Normal operating temp for a 300 V8???

What is the normal operating temp for a '64 skylark w/a 300 4bbl v8?

Mine runs between 180 & 210, seems to run cooler the faster it goes. Is this normal or is the engine running too hot?

The engine is newly rebuilt, 180 degree thermostat, new waterpump, 50/50 antifreeze mix, new heater core. I put in a 6 blade thermo-clutch fan (replaced the factory 4 blade fan). It's the stock downflow radiator.

According to the factory service manual, temperature in excess of 212 (boiling) is normal for this engine (don't remember the page number from the book but that's what it says, I just read it last night). This of course as long as the antifreeze mixture doesn't allow boilover.

I'm not boiling over, just concerned as I've spent a lot of time / money rebuilding the engine & don't want to damage anything.

Thanks

 

When you rebuilt the engine did you have the rad cleaned and flushed? If its the original it could be partially plugged.

 

Larry,

Are you running a 160 thermostat in your GS?

I have a 180 thermostat in my Buick with a new fan clutch and 3 core radiator, and I am crusing around 195 to 200. Do you think that is to hot?

Do you think I should put in a 160 thermostat??

 

Hmm, I am curious what thermostat people are running.

Mine is failling on me, and I've been debating on a 160f or 180f. I do have a new 4-core crossflow radiator.

 

I'm running a 160... swapped out a 195... helped some with a temperature problem (detonation was reduced by about 30% so I would assume)... car just seems to run better in the summer as well.

 

I pulled mine out when I rebuilt the heads due to it sticking shut. I still haven't replaced it. Since it's not 30 degrees out, I don't mind yet.

 

thermostats

Hi, I played around with 160 and 180 thermostat temperatures for a while with a range of outcomes. If the cooling system components (radiator, cap, hoses, pump, fan are all in good order and timing and fuel mixture are correct the original 180 should work just fine. The temperature stated is what the thermostat opens at.

Often good practice to check this temperature by immersing it and a good thermometer in cold water and bringing it to boil. Check that it fully opens and closes several times and is not sticking or jamming on the side. Pressure test the radiator cap and the cooling system too. Often you will find minor leaks when under pressure.

Good to check belts for tension, wear and slipping too. Often 160 thermostats make the engine run far too cold otherwise GM would have them as original standard equipment.

Pays to check that the temp gauge reading you are getting is correct too as it may not be right either. Just some things to think about.

 

Thanks Larry,

I take it that you have a 160 stat in your GS..

I also would like my Buick to run around 175-185. I'm going to look into a 160 Thermostat.

Thanks,

 

im running about 190 to 200. dont know what stat i have in there though. never thought to ask but the engine is all rebuilt so it has a new waterpump and stat, but the radiator is the same. seems it was replaced since its hard to beleive a 30 year old radiator would still be cooling that well... im looking in to getting a fan shroud since mine looks like it were chewed up by a dog or something. anhow, how much cooler should it run with a new radiator and shroud?

pete

 

Larry,

I installed a 160 stat in my Buick today, took it for a ride and the temperature is sitting around 180.

Thanks again.. :TU:

 

cooling problem

I had the same problem with my 300 when i would sit some were it would heat up to about 215 degrees which i didn't like it had a 180 thermostat and and orginal 2 core radiator being a GS340 no air. I bought a 67 pats car that orginally had air and had a good 4 radatior i put in a new thermastat 180 degrees and a new water pump the fan is stock without a clutch. In the garage it will stay at 180 to 185 all day. Some othr things to thinck about would be a tranny cooler to get the tranny heat out of the radiator. Another possibility is the the housing behind the water pump may have corroded enough to efect the water pumps perormance

Adam

 

Thanks for all of the suggestions, I'm thinking the radiator is clogged - wish I would have done this before but I just didn't think about it.

The timing cover & waterpump were replaced during rebuild with brand new parts (along with pretty much everything else).

I have to believe the 6 blade clutch fan is better than the stock 4 blade fan - no?

I'm going to backflush the radiator this weekend.

 

Operating temp for 300

John;

With the 160-degree thermostat in my '64, water temp ranges from 140-150 when the outside temp is below 60 and 160-180 in 70-80 degree outside temp, both in normal traffic. When it sits in stop-and-go crap it runs in the 190-200 range. I'm a freak for running these old aluminum heads and intake as cool as possible.

