How do you bypass the heater core on 86 vette
any pics would be great?

Shouldn't be to hard...connect the hose that goes in to the hose that goes out using a short piece of pipe or remove both hoses except for about a 2 or 3 inch length and plug.

both pipes coming out off the firewall have water
flowing in same direction top pipe flowing into TB lower pipe into engine

both pipes coming out off the firewall have water
flowing in same direction top pipe flowing into TB lower pipe into engine

Think about it for a minute and you will realize that is impossible. Bottom hose is into the heater core, top is return.

Think about it for a minute and you will realize that is impossible. Bottom hose is into the heater core, top is return.

Yup...and all you got to do is connect 'em together and you've bypassed the heater.

I just did this...
Carefully loosen the hose clamps at the diverter valve assembly (to the 2 3-4"hoses going into the firewall). now remove the 10mm nut holding the div. ***. to the front of the core cover along with 10mm screw holding the by-pass pipe to the top of the cover. Use a screw-driver (or 2) to work the hoses loose then pull the diverter off of them. it will loose about a cup of coolant max if the car is level. Now take a manifold to throttle-body hose (under MAF hose) and the 2 clamps you just got loose to make the water flow from the top to the bottom of the diverter. If you don't have an extra TB to manifold hose just remove the one from your car and get a longer hose to go from the diverter assembly to the manifold...that also by-passes the throttle body and keeps your intake air a little cooler.

Disconnect the hoses at the engine end and cap with 5/8" rubber caps from auto store

Disconnect the hoses at the engine end and cap with 5/8" rubber caps from auto store
If only it were that easy...
You still would have the line from the rear of the manifold leaking everywhere. And with the reverse flow of this engine it could lead to serious hot-spot issues in a short while. You need to keep the flow through the intake.

I was just wondering, why do you want to bypass the heater core in the first place? If it is blocked or leaking wouldn't you want to replace it rather than bypass it? I know living in a warmer climate you don't use heat much, if at all, but there will probably come a day when you will decide to sell the car and it will affect the resale value. Just my opinion.

Think about it for a minute and you will realize that is impossible. Bottom hose is into the heater core, top is return.
95vette did you forget that the heater core manufactures water?



1. Remove one heater hose from the tube sticking out of the firewall to the right rear of the engine.

2. Insert a spare piece of tube or pipe into that hose just removed. Install and tighten a clamp on the hose at the tube you just inserted.

3. Remove the other heater hose from the other tube sticking out of the firewall to the right rear of the engine.

4. Install the second hose (removed in step 3) onto the other end of the tube or pipe you inserted into the first hose in step 2. Install and tighten a clamp on the second hose at the tube you just inserted as in step 2.

5. Go have a beer and congratulate yourself for successfully bypassing the heater core.

RACE ON!!!

CFI, I am fairly certain that this is just a temporary by-pass to test the A/C... at least in my case it is temp. untill i can get another shut-off valve manifold chromed.
On the 86s and 87s there is a 3/16" line that takes coolant from the rear of the intake into that by-pass valve manifold. The 2 metal lines from the manifold to the core are welded together keeping the lines about 1 1/2" apart and that manifold runs almost the length of the engine making just running hoses a giant PITA. All he needed was a temp. by-pass to let the a/c work untill he can get a new manifold with the shut-off valve that works. On this manifold the top hard line is slightly larger than the lower compounding the problem of finding a line that will make that tight of a bend to attach the top to the lower. The pre-bent hose at the front of the engine for the TB to intake is perfectly sized to accomplish this and allow quick return to stock.
By-passing the coolant from the TB helps the engine stay cooler. In my case that is a giant plus with all the chrome.
Is there any-one out there that knows how to rebuild just the valve in the by-pass manifold? I am also looking for bad ones that any-one might donate to me (I'll pay shipping if cheep) so that i can dissect them and learn how to fix the valve with-out replacing the entire thing.

And with the reverse flow of this engine it could lead to serious hot-spot issues in a short while. You need to keep the flow through the intake.

Wrong engine ;92 -97 LT1 has reverse flow coolant.
The Vette L98 pump rotates the opposite direction to a regular SBC pump ; not the coolant flow.

Myself and many others have had the steam vent (is only a steam/ air vent; no major coolant flow ) outlet at rear removed for years with no problems.

None of the aftermarket intakes for L98 's have it neither do any of the carb intakes that fit the same SBC engines and they do not have cooling problems.

I am not certain which years went complete reverse so that is probably my over-sight. But not having that flow will not let the egr sensor get correct readings at the least.

None of the aftermarket intakes for L98 's have it neither do any of the carb intakes that fit the same SBC engines and they do not have cooling problems.
I know my TPIS Big Mouth intake has it.

But not having that flow will not let the egr sensor get correct readings at the least..

EGR temp sensor (86 - 91 ) is mounted in and gets it's temp from the exhaust crossover tube that goes from exhaust manifold to intake rear;
unrelated to coolant temp.

As I said , I have 10 years of running without the steam vent at rear; no codes and no problems.

Wrong engine ;92 -97 LT1 has reverse flow coolant.
The Vette L98 pump rotates the opposite direction to a regular SBC pump ; not the coolant flow.
:iagree:



EGR temp sensor (86 - 91 ) is mounted in and gets it's temp from the exhaust crossover tube that goes from exhaust manifold to intake rear;
unrelated to coolant temp.
:iagree:
There seems to be an awful lot of misinformation in this thread.



CFI, I am fairly certain that this is just a temporary by-pass to test the A/C... at least in my case it is temp. untill i can get another shut-off valve manifold chromed.
Fine! It really doesn't matter how long you leave it in place. The method is the same regardless. My instructions in post #10 failed to mention adding a short length of hose, if necessary to connect the hoses to the tubes. That is what happens if I assume every reader has the common sense to figure out the obvious. The method is valid for any year, regardless of the direction of the water pump rotation or the coolant flow. The EGR is a non-issue.

RACE ON!!!