Big Block Overheating--partial Cure ???
08-25-2005, 12:51 PM
#1
Drifting
Thread Starter
Big Block Overheating--Partial Cure ??? Aluminum Radiator ???
Hi all,
I have a 67 435HP convertible. As all of the 66 425's & 67 435's do, mine runs hot, and if the weather gets up in the 90's, I won't even drive it. Many years ago, in Vette Vues magazine's "Factory Facts" section, there was a story about hot running 68 427 solid lifter engines, and Chevrolet's try at a cure was in there. It was as follows:
Replace the 1968 1st design large water pump pulley (same diameter as 66-67--about 7 inches) with the second design 1968 pulley, which was about 1 or 1 1/2 inches smaller. Swap the 5 blade fan with a 7 blade fan--retain the same clutch. Add all of the shroud and radiator support seals that an air conditioned car uses, add the fan shroud extension, and lastly, make sure that you use an OEM Delco thermostat, as they have a small hole for coolant flow. I even went 1 step further, and installed the license plate bracket for an air conditioned big block car which moved the plate to the left side of the car, under the bumper, away from the center of the grille where most of the air enters.
Their thinking was to speed up the fan for more air flow, make sure that ALL the air that enters the grille went through the radiator, and slow down the coolant flow (so the coolant stays in the radiator longer) with a small hole in the thermostat. I did all of this to my car back in 1989 or 1990, while that pulley, fan, and fan shroud extension were all still available from GM. Believe it or not, it partially worked. However, if I get stuck in traffic on an 85-90 degree day, the temp still climbs past 210 degrees and I have to shut it down. It used to be, before this mod, if my temp went up to 210, even if I got moving, the temp would not go down. Now with the mod, the temp DOES go down, but it has not fixed the problem of overheating if I get stuck in traffic.
I even changed the vacuum advance to full time---temp still climbs past 210 in traffic. I am thinking of installing a DeWitt aluminum radiator. I hear that an aluminum radiator might cure my problem, and maybe even enable me to reinstall the large water pump pulley (I've gone through 3 pumps since 1989--bearing & seal failure, evidently due to higher pump RPM). Have any of you 425 & 435 HP guys installed the DeWitt aluminum radiator ??? DOES IT WORK ??? Is the car manageable in traffic ???
Only 1 thing bothers me. I own a service station in N.Y. A while back, a friend of mine brought his 454 Chevelle by for me to check out. He had an aluminum radiator in it. I removed the radiator cap to look inside the radiator, and when I did, some aluminum shavings came off along with the cap--same thing when I reinstalled it. Does this always happen ??? How many times can you pull the cap before the neck wears out ??? Right now, that's the only thing that's holding me up. Any ideas ???
P.S. In 1969, GM just about eliminated the hot running problem. They increased the width of the radiator by 5 inches--Something they should have done many years before.
I have a 67 435HP convertible. As all of the 66 425's & 67 435's do, mine runs hot, and if the weather gets up in the 90's, I won't even drive it. Many years ago, in Vette Vues magazine's "Factory Facts" section, there was a story about hot running 68 427 solid lifter engines, and Chevrolet's try at a cure was in there. It was as follows:
Replace the 1968 1st design large water pump pulley (same diameter as 66-67--about 7 inches) with the second design 1968 pulley, which was about 1 or 1 1/2 inches smaller. Swap the 5 blade fan with a 7 blade fan--retain the same clutch. Add all of the shroud and radiator support seals that an air conditioned car uses, add the fan shroud extension, and lastly, make sure that you use an OEM Delco thermostat, as they have a small hole for coolant flow. I even went 1 step further, and installed the license plate bracket for an air conditioned big block car which moved the plate to the left side of the car, under the bumper, away from the center of the grille where most of the air enters.
Their thinking was to speed up the fan for more air flow, make sure that ALL the air that enters the grille went through the radiator, and slow down the coolant flow (so the coolant stays in the radiator longer) with a small hole in the thermostat. I did all of this to my car back in 1989 or 1990, while that pulley, fan, and fan shroud extension were all still available from GM. Believe it or not, it partially worked. However, if I get stuck in traffic on an 85-90 degree day, the temp still climbs past 210 degrees and I have to shut it down. It used to be, before this mod, if my temp went up to 210, even if I got moving, the temp would not go down. Now with the mod, the temp DOES go down, but it has not fixed the problem of overheating if I get stuck in traffic.
