Flow Restrictor - What's inside? - Chevy Impala SS Forum
 
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post #1 of 10 (permalink) Old 10-26-2016, 10:48 AM Thread Starter
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Flow Restrictor - What's inside?

After some recent discussion about the Flow Restrictor that's located on the Heater Hose, I wanted to post some pics of this part. There have been many discussions on this part and if it needs to remain in the system or not and what GM's thinking was in having this on the LT1's.

While some members have removed it without issue, there are some that feel it is important to keep it. It was believed that this was just a piece that had a smaller end to it to restrict the flow but this is actually a variable restrictor. I took pictures of one opened up and posted before but had a heck of a time finding that link. So to make it easier for the next "Searcher", I thought this thread title may make it easier.

https://www.impalassforum.com/vBullet...26-post20.html

While there is other info on this piece with links to other Forums that may better explain this part, hopefully others can add to this Thread as these links pop up. Feel free to add away and anyone looking for info on the Flow restrictor may find it all in one spot.

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post #2 of 10 (permalink) Old 10-26-2016, 11:15 AM
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While mine's still installed in the heater hose circuit. I suspect it serves little (if any) purpose for those of us with electric water pumps that always turn around the same speed,and rate of flow...

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post #3 of 10 (permalink) Old 10-26-2016, 11:37 AM Thread Starter
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Quote:
Originally Posted by 1slow96 View Post
While mine's still installed in the heater hose circuit. I suspect it serves little (if any) purpose for those of us with electric water pumps that always turn around the same speed,and rate of flow...
Think you hit on something there. I seem to remember a link from another Forum that said GM added it to get Flow lower at high RPM's. This is assuming stock Mechanical Water Pump.

So I think you are right that is running a Electric Pump that flows the same, you could probably just remove the restrictor. Another Plus maybe for those considering going electric. Read here somewhere that those that removed the Flow restrictor, instantly had better Heat in the car.

If I find that link, I'll add it here later. Always good to try and keep info in one link if we can and why I decided to start this thread. Often times the info is out there, you just got to dig through numerous threads to find it.

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'95 Caprice SS conversion - Bonny Buckets - 96 Column, Shifter and Console - 3.73 Gear and Herter tune - Z/28 Cluster - Blazer OH Console - Green/Pink bushings - Chromed Impala Wheels - Eibach Springs and Bilstein Shocks - Corvette Engine Dress - the list goes on and still more to do...it never ends.
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post #4 of 10 (permalink) Old 10-26-2016, 01:11 PM
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my assumption was the re-stricter was to prevent full water pressure from entering the heater core when the stock WP was spinning at higher RPM's. IDK if it was to prevent the heater core from rupturing when motor was being operated at high RPM's

Agree that a EWP would likely mean the re-stricter is not needed...but I have one with my EWP. Also running a 160 so my heater is not a oven like my other cars but does work...although here in SoCal it is rarely used.

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post #5 of 10 (permalink) Old 10-26-2016, 04:52 PM
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The 91 models did not have a restrictor as such. They used a vacuum activated valve, that diverts some or all of the water back to the radiator when the AC is engaged. I do not know why GM changed it except that it is a lot more expensive than the restrictor, and more subject to failure, because it has moving parts and a potential vacuum leak.

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post #6 of 10 (permalink) Old 10-26-2016, 06:10 PM
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The 305 running out of power around 4000 rpm may have something to do with it...

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post #7 of 10 (permalink) Old 10-28-2016, 09:48 PM
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Quote:
Originally Posted by Fred Kiehl View Post
The 91 models did not have a restrictor as such. They used a vacuum activated valve, that diverts some or all of the water back to the radiator when the AC is engaged. I do not know why GM changed it except that it is a lot more expensive than the restrictor, and more subject to failure, because it has moving parts and a potential vacuum leak.
The boxes (with A/C) had the same setup. They also had the HVAC suitcase on the engine side of the firewall--much less contortion required to R&R either the heater core or the evaporator.

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post #8 of 10 (permalink) Old 01-28-2017, 10:08 AM
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Is this it

Recently as I was driving home the Fleetwood it began to stumble. I felt that if I didn't continue to press accelerator (letting my foot on/off) that the car would turn off. Pulled to the side and parked it. Press the accelerator gradually and before I knew it STEAM began to come out on either side of the hood.
Towed the car home as it was already dark and couldn't do much. Next day I checked and realized it was this restrictor valve (missing pieces as it crumbled when removing):




As someone already mentioned in another thread there is a spring inside of it so it's not just a hollow plastic piece.
Good thing replacements are still available.

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post #9 of 10 (permalink) Old 01-28-2017, 10:33 AM
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Compared to the pics in Post #1 mine came apart clean at the glue seam. Your looks all the world like it got burnt (or excessively heat-baked) on something.


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post #10 of 10 (permalink) Old 01-28-2017, 11:13 AM
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Baked

Baked indeed. I blame the BORLA HEADERS...I should have protected it better.

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