I've been trying to sort out the car ever since I tried to drive it to Tucson over a year ago, and it's been through a lot of parts to just to try to get it back to being fully functional. New water pump, alternator, control arm bushings, front wiring harness, HEI cap and so forth. Here's what happened: On the drive to Tucson, it started overheating, and blew the bearing in the water pump. It got towed to Phoenix, where I got hold of a new water pump, but that didn't fix it. I installed a thermostat (didn't have one), and it was still overheating. The weird thing is that it only overheats when going over a certain RPM/speed, so I was able to limp it back to LA. I then see that the carbon brush in the HEI has burned off 1/3 and melted parts of the plastic surrounding it. The car also seemed down on power. I buy a new HEI, and replace the carbon brush with a low-res version from MSD, to tackle the possible melting/burning. I only install the cap, since there was an obvious problem there, and I don't have to mess with the timing. The power seems to be back up, but when I took the car on the freeway, it still overheats, and there seems to be a misfire when going into the higher RPMs, like a bit of intermittent hesitation. The oil pressure also seems low when idling, I thought it was always 25PSI, but now it's 25 psi in (P) @ 900 rpm, and 12 psi in (D) @ 500 rpm. What to do next? Should I install the rest of the HEI (body), and check the cap so it hasn't burned the carbon tip again, or do wires/plugs? Check compression? The big question is, is something really hurt in the engine, or is it some peripheral component that's causing all this trouble? Any thoughts? Thanks!
Where is the timing set? initial and total? Do you have a clutch fan? is the fan shroud installed and in good condition?
Haven’t touched the timing since before it overheated, but I’ll take a look, something could have happened. It has a seven blade fan with a clutch and a fan shroud.
I had a similar issue... You mentioned a misfire, did you check all your plug wires? I had a Taylor wire that failed intermittently. Worked fine at idle and failed at higher revs. Thermal noncontact thermometer showed lower temp on head at 1 piston. Good luck!
I'd just do the basics - Fuel, air, and spark. Check for intake leaks that might cause a lean mixture. Are the plugs good? For the record, it would be my opinion that the water pump bearing failure caused the overheating, not the reverse. I have seen cases where the engine overheated to the point of seizure; the water pump was still good.
A distributor can lose it's advance travel with age and years so don't assume the timing is where you last set it. It might be the same at initial and not advance mechanically with rpm. This could definitely run an engine way too hot along with the other things mentioned, esp. at a higher speed. Any chance that there's a full 12 volts going to the distributor to melt things? I have no idea how long it would last like that, just that it burns stuff up. [With respects given to factory HEI needing 12v vs. some aftermarket systems using a resistor]
You may have multiple problems but if the engine heats up with higher RPM/speed and cools down when RPM/speed is lowered, I'd look at radiator flow. Have the radiator pressure tested. The miss may be another issue altogether.
A engine that had been fine temp wise and now still overheats at highway speeds after what you have replaced has 4 major things to get looked at . 1) Problems with the Carb and today's fuel after down time making for restricted fuel passages and a lean condition. 2) radiator blockage which can be checked with a thermal gun. 3) If the motor has a clutch fan that does not freewheel at highway speeds then the fan is accutally blocking off the air flow thru the radiator! Above 30 to 35 mph road speeds you do not need a fan if all is well with the cooling system. 4) timing chain very stretched which can easily be checked by rocking the Crank back and forth with plugs out while viewing the distributor for movement lag. Retarted timing makes for added head because the motor can't pump out the Exh as well. And then I guess number 5 a combination of some of these things!
Thanks guys, I’ve been sick and now I’m out of town, so I haven’t been able to take another look yet. I appreciate all the input, and hopefully this somewhat odd equation can get sorted out shortly.
Ok, I have run into wacky overheating probelms before and just recently fixed a 63 Caddy with unknown overheating issues. Given you ignition problems, pull the whole distributor and swap your new one in, make sure coil and module are new, use nothing from the old one except for your new cap/rotor. Pull all the spark plugs and check them, if not fouled out re-install(make sure plugs are grounding properly-tighten good and make sure threads/contact area is clean). maybe bring gap down to .35-.45 for now until you confirm your problem is solved. Check the resistence of your plug wires, all of them. They are mesured in ohms, lower the number the better. Let me know what the results are. Set total timing to 30 degrees for now. Have someone rev the motor to 3-4000rpm to verify. Total timing is more important than initial and the china hei dist could have all kinds of variation from one to another. After doing all that, plug in the vacuum advance and check and see how much advance it is giving you with it hooked up. Around 10-12 more is fine, more than that is too much. Also, change your oil. If you overheated it that bad, oil is shot. Put some Rotella 15w-40 in it and go from there. Good luck!
