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Engine temp

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Engine temp

Post by Duehew on Mon Aug 15, 2016 7:27 pm

I am not an engine guru and need some info. Last year we had a Jasper 355 Cu. In / 300 HP engine installed in our car. It seems to run around 195 to 210 degrees. Is this a normal operating temperature?

Also we have an Edelbrock 1826 Carb on the Performer intake. We only get about 10 MPG. I do get on it once in a while but not very often. Is there any reason why I should not be getting 18-20 MPG??? We are also running a TH400 trans and a 7.5 Ford rear. I think the ratio going by MPH, RPM and tire diameter is about 3.38:1. Driving speeds are usually 45-60 MPH. Thanks for your input.
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Re: Engine temp

Post by Hotrod on Mon Aug 15, 2016 9:35 pm

Are you running vacuum advance in the distributor?  It will help with both temp and mileage.  Depending on what heads you have, you might need 40+ degrees of total timing at cruise and idle.  

Because of the lack of turbulence in the combustion chamber at low engine speed, the fuel mixture needs to get lit sooner in the cycle for an efficient burn.  Without adequate advance, the mixture will still be burning when the exhaust valve opens.  This will heat the exhaust valves, exhaust seats and ports as well as the exhaust manifolds or headers.  All of this just wastes gas as excess heat.

I have had best luck with SBC's with the vacuum advance hooked up to a constant manifold source.  Ported vacuum is a relic of the early years of smog controls when engines were run retarded at idle so that unburned fuel could be burnt in the air injected exhaust manifolds.  Sounds crazy, but that was how the early smog systems worked.  I think it was to reduce oxides of nitrogen (could have been hydrocarbons).

Of course I have to insert my standard disclaimer.  If you want to start a war on a hot rod forum, just talk about politics, religion, or vacuum advance and it's source.  What I posted is my personal experience.

Also, it has been my experience that Edelbrock carbs come jetted a little rich out of the box.  It's safer for them.  I've never had an issue going 2 steps lean on the cruise portion of jetting.  If the Jasper engine came with the carb, it might be jetted correctly.  If you are unsure how to do it, you might want to find someone that can do dyno tune with a wide band O2 sensor.  Jetting too lean can burn pistons.  Just a warning.  

Another issue with Edelbrocks is fuel pressure.  They don't like more than 5 PSI as a general rule.  Any more and the fuel can leak past the needle.  Even if the carb doesn't flood, the higher fuel level can change the mixture to the rich side.

Another possible cause of the extra temp is the thermostat temp.  You could have a 195* or higher thermostat.  A modern engine with modern oil and gaskets should take the temps you listed well, though.  Some modern EFI engines run as high as 230* safely.  I'm old school though and prefer something less than 200*.

Sorry for the long post.
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Re: Engine temp

Post by Hotrod on Mon Aug 15, 2016 10:03 pm

Just so you'll know that I practice what I preach, the engine that was in my Sebring was a fairly stock 350 SBC with an Edelbrock Performer manifold, Rochester Quadrajet carb, cast iron exhaust manifolds and a very restrictive single exhaust.  It also had a 5 speed trans and 3.00 gears.

After tuning the vacuum advance and the carb jetting it went from about 10 MPG to 22 MPG.  It also would idle in traffic without overheating.  

I pulled that engine when I started the current rebuild of my car and installed it in my 46 Ford street rod.  After adjusting the tune for the better exhaust in that car, it still gets 18 MPG in a car that weighs over 2 tons loaded and is as aerodynamic as a brick.
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Re: Engine temp

Post by David V. on Mon Aug 15, 2016 11:47 pm

HotRod's hit it pretty much on the nose. I'll try to add something to that if I can  Razz
(Sorry in advance if I happen to contradict anything HotRod's said. I would take his word over mine. He has more experience).

For the gas mileage it's most likely your carb tuning or vacuum advance as HotRod described. It could be your final gear ratio...maybe?... just to make sure, how many revs are you pulling at 74-75MPH in final gear (weird number I know, but I'm Canadian so I had to convert)?

My car usually runs from 180 to 200. I shut it off if it goes anywhere over 200. (Aluminum heads are prone to warping so I don't take chances)

1) Check total timing. If your timing is off (or not as it should be for that particular engine) you're pretty much guaranteed to have heat issues.

