Aluminum Head Nipple Restrictor Mod?
 

It's been mentioned here several times that a restrictor should be inserted in the hose from the passenger side head to the heater core, particularly when using aluminum heads as the nipple screwed into the head does not have a restriction. Sometime ago, I saw a post showing a pipe plug screwed into the threaded end nipple. I'm curious what was done to accommodate a pipe plug as a 1/4" is too small in diameter and a 3/8" is too large?

Pic of the type of nipple that goes in the aluminum:

Cant comment on the barbed fitting, but another way to restrict the coolant flow to the heater core is to use a thick stainless steel washer placed right at the heater core inlet, I did that on my aluminum head engine 10+ years ago and it seems to be working fine, no problems with the heater core... but I have also read & seen where nothing was used to restrict the flow and no problems with blown out heater cores.

I have not used a restrictor on my KRE headed engine for 10 years and have not had any issues. Original heater core to the car as well.

I didnt want to chance it so i put a small rubber hose inside the heater core hose. seems to work fine with the 15yr old heater core. E-heads fwiw

Thanks all - some good Ideas! To me the small effort is worth it. Not doing the mod and not having issues is only anecdotal evidence, and I suppose the same for those who have done the mod and haven't had issues - but certainly a cheap price to pay.

indimanjoe - that's pretty slick - is it like a 1/2" hose you used?

If you look at the original heater core (if you still have it) the inlet is restricted so another restriction would not be needed. The tube of the heater core is bent inward in about 4 places at the very end where the hose goes on.

Yep - I've seen that on my 69's heater core- apparently the factory wanted a restriction. Unfortunately, the replacement core has a round opening.

LOL i wish i could say what size it was. it was in my box of hoses etc.. it was a tight fit but so far no issues. roughly 3k miles this summer and no issues.

Since your hole size is somewhere between fitting a 1/4 or 3/8 pipe tap find a regular straight thread tap and thread it for a non-hardened set screw. Loctite the set screw in place then drill a 1/4” hole through it.

It’s not like you need to seal it so a pipe plug isn’t necessary.

Just crimp the tip of the brass core inlet tube

If you are using a brass fitting just solder the hole closed and drill a new hole any size you like.

I used this on my new build with KRE heads. Ounce of prevention:

https://jagsthatrun.com/products/hea...=6291689799723

I'm late to the party again. Originally installed the restrictor from the bottom, but now installing them from the top.

where did you get that setup

The nipples came with the heads and the inserts were whatever I could find in my brass fittings bucket. The second pic insert started out as a pipe plug and I drilled a 1/4" hole through it and chamfered the hole.

It seems a lot of us did the same thing with drilling an insert in the brass fitting for the Edelbrock head. Mine was drilled a 1/4" also.

Edelbrock heads, replacement heater core, ac pullies, high flow water pump. Worked for 25 years, no restrictor, no issues.

If you have an older (or original) heater core, you'll see that the end of the 5/8" hose nipple is "crimped" which acts as a restrictor. New heater cores haven't had this feature for many years. You should probably run a restrictor with a new heater core. A piece of 5/8" OD teflon round stock with a 1/4" hole worked for me.