Overheating BBC 468 Pro Street Willy's Coupe

[topradman]

Actually, I guess your mod might have changed pressure in the block after all because you eliminated the cavitation so then it was pushing coolant instead of trying to push vapor.

My problem still remains in that I really don't think this pump can cavitate since it is not rpm sensitive and probably moves comparable water to a stock type pump at say 3000 rpm.

[pamotorman]

when I started racing BBC in 1966 we had heating problems and the people at GM racing told me to check the internal pressure in the block and heads. the pressure was low because of water pump cavitation at high RPMs so removing every other fin from the water pump Impeller raised the pressure in the block and it cured the heating problem.

That makes very good sense. My problem comes in that I have doubts as to the ability of a Meziere 55 gpm pump to cavitate since it is electric. It is not rpm sensitive.

I think what you would have experienced with your bbc is that once a pump cavitated from high rpm, it had vapor it was trying to move inside the pump itself. I feel like removing every other blade on the impeller actually slowed the movement of coolant but the desired result you got was that is was no longer cavitating ( beating the crap out of the coolant ), not that it raised pressure in the block.

Does that make sense or am I way off here?

put a pressure gauge in the intake pipe fitting next to the thermostat housing and turn on your water pump and see what pressure you have in the block. this is how I found my lack of pressure but I had the run the engine since I was using a belt driven water pump.

[topradman]

when I started racing BBC in 1966 we had heating problems and the people at GM racing told me to check the internal pressure in the block and heads. the pressure was low because of water pump cavitation at high RPMs so removing every other fin from the water pump Impeller raised the pressure in the block and it cured the heating problem.

That makes very good sense. My problem comes in that I have doubts as to the ability of a Meziere 55 gpm pump to cavitate since it is electric. It is not rpm sensitive.

I think what you would have experienced with your bbc is that once a pump cavitated from high rpm, it had vapor it was trying to move inside the pump itself. I feel like removing every other blade on the impeller actually slowed the movement of coolant but the desired result you got was that is was no longer cavitating ( beating the crap out of the coolant ), not that it raised pressure in the block.

Does that make sense or am I way off here?

put a pressure gauge in the intake pipe fitting next to the thermostat housing and turn on your water pump and see what pressure you have in the block. this is how I found my lack of pressure but I had the run the engine since I was using a belt driven water pump.

Have already done that see previous page w/engine drawing. Meziere says pressures are fine. Meziere is new.
Same results with previous electric pump. I don't think it is pump related.

[Keith Morganstein]

The radiator, fan and water pump are at least functioning at the minimum acceptable level. I would rather see a 15* deltaT across the radiator (than the 12* you are seeing now). I'm sure the double pass radiator had better performance and if with a good engine, there is still not enough capacity, the double pass would be a positive change.

Considering the temps recorded, the mismatch of engine parts and all the other indicators of engine issues, it's clear that you have an engine problem.

I would put this all back on the owner of the car to replace the engine with one properly built with compatible parts. I wouldn't even try to correct/repair the engine. Otherwise, It's a "no win" situation for you at this point.

[topradman]

The radiator, fan and water pump are at least functioning at the minimum acceptable level. I would rather see a 15* deltaT across the radiator (than the 12* you are seeing now). I'm sure the double pass radiator had better performance and if with a good engine, there is still not enough capacity, the double pass would be a positive change.

Considering the temps recorded, the mismatch of engine parts and all the other indicators of engine issues, it's clear that you have an engine problem.

I would put this all back on the owner of the car to replace the engine with one properly built with compatible parts. I wouldn't even try to correct/repair the engine. Otherwise, It's a "no win" situation for you at this point.

I agree there is an obvious engine problem. I just was concerned about pulling the heads and correcting the mismatch problem, then reassembling and experiencing lack luster results because I missed something in the lower end that isn't right either.

I believe customer has seen what all we have gone through and will be willing to pay for engine work. Like it said though, just don't want to miss something in the bottom end.

[Keith Morganstein]

I'm sure we'd all like to know if it's the head gaskets causing the flow issue. (Like you, I'm pretty relentless in finding the root cause of problem) it's tough to stop sometimes...

