69 BB cooling issue with reverse pump
Thread Starter
Instructor
Joined: Jul 2006
Posts: 208
Likes: 0
From: Hamden CT
St. Jude Donor '12
69 BB cooling issue with reverse pump
Hello All,
I have a 69 shark running a 496ci. It has brand new aluminum rad and a Vintage Air serpentine belt setup which uses a reverse flow water pump.
It also has a mechanical flex fan bolted directly to the water pump studs (no fan clutch). Right now there is no thermostat in the car. After running the car at idle in 90 degree temps yesterday the gauge went up to about 195. I shut it down as I didn't want it to get any hotter.
Does a reverse flow water pump not cool an old school big block properly? I have run 69 Chevelle 454ci w/copper rad in 100degree temps with no thermostat and the engine temp never got over 160. I normally run a 180 therm in both cars. I've never seen a motor get this hot with no stat in it.
I'm pretty sure there's no air pockets. When it reached, 190 fluid started dumping out the overflow hose as well.
Any suggestions would be greatly appreciated.
I have a 69 shark running a 496ci. It has brand new aluminum rad and a Vintage Air serpentine belt setup which uses a reverse flow water pump.
It also has a mechanical flex fan bolted directly to the water pump studs (no fan clutch). Right now there is no thermostat in the car. After running the car at idle in 90 degree temps yesterday the gauge went up to about 195. I shut it down as I didn't want it to get any hotter.
Does a reverse flow water pump not cool an old school big block properly? I have run 69 Chevelle 454ci w/copper rad in 100degree temps with no thermostat and the engine temp never got over 160. I normally run a 180 therm in both cars. I've never seen a motor get this hot with no stat in it.
I'm pretty sure there's no air pockets. When it reached, 190 fluid started dumping out the overflow hose as well.
Any suggestions would be greatly appreciated.
Race Director
Joined: May 2006
Posts: 18,755
Likes: 2,589
I was always under the impression that running with no thermostat causes the fluid to pass too quicky through the radiator preventing proper heat transfer. Even without a thermostat there is supposed to be a restrictor plate, a thermostat with no guts, sitting in the housing.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
You have an air pocket or some kind of restriction in the system. Could it be that the reverse flow pump is sucking down the upper radiator hose? (do you have a 'standard' upper rad hose or one made for suction support?)
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
195 is not hot. Many later Corvettes have that as the MINIMUM operating temp. 230-245 is hot.
Oh, and put in a thermostat. It cannot and will not hurt anything.
Le Mans Master
Joined: Jan 2006
Posts: 6,506
Likes: 139
From: Butler Pa
Thread Starter
Instructor
Joined: Jul 2006
Posts: 208
Likes: 0
From: Hamden CT
St. Jude Donor '12
All the seals are new and in place. I will try it with a 180 t-stat and a 160 t-stat. It has a cool-flex upper hose and a stock lower hose with the spring in it.
I guess my main question is does a reverse flow pump with a mechanical fan not cool as well as a standard rotation pump?
Here's my thoughts: with a standard rotation pump it pulls water from the bottom of the rad (usually cooler than the top of the rad) into the block when the t-stats opens. If running a reverse pump, when the stat opens the hotter upper rad water will flow into the block and down back into the bottom of the rad. The cooling efficiency seems it would be off or am I smoking something?
I guess my main question is does a reverse flow pump with a mechanical fan not cool as well as a standard rotation pump?
Here's my thoughts: with a standard rotation pump it pulls water from the bottom of the rad (usually cooler than the top of the rad) into the block when the t-stats opens. If running a reverse pump, when the stat opens the hotter upper rad water will flow into the block and down back into the bottom of the rad. The cooling efficiency seems it would be off or am I smoking something?
Last edited by ja1724; Aug 17, 2009 at 12:38 PM.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Melting Slicks
Joined: Jan 2003
Posts: 2,877
Likes: 13
From: Doha
St. Jude Donor '08
Based on you description of the problem, I have 3 scenarios in my mind regarding your problem :
1- If your water pump is rotating counter-clockwise, and a mechanical fan is hooked to it, then you're basically "pushing" air into the radiator instead of pulling it through, and thats enough will cause you all sorts of overeating problems.
2- In case you have a reverse flow water pump that would circulate the coolant to the cyl. heads first then the block, then I dont think the MkIV blocks are compatible with that cooling mechanism.
3- If you are using a standard rotation water pump and use it in a serpentine belt system, and thinking that this may work as a "reverse flow" cooling mechanism, then you are incorrect, the vanes inside the water pump will rotate in the wrong direction causing all sorts of turbulences and will eventually cause the engine to over heat.
With such a large engine in a tiny compartment with A/C running and setting idle in 100F ambient temps, 195F is not bad at all, in matter of fact I would be surprised if your engine will stay at that temp! .. my '71 with a BB engine will idle at that temp in a similar ambient temps but I'm using a large aluminum radiator and dual 11 in. electric fans.
