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?wtr pmp bleed hole?

Jack

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Dec 27, 2000
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1,825
Location
Florence, SC (Timmonsville SC)
Corvette
71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
I have a few questions about a small (3/8" diameter) coolant hole in both block and water pump of my 71 small block. When viewed from front, this hole/passage is on left side of block ... at flange where water pump bolts to block. The hole/passage continues through the stock iron water pump's casting ... dropping/connecting into the lower radiator hose bib.This hole is not threaded ... and it is NOT the (weep) hole just below the wp shaft.

I have a Weiand Team G pn 8222 aluminum hi-po water pump that does NOT have this hole/passage ... and this pump is supposedly designed as anti-cavitation.

:confused What is purpose of this hole & passage? :confused Can it be closed off without having problems?:confused

:confused Can I use the Weiand as is ... without hole? :confused What are likely pitfalls of NOT having the hole/passage open & operable?:confused

JACK:gap
 
R

rpounds

Guest
I agree with Keith . . . it is the bypass hole. You don't particularly need it, but if it is of concern to you, simply drill a 3/32" (.09375) hole in the flange of the thermostat, slightly inboard of the housing. This will allow passage of a small amount of coolant until the TS opens. It also helps by eliminating any air trapped in the upper radiator hose.
 

1979toy

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Mar 20, 2001
Messages
263
Location
Wichita, KS
Corvette
Red on Red 1979 L-48
The bypass hole functions before the thermostat opens and has no further use after the thermostat has opened. To avoid cycling hot water back through the motor without going through the radiator the hole is pluged on some high performance pumps. On these pumps you need to drill bleed holes in the thermostat to keep the internal pressures from becoming excessive. Using this style of pump will lower your water tempeture 10 degrees or so and cause your car to take longer to warm up. I think it's a good trade off in a Corvette.
 

69MyWay

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Jul 3, 2001
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4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
On the V8 Fiero conversion, that hole has to be tapped and threaded for a water tight plug. The same on a stock style water pump, then the water pump gets turned upside down to fit in the frame rail.

The machine shop that did my engine machine work threaded it for me. He told me that is a very common procedure on race engines and there would be nothing wrong with plugging it off. Turns out he was right.

He always suggested putting a threaded pipe plug in the hole.
 

Jack

Well-known member
Joined
Dec 27, 2000
Messages
1,825
Location
Florence, SC (Timmonsville SC)
Corvette
71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
Must block's bypass hole be plugged?

OK guys ... Thanks! It seems the bypass hole may NOT be necessary for me. However, if I do choose to close it off by simply using the water pump having NO passage/hole ... :confused DO I ALSO HAVE TO THREAD & PLUG THE ENGINE BLOCK??:confused Will simply closing-sealing via holeless pump & gasket set me up for a pressure leak at that joint? Can I just bolt the holeless pump up without a plug in block ... or is likely to leak with no threaded plug?

Chris ... was your machinist's suggestion to always thread&plug off meant for most/all sbc; regardless of intended use?

BTW ... Weiand's online tech support is not responding:(.
JACK:gap
 

69MyWay

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Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
Jack,

He only did that on race engines, and my application as it was called for.

Tapping and threading it is fairly easy. You just have to watch the metal shavings.

I think the pump housing and gasket will hold it fine. However, if it was me I would go ahead and thread a plug in.
 

Jack

Well-known member
Joined
Dec 27, 2000
Messages
1,825
Location
Florence, SC (Timmonsville SC)
Corvette
71 War Bonnet Yellow VERT 71 BH Blue CPE (SOLD)
Thanks again guys ... I may go ahead (w/a little grease in the hole to catch the chips) and plug the block. Easy access NOW ... motor's on stand ... once in bay, it could be a $%@&%.
JACK:gap
 

69MyWay

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Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
Jack,

I forgot to mention, that I eventually took that engine out of the Fiero and put a less powerful one in it's place. Here is how I plugged the second one.

I am pretty sure I used a 3/8" tap. Tapped out the block using grease, vacuum cleaner, and a small magnet. Then, I took a low grade bolt with thread tape and screwed it into the block. I then took a hacksaw and cut off the remaining portion of the bolt.

This is how the fellow that invented the V8 Fiero kit instructs the procedure to be done. I think I spent about 15 minutes on it and it worked like a champ.

The other block got the royal treatment with a nice pipe thread plug that has a internal hex (allen wrench) type head.
 

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