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RUNNING HOT 68 MUSTANG GT

 
andy2foot
New User
Posts: 9
Joined: 07/09
Posted: 07/01/09 03:21 PM

I am at my wits end and desperately need some help. I bought a 68 GT S code that someone has put a 289 with 302 heads, I say it is a 289, it has 289 crank. The car will not run more than 5-6 miles before it starts running Hot. I have replaced radiator 4 core, new water pump, new hoses, 4 thermostats 160 to 190, reworked heads. I have two temp gauges and they both show hot, and lazer pyrometer confirms. I dont know if it is relevent but the stock dash gauge registers very high when manual gauge shows 160 degrees the dash gauge is about 1/4 of an inch from the H in the gauge. when the manual gauge shows 220 the dash gauge is on top of H. The cam in the engine seems to be a performance would that have any thing to do with the temp? Timing is a little high but not much. Any suggestions?  

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jlg2002
Guru
Posts: 1410
Joined: 03/08
Posted: 07/02/09 12:43 PM

A couple of questions:
1. does it run hot going down the road at highway speeds or at low idling operation?
2. do you have a fan shroud?

Believe the gauge that matches the pryometer. Within the last few weeks I've read here in the forum about aftermarket WP's having the wrong impeller sizing and that fellow ended up with the Ford WP to solve his overheating problem.  

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andy2foot
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Posts: 9
Joined: 07/09
Posted: 07/02/09 01:57 PM

Yes it runs hot going down road and any time you keep RPMs at around 1900 to 2200. Does have shroud and today we pulled thermostat out and got it up to 200 just idling. I read about the WP and the OEM had 7 impellors were as mine has 6.  It seems to circulate well until temperature get to 200 and seems to slow circulation when looking in top of rad. with cap off.  Have contacted every mechanic and Ford man in area and all are stumped.  Timing is set at 10 degrees over. STILL PULLING MY HAIR OUT!!!  

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shiftthis
Enthusiast
Posts: 285
Joined: 04/09
Posted: 07/02/09 02:46 PM

if the head gaskets are installed backwards it will run hot. the part of the head gasket that says front of engine must be installed at the front of the engine so all the water holes line up. if the timing is 10 deg. over what is recomended it could over heat and burn a piston/valve no more than 36 deg total advance checked at 3000 rpm with vacuum advance disconnected  

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Jbirch
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Posts: 623
Joined: 05/09
Posted: 07/02/09 02:57 PM

Maybe the carb primary jets are too lean and causing part of the problem. A too lean engine will run hot. You can sometimes tell by looking at the spark plugs. If the insulators are very white it may be running too lean and requires you move up 2 jet sizes or more to richen the mixture and cool the engine down.
Worth a try.
Is the fan on backwards? Don't laugh. I've seen it happen.
If all else fails do a compression check and see if you have a bad head gasket.
Usually a bad head gasket will allow air bubbles to be seen inside the radiator coolant when you look in with the cap off and the car is up to thermostat opening temp. Only remove radiator cap when engine is COLD. Start car and watch for
air bubles in coolant after car reaches normal operating temp.
 
Do you have A/C? Is there anything in the front of the radiator that restricts air flow?
What is your torque converter stall speed if you have an automatic trans? Sometimes a big cammed motor will idle faster than stock and if you have a tight converter the converter will actually be pre-loading the engine down at idle causing it to get hot faster.
Stock Mustang converter stall specs are about 1700-1900 rpm. You might need a 2200 or more if you have a hot street cam. Or try to tune your idle speed to the rich side and down a little so it is below the converter preload point.
What engine oil are you using? How many miles are on the motor since last rebuild?
Are you sure you have the right heads? You say it is a 302 block with a 289 crank (rods and pistons too?) Are the heads original and compatible to the 302 block being used?
Is the cam hydraulic or solid lifter? Improperly adjusted lifters will impact engine temp.
Do your brakes drag and are your tires underinflated? These will cause the motor to really work harder and heat up faster too.
Need your feedback.  

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andy2foot
New User
Posts: 9
Joined: 07/09
Posted: 07/02/09 06:07 PM

The gasket is right and I dont know what size cam is in car but with vacuum unhooked it dont go past 20 degrees when running up motor. It just seems that radiator doesnt flow as well temp is up on motor, looking through rad neck but even with the thermostat out and idling it still gets hot.  

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andy2foot
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Posts: 9
Joined: 07/09
Posted: 07/02/09 06:25 PM

The plugs look OK I will check again tomorrow have not checked since right after had heads done, I will see if I can check into the jets, the fan is pulling a LOT of air back across motor so its not backwards. I will check compression tommorrow  checked before heads were done and they were good except for the 2 that were leaking exhaust on gasket. There seems to be a lot of air in radiator burping out after thermostat opens and looks like the water doesnt seem to circulate as well when temp is up. Does have AC and cond is in front of rad but still pulls a lot of air and running AC does not have any effect on temp it runs hot either on or not, dont know about torque conv but it gets hot when in park and runnning up 1900 to 2200 or idling. The oil is castrol 10w40.  I dont know if right heads they are 302 cause they have 302 stamped on them cannot find any info on block but the crank has 3 bolts so that is a 289 right? The pistons are not at the top of hole and has no ring grooves but other than that I dont have any info on rebuild, lifters are hydraulic brakes dont drag and tires are good. Help  

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Vegard
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Posts: 1
Joined: 07/09
Posted: 07/03/09 02:21 AM

I have heard examples of overhauled engines where the engines internal cooling lines have been forgotten.. Resulting in an engine with performance parts requiring more cooling than stock, and cooling lines in the block that are clogged partially or completely by corrosion and old tear and wear..

