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Overheating on Hwy 350 SBC

jonrpick said:
I was mainly eluding to the fact that I didn't think 9.78:1 was considered really high compression.
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9.78:1 is ALOT of compression with an iron head in a 6000lb. vehicle. If the heads were aluminum then you can get away with more compression but this isn't the case. Also, a 72cc head with a domed piston is going to net more than 9.78:1 compression. If he can give me specific numbers i can tell exactly what the compression ratio is. Highy doubtful though that he has all the required numbers to accurately figure it out.

Just checking with some easy numbers he's already looking at closer to 10.2:1 CR
 
4X4HIGH said:
9.78:1 is ALOT of compression with an iron head in a 6000lb. vehicle. If the heads were aluminum then you can get away with more compression but this isn't the case. Also, a 72cc head with a domed piston is going to net more than 9.78:1 compression. If he can give me specific numbers i can tell exactly what the compression ratio is. Highy doubtful though that he has all the required numbers to accurately figure it out.

Just checking with some easy numbers he's already looking at closer to 10.2:1 CR
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gotcha...
 
buefchris said:
Did you put in the right clutch fan? They are based on your gear ratio.
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Tell me more about this... I had a tranny swap AND went to lower gears before the overheating started in mine. Again, mine overheats while going down the road, but will idle happily all day long.
 
jonrpick said:
Tell me more about this... I had a tranny swap AND went to lower gears before the overheating started in mine. Again, mine overheats while going down the road, but will idle happily all day long.
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cooling fans don't even come into play at cruise speeds. If you're having overheat issues at cruise speeds then you either have a radiator that's not up to the cooling task or a missing or stuck thermostat allowing water to flow too quickly which doesn't give the radiator time to do it's job, or compression ratio too high for extended periods of driving at speed. High compression ratios mean hotter internal combustion temps which will revert back into the cooling system being able to perform it's job.
 
4X4HIGH said:
cooling fans don't even come into play at cruise speeds. If you're having overheat issues at cruise speeds then you either have a radiator that's not up to the cooling task or a missing or stuck thermostat allowing water to flow too quickly which doesn't give the radiator time to do it's job, or compression ratio too high for extended periods of driving at speed. High compression ratios mean hotter internal combustion temps which will revert back into the cooling system being able to perform it's job.
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Not to hijack someone else's problem, but...

2004 - New, bigger engine (305 to 350) and bigger radiator installed in 2004 - no overheating

2005 - Rear axle rebuilt with 3.73 gears (up from 3.08's). Tranny (700R4) is replaced. Convertor is no longer electronic lockup. Instead uses some "kit" installed by tranny shop. No idea what/how it locks up now. Truck now overheats

2006 - 2-3 months spent trying to stop the overheating. Radiator (1.5 years old) is removed, cleaned & inspected (by me, not a shop), no problems found. Many cooling systems cleaners used. Thermostat changed. Heater core bypassed (just to see). Overheating persists.

Fast forward to today, I'm sure if I were able to drive it down the road, it'd overheat. The two major things that happened before the problem started were the tranny and axle. Other than that, it's spent 90% of that time not being driven.

I have suspected the tranny, but was never given a concrete answer on whether it could cause the temperature gauge to show that the engine is overheating. The tranny is cooled through the radiator, as it should be, with an inline tranny cooler added (added well before the problems started). It stands to reason that this non-electronic lockup installed by the tranny shop isn't locking up properly, and the resulting slippage is causing the tranny to overheat. Then the heat is transferred to the engine, and therefore he temp sensor shows that the truck is overheating.

Here's my original thread on it...it really went nowhere. Help!

http://coloradok5.com/forums/showthread.php?t=227242
 
If you have a tach in the vehicle it's easy to see if the convertor is locking up or not. When the convertor unlocks the RPM's should go up about 300rpm or so. The way you test this is to go down the road at least 50mph, faster would be better so you know it should be locked, now gently tap the brake pedal and the RPM's should go up like i said if not then the convertor is not working properly and the engine (could potentially run a little hotter) but you'll kill a 700R4 without the convertor locking up since it builds way too much heat. If you have a trans temp gauge you can always look at it as well to figure out if you have an issue with the trans. Normal operating temp for a 700R4 is somewhere between 160-180 degrees.
 
4X4HIGH said:
If you have a tach in the vehicle it's easy to see if the convertor is locking up or not. When the convertor unlocks the RPM's should go up about 300rpm or so. The way you test this is to go down the road at least 50mph, faster would be better so you know it should be locked, now gently tap the brake pedal and the RPM's should go up like i said if not then the convertor is not working properly and the engine (could potentially run a little hotter) but you'll kill a 700R4 without the convertor locking up since it builds way too much heat. If you have a trans temp gauge you can always look at it as well to figure out if you have an issue with the trans. Normal operating temp for a 700R4 is somewhere between 160-180 degrees.
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Why would tapping the brakes raise the RPMs???
 
