Cap in stock place or an offset pressure cap?? No pressure stock would be OK, but there are actual cooling advantages to pressure (not the "pressure will allow you to drive 15 seconds longer before it boils" crap!) If you go to an offset and want period, see if you can get a big diameter cap flange as in early Ford. Then you can use a Ford pressure cap, still available because apparently it has truck uses.
Then...modern or original radiator/tank?? Big old tanks really do have too much flex under pressure to take much. Even on my '48, I have watched the tank bulge and relax under warmup and cooldown. I would assume a modern streetrod tank would be braced. The postwr '46-8 cap is big, so it doesn't look common, and available new. There's one in my kitchen somewhere, If I can find it I can give you a number. I think suitable necks must be out there as big truck parts...apparently they still use the early Ford style flange.
A couple of thoughts that might be of interest... I'm running a stock 49 Merc with an original Deuce radiator and the stock chrome non-pressurized cap. If you want to fill the shell and still run a period cap be careful of the neck that you get. Most of the radiator necks on street rod radiators are made for the modern pressurized cap. It might be difficult to find a period cap to fit the modern style. I'd get the cap first and get a neck to fit it. Mac's sells non-press. period correct caps (35 up) and rebuild kits. They also sell a 4# cap but it has "Mexico" stamped into it. Most people would not care but I believe you might. I have cooled a few relatively stock engines with non-press stock Ford radiators and I personally believe a press. cap is not needed until you get to large cubes or add on AC. etc..
My car is already done i just need a cap that looks good.not a auto zone one .i have stock rad with off set neck.billy
The Jalopy Journal
