#61  
Old 03-25-2004, 01:57 PM
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Let's review what we have found during the course of this discussion:

To cool better we need to:

1. Create less heat: make the engine run as efficiently as possible, timing, mixture, etc.

2.Improve coolant flow: efficient pump, remove blockage, reduce restrictions, i.e. high flow thermostat.

3. exchange heat from radiator to air: more radiator surface area, and more airflow.

Now I'll make the assumption that a 4 row radiator has better flow characteristics since there is an extra row of tubes, therefore at the same pressure differential more flow thru the radiator. Also, since it is larger, there is more surface area, which improves heat transfer to the air. So that is a Good Thing (thanx Martha).

A smaller pump pulley would increase flow rate so that is a Good Thing also, but finding pullies & belts is not as easy...

A high flow thermostat would also help flow rate.

A clutch fan helps because it creates less drag (less wasted power) at high speed, where there should be enuf airflow thru the radiator anyway, and if the air temp thru the rad. is high enuf, it automatically increases air flow.

A shroud also helps at low vehicle speeds because it takes the max airflow created by the fan and passes the air over more of the surface area of the radiator (than without a shroud).

In fact, isn't a fan with a shroud similar in action to optimizing the clearance to the pump vanes (less leakage aroound the impeller)?

This all is assuming that attempts at increasing flow rate isn't limited elsewhere by constrictions in cooling jackets, cavitation, etc.

that's the way I see it.....

George

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Old 03-25-2004, 05:05 PM
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All sounds good to me. By the way, PMDRACER where are you? You started all this and you just sit back and let us go at it while you chuckle? I notice that there are 1111 hits on this post. Could it be lots of folks are checking this out in the shop? Come on, lets hear from you guys.
Charles

  #63  
Old 03-25-2004, 10:14 PM
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As an engineer who works with pumps and also the owner of an 68 Firebird with a 455 prone to overheating, I was amazed to read that the vane to plate clearance was as high as 0.25"! My God, how did that pump pump anything! A typical clearance for this style of pump would be 0.030" and that is for a much larger pump. I think clearance should be tighter than even 0.1", but I guess if it works.........
This variation in clearance maybe explains what has always puzzled me - Pontiac designed these cooling systems to cope with Death Valley ambient temps, fully loaded vehicles, towing, etc., but now they cannot handle gentle cruising about town! Maybe this summer I will be able to wait in the drive-thru lineup without watching the damn temp gauge.
By the way, pump flow goes up directly as RPM and demanded pump power goes up as RPM *cubed*, so pump power demanded at 5000 RPM is theoretically eight times the power demanded at 2500 RPM. But it is not that simple in an engine cooling system because as RPM (and flow) increases, the temp rise of the water decreases, so T/S closes down and throttles the flow, which reduces power demand of pump. The power demanded by the pump goes up as RPM rises but not as rapidly as RPM cubed. So a T/S will reduce pump power demand across the board but especially at higher RPM. The worst situation for power loss seems to be running with no T/S at high RPM, i.e. pump is pumping full bore through an unrestricted cooling system. This may be why some of the dyno tests show water pumps consuming 10-15 HP at max RPM.
Pump suction pressure is 15 psi or whatever rad cap is set at, but I have no idea what pressure rise across pump is. Pressure increases as RPM squared so it probably gets pretty high at 5000 RPM, as I experienced when my heater core exploded while overtaking somebody. Say pump discharge pressure gets up to 50 psi. At a flow of 48 GPM (what the SBC was originally designed for at 4400 RPM), the power demand calculates to be about 2 HP. So I don't think a pump run with a T/S (especially a 195 T/S) takes much power.
To get demand of 10 HP requires 100 psi discharge pressure and 100 GPM flow. Maybe that is what these high performance pumps are putting out.
Sorry for the long post, but this subject combines two of my favorite topics!
Malcolm

  #64  
Old 03-25-2004, 10:53 PM
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Malky, thanx for the info! Great to have you on board!

George

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Old 03-26-2004, 05:41 AM
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This I will have to try on my 73. I have 2 different pumps, one on the car and one in the garage. I just changed the timing cover, installed new divider, but never checked clearance. I did notice, tho, that the two pumps, although both with cast impellers, had slightly different size and shape of vanes. Both are aftermarket replacement 11 bolts.

I have been having cooling issues since I bought this car in 1999. As soon as I get one thing fixed, another problem pops up! AZ heat doesn't help either!

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  #66  
Old 03-26-2004, 06:28 AM
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Squid, I'll be checking out that Az heat next week.

George

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Old 03-26-2004, 02:23 PM
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George fyi with a stamped impeller the vanes are consideribly smaller and they have on one the one i removed from my car a 3mm gap to backing plate. I measured them with feeler guages to find the gap measure . The vanes on the steel impeller do not come close to the opening of the pump 1/2 inch from center opening. The cast impeller come to the opening and were on the pump with cast impeller i have 2mm from the backing plate. I closed the gap to 1 mm as per your sketch. Sorry were metric up here . Scott

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  #68  
Old 03-26-2004, 04:03 PM
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Scott, thanx for the info. I suspected the stamped vanes were smaller, but I don't have one to inspect. Perhaps Malky has some info on how the stamped vanes perform compared to the larger cast ones.

