Ive got a 1968 Pontiac 350 Coupe Ive owned for around 8 years. I have tried several things to reduce engine operating temperatures but, had very little success. I was reading an old Chiltons manual and they referred to these Firebird motors as C.S.S. motors or Combustion Control System motors. They were designed to run at a engine temperature of 195 degrees. The manual says it is done by running the carborator leaning and timing differences...Ive tried changing timing and have put an Edelbrock 4 barrel on it. I changed the water pump and the distribution plates. I swapped the intake for a GTO 4 barrel intake and swapped out the distributor for one of those one piece Ebay aluminum specials...Still the motor runs around 195..After sitting idle it will climb to around 210...Ive tried changing the thermistat to a 165,3 different throttle plates, 180 and finally back to a 195. It seems to run coolest with the 195 in it. What gives? Is there extra webbing in the head or block that is restricting the coolant flow? Id really like to reduce the operating temperature of this motor to around 170 like a small block Chevy...Any advise >????
I've got a '69 Custom S (Tempest). I was told of this problem but have not experienced it in the 8ish years that I've owned it. That was with sit and go LA freeway traffic. The only changes I've made were an aluminum performer manifold, 610 Edelbrock 4bl and an electronic ignition. I dove it through Nevada, Utah, and across I-70, through the mountains in a couple days without a hint of overheating. Before I owned it it had been overhauled @ 108K.It was bored .030 but, other than that was a straight rebuild. Don't know the answer for you but I am curious to know. Sooner or later it may become a problem for me as well.
One thing to check is behind the water pump. If you've replaced the water pump, it may have to much clearance to the divider plate. Or may just have too much clearance from the pump thats on there now. What I mean by too much is .250", it needs to be reduced down to .100 by massaging the divider plate with a hammer to reduce the clearance. Or may have to do with if it has a cast or stamped impeller. This would be a really long read , but alot of good info here about it http://forums.performanceyears.com/forums/showthread.php?t=411256
You don't say if you are running a fan shroud or not but that 1 thing will make a differance for the better. Also I took the fan clutch ass. off and repalced with a flex fan. Went from 200-215 degree to 185-190
Lets start out by clarifying what operating temperature is, or what it is not. That 195 temp is going down the highway not sitting and idling. Now let's dig a little deeper, you don't lean your carb to make one run cooler you make it richer. One that runs fat will always run a bit cooler than one running on the lean side. You have done well to go for the 195 stat, the higher stat allows everything a bit of time to cool off. That would be the coolant in the radiator as well as giving the coolant in the block a bit more time to absorb heat. While on the subject of coolant what is you coolant mix? Or what are you using for coolant? Water absorbs heat better than Glycol, most folks believe that you should mix it about 50/50. That is half what comes out of the jug and half what comes out of the spiggot. You didn't say what you are using for a water pump. My experience has been that the cheap rebuilt pump that came from the "Zone" (or any other place for that matter) may or may not move coolant. I had them that didn't do much more than stir the water around. I personally use Flow Cooler high flow pumps these days, they do make a difference. But they aren't the only company that makes a good pump just what I've had luck with. Now the next big question is about the radiator. Not so much is its clean although that is something that you may want to take into account. But is the air passing through the radiator or can it go around it? Are all the little rubber things in the proper place that seal it to the core support and too the hood? A little air not passing through the radiator makes all the difference in the world. Just a few things for you to think about or check.
What sort of radiator does the car have? It's been my experience that Pontiacs need more radiator than a sbc. My GTO never cooled the way I wanted it to until I replaced the 3 row radiator with a 4 row HD core.
Ok thanx for the input...I put a flex fan on it already. it has a 4 core radiator that I removed and took to the radiator shop to get flushed out. The guy at the shop told me it was a waste of money and looked like a new radiator inside. The pump I put in it does had a steel impellor where the old one was cast. As for engine temps it will run 195 all day long. The only time it will climb is if im sitting in a line of traffic or a long light.. It does have the factor shroud on it too. The replacement pump came from Performance Years along with the distribution discs. A local guy told me that I should dump the flex fan and put a 5 blade fixed fan on it and it would make all the difference.It originally had a 4 blade. Another guy told me to ditch the cast iron intake for a after market aluminum job, stated the cast intake restricts water flow. I have new hoses on it and there is a spring in the bottom hose so its not sucking itself closed. As for coolant Ive tried a few different product. Right now I'm running Prestone premixed. I also tried that product that says it will drop your engine temp 10 degrees garranteed, it didnt!
I personally see nothing wrong with it if it runs 195 while you are moving and goes up to 210 if you are stopped for a while. Thats a whole 15 degree climb! Does it start to puke out at that temp? Remember water boils at 212, adding antifreeze/ coolant raises that number and so does putting it under pressure by haveing a good radiator cap. At 210 with a system that everything is in check you should be just fine and need not worry about it. I have never really understood why everyone wants their engine to run so cold. My 472 Caddy engine runs 195 - 200 all day goin down the highway on an 80 degree day.