2) Check vacuum advance (as Hotrod said), however in my experience total timing is the more likely suspect. I don't run vac advance at all (because of the weber carbs) and while she does tend to have slightly higher temperatures if left idling on a hot day. My running temperature while cruising hasn't changed at all.

3) Check you have the proper thermostat (as per Hotrod's instructions)

4) Check that the thermostat isn't stuck (especially if the overheating is a new occurrence). Sometimes I'll start her up and drive like a granny, and even if the coolant in the block heats up the thermostat sometimes sticks, preventing it from flowing to the radiator. Then the temp starts shooting through the roof. If you catch it early just accelerate hard and the increased pressure from the waterpump will unstick it. (Note: do not floor it if your temp is already crazy. shut it off and cool it down a bit first)

5) Try another thermostat. Its happened that I've bought a thermostat that was faulty right out of the box. And they're usually pretty cheap, so why not.

6) Check carb tuning. Its a good idea to have a good carb tune for all the reasons (performance, fuel economy, and temp). But if you just want to do a quick check, pull the spark plugs and check them against the spark plug chart inside any Heinz workshop manual. If your fuel mixture is off enough to show at first glance on the plugs then it's most likely the problem. Otherwise carb tuning may only slightly improve your temp.

7)  Check for exhaust leaks, particularly where the header tubes meet the head and where the collector meets whatever pipe runs under the car.

If none of that solves it you'll have to resort to more drastic measures

8- I've heard good things about Evans Waterless engine coolant, but never tried it myself. I would do some reading first.


9) Take the hood off and go for a drive. If she runs cooler, especially at slow speeds, then your problem is caused by high under-hood temperatures in which case your only options are
         -more heat shields/shielding
         -wrapping or ceramic coating the exhaust headers/manifold
         -more vents
         -bigger/badder/better cooling fans
         -having a fan with a fan shroud (especially if your temp problems occur at low speeds)

Last last last resort: better radiator (depends what you're currently running. Wouldn't really recommend it) Only really worth it if you are switching from a copper radiator to an aluminum one.
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Re: Engine temp

Post by David V. on Mon Aug 15, 2016 11:54 pm

Oh and just a thought, do you have an engine oil cooler?
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Re: Engine temp

Post by Duehew on Tue Aug 16, 2016 12:27 pm

No engine oil cooler. I have been thinking of a trans cooler though. Which would be better??

Thank you both for all your suggestions. I will have my mechanic check them all out. Once again, Thank You.
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Re: Engine temp

Post by David V. on Tue Aug 16, 2016 9:32 pm

Engine oil cooler for sure if you want to help get temperature down. However they are always a bit of a compromise.
            -If installed in front of the radiator (like mine) they may reduce radiator  efficiency a tiny bit (I find this outweighed by the oil cooling effect). And same as the radiator, its efficiency at low speed or idle depends on how much flow you get from your cooling fans. *Bonus points* I've found its protected my rad from flying rock debris when following someone on the highway (I have the more spread out grille bars).

      -if installed under the car (similar location to a trans cooler). Won't affect radiator  efficiency in any way, but you won't have any cooling effect at idle and much less at low speeds because nothing is driving air through it.

A transmission cooler is only really necessary in two situations:
     -Dedicated track car/race car (circuit racing or drifting)
     -towing heavy loads or doing extreme off-roading and rock-crawling

P.S. If ever you take your Sebring Rock-Crawling be sure to send me some pics! Wink
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Re: Engine temp

Post by Hotrod on Tue Aug 16, 2016 9:38 pm

Seems that Dave and I attempted to answer this at the same time.  So consider this an addition to what he said.

An engine oil cooler will help keep the engine temp down, but I would run a thermostat bypass in the line.  Oil needs to get hot enough to burn off water.  Since you live in Michigan, you will see colder air temps.  Cold air and oil coolers = low oil temp.  The thermostat will bypass the oil around the cooler until the oil temp gets high just like the thermostat in you engine coolant.  You could get by without the bypass if you remember to cover the cooler in cold weather or just don't drive in cold weather.  Since Dave lives in Canada, I will have to defer to his opinion on this.

I will add one thing about a trans cooler.  It will remove a heat source from your radiator.  If the radiator has enough cooling capacity, an external cooler is probably not needed on a car as light as a Sebring.  That is unless you have a higher stall converter in your TH400.  Any time you run higher stall, you need an external cooler.  The HS converter will generate a lot of heat.

