Quote:

The sending units with return niples use 1/4" return... even if the supply nipple is 1/2". Since you will get supply from the sump, you could use the main supply nipple on the sending unit as return... buy whatever size sending unit you want up to 1/2".

1/4" return is pretty restrictive and may make it hard or impossible to get fuel pressure where you want it for the carb depending on pump output. I used the 1/4" return nipple for a while with EFI and an A1000 pump. With that pump, the lowest pressure I could achieve was around 30 PSI... OK in my application since I was shooting for 45 but not so good for a carb.



Thank you for this info! I had no idea the nipples were a standard size, I thought they followed the size of the pickup. In that case, if I go with a 5/16" sending unit, I can run my 5/16" line back to it and it would already be in the right spot...But im just wondering how the fuel would like going through the sending unit backwards so to speak?