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TR2/3/3A 4lb. TR3 Radiator Cap

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prb51

prb51

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Gents,
Is there a down side to using a Rad cap rated for more lb.s pressure if you've replaced your radiator with a new alloy unit?
Is the 4lbs psi related to other components in the system (figure 8 seals etc.?)?
What psi would you rec other than stock?
 
Weak link may be the heater if you have one installed. If not, though, I'd think you could easily go up - TR4s for example use a 7 lb cap.

Randy
 
Randy,
I do have a heater and good point. Right about the 7lb unit though....does the TR4 use the same smiths heater?
 
Can't prove it, since my TR3A didn't have a heater; but I'm guessing it would handle the extra 3 psi. The output pressure from the pump goes much higher than the cap pressure anyway, and the heater sees most of that.

TR4 heater is definitely different, tho.
 
Yep, TR4 heater is different - no proof but I suspect it is the same as a TR6, and I think they use a 13 lb cap, which makes me think they were pretty conservative on the cap ratings.
 
I'm using a 7# cap on a heated TR3. No problems (yet). The Tr4s, with the same fo8 gaskets as a 3, use the 7# cap, so that's not not going to be the problem.
 
I'll try the 7Lb. Want to raise the boiling point a bit. My heater is rebuilt and in good shape and I suspect the extra 3 lbs of psi wouldn't affect it much.
Thanks for the input.
 
Everything in mine is new and I still use a 7lb. cap. It's fine in the summer and winter, so I leave it alone.
 
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