It ran a lot hotter before I swapped out the side-flow radiator for a correct-year down-flow model. Also added an aftermarket 6-blade fan and non-termal clutch.

I believe it would run even cooler with a stock or milder hp cam than the one that's in now.

Mark

 

Well thanks for the comparison. Maybe what I'm seeing is normal. My concern is the stop & go crap - I'm between 190 & 210 with the 180 thermostat. As long as it's moving it runs around 180 - 190.

I have an aftermarket Cam, headers, dual 2.5" exhaust, 10.25 comp. Pistons. New afb carb, new everything else - I put a new electrical temp gauge instead of the idiot light. I'm not using Aluminum heads, I replaced the stock heads with '65 cast iron heads & 4bbl intake. I would think your aluminum heads would dissapate heat much better than the cast iron.

 

operating temp for 300 V8

Hey John;

Looks like our cars are similar except for the cast iron pieces. You're probably correct that the aluminum pieces dissipate heat more effectively. The concern with aluminum is that over time, it fatigues more quickly than iron, just due to the rapid expansion rate of aluminum. I've had the pleasure of warping aluminum heads before. Not pretty when it's over 80-degrees outside. Smelly too.

Are you using the Poston headers? I've seen threads that indicate the fit isn't that great. I have an unused set that I've been saving for a '65 engine 4-barrel engine that I'm building this summer. Be interested to know your opinion. The engine is being swapped into a '67 Special that has a 2-barrel low comp motor and ST300 trans. I have a Turbo 350 that will replace the ST300.

I'll be posting my 64 hardtop for sale within the next two weeks. Just have to buy a digital camera to post decent photos.

Mark

 

I do have the Poston headers - they make a big difference with the other modifications I've done - they sound great as well with the dual 2.5" exhaust.

I can say that the fit appears to be perfect on the passenger side. On the drivers side, the headers fit around the steering column & brake lines without any issues as well.

I did run into a problem with the last cylinder on the drivers side in my case since I also switched to a 4 speed transmission. I had to have the last pipe cut & moved to avoid the clutch z-bar. This added about $100 to the total cost (had to buy mandrel bent tubing & pay a local guy to cut / weld them for me). You could certainly get by cheaper.

As far as the automatic linkage, I cannot answer since I went the 4 speed route, although my headers came with an adapter for the trans linkage - looks like it should work.

Under the car, the headers go right up to the crossmember, but aren't blocked by it - it's a nice fit down there as well. The only issue you might have is with the automatic linkage - probably should hit up someone else on that though since I can't say.


Hope this helps!

 

John, I also have a '64 skylark with the original 300 4bbl and a factory 4-speed. I put a set of Poston header on it when I restored the car about 5 years ago. I ended up completely re-routing the last two cylinders on the drivers side to get around the clutch Z-bar like you were talking about. Once I did that and had them Jet-hot coated, they work great.
As for the cooling issue, I also have a '65 Special with the 300 4bbl. engine, which is equivalent to your '64 engine with the cast iron intake and heads from a '65 on it. I never got rid of my overheating problem or spark knock/detonation until I put a 3-core radiatior out of an AC car in it. Once I did that, haven't had even a hint of overheating or spark knock since. You can buy the radiators brand new from Year One and I am sure other places as well.
The reason for your problem is two fold. First the AL heads do dissipate more heat, so the engine runs cooler with them and you can get away with more compression too. Second of all is todays fuel. These engines and their cooling system were designed to run on 100 octane fuel. All we have now is 93 (unless you have some serious $ to spend on fuel). A lower octane fuel actually has more engery than a higher octane, and therefore generates more heat for the same amount of fuel burned. That is why most people have to go to a larger radiator on the non-AC cars to keep them cool and to not spark knock (on the high compression ones). Go ahead and spend the money for the thicker radiator--you will be happy you did once you see the difference.

 

Mine 350 runs around 200...EXCEPT TODAY.
It's getting hot in the valley and I saw it creep up to almost 230:eek2:

I'm gonna to get a 160 and see if that'll help. :TU: