VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 Water Pump Baffle Plate clearance

I removed my water pump in order to replace it with a new one.

During the process I was checking the baffle plate as best I could since it's hard to see it with the radiator in place.

With some simple (crude?) measurements, I found that the center of the baffle plate is slightly bowed-in about 3/16".

So the question is "Is that too much?"

In thinking about the cavity where the pump fins turn, I would think that any excessive width would greatly decrease the efficiency of the flow rate. But how much is too much?

Thoughts?

Here's a draft web page where I've posted photos and comments.

--Bill B

Hello Bill Barker,
I bought both new style pump and baffle plate from the Filling Station at the time when the pump had the reduced price. It's another of those 'in the future jobs', so it's still waiting to be done. Now that I've read your article discribing the change over, I am less baffled about the baffle plate. A 'what if' question please. What would be the fix if for some reason the new baffle plate is loose when pressed into position? I don't anticipate this, but 'what if'? Thanks for sharing your knowledge.

Having experienced that problem, I can tell you how I dealt with it: I simply "staked" the brass baffle plate in place using a center punch. By center punching all around the edge of the disc, it expands it enough to hold it firmly in place. I placed punch marks about every 1/4 inch all the way around the plate and about 1/8 inch from the edge. Worked like a champ. Hope that helps.

All the Best, Chip

There are several other ways to correct the problem too and that is to install the baffle plate with either JB Weld or Marine-Tex. The flange on the block has to be very clean when this procedure is performed.

Another way to correct the problem (it is a lot more work and more expensive) is when the engine is out for a rebuild, take the bare block to a machine shop and have a new, oversized flange cut into the block with a mill and then press in a new, oversized baffle plate.

In the past, I've staked tapered bearing races that have spun in a hub in similar fashion. The difference is that you center punch the hub itself to "raise" the metal where the outer race is pressed into. You go around at the same sort of intervals and depending on depth, one, two, three, etc. rows of dimples. Then press the race into the hub and it stays locked in place. Not sure if doing the outer block first, then press the baffle plate would work the same way. Luckily, when I put in the new BB water pump my baffle plate and block were in excellent shape and didn't have to contend with this issue.

Four replies.... but nobody is addressing the question "Is 3/16" too much indentation on the original plate?"

I think "yes" since a replacement plate wouldnt' have any indentation - ever!!



-bb

I think you are correct. The plate should be flat for best efficiency. The center is mostly covered by the impeller so it is not a much of a problem as at the edges.

Hey Bill,

Thinking about this last night some. I would think your correct about this being too much. Question, what is the outside edge like? Could this be from when someone installed it? Or could it be form the guys that did your engine work? Being that this is just a very large freeze plug, I think the dent is maybe from installing it. Also it the dent is mostly in the center, I would agree with Chip as it might not be as much of a problem as at the edges.

Can you measure the diameter of the propeller and measure the depth in that area on the baffle plate?

There really has me baffled!

Just talked with Steve Kassis about this too. I "think" that the tolerances in these old engines were sufficient to get-by with this kind of slack. But, in reality, they were DESIGNED to be closer tolerances.

Being a blue-water sailor, my initial concern was cavitation being introduced by this wide area on both sides of the impeller (ie. high and low pressure sides of the spinning fins).

I'm thinking that this might be a good "learning" experience to pull the radiator and replace the existing brass plate (cup-style). I'm trying to think of how to measure the water-flow of this contraption (outside the car).

-bb

Would applying heat concentrated in the center then quickly cooling it help shrink the dent out? Not sure if it would work on the plate as it is brass isn't it? I know mine looked like brass.

I don't think the difference would matter much as the pumps are not high volume or pressure and the tolerance shouldn't come into play that much. Good flow through a good radiator is more important than that small difference.

While you're thinking about this, can anyone describe what the purpose of the "drain hole" in the bottom was for?
Steve thinks that it was gone by 1935 or so.

Did it provide a feedback loop to keep water in the lower section of the impeller fins? Again as insurance against cavitation?

(yes... I've got cavitation on the brain)

Now up to 40 photos on this web page.
http://1931chevrolet.com/waterpump.html

I should have titled it:
Everything that you didn't need to know about a water pump.