I even changed the vacuum advance to full time---temp still climbs past 210 in traffic. I am thinking of installing a DeWitt aluminum radiator. I hear that an aluminum radiator might cure my problem, and maybe even enable me to reinstall the large water pump pulley (I've gone through 3 pumps since 1989--bearing & seal failure, evidently due to higher pump RPM). Have any of you 425 & 435 HP guys installed the DeWitt aluminum radiator ??? DOES IT WORK ??? Is the car manageable in traffic ???
Only 1 thing bothers me. I own a service station in N.Y. A while back, a friend of mine brought his 454 Chevelle by for me to check out. He had an aluminum radiator in it. I removed the radiator cap to look inside the radiator, and when I did, some aluminum shavings came off along with the cap--same thing when I reinstalled it. Does this always happen ??? How many times can you pull the cap before the neck wears out ??? Right now, that's the only thing that's holding me up. Any ideas ???
RON
P.S. In 1969, GM just about eliminated the hot running problem. They increased the width of the radiator by 5 inches--Something they should have done many years before.
Last edited by rongold; 08-25-2005 at 06:49 PM.
08-25-2005, 01:16 PM
#2
Drifting
Member Since: Dec 2004
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OK, while my set up is far from stock, the principals are the same.
YES, go to an aluminum radiator. Current aluminum radiators are far more advanced than a few years ago. I have Be Cool radiators (yes 2) with twin 10' SPAL electric fans. All the double stuff is because my radiators are in the rear and smaller than stock, but then again, my blower big block makes a LOT more heat and I can sit in traffic all day long in 98* temps without overheating. I ALSO suggest you replace the mechanical water pump with an electric one from one of the large manufactors, Moroso, CSI etc. These mods along with the restrictor in the thermastat housing WILL keep you from overheating. The electric fan and water pump will make the biggest differance of all the changes. It's all about flow. Hope this helps. Glenn
YES, go to an aluminum radiator. Current aluminum radiators are far more advanced than a few years ago. I have Be Cool radiators (yes 2) with twin 10' SPAL electric fans. All the double stuff is because my radiators are in the rear and smaller than stock, but then again, my blower big block makes a LOT more heat and I can sit in traffic all day long in 98* temps without overheating. I ALSO suggest you replace the mechanical water pump with an electric one from one of the large manufactors, Moroso, CSI etc. These mods along with the restrictor in the thermastat housing WILL keep you from overheating. The electric fan and water pump will make the biggest differance of all the changes. It's all about flow. Hope this helps. Glenn
08-25-2005, 01:54 PM
#4
Le Mans Master
First, I don't own a BB C2, but a SB C2. But this forum is littered with posts like "help! my C2 is runnig hot!", especially in the spring and early summer - it's like the sparrows returning to Capistrano - and it seems most of THOSE posts are from SB owners. So this would not seem to be a BB only issue.
And when I bought my 65 (a solid lifter SB - 365) I now know that the seller had lost his taste for it after a year because he was chasing an overheating condition like yours - couldn't even take it out on a 90+ day. What a shame. Had all manner of electric fans, special main fan, newly replaced [brass] rad, etc. I brought it under control, but it took awhile, and I learned some things - mostly from reading all of the posts and advice on here. Let me share the major points with you, because I think it is a shame that the situation has got you afraid to take the car out on hot days, and has you saying "oh no" when you encounter a stop and go traffic situation with your C2 on a sumemr's day (I know the feeling). And no one likes to drive around with their eyes constantly glancing at the temp gauge.
First question looks like this: Is it really running as hot as the temp gauge has you believing? In other words, do you have coolant puking out, or perhaps it really isn't overheating after all?
That issue can be put to bed by getting or borrowing an infra red temp gun, shoot the upper rad hose near the t-stat and compare that with what your temp gauge says. You might be suprised.
Second question is: what radiator do you have in there now, and how old is it? I would urge you to replace it with a new aluminum Dewitts restoration rad. If you want even more cooling, you might consider the 3007436 (the L88 rad) but that would require a different fan shroud, I would guess.
I also respectfully disagree with the folks who suggest adding electric fans to cure a run hot condition - you are not addressing the problem itself, and they often do not cure the situation, sometimes excaserbate it too.
