Thermostat size. Not temp.

[TagAllen]

I recently put a Edelbrock Performer RPM Intake Manifold 7161 on my 454.

What size thermostat do I need for this? I noticed the hole looks larger then the stock manifold and the thermostat just falls to the bottom of the coolant passage. Also the housing bolts dont fit. Maybe these questions would be answered but no documentation or hardware such as plugs or bolts came with my intake. I think stuff got left out from my box.

 

[Schurkey]

I'm told that some 7.4L (454) engines used a small-diameter thermostat. No doubt with metric bolts on the thermostat housing.

I expect the Edelbrock uses the old-fashioned "standard" size thermostat, and the manifold would be drilled 'n' tapped for SAE hardware--probably 3/8-16.

I've got half-a-case of the proper-sized, high-flow Robertshaw thermostats from an eBay lot of NOS parts, but they're all 160-degree jobs; as such they're about useless.

I think you're looking for a "53mm" thermostat like this one:
https://www.summitracing.com/parts/sum-359-195

Common as dirt, they fit millions of engines from AMC to Pontiac; 4, 6, and 8 cylinders. Every parts store in America will have something to fit, in stock.

 

[454cid]

I'm told that some 7.4L (454) engines used a small-diameter thermostat. No doubt with metric bolts on the thermostat housing.

GM went to a rubber gasket/O-ring type deal..... really easy to replace as there's no scraping old gasket material. I think the associated thermostat is smaller..... I know my thermostat is smaller than what I used to see. I'm not sure when the change took place. Sometime in the TBI years, I'm thinking.

 

[TagAllen]

I ordered a thermostat. Hope it is the correct one. I believe that is the problem my 454 is from a 96. Older BB had larger thermostats.