No problem with the metric measurements, have calculator, will travel.

George

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Old 03-26-2004, 07:42 PM
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GK,

Gonna be checking out the Pontiac Heaven event? It should be a good time!

I checked my spare pump vane clearance with my spare divider plate, and found about .4" gap, even without the gasket! I mashed on it with the hammer without the gasket until it made contact. Then I put the gasket between the pump and divider, and I have a perfect gasket-thick clearance. I will try it out probably Sunday. It will be interesting because I currently run about 210 on the highway, with new oem style radiator, 180 stat with 3 small holes drilled in it, all on a stock 1973 230 400ci - no radical combo, timing all stock, etc.

It will be a good chance for some before and after, as this is the only mod I plan on making right now.

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Old 03-26-2004, 08:20 PM
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Squid, I'll look forward to your report. Gotta pack now, heading out tomorrow morn.

One more post and I'm at 1000!

George

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Old 03-26-2004, 08:36 PM
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I just remembered I still have the original low-mileage pump for the 73 455 in my FB. So I checked it out to see how Pontiac meant it to work. Unfortunately, I don't have a digital camera. The impeller is nicely cast with 8 well-shaped, properly designed vanes. It is 4.4" OD. The vanes are 0.70" high above back plate at the inlet and 0.50" high at the OD. The inlet tips of the vanes have exactly the same diameter as the inlet hole in the plate, which is 2.4" so the impeller eye matches the hole perfectly. The vane contour exactly matches the plate, i.e. the gap between the plate and the vanes is 0.06" at the inlet and it stayed 0.06" (I checked with clay) right out to the impeller OD. The impeller has 3 balancing holes in the back plate to balance thrust and reduce load on the bearings.

I then checked a new aftermarket pump I have with a stamped impeller. Impeller eye was bigger at 2.85”. OD was same. Vanes were same height above back plate. Vane contour matched plate well, but gap was a bit high at 0.13” The thing that really struck me was the inefficiency of the large cutouts in the impeller back plate (see photo in this post) which allow water to shortcut back to the inlet behind the back plate. The back plate to pump housing gap was 0.09”. To me, this explains why stamped steel impellers don’t work well.
The cast pump impeller in the second of Old Goat’s photos looks crude by comparison to the Pontiac one and also does not seem to match the plate contour very well. That large cutout in the plate will not help either as it allows water to spill back to suction. The ‘73 455 plate did not have that.

Malcolm

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Old 03-26-2004, 08:46 PM
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Thanx Malcolm. So it seems that even if the clearances were optimized, the stamped impeller would never be as efficient as a properly matched cast impeller. The parts stores had better stock up with cast impellers!

1000 posts!

George

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  #73  
Old 03-26-2004, 08:53 PM
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Remember too that these cars were built before the CIA started zapping nuclear laserbeams into the atmosphere to communicate with planet venutia. The big three and Japan designed modern engines with that in mind. After much agony I've concluded that's why these cars run hot.

You could go with the plate gap theory, but that's bordelrline paranoia. Seriously that does sound like a good idea. Reading all the posts about overheating on this forum that's the most practical thing anybody has come up with yet

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Old 03-26-2004, 10:23 PM
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<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Remember too that these cars were built before the CIA started zapping nuclear laserbeams into the atmosphere to communicate with planet venutia. <HR></BLOCKQUOTE>

Uh, Oh... I guess I better start wearing my RF shielded aluminum foil helmet to keep the Venutians from controlling my brain with the nuclear powered beams! LMAO!

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  #75  
Old 03-27-2004, 08:14 AM
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I just wanted to thank George for his brilliant suggestion, I was running hot at idle, going up to 215 and beyond and not really cooling while moving. Ive tried going with the 160 t-stat with no success. Ive got a 4 core in there and was about to get an aluminum when I saw this post. Pulled the pump, had about a quarter inch gap between the plate and impeller, did what George suggested and bent the plates in as much as possible without touching and now Im running at 160-180 on a hot day!!! Im actually enjoying the ride instead of having one eye on the gauage! Thanks George!

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Old 03-27-2004, 08:50 AM
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Contrats on the 1000 post George

I'll be trying the water pump trick this weekend as my temp would rise to 220 in traffic.

Thanks for the great tip

Andy

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  #77  
Old 03-27-2004, 06:02 PM
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Thanks Malky and Mitch! Sure nuf, when more people report success with George's suggestion, as we have, everyone WILL take notice. Ain't it great not to worry about high temp anymore!
Congratulations George, what better way to make 1000 than with this idea that really works.....
Charles

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Old 03-27-2004, 06:22 PM
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A thank you is inadequate, but thank you anyway.
I can hardly wait to look at both my SD-455s. Wow, a chance to drive and not worry about traffic.
Best Regards

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Old 03-27-2004, 07:29 PM
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You know, I think once word of the Kujanski plate fix gets around, Rodney Red is going to wonder what the hell happened to the steady Pontiac business they had.

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Old 03-27-2004, 07:31 PM
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&lt;---- I love George.

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