Third question is the "usual suspects" category - how is your fan clutch, and how is the timing and advance on the car - needs to be to OE spec to eliminate run hot issues.
and one more thing - the car, when new, was perfectly capable of being run on 90 degree days without overheating - so you can get it back to that state.
And when I bought my 65 (a solid lifter SB - 365) I now know that the seller had lost his taste for it after a year because he was chasing an overheating condition like yours - couldn't even take it out on a 90+ day. What a shame. Had all manner of electric fans, special main fan, newly replaced [brass] rad, etc. I brought it under control, but it took awhile, and I learned some things - mostly from reading all of the posts and advice on here. Let me share the major points with you, because I think it is a shame that the situation has got you afraid to take the car out on hot days, and has you saying "oh no" when you encounter a stop and go traffic situation with your C2 on a sumemr's day (I know the feeling). And no one likes to drive around with their eyes constantly glancing at the temp gauge.
First question looks like this: Is it really running as hot as the temp gauge has you believing? In other words, do you have coolant puking out, or perhaps it really isn't overheating after all?
That issue can be put to bed by getting or borrowing an infra red temp gun, shoot the upper rad hose near the t-stat and compare that with what your temp gauge says. You might be suprised.
Second question is: what radiator do you have in there now, and how old is it? I would urge you to replace it with a new aluminum Dewitts restoration rad. If you want even more cooling, you might consider the 3007436 (the L88 rad) but that would require a different fan shroud, I would guess.
I also respectfully disagree with the folks who suggest adding electric fans to cure a run hot condition - you are not addressing the problem itself, and they often do not cure the situation, sometimes excaserbate it too.
Third question is the "usual suspects" category - how is your fan clutch, and how is the timing and advance on the car - needs to be to OE spec to eliminate run hot issues.
and one more thing - the car, when new, was perfectly capable of being run on 90 degree days without overheating - so you can get it back to that state.
Last edited by ctjackster; 08-25-2005 at 02:02 PM.
08-25-2005, 02:07 PM
#5
Le Mans Master
Originally Posted by nassau66427
nassau66427 pretty much summed it up right there with that simple link!
08-25-2005, 03:02 PM
#7
Race Director
Member Since: May 2000
Location: Redondo Beach USA
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210 is within the normal/acceptable range for a BB in hot weather traffic. With a 50/50 blend of antifreeze/water and a 15 psi cap the boilover point is 265. If it frequently gets to 230 or more, THEN you should think about some cooling system major maintenance.
How long has it been since your radiator was removed disassembled and the tubes rodded out?
If you have a replacement fan clutch, their engagement temperature is higher because they were set up for emission controlled engines with 195 degree thermostats.
The themostat opening point (like 180 or 195) establishes the MINIMUM operating temperature, and they are not full open until about 30 degrees higher than their rated opening temperature.
Regarding the vacuum can, the OE L-71 can according to the '67 AMA specs is not pulled to the stop until 15.5", but your engine only pulls about 14" at idle, which is not enough, so your total idle timing is less than ideal. Install a NAPA/Echlin VC1765 which is pulled to the limit - 16 degrees - at 12", and increase your initial timing to the detonation limit or about 12 degrees max. This might improve the hot running situation and only costs ten bucks plus a little time.
When switching to full time from ported vacuum advance the can usually must be changed to comply with THE RULE:
http://forums.corvetteforum.com/show...post1551749816
Duke
How long has it been since your radiator was removed disassembled and the tubes rodded out?
If you have a replacement fan clutch, their engagement temperature is higher because they were set up for emission controlled engines with 195 degree thermostats.
The themostat opening point (like 180 or 195) establishes the MINIMUM operating temperature, and they are not full open until about 30 degrees higher than their rated opening temperature.
Regarding the vacuum can, the OE L-71 can according to the '67 AMA specs is not pulled to the stop until 15.5", but your engine only pulls about 14" at idle, which is not enough, so your total idle timing is less than ideal. Install a NAPA/Echlin VC1765 which is pulled to the limit - 16 degrees - at 12", and increase your initial timing to the detonation limit or about 12 degrees max. This might improve the hot running situation and only costs ten bucks plus a little time.
When switching to full time from ported vacuum advance the can usually must be changed to comply with THE RULE:
http://forums.corvetteforum.com/show...post1551749816
Duke
08-25-2005, 09:17 PM
#8
Pro
Originally Posted by SWCDuke
210 is within the normal/acceptable range for a BB in hot weather traffic.
Duke
Duke
