Technical SBC Thermostat fit question

I've got a fresh Offenhauser 3x2 intake manifold on an SBC. The bore for the thermostat is cut .0685" deep. The thermostat itself is only about .0485" thick. So its got about .020" of slop. When I bolt the water neck and gasket down the thermostat can still rattle up and down in the bore. It seems like the water would just run right around it when its supposed to be closed. Is there a thicker variety of thermostat I should be on the lookout for? Could it be that the intake was overcut at the factory? Am I overthinking this entirely?

IMG_1652 by Cali4niaCruiser posted Jul 18, 2023 at 5:39 PM

 

Could always put in an o ring. Love your engine btw

 

Little bit of your favorite sealer and you'll be good.i prefer The right stuff gasket sealer

 

Good find.... but it looks like this o-ring fits round the thermostat as it has an inner groove. The video does not show that.

 

Thank you for the suggestion. From what I can tell, those thermostats came in some GM vehicles from 1988 to 1998. The thickness of that gasket is about 1/8". Tha'ts about double what I can fit in the bore. Seems like a need a thin gasket / shim.

 

Hmmm...this is new news to me. I have an engine that doesn't want to get over about 150 degrees. I have a 180 degree thermostat in it. I bought a 190 degree thermostat to replace it, to get the temp up. After seeing this info on the rubber ring gasket, it may be that my thermostat is loose in the manifold, causing coolant to flow around it, keeping the temp down. I'll be checking to see if this is causing my issue....bet it is.

 

Gotta remember it'll compress a good bit. And will shrink over time

 

Guess I never even checked or worried about thickness? I just slapped them in and never have an issue in over 50 years?

 

I had the same problem, long time to warm up and then wouldn't maintain temps driving. I ended up filing the manifold and using some right stuff and now works well.

 

Good quality sealer matched to your intake. Ultra grey will lock it place and don't forget about the burp hole.

 

You'll be fine with what you have........People have been drilling hole's in t-stats for years, hence by-passing. It will just take a fraction of seconds to fully open the t-stat with a lil leaky.......Just run it, and you'll never notice it.

 

That dude is totally from Pine Ridge by the sound of his voice!