low_psi

Don't need to get into all of the details, but long story short I had my 496 PCM Flashed with the Whipple Stage II Flash, which when sold as a kit runs a 120 degree thermostat and 91 Octane Fuel (minimum). However I currently don't have a 120 thermostat..... I am waiting to hear back from Dustin @ Whipple, but in the meantime would ike to here from you guys.... Would it help matters if I swithced to a 140 degree thermostat until I order/receive the 120 degree thermostat from Whipple? Would running the stock 160 thermostat be safe or am I looking at major detonation (bye bye hyper pistons...)?

low_psi

Would pulling the thermostat out and running without it be ok for the weekend (until I can take delivery of the 120 t-stat)? I want to use the boat this weekend but I also don't want to damage it either.....

The 140 t-stat that I found is looks a bit different from the 496 160 t-stat. I have included pics of each. Outside of appearance is there a major difference in their function?

I am not trying to cheap out. I WILL be buying the 120 stat from Whipple, I just need a temp solution to get me through the weekend...

The standard 496 160 degree t-stat:


The 140 t-stat that I was able to find locally:

MikeyFIN

drill a few small holes 2-3 in the flange , that will keep your temps down and even. Doi not run without a T-stat.. you'll get too much airpockets and hotspots in your heads. Never IMO run without a T-stat unless you plan to run on IDLE ONLY as the waterpumps flow too much to cool properly even at idle.

low_psi

I tried out the 140 T-stat pictured above. I also added 4 small holes in it to keep the water pressure from blowing the t-stat open. I was told by my mechanic the plate/sping in the 160 t-stat pictured is to keep the water flow/pressure from forcing the t-stat open. Anyway, I am not sure it did any good as my gauge still reads about 170 degrees. I took it for a ride and it runs very strong, but I will keep out of the throttles and take it easy until I receive the 120 t-stat from whipple.

But I will say this, what a difference the flash made. Because mine was running so damn rich before I was never really able to get it to run much harder than 4500 rpm. Now it hits 4500 rpm with a ton of throttle left. Mid range feels very strong, and time to plane was cut almost in half. I am a very happy boater!!!

Back4More

Did you get the 120 stat in yet? What temp does it run?

fountaincruiser

Has anyone used the 120 thermostat in a stock 496 HO?

If so... how did it perform?

Does anyone know of a 140 deg replacement?

low_psi

I did get the 120 in. It now runs at about 150 - 160. At idle she hits 140. But at no time (so far) has it gone over 160. I see a bit more soot on the back with the 120 stat but i can live with it.

fountaincruiser

Thanks.

I am in South Florida... so the water is usually pretty warm to begin with.

low_psi

Unless you have had the PCM flashed with a STage 2 program, i don't think there would be any benifit to running a 120. As a matter of fact it would probably soot up pretty bad and get poor fuel economy..... I had the stage 2 flash put on my PCM and it requires a 120 t-stat. A stock PCM is designed to run a 160 .....

Back4More

Merc does make a 143....had those in my 502's way back when.