What have you done to your square lately??

[Ricko1966]

I have noticed many of those "restricted" nipples over the years, but never put 2 and 2 together. I always just assumed that the nipple was a thick casting for some manufacturing reason.

My ignorant self has replaced them several times with more open fittings and never noticed a difference in heater performance. Maybe it doesn't matter so much, or maybe I'm just ignorant... it could be either, lol.

Or lucky. They restricted the flow to prevent heater core failures. We had one guy on here that his suburban wasn't warming up fast enough on the gauge. He said once he put the correct fitting in his problem was cured the heater core was bypassing too much coolant. I've only heard that once.

 

[Grit dog]

I have noticed many of those "restricted" nipples over the years, but never put 2 and 2 together. I always just assumed that the nipple was a thick casting for some manufacturing reason.

My ignorant self has replaced them several times with more open fittings and never noticed a difference in heater performance. Maybe it doesn't matter so much, or maybe I'm just ignorant... it could be either, lol.

Same.
Makes total sense but if I had to guess it may be for quicker warmup and the Heater doesn’t need full flow to pull good heat.
I do know a heater core and fan will pull a lot of heat off.
Used to cheat in demo derby and keep coolant in the system (rules were water only because 90% of cars would loose their coolant getting smashed.
I’d hook the upper and lower rad hose together and leave the heater cranked on high temp and fan. It was enough to keep the engine alive and you could go around smashing cars with the front of f your car without busting the radiator!

Edit. Dint read Rick’s last post before posting

 

[Tank6x2]

Spending the weekend on mounting the new fuel tank /rear crossmember, ordering more insignificant/random don’t need now need later parts, Merry Christmas to all next week!

 

[gilby959798]

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Working on the rust repair little by little

 

[Blue Ox]

Or lucky. They restricted the flow to prevent heater core failures. We had one guy on here that his suburban wasn't warming up fast enough on the gauge. He said once he put the correct fitting in his problem was cured the heater core was bypassing too much coolant. I've only heard that once.

Extra bypass may be another effect, but they're usually made with a restriction because heater cores can moan during acceleration if they're not flow restricted.

 

[Terlingueno]

Or lucky. They restricted the flow to prevent heater core failures. We had one guy on here that his suburban wasn't warming up fast enough on the gauge. He said once he put the correct fitting in his problem was cured the heater core was bypassing too much coolant. I've only heard that once.

What does one of these "restricted" units look like?

 

[Ricko1966]

What does one of these "restricted" units look like?

Bottom right corner of the manifold

 

[Terlingueno]

Bottom right corner of the manifold

Were they only on Corvettes? I am using the OEM unit off the original manifold on my Edelbrock and I don't think the hole is that small in diameter.

 

[Ricko1966]

Were they only on Corvettes? I am using the OEM unit off the original manifold on my Edelbrock and I don't think the hole is that small in diameter.

No it wasn't just on Corvettes. I don't have a definitive list as to whether every small block Chevy made had one but even the smog dog 71 307 that I checked for @PrairieDrifter had one.

 

[Grit dog]

@gilby959798 and @Tank6x2 lots of awesome work going into those trucks! Kudos

 

[Old Guy Bill]

Almost every heater hose system in that era had two hose sizes, 5/8" on the
restricted (outgoing) and 3/4" on the input side of the core.

 

[Terlingueno]

Almost every heater hose system in that era had two hose sizes, 5/8" on the
restricted (outgoing) and 3/4" on the input side of the core.

Mine is 5/8" from intake to core, 3/4" from core to radiator. The ID of the unit in Ricko's pic looks smaller than the ID of the one on my truck. Perhaps my eyes/memory is fiddlin wid my perception

 

[Ricko1966]

Mine is 5/8" from intake to core, 3/4" from core to radiator. The ID of the unit in Ricko's pic looks smaller than the ID of the one on my truck.

The one I measured is a loose 5/16ths

 

[PrairieDrifter]

I have noticed many of those "restricted" nipples over the years, but never put 2 and 2 together. I always just assumed that the nipple was a thick casting for some manufacturing reason.

My ignorant self has replaced them several times with more open fittings and never noticed a difference in heater performance. Maybe it doesn't matter so much, or maybe I'm just ignorant... it could be either, lol.

I've done the exact same thing. We're the smart ones ya know

"nEeDS MOrE fLOw"

****** hilarious lololol

 

[xm20k]

Almost every heater hose system in that era had two hose sizes, 5/8" on the
restricted (outgoing) and 3/4" on the input side of the core.

You have that backwards 5/8 feeds the core and 3/4 is the out flow. The different hose sizes are to maintain an optimal pressure differential as the fluid expands into the larger space of the core it also reduces back pressure and slows down allowing for more contact time to transfer heat.

Gm used to use 5/8 for both untill the late 50s. The inlet is almost always on the lower side to prevent noise from air flowing into the core and causing a gurgling or burbling noise.