However, with others posting having problems with gen5 heads on markIV blocks, can it ever be made to work well? Then there's the low cranking compression and suspect leak down numbers. Even if coolant flow issues are corrected by different head gaskets, that engine will likely be a continuing problem for the customer.

[Keith Morganstein]

On another note, (and maybe Topradman has some insight), on the system I posted numbers for. I pulled the intercooler and radiator. It's a typical plastic tank, aluminum core deal, but much larger than an automotive radiator.
I could see light through the fins, but went ahead and cleaned it. It had "oily, greasy, chopped up bird feathers" in it. I'm going to reinstall and retest. However I find this type of radiator seems to degrade in it's ability to transfer heat over time. They can look "OK" and be totally clean on the inside, but for some reason, heat doesn't transfer to the fins. I'm not sure why, maybe they lose thermal bond from the tubes to the fins?

[topradman]

On another note, (and maybe Topradman has some insight), on the system I posted numbers for. I pulled the intercooler and radiator. It's a typical plastic tank, aluminum core deal, but much larger than an automotive radiator.
I could see light through the fins, but went ahead and cleaned it. It had "oily, greasy, chopped up bird feathers" in it. I'm going to reinstall and retest. However I find this type of radiator seems to degrade in it's ability to transfer heat over time. They can look "OK" and be totally clean on the inside, but for some reason, heat doesn't transfer to the fins. I'm not sure why, maybe they lose thermal bond from the tubes to the fins?

I have yet to see an aluminum core loose bonding of tube/fin joints. These are vacubrazed and unlike a brass/cu radiator w/solder attaching the fin to the tube, the aluminum braze material melts very near the melting point of the aluminum and is very nearly a weld. On a brass/cu radiator, the solder melts much, much lower temperatures than the parent metals.

That being said, fin separation on brass/cu radiators is usually the product of pressure & heat cycles which expands and contracts the tube until it pulls the solder joints between the tube & fins.

Aluminum cores, again, being very nearly "welded" together will not usually experience this. I have seen where aluminum radiators were so overheated and over pressured that a softening of the tubes took place. This caused them to oval out under pressure rather than stay in original shape and buckled the fin material. Once the tubes oval out, you can only get laminar flow through the tubes and it also shuts down air movement through the core by a considerable amount. You can usually hold them up to a light and see the tubes nearly touching one another in the center of the tubes ( front to rear ). Most of the radiators I have seen that have this damage look normal at a glance but on closer observation, you can usually see a slight wave in the fin material between each tube. This is usually a dead giveaway that tubes have ovaled out. Most of these I have seen were on roundy-rounders.

[topradman]

Ok, so our final test was to again set up a remote radiator outside the car to see how it will behave. We did this once a few weeks ago but in my haste, I didn't have the guys hold the rpms up to highway speeds.

So, we took a radiator for a 1994 Chevy G van w/454 and set it up in front of the car with a dual fan Derale set up and plumbed it up. After warm up to 195F and fans just turned on, we held the rpm at 2800 ( highway speed ) to see what it would do. Since the radiator is exterior the car, it does not pick up the engines radiant heat like the one in the car so test is not apples and apples but an attempt to see if it can be cooled at 2800 rpm at all. With 7 gallons of coolant to fill it this way, after 17 minutes of sustained rpm we reached 218F and still climbing, slowly. The fuel just started to boil in the front bowls so we shut it down. I am convinced now with all the evidence that there is definitely an engine issue and can feel very comfortable presenting this to the owner. Both setups perform comparably, but the remote set up has so much more coolant that it just takes longer to heat.

My custom radiator is about 1220 cui of heat sink. Fan pulls 4000 cfm, 45 amp continuous.3.7 gallons of coolant.

Test radiator is 1190 cui of heat sink. Derale fans pull 4000 cfm as advertised. 7+ gallons of coolant.