Curious, is it losing water at all anyplace? Is the oil remaining clean and normal colored? No white/milky look to it? This would be indicative e of a possible cracked head or blown head gasket as a result of the overheat. Make certain the heat riser flap door is opening on the passenger side exhaust manifold. Last thing you want is hot combustion gasses from the passenger side head all forced through the intake manifold while cruising down the freeway. If it still has the original carter carb check that the thermal valve isn’t stuck open and that the baseplate and stainless metal gasket are in place. This would also cause a constant ingestion of exhaust into the induction system. Timing as others mentioned. Start with 27-28 degrees full advance at around 2800-3200 rpm. Checked using a dialback gun. Base time should be around 2 deg btdc at idle with the vac advance disconnected. As some of the others mentioned the distributor (if still the factory one) has a mechanical advance inside and you want to be sure the correct limiter bushing is intalled. Same goes for an aftermarket unit. Of course this is all assuming the radiator has been rodded out, pressure tested and cleared. Or replaced. Hope you get it sorted out
I had some time to take a look at things yesterday, and I got a few things sorted, and a few a still left to do. "Problems with the Carb and today's fuel after down time making for restricted fuel passages and a lean condition." Would the plugs tell the story? Please see pics below. "If the motor has a clutch fan that does not freewheel at highway speeds" I'd think that the engine would run better with so much air coming through it, that this would be a more likely problem at lower speeds? "timing chain very stretched which can easily be checked by rocking the Crank back and forth with plugs out while viewing the distributor for movement lag." Haven't checked this. "Do you have a clutch fan? is the fan shroud installed and in good condition?" Yes, and yes. "Where is the timing set? initial and total?" "Check the timing at cruise RPM, vacuum advance connected." "pull the whole distributor and swap your new one in, make sure coil and module are new, use nothing from the old one except for your new cap/rotor" - Changed the distributor to the new one and used the new rotor/cap, and set the initial timing to 10 degrees (same as it was). I can't check the all-in advance since I don't have a dial back timing light, and I haven't figured out how to mark the balancer at 30 degrees etc, not sure where to make the mark (there's a formula to calculate this based on the diameter etc.) I didn't check it with the vacuum advance connected. "Pull all the spark plugs and check them, if not fouled out re-install(make sure plugs are grounding properly-tighten good and make sure threads/contact area is clean). maybe bring gap down to .35-.45 for now until you confirm your problem is solved." - Pulled all the plugs and noting looked too out of the ordinary (pics below) "You mentioned a misfire, did you check all your plug wires? I had a Taylor wire that failed intermittently. Worked fine at idle and failed at higher revs." "Check the resistence of your plug wires, all of them." - Checked all wires (pic below), and with the meter set at the 2,000 ohm range, the wires came in at 370-1050 depending on the length, it didn't seem like one of them was way off or anything. "Also, change your oil. If you overheated it that bad, oil is shot." When I started the car, the oil pressure was back to 25 psi in both "park - 900rpm" and "drive - 500rpm", so the integrity of the oil might be compromised when hot, which it was last time I checked. I didin't have any oil on hand to change with, so that will have to come later. "Curious, is it losing water at all anyplace?" Not losing any water, I changed the radiator cap when it was overheating, and it seems to hold well. "Is the oil remaining clean and normal colored? No white/milky look to it?" Oil looks fine, please see pic below. "Make certain the heat riser flap door is opening on the passenger side exhaust manifold." This has been removed and welded. "How old is the radiator?" "radiator blockage which can be checked with a thermal gun." "Of course this is all assuming the radiator has been rodded out, pressure tested and cleared. Or replaced." I haven't done anything with the radiator, and I'm not sure when or where it came from. I think it might be a replacement, since the trans-cooler lines are on the driver's side. If I come across a heat gun I'll take a look.
Left side is "old" distributor, right side is "new" distributor. I suspected they would be identical, but it doesn't seem like they're from the same batch.
Here's a shot of the old cap, where you can see how the plastic is melted around the carbon brush (new). The old carbon brush is on the side, and is about 1/3 shorter in length after melting/burned. This is not the cap I'm using, I guess I was messing around with it at some point and installed the brush in the old cap. I installed a new MSD low-res carbon brush in the new cap that's now being used.
Plugs dont look too bad, that is a good thing. Wires are toast, get some MSD Super Conductors or even the MSD Streetfires. Best I have found for the $$$. You really need a dial back light, otherwise you are shooting in the dark. Overheating at highway speeds is usually only a few a things. Other thing to check is to make sure your lower hose is not collapsing at speed. Can't tell anything about the oil, but I would change after it getting hot, especially more than once.
