. Compression is 120-122 PSI on all cylinders. Cylinder leak down test is in the green, between 30 and 35%. I wasn't there to see it (I'll look when the owner gets back in town), but the owner says that timing is correctly set. Book calls for 8 degrees BTDC at idle with the vacuum advance line removed and blocked. I haven't been able to find other advance numbers (such as "all in" amount and at what engine speed) for this engine. If you happen to know where I can find them please let me know. The engine seems to run pretty good, no ping, lots of pep (for 120 HP), so I'm guessing the ignition timing is pretty close. Assuming you don't over fill the radiator, the car does not puke out or use any coolant. The harmonic balancer had failed and an overhauled one has been installed. I assume that the timing mark is in the right position, but have not verified it with a piston stop. We've had 3 water pumps on it. One had about 1/10" clearance between the impeller blades and the casting, so we are not using it. It MAY have run slightly warmer than the other two that had about 1/2 that much. One thing that is slightly strange: All 6 spark plugs are very light (almost white) on one side of the electrode and a much darker shade (darker than I'd like to see, but far from fouled) on the opposite side of the electrode. Plugs are pretty new. Fan is stock 4 blade without a shroud. Fan belt is tight. Any ideas from the Peanut Gallery?
I'll throw my 2 cents in... 1. maybe an engine flush with Nate's Citric Acid concoction is in order, if the heat can't get to the coolant, it can't get carried to the radiator. 2. could the old girl be running lean at operating temp? 3. and as far as the plugs having uneven color... maybe oil-control rings stuck in ring land? (wouldn't show up in compression test) 4. here's a far-out question: Is the exhaust restricted or crimped? That's all this peanut gallery can conjure up. Good luck!
I know you say the radiator has been serviced, but that doesn't mean much to me. There aren't that many good radiator places anymore around here and I trust NONE of them. How old IS the radiator? I would have it checked again by a different shop for cooling ability and flow tested. Andy
Let's get it down to the basics; air flow, coolant flow, and heat exchange. Air flow--does placing a high flow box, or even better, squirrel cage fan in front of the radiator result in any temp change? Coolant flow with no thermostat--disconnect top hose at the radiator and direct flow into 5 gallon bucket with a garden hose keeping the radiator full . Time how long it takes to fill bucket and then extrapolate to amount in one minute. Look up acceptable flow rate which is in gallons per minute (gpm). If the assisted air flow makes no change and the gpm is within specs then the heat exchange is the culprit, usually from mineral scale build up inside the water jacket. Of course timing and exhaust restriction are not ruled out with these tests but the cooling system is revealed. Drop the exhaust pipe from the manifold and check out. On an unknown timing mark, make a piston stop and carefully rotate engine, by hand, clockwise and ccw till piston touches stop with a mark on the balancer in each stop point location. Halfway between these marks is top dead center. Measure balancer diameter and divide that into 360 giving the degrees per inch. Example: 6 inch balancer has 60 degrees per inch, 30* per in 1/2 in, 15* in 1/4 inch, etc. You can then make a timing mark at very close to what is called for. REMOVE STOP.
Where do you find coolant flow specs Evan? Shouldn't a 6" (diameter) balancer have a little over 19 degrees per inch? I think you forgot to multiply by pi on your calculation for degrees per inch.
Of course I forgot to multiply by pi, it's the circumference divided into 360 not the diameter. Back in the 60's we had a radiator shop that had flow charts. Only worked on American cars then and now they have hundreds of brands from a dozen countries so maybe they don't have them anymore. I googled radiator flow rates and got some hits that should be up an engineers alley.
As it runs cool enough at idle but heats up at road speed , I'd check the all in timing to not exceed 32° B.T.D.C. with all hoses connected . BTW : there MUST be NO vacuum signal to the dizzy @ idle ! . If it has vacuum @ idle , the advance hose is on the WRONG NIPPLE ! . Agreed the water jacket or radiator core may not be flowing properly but always check the other things first ~ white spark plugs is bad , might indicate a vacuum leak some where . Let us know what you find ! .
