Hello all,I have a Holley 390 cfm carb comming and I already have the late B manifold ready to install.I want to use a phenolic spacer.Is the Mr.Gasket 3404 going to be correct for this setup.I am not after power just want a good running stock motor.I will also install a new thermostat at the same time.What temp should I use?By the way I do already have the 57-up distributor.Thanks Mark

  

Dunno about part numbers from the other vendors - but Speedway has a 1/2" phenolic spacer P/N 545-64945 ($31.99). It is made for the smaller base plate carb - like the 390 CFM Holley. The bores are 1.467 diameter.

Get a "Number 6"  thermostat from NAPA - assuming you have one nearby. It has the larger 1-1/2 poppet opening and has a 170° opening temperature. Alternately - get a Mr Gasket 160° "high flow" thermostat (also 1-1/2 poppet size) for a big block Chrysler (also fits the Y-block) and modify it with the three extra 3/16" holes shown in this photo.

 

Visit the Stewart waterpumps site for an explanation of the "pressure balancing" holes. They are easily drilled at home - or you can buy the modified part directly from Stewart. My guess is that they add maybe another 5% to the flow capacity of the "Robertshaw" type thermostat (which is reported to flow better than the other poppet styles). 

 
 Steve Metzger       Tucson, Arizona