RIJVETTES

Hi guys. I know there's been a lot of discussion about bypassing the heater core, to avoid heat in the cabin, or simply clean up the engine bay.

Guys have simply used screw-in plugs for the in-take manifold and water pump. Some have argued that the plugs cause heat spots and insufficient water thru the pump.

Others have recommended installing shut off valves on the heater hoses- to allow or cut off flow thru the core, depending on weather conditions. This seems to makes a lot of sense for those with hot summers and cold winters.

Still others have created a bypass hose whcih simply connects the manifold to the water pump- and keeps the fluid running, but bypasses the heater core. The trouble is , the water pump connection is 3/4" and the manifold is 5/8". Difficult to find a single hose; or a little clumsy to install a plastic reducer and clamps between the 2 hose hose sizes.

I have a modified 80 vette with a 350 and AC delete. I live in San Diego and have never used the heat. I also wanted the clean up the engine bay by eliminating the heater hoses. After long on-line research, I've found the PERFECT FIT BYPASS HOSE FOR AC DELETE 350 ENGINES:

AC Delco no. 20337 S.

The hose is 18" long, the perfect U-shape and has 5/8" and 3/4' ends. Easy install with 2 clamps on the manifold and water pump. I think it was about $18 or less at Rock Auto. There are comparable hoses from other makes , but their photos seem to show that one of the U shaped arms is too short. I have never seen their actual product and I went with the AC Delco which raised no issues.

Now for the fun part. It twas designed for a 6 cylinder IZUZU!..... Hey, get over it. Its a good hose that fits!

oldalaskaman

excellent , saved,

CA-Legal-Vette

Well done!

I'm not sure that I buy the issue about using pipe plugs, but if you already have the pump outlets, this is a perfect solution.

flaco1801

Seems a 18 hook is too big....are you cutting the hose in the middle and adding a coupling with hose clamps to make the right fit? good work thanks,,,

RIJVETTES

No modifications. Remove the 2 old heater hoses. Install the bypass hose with 2 clamps. Consider if you want to wrap part of the new hose with thermal wrap, as its 1/4 " away from the valve cover. And yer done.

BKbroiler

That bypass hose will look pretty crude. If you're trying to clean up the engine compartment, it is counterproductive. The 2 plug solution works perfectly. I've been running that setup for about six years. Driving and drag racing in summer conditions, no problems.

wcsinx

You do realize that from a fluid dynamics perspective, these 2 solutions are the same thing, right? It doesn't matter if you shut flow off at the pump or in the middle of a hose. No flow is no flow.

The only potential problem I've heard of but never personally seen happen is that eliminating the heater core fluid circuit can cause a reduction of flow over the thermostat keeping it from opening and closing properly. The solution is to have a bypass hole through the thermostat which most have anyway.

My heater ports are completely, permanently blocked at the pump, and I've never had any issues even in the middle of a Florida summer. I also have a cutoff installed in the heater lines of my C5 ... also no issues.

RIJVETTES

Good for you! I'm glad you had no issues! This is the BEST result!

I'm simply reporting what some other FORUM folks have said. Apparently. some have had problems with the plugs, and other haven't. Some say to drill a hole in the therrmostat, and this solves the heat problem; and some don't trust this. Your remedy is certainly the easiest!

On the other hand, I'm simply posting a very clean and simple alternative remedy. I want to emphasize that its SIMPLE N CLEAN. If you want to use a bypass hose, like I do:

The AC Delco No. 20337 S is a perfect fit.

noonie

Or you can just replace the 3/4" hose x 1/2"npt fitting in the water pump with a 5/8" x 1/2"npt fitting an get bulk heater hose cheaper at any auto parts, should you ever need it.

wcsinx

You did a little more than that with your comment that solution #2 "seems to make more sense". I was simply pointing out that solution #1 and solution #2 are actually the exact same situation with regards to the fluid dynamics.

So to recap

Solution #1 = A
Solution #2 = B
Makes sense = C

Since A = B
And B = C

we can deduce that A = C (Solution #1 = Makes sense) also using the transitive law of mathematics

flaco1801

Anyone have a pic of this Izuzu hose installed on their C3? thanks, Jeff