I'm wanting to completely bypass the heater diverter valve and throttle body, and just run 2 heater lines straight to the heater core, like the early cars had. I am aware that this might make the A/C not blow as cold, but I'll worry about that later. Right now I just have the heater hose outlet from the radiator capped off, as well as the coolant port on the front of the intake. I'm wondering how to remove the hard coolant line that runs under the engine, and how to route the hoses. I'm thinking I will probably just cut the hard coolant line, so I can get it out - it doesnt look like it will come out with the engine in place. Also, I just wanted a sanity check on how I plan to route the new heater lines. I don't think it matters which port on the heater core is in/out, but I was planning to run one hose to the fitting on the front of the intake, and the other to the fitting on the radiator, by the cap. The engine is an 88 305TPI. Will this routing and setup work?

 

Yes it will work fine. That was how nearly all cars used to be plumbed.

The fitting on the intake is "hot", and should be a nipple for 5/8" hose; the one on the radiator is "cold", and is for ¾" hose. You'll find that these conveniently match the ones on the heater core.

 

Thats how Im running my LS1 swap right now. It DOES look much cleaner, and its much more simple. However I went to great lengths to retain all of the 4th gen A/C components, and got it working fairly well. But I can confirm that the heater core will cause your a/c to not blow as cold. you have 190 degree coolant flowing through the heater core constantly, and its enough to bust down the cool air.

But...if that doesnt matter to ya...by all means ditch that valve. It will simplify things under the hood quite a bit.

J.

 

The A/C doesn't work at the moment, so it's no biggie. If it makes a big difference, I'll get a manual heater control valve (had one on my 83) and just close it in the summer.

 

Yeah I wish I could just get a valve to put in one line and cut the coolant off. However on the LS1, the coolant needs to flow through the heater lines all the time. There is no heater control valve on the LS1 cars. So...whatever valve I dig up has to have a bypass that allows the fluid to loop around and not go to the core, but go back to the water pump...

Fun stuff. haha

Well if your A/C is bunk, I say go for it! Less hoses and do-dads the better!

J.

 

You can do that.... AFAIK there's no "requirement" that anything "bypass" the radiator and allow coolant to always flow around it.

Just go to NAPA or wherever, and look through their catalog; and find one that opens, or closes, whichever you need, when vacuum is applied. Which you can easily determine by just checking your vacuum line and seeing whether it has vacuum in the full cold position of the temp slider, or in any position requiring heat.

 

I think the LS1 has external coolant crossover passages (instead of in the intake), that might be what he's talking about. Also, for this to work on a TPI car, you pretty much have to do the TB coolant bypass, which I've already done.

 

Yup...the LS1 has the thermostat in the water pump. And in order for the cooling system to work 100%, it needs to circulate.

You should do the throttle body bypass anyway. That was one of the first mods I did to my 87 wayyyy back in the day when I first got it and was all about the TPI.

J.