Ive heard that before. I guess my main objection is that the car is about as big as a Vega and that motor sits a 1/4 inch off the firewall. It gets frickin hot inside. And it just dont seem right. If its in the heads Id even be willing to ditch them to get it to run cooler..
Dude, I think 53chieftan is right. I have noticed similarities in my Pontiacs past and present. And My '64 GTO that I sold ran a '66 421 with with tripower and too-low gears. It acted the same as yours does, and scared me to death... Now I realize it never malfunctioned or "over" heated necessarily at all. It was just my paranoid attitude every time I looked at the Temp gauge. Plus, I have noticed the Pontiacs seem to run a little hotter on the heat issue. I may be wrong, but my SBC in my '54 Bel Air keeps plenty cool all day long with the stock '54 radiator. And my wimpy '70s era Ford 302 in my '27 Roadster project stays cool with a little tiny junk Japanese radiator (It was the only one that I could fit in the small radiator space I wanted to keep for this car).
Crap, good point...I posted too late! Maybe it's worth the discomfort- I mean, Poncho engines are the bees knees!
First of all a Pontiac is not a small block Chevvie and you should never want it to be. Forget all your SBC knowledge, it is of little use to you now. Second, 210 is perfectly fine. Third, do you have a pic of your engine? And/or your car? We might be able to spot something with a pic. Also..I just plain dig pictures of hot rods with Ponchos in em. Good luck, -Abone.
I bought a '65 GTO without an engine in '68. After snooping around for a while, I found a guy in St. Paul who had a freshly rebuilt 421. I figured, "that's the ticket" and bought it and installed it in the GTO. After I got it running, I had real inconsistant overheating problems with it. After all kinds of teardowns and attempted fixes, I discovered that the guy who rebuilt the engine had left ot the sheet metal plate that goes behind the waterpump when it's mounted in the housing on the front of the block. Got the plate and installed it and problem solved. I notice someone early on in this post mentioned clearance between the water pump and the plate; from his experience and mine, I think I'd take a second look at it.
I dont think you have a problem, newer stuff runs hotter it is supposed to make engines more effcient and wear longer. i dont know how to spell eff.?
What kind of Temp Gauge are you using? Check it against a candy Thermometer in water. It should track the thermometer pretty close. The outter ring of Harmonic Balancers can slip. The Timing mark is in the wrong place when you time it (retarded) and the engine runs hot. Love those Pontiacs, keep em flying.
bought a 4- row radiator aluminum from some speed shop down south [ alabama] the boys down there said " it il keeper cool up to 800 hp er so son " MY rod will not get over 120 Degrees. Had to pull the thermostat out and put a 195 in it. Still cant get car to over heat no matter what . this radiator is heavy ga aluminum cost 400 dollars plus shipping , welds look pretty as can be. I will try and remember the name look for reciept. cant think off hand who i purchased from it was 3-years ago Later Russ
I have run and worked on Pontiacs for years. The guy is right about the water pump spacer also the cast impeler moves more flow. I suped up my last water pump to the point that i blew two freeze plugs out.After that i JB welded them in. Was running a 17 lb, cap. Now the only fan i can get to work good is a straight fan.not a stupid flex fan or a clutch fan. Speedway Motors have good fans,and spacers....jobob
I am no expert,but I did own and drive a 1968 Firebird with the original 350 for years.After I did a mild performance rebuild I thought it ran to hot also.All I did was to get an eight bladed non flex fan and moved it closer to the radiator and it would run 180 degrees all day long in traffic and even cooler on the open road.
My T/A runs at 195 all day with no trouble. The factory built it that way (1980 smogger motor) It's a Pontiac engine with a 195 degree 'stat and it never boils over. If you're concerned, definately check the clearance on the pump divider plate. You need it to be very close but not touching the impeller. Some of the rebuild shops are not that careful during assembly. BTW, the repop places like NPD, Year One and Performance years simply buy off-the-shelf pumps just like your local parts store does. Only difference is that the repop shops charge more. Shawn
Yeah man!, It looks like the pump might be the ticket. Im gonna pull the whole assembly and adjust the distribution plate on the bench. It just make sense. When the motor is up on RPM its moving enough water to cool it and when it slows to an idle its just not enough....Thanx man, Ill let you guys know how it played out.. Thanx again folks, I appreciate everyone help...
If it isn't losing coolant, what's the problem? What I mean is, if the recovery isn't blowing over, the temp comes down quick when you go to fast idle or drive it from a stop in traffic, then it's acceptable to me. If it is REALLY overheating you would be losing some coolant, having to add some every so often.
when installing a Pontiac intake,the recommended procedure is to run down the head bolts,but before torquing,tighten the water pump to intake bolt securely to mash the litle rubber dough nut in the cross passage to the manifold water crossover
Amen on spacer had to add a freeze plug un-used port on intake mate side water would blow through gasket material. Flow is good when set up correct. I am also runnin a straight steel fan off a stock 62 motor, close to radiator. Radiator is the icing on the cake providing all else correct.
As someone else has posted, you need a water pump with the cast impeller, NOT the steel one that you say you have. It might take some effort to find one, but they are out there.
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