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Reply to "Question for the team regarding 351C thermostsats"

 I do not have a degree nor any training in fluid dynamics.  Therefore, I can only respond using the figures provided by Marlin and the facts as I know them.

 One would assume the Ford engineers who designed the Cleveland plate and thermostat hat DID have training and/or degrees that would allow them to professionally design and engineer the coolant bypass feature found in a Cleveland small block. 

 The Ford engineers certainly could have designed the system with a clearance greater or less than, according to Marlin’s posted figures, the .100” clearance design they chose. But they didn’t.

Marlin chose to re-design (in his words, “improve”) both pieces of the Cleveland bypass system to allow for a clearance of just .001”. 

 If just Marlin’s thermostat is installed while retaining the Ford plate, the bypass will have a clearance of .017”. 

In summary:

.100” OEM clearance

.017” clearance with OEM plate with Marlin’s thermostat

.001” clearance with Marlin’s plate and Marlin’s thermostat 

 Any of those clearances MAY perform in a satisfactory manner. Or not.

 Removal of the plate is not an easy task; I have done this in the past. Removal may cause displacement of 45 year old debris.  The plate is not subject to wear or deterioration.   Dennis’ motor is not a bare block on an engine stand but is currently in his car.  In light of these facts I would not advise him to remove the plate, as there is no need to do so. 

 This would leave Dennis with two clearance options :

.017” using Marlin’s redesigned hat (skirt)

.100” using an OEM-spec hat

 My choice would be to retain the coolant bypass system as designed by the Ford engineers, and in order to do that I would purchase the thermostat currently offered by Tim Meyer. 


Last edited by lf-tp2511