I think that the vendors of the thermostat vary the design a bit. I know what you mean about drilling the hole into "unknown" territory - but the "pill" that operates the thermostat has plenty of space back there if you go easy at it. Mine have been done by using a spring centerpunch and 1/16 starter holes. The one in the car now is the 180° part. 

 
 Steve Metzger       Tucson, Arizona

Steve,



Is that a photo of the "Mr. Gasket" 180? It looks slightly different than the one I have (mine has a raised shoulder between the poppet and outer rim).

I just did the "stove-top" test: It STARTS opening at 160, goes to 1/8" at 180, and doesn't open fully (1/4" plus) until it hits 195-200. Wish I had a spare to cut open & examine, so could be more confident/precise with the drill.

6 VOLTS/POS. GRD. NW INDIANA

I believe the "big poppet" NAPA thermostats - have 1.50 internal openings too - with a narrow 360° rim of tin around them that spans over to the opening in the intake manifold. That is where you might look to drill some holes. I don't have a feel for what sizes might fit the space.

The 5/8 tube (original bypass) has about .2 in² cross-sectional area and this arrangement we are talking of using has about .11 in² total (4 x.188 holes all together).

 
 Steve Metzger       Tucson, Arizona

I'm running the NAPA #6 stat, if I restrict the by-pass, is there a way to modify the stat for some constant flow? Gary

       

Gary, 55 Vicky, St. Germain, Wisconsin

 

I don't quite know what to think about the low(er) temperatures I was seeing - below the 180° rating anyway. I haven't looked for a 195° version of the big poppet thermostat - but I don't think Mr Gasket offers it in the large OD size (if at all). Maybe Stewart Components?

It makes sense to me that allowing the bypass water through there would be slowing the warm-up temperature some - but after 15 minutes in the garage at idle (even at 65°) - it should have been wide open. The Mr. Gasket "Robertshaw" style of thermostat has a 1.50 poppet and opens about .43 inches when its wide open - so there is a pretty big passage when it needs one - but at the tested temp, it would barely be cracked, if open at all. Maybe this particular t-stat is just calibrated slightly on the cool side. 

My only other explanation is that the increased pump and fan speed is doing some other deeds in this equation - like feeding cooler water into the engine and circulating it more rapidly. I am guilty of making too many changes at the same time here. Should have installed the modified thermostat - tested for a stable idle temp....then fitted the bypass plug...... and after that, fitted the pulley.

 
 Steve Metzger       Tucson, Arizona

If the additional bypass holes in the thermostat lower it's minimum running temp in every case (?), them maybe starting with a 190 degree model might be best?

Also, I'm considering this mod. (plus bypass hose restrictor) as a form of thermostat failure insurance (I believe the fail-open brands only come in high-temp/small opening configuration?).



6 VOLTS/POS. GRD. NW INDIANA

Steve; I really didn't care for the look of your "Caution Fan" sticker, either- I pondered it for a few days and (believe it or not) did the same thing on my fan Great minds do think alike.... /Duck

BOO- YA!!!

Steve, love that propeller! should have the T bird goofs rolling in pain, ha, ha.

  AussieBill            YYYY    Forever Y Block     YYYY

 Down Under, Australia

I finally got a chance to go out in the garage and put all of the danged watersupply parts on the T-bird. Everything fit together OK - and that small pulley really makes the fan whiz (its about 20% overdrive). The extended nose of the 302 pulley doesn't look too bad in there, but T-bird guys will know the nose spacer is missing right away. It reduced the required fan belt size from 40-1/2 to 40 (I've also got a reduced size alternator pulley in the mix too). I put the restrictor in the bypass hose with a 3/16 hole as Ted recommended.

Testing....The temperature here wasn't cool enough (below 60°F) to see the "cold weather" performance - and it won't get over a hundred here until May. In a short term idle test, the thermostat housing was running right at 170°F - still true to the 100° over ambient I found before. With the radiator cap off - and looking in there with a flashlight - things seem to be stirring a bit more than before. Seems like there could be a calibration problem with the 180° thermostat - or the three holes in it are passing  plenty of water for idle cooling at this ambient temperature with the fan and pump cranked up. 

I understand why Eddie Paskey is running a clutch fan on his outfit......but at idle it would still be moving right along as long as it is a speed type clutch and not a "thermostatic" type.

Got rid of the goofy "Caution - Fan" sticker I had on the shroud and painted the fan tips like a prop....

 
 Steve Metzger       Tucson, Arizona

"I see.....said the blind man" - the air bleed-back feature, when the engine is stopped vents air bubbles up to the intake manifold. Drilling the brass plug for an air bleed won't be a big deal for sure.

For those that haven't seen the thermostat modification -here's the place where the three holes get drilled in the "Robertshaw' style of t-stat to replace the bypass.

 
 Steve Metzger       Tucson, Arizona