Another overheating problem.
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From: Sharpsburg Georgia
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We did a test to check for the presence of combustion chamber gasses in the cooling system and it came back negative, no bubbles and no smoke, so at this point we are ruling out a head gasket leak.
We have no external leaks.
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Race Director
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From: Sharpsburg Georgia
GA Events Coordinator
How much can you take off of a L98 head before you would run into a overheating problem.
These head have been done 3 times that I know of, even if they only need a slight cut like last time of .008 x3=.024
These head have been done 3 times that I know of, even if they only need a slight cut like last time of .008 x3=.024
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From: oregon
decking the head will bump compression but .024 isn't anything too extreme. normally a knock sensor will come on & pull timing to prevent detonation. of course detonation can increase coolant temps but you shouldn't be having any. i'm kind of stumped on this since coolant systems are fairly simple. just going down the line checking things off. have you made sure the temps are correct and a sensor isn't blitz. have you made sure the water pump is moving water, that the thermostat isn't stuck and the headgaskets are not blown? next is on the radiator and it being able to cool the water, the easy test is to run cold water all over it when the car is hot. if temps drop quickly the radiator isn't able to keep up. i actually replaced the stock unit in my 1990 with a new one from corvette recycling in order to help out temps. you really can only clean so much out of an 18yr old unit. i think you have done most if not all of this but there really isn't much left to check in the cooling system besides pinched or clogged hoses which should manifest themselves in the flow check.
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From: Sharpsburg Georgia
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I was just using the figure of .024 as three times what was done last time, my guess is that it is more than that.
I am going to take the thermastat out and do a flow check.
If that looks good as I think it will I am going to order a set of AFR's after I pull the heads off.
the radiator is a three year old "Griffin" and it looks good inside and out.
Greg
I am going to take the thermastat out and do a flow check.
If that looks good as I think it will I am going to order a set of AFR's after I pull the heads off.
the radiator is a three year old "Griffin" and it looks good inside and out.
Greg
decking the head will bump compression but .024 isn't anything too extreme. normally a knock sensor will come on & pull timing to prevent detonation. of course detonation can increase coolant temps but you shouldn't be having any. i'm kind of stumped on this since coolant systems are fairly simple. just going down the line checking things off. have you made sure the temps are correct and a sensor isn't blitz. have you made sure the water pump is moving water, that the thermostat isn't stuck and the headgaskets are not blown? next is on the radiator and it being able to cool the water, the easy test is to run cold water all over it when the car is hot. if temps drop quickly the radiator isn't able to keep up. i actually replaced the stock unit in my 1990 with a new one from corvette recycling in order to help out temps. you really can only clean so much out of an 18yr old unit. i think you have done most if not all of this but there really isn't much left to check in the cooling system besides pinched or clogged hoses which should manifest themselves in the flow check.
Last edited by blown87; May 24, 2008 at 05:03 PM.
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From: The Top of Utah
Originally Posted by racebum
decking the head will bump compression but .024 isn't anything too extreme. normally a knock sensor will come on & pull timing to prevent detonation. of course detonation can increase coolant temps but you shouldn't be having any. i'm kind of stumped on this since coolant systems are fairly simple. just going down the line checking things off. have you made sure the temps are correct and a sensor isn't blitz. have you made sure the water pump is moving water, that the thermostat isn't stuck and the headgaskets are not blown? next is on the radiator and it being able to cool the water, the easy test is to run cold water all over it when the car is hot. if temps drop quickly the radiator isn't able to keep up. i actually replaced the stock unit in my 1990 with a new one from corvette recycling in order to help out temps. you really can only clean so much out of an 18yr old unit. i think you have done most if not all of this but there really isn't much left to check in the cooling system besides pinched or clogged hoses which should manifest themselves in the flow check.
blown87, If you want new heads, fine, but the heads aren't the problem. I'd be surprised if the heads have had .024" removed, but even if they have, they are nowhere too thin. New heads COULD bring about a cure, but not because of the new heads, but because of the "do over".
RACE ON!!!
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From: Sharpsburg Georgia
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Atta way to read a thread! Most everything you asked or suggested has been answered or tried.
blown87, If you want new heads, fine, but the heads aren't the problem. I'd be surprised if the heads have had .024" removed, but even if they have, they are nowhere too thin. New heads COULD bring about a cure, but not because of the new heads, but because of the "do over".
