58 Chevy Biscayne, 350/350, recently rebuilt. Had cooling issues last year so took the winter and did some upgrades that I thought would solve a lot of small problems I was having. I figured I'd fix up some things and either love it or move onto the next ride. So over the winter I replaced the radiator, water pump, intake manifold, distributor. Got new plugs, 4 brl Edelbrock carb and has been running really really well until today. Now I'm in Florida and it hit 80 outside today, but after about an hr on the road it started getting hot and had to keep pulling over and letting her cool. Any ideas on the problem this time? Im sure Im leaving something out, so just ask, I appreciate the help.
If you replaced all that stuff and it was okay for a while, then it's one of three things: 1) Thermostat. They do stick from time to time 2) Head gasket leak. Check to see if the system is pressurized when it's hot - if not, you could have a problem. 3) Cracked exhaust valve pocket - similar symptom as 2). Will show up as a sweet smell out the tail pipe - or in colder climates, steam out the pipe. I'm leaning towards #3 - sorry. Reason is, a cracked head acts like a normal one to a certain temp; then goes all wacky went a steam pocket develops in the cooling system Steam does not cool well; the engine rapidly overheats.
Might be a good idea to get an oil sample checked for bearing residue. Worst case scenario would be that the rebuild was not done right and the bearings are too tight. If so...the whole thing may be getting ready to spin a bearing and ruin your block,crank + ... It can be saved if you tear it down before a bearing seizes. Sorry to be so negative but I worked in a rebuild shop when I was young and saw this too often. Hope it's not that but it sure might be!
How do you check for a cracked exhaust valve pocket? And method to fix if this is it? I was leaning towards a head gasket problem, but hadnt has an issue like this before.
Easy way to do the check w/o teardown is to run the engine up to temp with the radiator cap off, and check for bubbles. If the coolant in the header tank has bubbles in it, it's from exhaust gases entering the coolant system. What age are the heads? Iron or aluminum?
I'm ***uming you have a good (big) fan, with a shroud, and you have good air circulation through your radiator? If you're overheating in traffic, the first thing to suspect is not enough fan. If you're overheating on the highway, the first thing to look for is good air flow into and out of the radiator. (The air has to have somewhere to go after it goes through the radiator!). Make sure that air can't get into your engine compartment unless it goes through the radiator - seal off everything else as much as possible. For example, my '53 Chevy will run cool all day long as long as I'm moving, because it gets good airflow and the radiator is big enough for the motor, but tends to overheat in traffic because I am limited as to how big a fan I can use in the cramped engine compartment. Adding a shroud helped quite a bit, but I'm also adding an auxiliary electric fan that I'm hoping will allow me to idle at a red light on a 100-degree day without my temp gauge climbing. Changing my water pump made no difference at all because the problem was air flow, not coolant flow.
Well I do not have a shroud on there now, and my buddy told me earlier that he thought that would help too. My compartment is huge, I actually had to put an extension piece on teh fan to get it closer to the radiator, but while it does get hot sitting now, I was actually going down the road when I noticed the temp starting to climb. It did take quite a while before it started to get hot though. I was thinking of adding an electric fan on to this also, but trying to go through one hurdle at a time being the cost of rebuilding so far. Thanks
On a small block Chebbie, make sure the distributor is getting manifold vacuum for the advance. Ported vacuum will cause overheating. So will a lean mixture. And straight water in the radiator won't cool as well as a coolant mix. Lastly, what temp do you consider hot?? Over 215ºF and I would agree with you; under that and it's still OK. Cosmo
I'll have to disagree - straight water is the best coolant as far as pulling heat out - the problem is it doesn't offer the water pump any lubrication nor does it offer any freeze protection. That said - A shroud will help pull air through the radiator at all speeds and should be added - heck I'm guessing you can find one in the junkyard off another vehicle that can be made to fit your radiator pretty easily. As for checking for a cracked head/headgasket problem - most good shops can check for hydrocarbons in the coolant (exhaust gas) - this is a good indicator that combustion pressure is entering the cooling system - how it's happening - well that's going to have to be up for a teardown and inspection of the gaskets and a mag / pressure check of the heads. Is your radiator cap the highest point of the cooling system (i.e. not the heater core, the thermostat housing, hoses, etc.) - this can cause there to be a huge air pocket in the cooling system. Try a couple things first: - ensure timing advance can is off manifold vacuum - Bump base timing a couple degrees (vacuum pulled/plugged) - drill a small 1/16" hole in the outer metal of the thermostat (lets steam pockets escape) - check lower radiator hose for kinks, bends, and the presence of the steel inner wire which prevents it from collapsing unde suction of the pump. - since you're in florida and it hardly freezes there run a 70% water / 30% coolant mix. - are you sure you're using a correct rotation water pump (i.e the late model chevy pumps which were used with serpentine belts are for reverse rotation...)