Further investigation reveals that highway speed is not required, just longer suburban driving will also eventually get the coolant temp to 210. We looked for an "all in" timing number but couldn't find one. Still looking. We did verify that the supply for the vacuum advance was "ported" (no vacuum at idle), however I'm old school when it comes to this and disconnect and plug the line unless the specs specifically call for measuring with the vacuum advance connected. Charlie bought a piston stop at FLAPS. Didn't work because it wouldn't adjust far enough into the cylinder. Stock plugs are AC R45XLS - a very long reach plug. So he made his own by cutting off the electrode that attaches to the threaded area, breaking the guts out of and tapping the inside of the remaining threaded barrel with a 3/8"x16 tap. Ran a nut all the way onto a 3/8"x16 3 inch long bolt that was threaded all the way. The nut is used to lock the bolt in the proper position. Used the tool to verify that the TDC mark on the new harmonic balancer was exactly correct. Rechecked timing with my 40+ year old timing light. It agreed exactly (8 degrees BTC) with Charlie's fancy set back light. Checked dwell. It was way tight at about 40 degrees, vs. 31 or 32 degrees specified by two different manuals. Reset the point gap to attain 30 degrees (as the block wears the dwell increases). Rechecked timing after the dwell adjustment and found it was now 17 degrees instead of 8. Reset timing to 8 degrees. Flushed the cooling system (again). Haven't done another road test, but we also have not done anything that should have fixed the problem. Still on the list of things to check are vacuum leaks using starter fluid (we haven't had a vacuum gauge on the engine yet either), clogged exhaust system and using an IR thermometer to verify proper coolant flow through the radiator. I'll keep you posted. Comments always appreciated.
You did, and I'm not doubting you Nate, but I'd love to see that number in GM print somewhere. Also, usually "all in" degree numbers are usually associated with a "by xxxx RPM" number.
If I were a betting man, I would place my bet with Andy. My experience with radiators is primarily with heavy duty ones. They can often times be "serviced", but, only by removing the bolt on top and bottom tanks. A simple exterior cleaning, boiling, and treatment with chemicals would never do. And, as Andy says, there are not many GOOD radiator shops left. The old guy that used to do mine, would push as hard as he could on the center area of the core, before we even unloaded the radiator from the pickup. He said he could tell if the core was "rotten" before we went any further. Then he would pull both tanks, and rod the core, to get it clean and functional. Then reassemble, and pressure/flow test. Since automobiles,at least modern ones, don't have easily removable tanks, I'm skeptical. Unfortunately, poor old guy's shop burned down a few years ago, and he was one of the old school fellows who didn't believe in insurance. He walked away and retired. The only other one I trust is in downtown Indy, in a neighborhood where you don't leave anything on the street after dark. And, he's in an old service station with auto garage bays... Now-adays, you can just order a cheap import core and bolt it together yourself. You just have to do it alot more often. I still have some jumbo-sized copper cores with holes in them. Might ought to sell 'em and finance part of my project. Steve.
" All in " never uses a specific RPM ~ what you do is rev. the engine until the advance stops , typically between 3,000 ~ 3,200 RPM . Agreed that good radiator shops are hard to find these days . One thing is to let the engine run until it begins to heat up then lay the flat of your hand across the front of the radiator moving it side to side as you work down . It should be hot at the top and cool as you go down , the heat shoul;d be even from side to side . Any cooler spots , even one , mean the tubes are clogged / damaged . Before giving up on a radiator , try the citric acid cleaning , it really does work *if* you take the time to do it right . Remember to leave the heater full on , you needn't run the fan though .
Here is where I am probably kicked off the forum for questioning a Nate response, but .... Nate: Your sentence below contradicts itself. The first part says there is no specific RPM while the second part specifies an RPM. As an example, my 52 GMC Maintenance Manual calls for: Centrifugal Advance ... Starts at 400 RPM 2 degrees at engine *** ... Intermediate at 1700 RPM 22 degrees at engine ... Maximum at 2600 RPM 32 degrees' at engine The reason I need an "all in" engine speed is to evaluate operation of the springs in the mechanical advance without dis-assembling the distributor to look at them. If one of the springs were broken, the "all in" RPM would be somewhere around half of the expected amount. If both were broken, "all in" would be at idle. *** Yes that does say that centrifugal (mechanical) advance starts by idle speed in my 228 GMC six. Tune up specs tell you to reduce idle speed to 350 RPM to set initial timing!!!