[Keith Morganstein]

On another note, (and maybe Topradman has some insight), on the system I posted numbers for. I pulled the intercooler and radiator. It's a typical plastic tank, aluminum core deal, but much larger than an automotive radiator.
I could see light through the fins, but went ahead and cleaned it. It had "oily, greasy, chopped up bird feathers" in it. I'm going to reinstall and retest. However I find this type of radiator seems to degrade in it's ability to transfer heat over time. They can look "OK" and be totally clean on the inside, but for some reason, heat doesn't transfer to the fins. I'm not sure why, maybe they lose thermal bond from the tubes to the fins?

I have yet to see an aluminum core loose bonding of tube/fin joints. These are vacubrazed and unlike a brass/cu radiator w/solder attaching the fin to the tube, the aluminum braze material melts very near the melting point of the aluminum and is very nearly a weld. On a brass/cu radiator, the solder melts much, much lower temperatures than the parent metals.

That being said, fin separation on brass/cu radiators is usually the product of pressure & heat cycles which expands and contracts the tube until it pulls the solder joints between the tube & fins.

Aluminum cores, again, being very nearly "welded" together will not usually experience this. I have seen where aluminum radiators were so overheated and over pressured that a softening of the tubes took place. This caused them to oval out under pressure rather than stay in original shape and buckled the fin material. Once the tubes oval out, you can only get laminar flow through the tubes and it also shuts down air movement through the core by a considerable amount. You can usually hold them up to a light and see the tubes nearly touching one another in the center of the tubes ( front to rear ). Most of the radiators I have seen that have this damage look normal at a glance but on closer observation, you can usually see a slight wave in the fin material between each tube. This is usually a dead giveaway that tubes have ovaled out. Most of these I have seen were on roundy-rounders.

I have t noticed ovaled tubes, will have to look for that.
I' guess my hypothesis of the fins losing contact with the tubes isn't what's going on.

[Keith Morganstein]

Ok, so our final test was to again set up a remote radiator outside the car to see how it will behave. We did this once a few weeks ago but in my haste, I didn't have the guys hold the rpms up to highway speeds.

So, we took a radiator for a 1994 Chevy G van w/454 and set it up in front of the car with a dual fan Derale set up and plumbed it up. After warm up to 195F and fans just turned on, we held the rpm at 2800 ( highway speed ) to see what it would do. Since the radiator is exterior the car, it does not pick up the engines radiant heat like the one in the car so test is not apples and apples but an attempt to see if it can be cooled at 2800 rpm at all. With 7 gallons of coolant to fill it this way, after 17 minutes of sustained rpm we reached 218F and still climbing, slowly. The fuel just started to boil in the front bowls so we shut it down. I am convinced now with all the evidence that there is definitely an engine issue and can feel very comfortable presenting this to the owner. Both setups perform comparably, but the remote set up has so much more coolant that it just takes longer to heat.

My custom radiator is about 1220 cui of heat sink. Fan pulls 4000 cfm, 45 amp continuous.3.7 gallons of coolant.

Test radiator is 1190 cui of heat sink. Derale fans pull 4000 cfm as advertised. 7+ gallons of coolant.

Did you have probes in? Just wondering how this system perfomed? I'm thinking the external radiator did a little better, but engine temps were showing the same pattern as before

[topradman]

I did not have probes in for this test. Through with tests. Will post my findings next week.

[topradman]

Got the cylinder heads off. The engine is NOT a 468, it is a 461 as pistons are .030 over, not what customer was told about his car, which makes the bore 4.280". It does NOT have a roller cam as customer was lead to believe. It does indeed have Mark IV heads on a Gen V block which we already knew from the casting #'s.

Here's what has me nervous.....The gaskets are a parallel flow design, Felpro #17046 "Marine/Hi Performance" on the gasket. I cannot find large amounts of debris in water jackets of the block although there is some scum, looks pretty typical. Same with the cylinder heads.

The gaskets and cylinder heads do block off both of the front water jackets in the block so coolant does not just go into the front portion of the block and loop right back to the t-stat housing/water outlet.

The cylinder heads do not appear to be cracked or show any evidence of water leaks however that will be confirmed by the local machine shop.

Any other ideas? I'm against a wall here.

[rp930]

Sounds like the head gaskets are ok. Do you have a picture of them?

[Keith Morganstein]

Somehow double posted.