Heater core bypass

[Oldsschool79]

Hello everyone, it's that time of year again. I am considering a heater core bypass valve to help keep the temp down in the car. I have the 403 and there is a vacuum operated heater valve on the back of the intake already. I am wondering if I should install an additional valve in line to the core. My question is what are the best choices and did blocking the line and interrupting the flow cause higher engine temps?
Thanks in advance for any help.

[roadking77]

I have a 400 in my 77. There was a blip on here a few years ago about how to do so. I simply put in a plumbers gate valve. It looks tacky but was easy and does the job. Havent noticed any adverse affects at all. I will post some pics later.

[Oldsschool79]

Thanks for the replies. I installed the typical ball valve rated for 400 deg. Took the car out for a long ride and I couldn't believe how much the temp dropped inside. The vents drafted ambient temp. , engine ran the same temp as well.
As for the valve on my manifold, Wallington called it, I purchased the intake used and it was most likely part of another application.

[sreta]

My 403 came from another vehicle and there was some rusted valve on the intake manifold. I bought a new one, but after reading this thread I'm not sure if this is the right part. Can someone post a picture of the original part for olds engine in Firebird ?!

[sreta]

New valve

[sreta]

Thanks for the picture. I guess I waisted 35$. Is that plug just the fitting with reduced diameter or it has some spring, rubber, whatever inside, like Pontiac style reducer ? I tried to find the answer online or the part itself, but no luck.

[sreta]

Thanks a lot. I'll get one made locally.

[Oldsschool79]

Engine is operating at normal temp. still with the 1/4 turn valve installed. I think I am going to remove the vacuum operated valve at the manifold. Wallington was correct these were never on the T/A's. Great resource here!

[Wallington]

NOS unit

GM NOS 417751 heater hose restrictor fitting 403 Olds Firebird (12) by Ben, on Flickr

GM NOS 417751 heater hose restrictor fitting 403 Olds Firebird ( by Ben, on Flickr

[sreta]

Perfect ! Ben you're a life saver. Can you measure the diameter of the outlet part ? I guess 1/4" for the small hole will be ok

[Wallington]

The pipe outlet suits a 5/8" hose. The inner ID is 1/2". The restrictor insert hole is 17/64".

[sreta]

Awesome, thanks a lot !!

[Oldsschool79]

Not sure what happened, So as I said I put a ball valve on the heater core line shutting it off. The engine ran fine, temp normal, inside temp down. Now since I did this my distributor failed. Either the stator or module went bad and shut the car down after a hot soak. This occurred twice until it finally would not restart. The distributor was only months old which less than 200 miles on it. Does anyone think blocking the line raised the temp at the rear of the block, heads or manifold causing the failure?
Thanks for the input!

[b_hill_86]

I wouldn’t think so. I’d put more money on a “new” part having poor quality control. I run a vacuum operated shutoff valve triggered by an electric vacuum solenoid/switch and keep the valve closed pretty much all summer. I arranged it so it opens when the key is shut off but I still doubt your valve killed your distributor.

[Wallington]

Not related.