Found the reference data through a friend who's on line handle is "Sun Tuned". He still has an operational Sun distributor machine that he uses to check and modify distributors for hot rodders. Anyway, above is an edited page from a Delco-Remy spec book dated 1965. I've chopped it up a bit to make it all appear in one picture. It shows my buddy Charlie's distributor (GM part number 1110280) with the following: 450 RPM 0 to 2 degrees 500 RPM 4 to 6 degrees 750 RPM 6.5 to 8.5 degrees 1500 RPM is 14 to 16 degrees Note that RPM is distributor RPM which is half of crankshaft RPM. Note that advance degrees are measured at the distributor which is half of what is measured at the crankshaft. So the maximum (all in) number for this distributor when measuring with a timing light would be 28 to 32 degrees at the crankshaft timing mark with the tach reading 3000 RPM. The bad news is that Charlie is out of town for a week, so it will be a little while before we can see if his distributor is up to spec. By the way, the "all in" number from the spec is right where Nate said it would be.
Had a couple of hours to work on Charlie's Nova this afternoon, but we still haven't found the cause of the running hot. Here is what we did today: When I arrived Charlie had already pulled the distributor. We removed the plate the points mount on and examined the centrifugal (mechanical) advance mechanism underneath. Didn't find anything wrong. Put a little dry silicon lube on the mechanical advance and on the three slide nylon points that the points mechanism pivots on when vacuum advance is applied. Re-assembled an re-installed the distributor. Hooked up the plug wires and .... No start. Timing light showed no spark. Only took a few seconds to remember to hook the points wire back to coil -. Started right up. Set idle timing to 8 degrees BTDC at 600 RPM. Set dial back timing light to 8 degrees and verified that timing now showed zero. Used a MityVac to apply vacuum to the vacuum advance with the engine idling. Found that advance started at 9" Mercury (book calls for 5-7 inches) and was all in at 18" (book calls for 11.5-13"). The amount of advance was correct, it just took a lot more vacuum to get there. We checked the MityVac's vacuum gauge against another vacuum gauge and they were within a half inch. We will continue to look into this as a problem, but ran out of time today. Left the vacuum advance disconnected and concentrated on mechanical advance. Using the dial back timing light we verified that all four specified speeds resulted in the proper mechanical advance, with the last being 29 degrees vs. a spec of 28-32 degrees. Did the Nate-specified touch test on the front of the radiator. Seems to be equal distribution of heat side to side, both near the top of the coils and at the bottom. Verified with hand-held IR thermometer. Used some spray ether (starter fluid) and found a VERY small vacuum leak near the carburetor base. At idle, RPM may have gone up 25-50 RPM with spray. I really doubt this has anything to do with our problem, but we will change the gasket soon. During the test drive we noticed that the temperature would actually drop 5 degrees when we came to a stop light and let the car idle in gear (automatic) for 10-15 seconds before the light changed. I do not understand this behavior. Ambient temp was around 90F. As I said before, comments are appreciated. And please don't take it wrong if I comment on your comments. It is all part of the troubleshooting process. Tune in again next week, when Robin says "Holy rotor, Batman!"
Had a little time over the weekend, so we tried two more things. First we replaced the vacuum advance unit, which was requiring more than spec vacuum to get the proper amount of advance. Using the dial-back timing advance we verified that the new vacuum advance unit was in-spec. Maybe a little help, but more likely it was 85 degrees air temp vs. 90 degrees on our last test run. Even though the General designed this Nova with ported vacuum to the advance, we went ahead and connected the vacuum advance to manifold vacuum. Again, no help. We are running low on ideas.
Have you tried opening the exhaust? Don't have to disconnect all the way, just drop down a half inch or so. Since you said the temp climbs in time sitting still this should be an easy check. Probably not the problem since restricted exhaust usually drops top speed by a bunch but it's one more thing to cross off the list.
Haven't tried the exhaust, but it runs so well that I had mentally crossed it off. But considering my mental state, maybe I'll talk Charlie into trying it when he returns from his current trip.
Charlie (owner of the Nova) drove up in my driveway this afternoon. Air temp was 95 degrees and he'd been driving over 25 miles. Coolant temp was at 195 degrees and Charlie had a big grin on his face. Problem solved and boy, do I feel like a dumba$$. Given all the things we have done to this car that COULD have fixed an overheating problem, we don't know when the final problem occurred. The car has had three water pumps in the last few months of trouble shooting. At some point (maybe even before Charlie bought the car, but more likely when water pumps were being swapped) the fan was bolted on backwards. The blades on this 5 blade fan are curved like an airplane wing, not flat like the stock fan. Even when installed backwards it still flowed some air through the radiator in the proper direction, but not near what it did when properly installed. Too bad I didn't find the problem, but at least I didn't cause it. I was never there when the water pumps were swapped.
HA!!!! Well that would be something I'd never suggest checking, but I will from now on! (Not in person, of course~ wouldn't want to get decked for being a smart ass or anything!)