RACE ON!!!
blown87, If you want new heads, fine, but the heads aren't the problem. I'd be surprised if the heads have had .024" removed, but even if they have, they are nowhere too thin. New heads COULD bring about a cure, but not because of the new heads, but because of the "do over".
RACE ON!!!
List for monday
Remove thermastat and check flow
Look at knock counts when hot
spray water on radiator
if that turns up nothing, then pull the heads again.
I just do not think that two full time mechanics who both checked for proper head gasket orientation would have both missed the up on the head gaskets, we did have to flip one of them over because I dropped it on upside down before we set the heads.
But I have screwed simple stuff like that up a few times.
Greg
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From: :45 minutes from everywhere / E-I-E-I-O
Timing that's too far retarded will cause the engine to run hot and will even cause the exhaust headers to glow a bright, pretty red. This is because the air/fuel mixture is still burning as it enters the exhaust. Burning should be completed before the exhaust valve opens.
At night, turn the garage lights off; makes a really pretty color.
Jake
At night, turn the garage lights off; makes a really pretty color.
Jake
BUT, that's was only when there was wires crossed, or some other timing/spark error. If the heads have been shaved 3 times, AND you got 60 over, you got a lot of air, and a pretty tight squeeze, even for only 6 before TDC. I'm goin' back to retard the fire to 4bTDC and watch...........
If the timing gets backed up to 4, or 2 before TDC, there surely will not be air/fuel mix still burning, by the time the piston is comin' back up to blow spent gas.
Right?
blown - what kinda oil temps are you gettin' when coolant maxes?
Have you actually checked the squeeze in all 8 holes with a comp guage?
Last edited by schrade; May 25, 2008 at 12:31 AM.
Thread Starter
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From: Sharpsburg Georgia
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The oil temps are running below the coolant temps, which has never been the case before.
I have seen retarded timing cause overheating problems, just like I have seen running to much total timing can.
At this point i think it is a coolant flow problem, for what ever reason.
I am also wondering about the heads being done three times and .60 over, that will raise CR just as sure as the sun is going to come up in the AM.
I just do not know how much has been taken off the head and how much is too much.
I have not done a compression or leakdown test on the car in the past six months, but I do not have a lot of blowby that I can see and since I am running a draft tube it would be evident if there was much..
I am going to fix this one way or the other, hell, I all ready have 25,000 in a $6,000 car, got to at this point.
Maybe a new motor and some other things, lets say $7,500 I might end up with a $7,000 car.
Greg 
I have seen retarded timing cause overheating problems, just like I have seen running to much total timing can.
At this point i think it is a coolant flow problem, for what ever reason.
I am also wondering about the heads being done three times and .60 over, that will raise CR just as sure as the sun is going to come up in the AM.
I just do not know how much has been taken off the head and how much is too much.
I have not done a compression or leakdown test on the car in the past six months, but I do not have a lot of blowby that I can see and since I am running a draft tube it would be evident if there was much..
I am going to fix this one way or the other, hell, I all ready have 25,000 in a $6,000 car, got to at this point.
Maybe a new motor and some other things, lets say $7,500 I might end up with a $7,000 car.
Greg
I've heard of headers lightin' up from fire outside the cylinder.
BUT, that's was only when there was wires crossed, or some other timing/spark error. If the heads have been shaved 3 times, AND you got 60 over, you got a lot of air, and a pretty tight squeeze, even for only 6 before TDC. I'm goin' back to retard the fire to 4bTDC and watch...........
If the timing gets backed up to 4, or 2 before TDC, there surely will not be air/fuel mix still burning, by the time the piston is comin' back up to blow spent gas.
Right?
blown - what kinda oil temps are you gettin' when coolant maxes?
Have you actually checked the squeeze in all 8 holes with a comp guage?
BUT, that's was only when there was wires crossed, or some other timing/spark error. If the heads have been shaved 3 times, AND you got 60 over, you got a lot of air, and a pretty tight squeeze, even for only 6 before TDC. I'm goin' back to retard the fire to 4bTDC and watch...........
If the timing gets backed up to 4, or 2 before TDC, there surely will not be air/fuel mix still burning, by the time the piston is comin' back up to blow spent gas.
Right?
blown - what kinda oil temps are you gettin' when coolant maxes?
Have you actually checked the squeeze in all 8 holes with a comp guage?
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