So short back story (and then long current story lol) im in the process of getting my truck back on the road after 4 years, put a new to me (not junkyard but sat for years and came out of an 89 truck) engine in and got it to sneak past the PA inspection so that I could actually use it and work on it. As soon as I got it home the thermostat housing was squirting out the bottom. I had replaced one of these in the past with no issues but I cannot get this one to seal for the life of me.

I have been through 4 different brands of thermostats and each one leaked equally. One was definitely my fault (the thermostat fell and blew out the gasket) but I'm wondering if there's anything else I'm missing. Each time I cleaned off the old gasket well and the last 2 times did the "sandpaper on a piece of glass" flattening trick to make sure the housing was flat. Also took a very fine file to the intake side (edelbrock torker 2) followed by 320 grit sandpaper to smooth it out and everything seems flat even the thermostat fits reasonably well into the channel.

I found a used OEM thermostat housing to replace the cheap parts store one (that's coming on Saturday) to hopefully help with the issue but then I came across the difference in gaskets when I cross referenced an 85 mustang thermostat and it's a completely different part number.

It seems as the one is more of a universal one and the other is a small block specific. I was wondering if the 35440 would fit and be worth trying. In my mind the block should be the same and it's made for 302's it should fit, but felpro doesn't push it like the other part number

If anyone has any knowledge on this It would be great, this constant leak is driving me absolutely mad

 

sorry but as far as felpro goes i refuse to use them , have suffered to many issues with head gaskets leaking oil or coolant,

 

What gaskets have you had luck with? I'm open to try anything at this point lol

 

I'd try the FelPro that's specific for the engine, not the universal one. Use sealant to secure the gasket on the thermostat housing then install it. Sorry, I can't help you with the 302 question, but I've used plenty of FelPro gaskets. They're the best.