Question on Temps

[Tommy Almond]

Just wondering what others may be seeing on temps? I have a 1981 stock with a 350/195hp GM crate motor installed. All ECM and other parts operating as was original. Today during a 80 miles run in upper 80 degrees I was having a water temp just below the 200 on the gauge and was around 220 on the oil temp. I was not running AC but was running about 65mph on interstate.
When I stopped for a few minutes at home while opening the garage when I went to refire the engine did start but was harder, had to spin out and pump gas a couple of time.
I know there is some heat build up in the engine compartment when hood is closed that could cause some of the harder starting since might be heating up the carb some but is my heat readings in normal range?
Thanks in advance for any answers.

 

[bill81vette]

Mine runs about those same temps.little hotter water temp with the a/c ......I don't have any problems restarting it.......

 

[Yoda]

Like Bill, my '81 runs around 190 on the highway at any speed, around 190 - 195 around town esp. in parades.. just a tad higher with air on. I don't think I have ever seen more than 200..

Never had any issues starting after a fuel stop or rest stop, just get back in and varoom and off we go. Don't know if timing might have something to do or it is the fuel system :shrug..

Enjoy the and ask a good mechanic that question about the restart one that KNOW Quadrajets :dance

Bud

 

[Tommy Almond]

Update on Info

I had a new stock GM crate motor installed last summer by Corvette Etc in Charlotte which is the premier corvette shop in this area and just had the q-jet carb re-manufactured by All-American Carbs in Florida so it is like new.
As you other '81 owners know the engine compartment when still as came off the assembly line is packed and crowded so I thinking my temps are running normal but that when stopped for a few minutes there is not enough open space in the engine compartment to allow for the heat build up to escape easily and that some of this heat rise could be turning some of the fuel in the carb's bowl or line to turn to vapor or similar effect.
Maybe simple to next time just pop the hood while stopped to let the heat have an avenue to get out so not to boil any of the fuel, if that is what is happening.
I'll call my mechanic and see what he says too but I do believe if the heat can't get out then temp inside the hood has to rise more with no fan or air blowing thru.
But the engine will restart just have to spin and pump more than cold startup and once refires she is alittle weak so have to baby the gas some to get her back to running smooth.
Lastly what gas are you all running in these stock engines? I've tried 93, 89 and even 87 octain and I've found no different in performance of the engine.

 

[Peer81]

Just run 87, good enough for the engine if your timing is setup about right (standard).
Mine is about the same temp but restarts with just tipping the key so I don't think the temp is the problem.

Greetings Peter

 

[Tommy Almond]

Just run 87, good enough for the engine if your timing is setup about right (standard).
Mine is about the same temp but restarts with just tipping the key so I don't think the temp is the problem.

Greetings Peter

Thanks Peter for your thoughts. I do feel my operating temps are okay and within range of what they should be, it's just when I'm out on the hotter days, mid-80/f and up and running the vette for a long run that when I shut off the engine the heat inside the engine compartment rises higher than is desired and may be boiling some of the gas in or to the carb. It stills cranks, but have to work it more to crank, not just hit the switch. If that heat build up was less or cooler then gas would not be boiling, if that is what is happening on restart. So my harder restarts are only on hot days after a good run.

 

[Peer81]

You are right that when you stop the engine the heat will rise up and the temp will go up inside the motorcompartment no doubt about that. But why is it a problem you have and not all of us? I can drive it for an houre or more in the mid 80's. Shut the engine and restart without a problem after 5 minutes or if you like within 2 seconds, no problem.

But if your logic is right then the problem is not the hot air (well it is..) but the problem is that the heat is reaching your carb and letting (so you say) boil your fuel in the fuelbowl.
You can easily test it but stopping the engine on a hot day, flip open the hood and restart after 3 to 5 minutes. Then you know if heat is the problem.
After that you can check if your thick carb gasket is still oke and replace it anyway, that is the only thing that is keeping heat from the intake getting to your carb.
Second I want to know if you touch your gaspedal when restarting, when the engine is hot there is no need to do that.

Assuming that you are right, are you also experiencing any problem when you drive on a hot day and have to wait for a red light for a long time (train passing?) As you stand still and the engine is running there is the same amount of heat buildup under the hood so boiling fuel will effect your driving I think.
Things to think about

Greetings Peter

 

[Tommy Almond]

Peter, not sure how the weather is where you are but here in the southern parts of the US we have some dry humid days, sometimes one can sweat even in the shade so not sure if humidity might have some play in it, I am going to go back and see if I can get the weather data for Saturday and see what the humidity was and note that and if problem comes up again, check to see what it is.

Most of the time my engine oil runs around 200/f but on those hotter days and longer runs the temp rises to about 220/f and that is when I have the problem with restarts at times. And no I am not at first pumping or hitting the gas but if it don't refire like it should then I have to pump a couple of times while spinning to get her fired.

As far as stopped at a light or train in hot weather, no problem except the ECM sometimes change the M/C mixture and idles it down more since reckon getting a richer O2 reading while sitting.

Also I have been getting the Check Engine light on, not setting but lights up for a few seconds to maybe 30 seconds and pulling codes I keep getting 13 the O2 sensor and 24 the Vehicle Speed sensor but I doubt either of them would have a part in this restarting.

So gonna watch the engine oil temp and if stopping and the gauge is showing above 200/f I'll pop the hood to let the heat rise out and see what that does for me.

 

[Bob Chadwick]

I ran a 77 here in Atlanta. Two pumps on the pedal when cold and just turn the key when hot no matter what the ambient temps. Started everytime. I don't think this is a temp thing and you probably need to look elsewhere.

 

[bill81vette]

I'm wondering if your timing is off a couple of degrees....

 

[Peer81]

I would also say. If you have the standard thermostat (190?) change it for a little lower 180. Mine never sees 200 nomatter what the temp or conditions are. You can also get another aux fan temp switch. Mid has ones that kick's in at 200 and stops below 185 (only with the key in the on or run position).
ps. the original fan kicks in around 230 and stops below 200.

Greetings Peter