Why By-Pass Holes in the Thermostat?

[2FAST4U]

I have heard it is best to drill several 3/16" holes in the outer flange of a thermostat when using an electric water pump (which I'm using). Can anyone tell me why?

2FAST

[CobraEarl]

Ive always heard its good to drill ONE 1/8" hole in the thermostate so you can easily burp the engine.

never heard about what you are speaking of.

earl

[Aaron Silidker]

Ive heard two 1/8 for burping purposes and that is it.

[2FAST4U]

Here is the reason holes are drilled in the thermostat when using an electric water pump (from another forum):

When the thermostat is closed it blocks water flow. With a conventional water pump there is a small bypass hose that allow limited water to circulate. With the electric pump you must block off this bypass. This means with the thermostat closed the pump will build up pressure in the block and increase the load on the pump. The holes in the thermostat allow small amounts of water to flow; this bleeds off the pressure and allows some water to circulate prior to the thermostat opening. Smaller amounts of water flowing allow the block to reach temp quickly, then the thermostat opens allowing full flow.

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[Cobra501]

Sounds about right. Make sure you use a Robert Shaw design thermostat though. Meziere says it has the best flow whice is desirable for electric pumps. You can purchace one thru Mr. Gasket.

[2FAST4U]

Thanks for tip Royce

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[Cobra501]

I got that information from the Meziere catalog in which I have the CSI catalog too. I have been doing all the research and have'nt decided which pump to buy. Another good tip if your interested.I found a answer for a expansion tank. Meziere has a waterneck with a radiator cap built in and a 1/8 NPT hole for a over flow tank.The p/n is WNOO14R(RED),WNOO14B(BLUE),WNOO14P(PURPLE ,your color) S FOR BLACK and U FOR POLISHED . Hope all this helps.By the way what made you chose CSI. [img]graemlins/grape.gif[/img]

[RoadRebel]

We use 1 single 1/8" hole and make sure its mounted with the hole at the 12 O-clock position.

Phil

[2FAST4U]

Royce-

I was thinking about the Meziere as well. Simply flipped a coin. CSI won. My short block is shipping today (Feb 13) from the East coast. Should be here next week, and then........let the fun begin

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[stang8s]

high hp motor like yours...not driven in the winter.... I wouldnt use any thermostat.

[wnstwolf]

Thanks Stangs8 I did not want to open that pandoras box but agree with you... this is what Engine Factory clearly states int he installation instructions that came with my 500hp 351... this is a debated topic but since they built my motor and stand behind it I am going with the experts.

[2FAST4U]

When I talked with CSI, they said to use a thermostat. I will try it first with a thermostat (180 deg) with a couple of holes drilled in it. If it shows signs of overheating, I will give it a try w/o a thermostat.

Thanks guys

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[bob c]

From my old racing days- no thermostat will allow the coolant to pass through the system too fast. A good compromise is to take a stock thermostat and punch the middle out. This acts like a restrictor and slows the water flow down so the water spends enough time in the radiator to cool properly. Bob