Hard to believe the trans can overheat the motor, due to the cooling size of the stock tranny cooler (which is why everyone adds another external). If the trans was getting hot enough to substantially affect engine temp through that little surface area, I would expect the trans to die in very short order.

However, if you think the trans is getting too hot, the solution is to put a gauge on it, not guess at the problem. If the trans is getting hot, fix that problem, then move on.

If a radiator is not flow tested, you should NEVER assume it is working at full capacity. Very few places can flow test, but I've had it done before, and it definitely showed the problem, even though the radiator appeared good from the small area I could see. Even after flushing, it was still terrible internally.

If it can still be found, find the Camaro thread (probably on thirdgen.org) where the guy finally tore down his motor and replaced the heads (and that was after every part you can think of before that), only to find that the 1 year or so old radiator was bad.
 
dyeager535 said:
Hard to believe the trans can overheat the motor, due to the cooling size of the stock tranny cooler (which is why everyone adds another external). If the trans was getting hot enough to substantially affect engine temp through that little surface area, I would expect the trans to die in very short order.

However, if you think the trans is getting too hot, the solution is to put a gauge on it, not guess at the problem. If the trans is getting hot, fix that problem, then move on.

If a radiator is not flow tested, you should NEVER assume it is working at full capacity. Very few places can flow test, but I've had it done before, and it definitely showed the problem, even though the radiator appeared good from the small area I could see. Even after flushing, it was still terrible internally.

If it can still be found, find the Camaro thread (probably on thirdgen.org) where the guy finally tore down his motor and replaced the heads (and that was after every part you can think of before that), only to find that the 1 year or so old radiator was bad.
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Dorian, i couldn't agree with you more. Most overheat issues are a bad radiator. People only see the few tubes that are visable through the radiator cap and think wow that's clean when in actuality the core is pretty plugged about half way down. The core can be tested fairly easy if you have an infrared heat gun. Simply get the engine up to temp (or in this case overheating) and check for cold spots on the radiator core surface. Any place that is cold is a plugged area of the core.
 
4X4HIGH said:
Dorian, i couldn't agree with you more. Most overheat issues are a bad radiator. People only see the few tubes that are visable through the radiator cap and think wow that's clean when in actuality the core is pretty plugged about half way down. The core can be tested fairly easy if you have an infrared heat gun. Simply get the engine up to temp (or in this case overheating) and check for cold spots on the radiator core surface. Any place that is cold is a plugged area of the core.
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Didn't think about the infrared trick... That's a very good idea. I need to try that.
 
Oh, and read the cooling article link here:

http://www.grapeaperacing.com/GrapeApeRacing/tech/index.cfm

Really have to think of the cooling system for what it is, a system. Help to understand everything going on. Didn't think about the fact that the block is pressurized further, sounds to me like antifreeze "boilover protection" is complete BS. 300* boiling point for plain water=misleading antifreeze claims.
 
My friend had his transmission converted from electronic lockup to "mechanical". In reality the converter is always locked except in 1-2, and none of the tests for an electric converter clutch will tell you anything. Not sure how you'd test it was working correctly.

Temp is the key.
 
dyeager535 said:
Oh, and read the cooling article link here:

http://www.grapeaperacing.com/GrapeApeRacing/tech/index.cfm

Really have to think of the cooling system for what it is, a system. Help to understand everything going on. Didn't think about the fact that the block is pressurized further, sounds to me like antifreeze "boilover protection" is complete BS. 300* boiling point for plain water=misleading antifreeze claims.
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That's good stuff... Thanks Dorian. :waytogo:
 
I do want to know more about having the right fan clutch...

Also...In my other thread kgblazerfive mentioned that:

kgblazerfive said:
Well if the fan clutch is not working it will the fan will spin slowly and actually block the air from going though the radiator to a point when you are moving. Or not work at all to pull air through the radiator
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In the meantime, I'll look for a shop that can flow test a radiator.

It just sucks that the truck sat for so long. I can say, the one time I drove it any real distance on the road after the axle rebuild/gear swap, it did NOT overheat, so the only other significant change was the tranny. After that, it got hot whenever it was driven. But between those two events, probably 6-7 months passed.

Would letting the truck sit for several months cause the radiator to clog? IIRC, it was filled with a 50/50 mix of standard green antifreeze...probably the generic "parts store" brand.
 
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