Two things: 1. Put a shroud on the thing right away. This makes a gigantic difference on fan efficiency. 2. What type/size fan are you running? 3. What is your timing set to. This again can have a dramatic affect on temperature. Try pulling a few degrees out and see what this does. Checking for bubles with the rad cap off, checking plugs and oil for residue are also good tests but i'd definitely address 1 thru 3 first.
#1, shroud. #2, shroud. #3 shroud. I have sen 58's that came with them and some that didnt. Tripped over one from a 58 last summer while picking thru one of my favorite spots in South Dakota.
Hay Cosmo, would you care to outline your theory behind this statement please? I'm not picking on ya, I'm curious.
Thanks for the tips, will work on it this weekend and see what I can figure out.One other note, I checked the radiator after it cooled down (about 10 minutes ago) started the engine, and did notice "bubbles" surfacing when shining a flashlight in it. I didn't let it get up to temperature however, was seeing if that cracked exhause valve pocket theory would still apply.
In all the years I've been on here, THAT has been mentioned the most often as a possible cause of overheating. The theory?? Not much, GM pulls manifold vacuum for the SBC dizzy, and they pay their engineers a LOT more than I make and have a lot more to lose if their wrong. Put the two together, and that's why I mentioned it. Cosmo
#1 shroud and a quality fan with a thermostatic clutch. #2 Timing. No vacuum advance or wrong advance makes it hot. #3 Water pump or radiator condition. A small block in a car with 8 square feet of grille shouldn't have cooling problems.
I played this game before, spent $750 in parts. Replace this, replace that and yeah there is this also to replace. Later, cheap *** Summit temperature gauge, was 15-20 degrees off to the hot side. Moral to story: dont buy cheap gauges and start replacing the cheaper stuff first!!
Also should I be using a higher temperature thermostat,195 degree or a lower 165? Car ran hot this morning already just coming to work, will have to address this issue sooner than later now
Couple of thoughts: 1) A shroud will indeed make a HUGE difference, but you said the car worked fine for a while and then started to act up. Do add the shroud - bit it may not solve your problem 2) To the water vs coolant folks - water cools better than water and glycol - period. The difference (***uming a 50/50 mix) is roughly 12-15%, accounting for viscosity correction (about 6%) and differences in thermal conductivity and specific heat (7%-8%). If you're having a prob with cooling and it's borderline - straight water will make a difference. 3) Vacuum issues - Some manufacturers use a vacuum advance, some a vacuum retard. Vacuum retard uses manifold vacuum to 'hold' the dizzy at full retard; using a timed port on a vac retard will cause the timing to be WAAY off and cause the engine to reject lots of heat to the cooling system at part load, as engine vacuum is pulling out timing - not adding it in.
I had a 48 Chev SD with an Olds in it that would overheat on the road. After adding the shroud, ensuring that all the air through the grille went through the radiator, messing with the stat, etc. it came down to a worn timing chain that let the timing change when it was at speed. It ran cool after that and everyone was happy. Pull the distributor cap off and turn the engine over by hand, watching the rotor. See if there's a lot of slop between moving the crank and having the rotor turn. Also be aware that a two piece SBC balancer can slip inside itself, allowing the outer surface (with the timing mark) to rotate in relation to the crank. That can cause you to time the engine at the wrong place in relation to the crank, even though the marks are correct.
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