I havent posted in a while, but I need some help. I installed a new Edelbrock Performer RPM. I'm having a problem finding the right size heater hose fitting. The one closest to the brake booster is 3/8. The passenger side is not 1/2 and 5/8 could take a thread. I dont want to cross thread anything. I know I could alwyas run the hose to the drivers side, but I still need to know the size if I were to block it off. Can anyone offer some insight?

 

Cut the head off of your old heater control valve and run your heater core line to that pipe.
If you want to block it off, just pinch the pipe closed and weld it shut.
Saves a trip to the hardware store.

 

That's supposed to be pipe thread, which are tapered. If the threads weren't tapped deeply enough, that could be the problem.

 

Joe,
Do you think i should run a 5/8 thread chaser through it? I'm trying not to ruin a brand new intake, ya know...

 

I would run a PIPE thread tap through it. I assume that's what you mean. A standard 5/8" straight thread tap is not correct.

 

Make sure you are trying a 5/8" pipe thread fitting and not a fine thread fitting, that could be your problem. You can find brass pipe thread fittings at the plumbing or hardware stores at least around here you can no problem. Good luck

 

I'm going to give Edelbrock a call on Monday. I measured the diameter and it looks like 15/16th's.

 

Well, the tap drill size for 3/4-14 NPT thread is 29/32", so that sounds about right.

 

This link might be helpful:

http://www.plumbingsupply.com/pipethreadsizing.html

 

Joe
I talked to Edelbrock and was told 3/4 NPT. I picked up a fitting and will try when I get home this evening. Thanks for the link the chart BTW. I'll let you know how it goes...

 

As Joe says pipe thread is not like std threads. I 3/4 bolt will fall through a hole for 3/4 pipe.

 

Gothcha. I went to NAPA during my lunch break. The fitting I picked up was 3/4 NPT as stated by Edelbrock. I'm hoping this works.

 

Seems like it is 3/4 NPT. I tried a bushing and was going to add a 1/2 heater hose fitting, but I don't like the look. I'm just going to order the correct part. Thanks for all your input guys...