I do need to clarify something.  My Sebring had an overdrive manual trans.  That was part of the reason for my high mileage numbers.  Your non-overdrive H400 car with a good tune should still get upwards of 18 I would think.

It's just a guess, but based on your ratio estimate, I would say you have a 3.27 ratio.  3.38 isn't a common 7.5 ratio as far as I know.  Since the converter will always slip a little, that could account for the extra RPM.
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Re: Engine temp

Post by David V. on Tue Aug 16, 2016 10:21 pm

Hmm good observation Hotrod. I don't have a thermostat in my oil cooler lines, and I've never had an issue, but I can see your logic. Coldest I've driven my Sebring in is probably about 4 degrees Celsius (39.2F), and that was only once or twice on a chilly morning. At those temperatures however (or really anything under 10 degrees (50F)), I'm really more concerned with the oil's viscosity properties at the time of start-up (when fully cold). So switching to a lower viscosity oil would be my first initiative if I was to drive frequently in these conditions. The engine bays are so small on these that the engine warms up pretty quickly.

My protocol in cold weather is to fire her up and let idle, increasing and decreasing revs by about a 100 rpm at first to help the oil pump out, until the needle just starts to lift off the peg on the temp gauge. Then I pull out of the driveway slowly (neighbours wouldn't like me very much if I let it idle long at 6am)
Then I drive excruciatingly slow for the first few blocks, really no more than 1200rpm, until the oil gets to operating temperature. Never noticed an issue so far.
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Re: Engine temp

Post by David V. on Tue Aug 16, 2016 10:26 pm

On a side-note. For anyone considering driving a small block chevy with upgraded valvetrain (especially stiffer springs and high lift cam) frequently in cold weather, your best friend will be a higher torque starter. I've never had problems with fueling in cold weather: starts right up. However, getting the starter to crank over fast enough on cold springs and oil is quite a challenge. A regular starter won't like it very much.
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Re: Engine temp

Post by Duehew on Tue Aug 16, 2016 10:46 pm

Thanks for all the great information. You guys are making my head hurt. Smile I am taking all this advice to my mechanic and see what we can do. Thanks again.
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Re: Engine temp

Post by David V. on Tue Aug 16, 2016 11:27 pm

Haha no problem Duane, it's fun stuff to talk about. I wouldn't trouble him too much with oil cooler stuff yet Razz You're best off finding the source of your heat increase first.
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Re: Engine temp

Post by Hermn8r on Wed Aug 17, 2016 3:05 pm

I use "water wetter" in my supercharged ford lightning with good results.
If I remember correctly it can lower temps 20 deg. just pour it in and go!


Last edited by Hermn8r on Fri Oct 21, 2016 3:34 pm; edited 1 time in total

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Re: Engine temp

Post by Duehew on Wed Aug 17, 2016 4:05 pm

Thanks for all the info. I might give "Water Wetter" first and then look into the carb issues.
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Re: Engine temp

Post by Duehew on Thu Oct 20, 2016 3:53 pm

Hi all, here is an update. The wrong plugs were in the engine. Had the correct plugs installed and they are about 1/8 th inch longer and should burn better. Timing was off about 6 degrees. Carburetor adjusted and runs smoother and idles much better. This new mechanic also discovered that the vacuum advance was NOT hooked up, another problem taken care of. This new mechanic looked the car all over and his remark was, "This is a well built car, whoever put it together did a great job". This was good to hear and I realized the mechanic that was taking care of us was just lining his pockets. Hopefully now we will get better MPG. On the ride home the performance was the best it has ever been. Getting much cooler now so next year we will find out more on how the car runs and performs. Again thank you for your suggestions.

Next I need to bite the bullet and get the doors adjusted better and remove the interior panels so I can install the new outside and inside door handles. Still thinking of finding someone who can reproduce the windshield finishers and grill surround in either polished aluminum or chromed steel. Have a great and safe winter.
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Re: Engine temp

Post by Hotrod on Thu Oct 20, 2016 9:35 pm

Glad you got it straightened out and thanks for the update.  You don't often get that and you wonder if the poster ever got it sorted.
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Re: Engine temp

Post by Duehew on Fri Oct 21, 2016 12:32 am

Thanks, that is why I updated the info as soon as I had it done things like this always have me wondering also.
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Re: Engine temp

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