The stock SA 12A manifold has a coolant passage between the housings through the manifold. Looking at pics of the RB replacement it has these passages blocked off.

Is this just a different modle or is it safe to block off the passage?

 

It is safe. The coolant passages going through are supposed to help engine warm up.

 

I did a write up on this last week.

It's near the top of the archive called How to install freeze plugs

20mm freeze plugs are a perfect fit for those two coolant holes and will block them off quite handily. Mine are blocked off and its a good thing because I've had to remove my manifold again thrice this week (something I couldn't have done with the coolant holes open).

Jon

 

Are these passages on the 13b SE motors as well? And if so, are they the same size as the 12a ones? I've never had the intake manifold off to see. The previous owner did the swap to carb.

 

Ok, I know it helps cool the carb fuel to enhance fuel atomization but I was unsure if it was a required passage for the motor flow of coolant. Thx.

 

No, it's just a little spot the coolant can go through. Blocking the holes doesn't stop the coolant from making it's usual journey from the front housing to the rear housing (at least I think that's the way it flows).

And I didn't know if it cooled the intake or warmed it. Depending on who you listen to it eitehr cools the intake for atomization or warms it early in the process to reduce the cold start time for better emissions (the faster you reach operating temp, the faster you reach better emissions at idle)

Either way, not necessary.

Jon

 

I did use on mine quaters (25cents) one on each hole and gray silicone to cover the holes works perfect and does not leak...

 

Well I busted into my coolant passage on P port runners and jb weld and such wont hold. So I thought about blocking it off and sealing the hole. But I might as well weld it up and all eaither way. Who knows I want it runing for the rotary meet this weekend and I want to finish the shroud, get rid of the gay temp one I got.