I'm still open for comments/suggestions. I'll probably publish the page this weekend.

The drain hole purpose is to allow the water that might leak past the seal to drain before it washes out the grease from the bearings and totally fails. Also a good indication it's time to replace the pump and if you do it before total failure you won't have to get towed or change the pump on the road.

The baffle plate front surface should be installed exactly 1 inch inside the cavity. Since the water pump impeller is an inch in thickness the gap between the impeller and baffle plate is essentially the thickness of the gasket plus maybe a tad.

I haven't given enough thought to the extra hole. Maybe after I sleep on it will have a brain storm.

I can recall a technical article in the G&D quite a few years ago where it was recommended to drill several holes in the impellor to improve efficiency , I can't recall the theory behind it but it would be interesting to read again if anyone can locate the article or knows who wrote it.

Thanks Steve. I'll do a "deep search" inside the pump tomorrow to see if I can confirm visually the packing drain idea. Sounds interesting.

Chip, the impeller is almost exactly 15/16 of an inch wide. So a 1 inch setback for the baffle provides 1/16" plus the gasket width. I think that that clearance is within tolerances and the pump would provide sufficient service.

What my problem is, is that the baffle is indented by about 2/16" at the MIDDLE of the baffle. I was trying to decide whether that was sufficient to warrant a replacement of the baffle. As you can see in my photos, that gap is pretty darn small, all things considered.

Michael -- I need to find that article. Standby......

The small extra hole in the pump body is at the lowest point of the block water passages,thereby helping you drain as much water as possible from the block if it doesn't have a drain petcock in it.The 4 cylinder water pumps had a similarly placed hole in the pump casting & water pump baffle plate for the same reason.

The article on drilling holes in the water pump is from the October, 1987 G&D titled:

Gaining Efficiency From the 1929-34 Water Pump

It was written by Larry Jackson, #04974. Larry took the pump to several pump experts and they all concluded:
"The design of the rotor causes a cavitation just in front of the baffle plate, rendering the rear fins almost useless."
Fascinating article. I thought about drilling holes in the pump on my '30 Coupe, but it runs ok right now, so I'll just let sleeping dogs lie.

Happy Motoring,

Dan

Thanks Dan. That's an excellent article.

I found it, and scanned it. I'll be adding it to the Members area (Archives) when I get a chance.

Well, the jokes on me. I scanned all four pages. Cropped them and cleaned them up a little bit.

Had to search for the Admin id/pw to get into the ARCHIVES database. Once I got there, I found that the full article was already posted!!!!

If you want to read an excellent description of the 1931 water pump and how to improve it, go to http://vcca.org/members and after you log in, go to the Resource Center, then G&D Magazine, then Articles-Archives. Search for "water pump Jackson".

Chow!!

Bill if you follow the logic of the Larry Jackson article the rear fins don't work anyway so the extra clearance at the centre of your baffle should make no difference.
I bought a 1930 Coach about 20 years ago that ran fine but had an intermittent overheating problem and when I pulled the water pump the baffle fell out and when I measured it it was 7mil or over 1/4 inch smaller than the opening and had obviously been spinning for years until it wore down enough to move back and forth in to the block and I suspect that the impellor rotation kept the loose baffle close enough most of the time but as soon as it moved back the heat rise was almost immediate and as soon as the impellor pulled it forward the Coach would cool down just as quickly.

Thanks Michael.

I came to the same conclusion this afternoon after reading the article and looking again at the new impeller. The majority of the "pumping action" is done in the front 2/3 of the impeller.

I reinstalled it with the original baffle plate. Then I raised the car and added a shim to one of the body mounts in order to raise the driver's door.

Lastly tonight, I took the driveshaft bell housing off. I'm trying to figure out how to stop the universal joint from rubbing against the bell.

Maybe tomorrow or the next day I'll put water back in the radiator and give the new pump a test.

To finish this discussion - I installed the water pump with the original baffle plate. Drove it about 6 miles so far. Looks good and sounds good.

http://1931chevrolet.com/waterpump.html

-- Bill B