1- If your water pump is rotating counter-clockwise, and a mechanical fan is hooked to it, then you're basically "pushing" air into the radiator instead of pulling it through, and thats enough will cause you all sorts of overeating problems.
2- In case you have a reverse flow water pump that would circulate the coolant to the cyl. heads first then the block, then I dont think the MkIV blocks are compatible with that cooling mechanism.
3- If you are using a standard rotation water pump and use it in a serpentine belt system, and thinking that this may work as a "reverse flow" cooling mechanism, then you are incorrect, the vanes inside the water pump will rotate in the wrong direction causing all sorts of turbulences and will eventually cause the engine to over heat.
With such a large engine in a tiny compartment with A/C running and setting idle in 100F ambient temps, 195F is not bad at all, in matter of fact I would be surprised if your engine will stay at that temp! .. my '71 with a BB engine will idle at that temp in a similar ambient temps but I'm using a large aluminum radiator and dual 11 in. electric fans.
Thread Starter
Instructor
Joined: Jul 2006
Posts: 208
Likes: 0
From: Hamden CT
St. Jude Donor '12
Based on you description of the problem, I have 3 scenarios in my mind regarding your problem :
1- If your water pump is rotating counter-clockwise, and a mechanical fan is hooked to it, then you're basically "pushing" air into the radiator instead of pulling it through, and thats enough will cause you all sorts of overeating problems.
2- In case you have a reverse flow water pump that would circulate the coolant to the cyl. heads first then the block, then I dont think the MkIV blocks are compatible with that cooling mechanism.
3- If you are using a standard rotation water pump and use it in a serpentine belt system, and thinking that this may work as a "reverse flow" cooling mechanism, then you are incorrect, the vanes inside the water pump will rotate in the wrong direction causing all sorts of turbulences and will eventually cause the engine to over heat.
With such a large engine in a tiny compartment with A/C running and setting idle in 100F ambient temps, 195F is not bad at all, in matter of fact I would be surprised if your engine will stay at that temp! .. my '71 with a BB engine will idle at that temp in a similar ambient temps but I'm using a large aluminum radiator and dual 11 in. electric fans.
1- If your water pump is rotating counter-clockwise, and a mechanical fan is hooked to it, then you're basically "pushing" air into the radiator instead of pulling it through, and thats enough will cause you all sorts of overeating problems.
2- In case you have a reverse flow water pump that would circulate the coolant to the cyl. heads first then the block, then I dont think the MkIV blocks are compatible with that cooling mechanism.
3- If you are using a standard rotation water pump and use it in a serpentine belt system, and thinking that this may work as a "reverse flow" cooling mechanism, then you are incorrect, the vanes inside the water pump will rotate in the wrong direction causing all sorts of turbulences and will eventually cause the engine to over heat.
With such a large engine in a tiny compartment with A/C running and setting idle in 100F ambient temps, 195F is not bad at all, in matter of fact I would be surprised if your engine will stay at that temp! .. my '71 with a BB engine will idle at that temp in a similar ambient temps but I'm using a large aluminum radiator and dual 11 in. electric fans.
18" CCW Flex-A-Lite
Last edited by ja1724; Aug 17, 2009 at 01:07 PM.
Race Director
Joined: Jun 2000
Posts: 10,049
Likes: 675
From: FL
Get rid of the POS flex-a-lite fans and get some dual Spal electric fans. They only run when the car gets hot. Mine have an on/off at 195/185 switch in conjunction with a 180 stat. Runs 180 on the highway all day long and fans cycle in town. Only way to go.
Thread Starter
Instructor
Joined: Jul 2006
Posts: 208
Likes: 0
From: Hamden CT
St. Jude Donor '12
You're 100% right on. That was my plan (one of my winter projects once I get some more money together). For now I'm out of cash. I'm going to try some of that radiator additive - supposedly lowers your water temp 10-20 degrees - put the high-flow 180 degree stat back in and see where she's at.
Drifting
Joined: Aug 2005
Posts: 1,682
Likes: 3
From: League City TX
Until winter, changing to something like this might help.
http://www.summitracing.com/parts/DER-17618/
Its still a flex fan, but I bet it pulls a bit more air than the one you are using now.
http://www.summitracing.com/parts/DER-17618/
Its still a flex fan, but I bet it pulls a bit more air than the one you are using now.
Melting Slicks
Joined: May 2002
Posts: 2,717
Likes: 121
From: Sulphur LA
St. Jude Donor '05-'06,'11,'13-'14,'16,'18,'19,'24, '25
that serp set-up puts all the acss. in the front of the engine which leaves very little room to install a fan and shroud. I've been fighting the same issue with my car. Would love to see pics of the fan and shroud installed if possible.
Neal
Neal
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