Just something to keep in mind if nothing else works...

Good Luck from NorwaySmile  

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Jbirch
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Posts: 623
Joined: 05/09
Posted: 07/03/09 12:10 PM

OK Andy,
You checked things out and have eliminated some possible causes.
If the heads say 302 on them and the block is a 302 then they are compatible. Just because the crank pulley has 3 bolts doesn't necessarily mean it is a 289 crank. You say the pistons don't go all the way to the top of the cylinders. How far from the top? If not very much at all then my guess is that you have a complete early 302 motor.

One thing that stood out in your answers was the fact that with the distributor set to 10 degress BTDC @ idle and the vacuuum line disconnected the engine couldn't get more than 20 degrees advance when revved up. That means you only have 10 degrees mechanical advance working for you. Not good. You should be in the neighborhood of 32-36 degrees total advance @ 3300 rpm with the vacuum disconnected and another 10-18 degrees on top of that when the vacuumm line is connected.

You say you took your thermostat out and flow is slow even when engine is revved up.
Bad coolant flow is a problem. You should drain your coolant, put in fresh water and some cooling system cleaner from an auto parts store and run per directions on cleaner can. Then flush all that out. Before replacing with good 50/50 coolant you should backflush the radiator by placing a garden hose in the lower radiator outlet with a rag wrapped around it to seal it as much as possible. This will force water through the radiator in the opposite direction it normally flows and will dislodge any or some foriegn matter that could be blocking your radiator tubes. Now put the garden hose in the radiator cap opening on top and place your hand over the top radiator hose opening and see how much and how fast water is draining out of the bottom radiator hose opening. If the flow going out is about the same as going in then you are probably good to go. If the flow out is not even close to what you are running in then you may have a blocked core and need to have the radiator rodded out or replaced.
How many rows of tubes is your radiator core? 2 , 3 or 4?
The other thing that slows flow is improper water pump operation and/or head gasket installation. Make sure your water pump fan pulley is the right size and the fan belt isn't slipping.
The A/C condenser in front of the radiator will tend to block air flow a bit and will tend to pre-heat the air a bit before it moves through the radiator when the A/C is on.
What is your idle speed? Let me know what your plugs look like and if any two cylinders are way off on compression compared to the rest.
I'd fix that distributor timing and do the radiator clean/flush before getting into other things.  

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andy2foot
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Posts: 9
Joined: 07/09
Posted: 07/03/09 06:30 PM

OK I will try that but the rad is a new 4 core aluminum, and i may have told you wrong on the timing advance it is around 10 to 30ish when run up to around 3 grand. While we were checking some vacuum with a gauge because the vacuum advance comes up immediately when hooked up to distributor instead of gradual, we noticed that when the engine is accelerated the vacuum fell off to 0, from around 12. Which our old ford manual says 12 vacuum means a wore out engine and dropping back to 0 means excessive back pressure in exhaust. Wouldnt that cause overheating?  

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Jbirch
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Posted: 07/04/09 11:40 AM

You need to hook your distributor vacuum line to ported vacuum not manifold vacuum.
What kind of carb are you running? An itital setting of 10 is good. A total of 30 is OK at 3000 rpm with vacuum line disconnected. With vacuum added you should see another 10-20 degrees for a total of 40 - 50 depending on the vacuum can/setting.

Manifold vacuum decreases to zero at wide open throttle. At idle in neutral you will probably see 16 - 20 on the vacuum guage depending on cam and tune. The more you open the throttle the less the reading will be. The bigger the cam the less the idle reading will be. What is your idle speed and manifold vacuum reading @ idle when the engine is at normal operating temp and in neutral? What is it idling in gear?

Even new radiators can sometimes be plugged from the factory or get plugged from engine gunk.  

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andy2foot
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Joined: 07/09
Posted: 07/04/09 05:42 PM

Idle is about 750 and 12 pounds of vacuum in park and around 550 in gear. I will try cleaning radiator to be on safe side. Thanks happy 4th  

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cushman350
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Joined: 07/06
Posted: 07/05/09 06:51 AM

What is the bore of the cylinders? Maybe it has been overbored and the walls are too thin.  

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Jbirch
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Posts: 623
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Posted: 07/05/09 07:31 AM

An idle vacuum reading of 12 in park indicates a fairly aggressive cam or some carb tuning might be needed. Try to get that vacuum number up higher by slowly closing-opening both idle mixture screws one at a time. Make sure to do both and then recheck back and forth until you get the highest steady vacuum reading. Then adjust idle speed in park down as low as possible (like 650 rpm) so car idles well but doesn't stall when you accelerate from a stop. If you have too high an idle speed and a low side of spec stock torque converter you might be preloading your engine at idle when in gear which will cause it to heat up faster.
The fact that your car drops 200 rpm from park to drive indicates this might be the case. Most auto trannys will drop about 100 to 150 rpm. Lowering your idle speed might help.
Does your cam have an agggresive "rumpity-rump" sounding idle? If it has a smooth idle like a stock cam makes and is still at a vacuum reading of only 12 then you might have something else going on. Let me know. What do the spark plugs look like?
Also check your lower radiator hose to be sure it has a spring inside of it.

If you can squish the lower hose with your hand so that the two inside walls of the hose touch then replace the hose with one that has a spring iside to keep the hose from collapsing and cutting off coolant flow.  

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andy2foot
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Joined: 07/09
Posted: 07/05/09 04:01 PM

I dont know what the bore is did not measure when heads were off. But I will check into it. Thanks  

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