Been trying to figure this out.

I have a 1980s LA 360.

I do have an Edelbrock EPS intake - which should take a stock thermostat.

I have a replacement thermostat housing that looks like stock.

I ordered what I believe is like a 53 mm or something thermostat from Summit (listed as stock size). It is way smaller than the thermostat I have from the engine before which is a 63 mm (didn't check prior to ordering - whoops). The smaller one fits fine on the intake but there is so much open space in the housing that it concerns me - like it might bounce around or something. I do have the gaskets both in place - still seems like it MIGHT be loose.

Do I need to find a different thermostat? I feel crazy but I'm actually struggling to find a 63 mm thermostat.

Thanks.

 

Up to 1978 is the larger, after is the smaller. The recess to hold it is in the housing, GM has the recess in the manifold. Aftermarket manifolds could be either and some put a Chev housing on which will bolt on but have the thermostat rattle and have a loose gasket edge which could break off and block flow. Take the time to get the right stuff.