boonie

On page 47 par #2 under the subheading Water Pumps and Thermostat in the book: TPIS Inside Hints, it stated there that the fellows at TPIS drill 4 .200 hole into the thermostat my question is why?
will my 91 L98 engine benfit from this?

pianoguy

It makes it easier to burp the air out of the cooling system - the little hole keeps air from getting trapped under the thermostat.

NEVRL8T

Read this before you drill holes


http://forums.corvetteforum.com/show...16&forum_id=48

Redeasysport

If an air pocket gets trapped under the thermostat it will not get hot enough to open at the right time.Air does not conduct heat very well. The little hole allows the air to escape. Some aftermarket stats come with it predrilled.

Chatman

The small hole will insure that you will not have an air pocket, and it will cause your engine to take a bit longer to reach its normal operating temperature. On my car, I did not notice a substantial difference. The idea is allow air passage and that doesn't take much of a hole.

My old Jaguar had two ball valves on the thermostat face that allowed air flow but closed under the pressure of coolant flow. Not a bad idea.

ultraviolet70

Yes, drilling large holes does defeat the purpose of a thermostat. A couple small holes will not cause negative affects though. I drill 2 3/32 holes in mine it doesn't cause any issues and filling the system is easier.

Matatk

I drilled two small holes in my t-stat when I put in the new one. The purpose was to help eliminate air in the system. I've noticed no ill effects, and my temp stays around a constant 195.

Matthew

Aardwolf

I have a balanced type 'stat in mine, it has a notch instead of a hole. One or two are fine, I wouldn't drill four.

bczee

Other than the temp statements.. it is also to increase flow of the water to aid in cooling. If you get a High Flow T-Stat, you can skip the drilling of the holes.

When you check the size of the opening and compare a check or stock one to a HP / High flow one, you will find the opening much larger.

anesthes

Why?

Mine is drilled to increase flow with the miniram. The thermostat hits the bottom before it is fully open, reducing flow. With a 180 thermostat, drilled out I get 175-185 temps with fans on at 195. Perfect for a 500hp supercharged engine.

What works for a nearly stock L98 isn't what works for everyone.

-- Joe

cwyates4

This is exactly what I experienced when I first bought my car. My thermostat wasn't opening all the way and coolant temps would never come down. I drilled 2 1/8" holes in the tstat and now my temps never get over 185.

Joe, they used to make shorter profile tstats. They worked perfectly for the miniram, but they are not made anymore. Any idea where us miniram owners may find one? I'd like to have one of those instead of having the holes in mine.

anesthes

I spoke with TPIS numerous times about it. The mfg is gone, forever. They even gave me some BS about upgrading the water neck to one that mounts the (long) thermostat above a raised gasket. After that didn't work and another phone call they told me the long thermostats need to be drilled. Drilled it, and eveything was fine.

I have some stickys on my board (TGO) about it:

http://www.thirdgen.org/techboard/al...t-efi-intakes/

-- Joe

cwyates4

That sticky is were I learned what my problem was, didn't know you wrote it.

I don't know about you, but my water neck has the recess in it, not the intake, but that still doesn't allow the stat to open fully; not what tpis told me though!

Aardwolf

Can you just make a light weight aluminum spacer for the 'stat housing? I'm not sure what the mini 'stat area looks like, just an idea.

anesthes

No. The water neck almost hits the throttle body as it is. The miniram is low profile, very short runner. It's basically an LT1 intake with a thermostat, dimensionally speaking.

-- Joe

hardlight

Those tiny holes will allow the air to bleed to the other side. The water flow across those miniscule crossections is negligable and dosen't defeat the thermostat function.

John A. Marker

I drilled a single 1/16" diameter hole in my thermostat and made sure that when I installed it the hole was positioned to the front of the engine. This way when I fill the radiator with coolant I usually jack up the front end any air in the system easily escapes because the hole is now the highest point on the thermostat. I have never had any issues concerning burping the system with this set up and it has not created any issues with tempatures. Several years back I drilled two 3/16" holes in the thermostat on my Blazer and it took forever to warm up. Corrected that with a new thermostat and a single hole and temp is fine.

1989TransAm

I also drilled a 1/16" hole in mine and have had no ill effects. As stated above a number of thermostats already come pre-drilled.

GREGGPENN

I have to assume you're referring to CCs last statement in the OP. I remember this post and was surprised by his inclusion of that last sentence. At the time, I didn't want to challenge the great and power OZ. (Seriously, it was a minor issue not worth debating. The real issue -- at the time of that post -- was several people who really seemed to think the thermostat has magical cooling powers).

As far as weep holes.... This is not a concern unless you turn your stat into swiss cheese. Keep in mind water has to FLOW to cool. A small hole will only create a trickle.

The normal small "burp" hole modification will not allow enough water to pass to create a measurable differnence. And, the ability to burp an air bubble is the reason TPIS created this tip.

mseven

I believe mfgs. of water pumps like stewart, have been saying this (adding a small hole, or 2 in stats) for quite some time.