Are there any unintended consequences I should be aware of in bypassing the heater core on a 1995 LT-1? This is New York car that is not driven from October until May. I have other things I prefer to spend $1200 on besides replacing a heater core. Thank you.
-
-
I can't specifically answer your question, but I can state what the potential issue is.
All engines have a bypass to allow coolant to flow back into the engine when the thermostat is closed. Otherwise the pump impeller can cavitate and that can cause impeller erosion and eventually lead to poor water pump performance/overheating. The higher the RPM the more tendency there is to cavitate, so I recommend keeping revs below 2000 until the thermostat opening temperature is achieved even if the engine has a proper bypass
Using the Gen I SB as an example the water pumps have a small hole above the machined surface of one the legs that is called an internal bypass. Some Gen I SB configurations also have an external bypass consisting or requisite fittings and a 90 degree molded hose between the top of the water pump and the inlet manifold cavity that contains the thermostat.
IIRC your Gen II LT-1 has a reverse flow cooling system, and since I'm not aware of all the design the details, hopefully someone can positively answer your question.
I have a heater core shutoff valve on my Cosworth Vega, and the only bypass is the heater circuit, so I am careful to keep revs low until thermostat opening temperature is achieved, which usually less than five minutes in moderate ambient temperatures as the all-aluminum engine has far less "thermal mass" that a cast iron engine and is quick to achieve operating temperature even with no bypass, and I don't think the lack of a bypass has caused any problems.
Duke -
Thank you, Duke. I am not an expert on the reverse-flow aspect of the C4 LT-1, so I thought it best to check. I do know enough about "systems" to know that you can't touch one thing without effecting ten other things. Have a great weekend.
PaulComment
-
I can answer this question as I am familiar with the operation of the cooling system in the LT1.
The "bypass" is incorporated into the water pump housing. The pump has two passages to the block on each bank. Inlet and Outlet. The passage between the two is controlled by the disc on the bottom of the thermostat.
A big difference between the LT1 and the SBC is that the L1 is a "cold side" thermostat. The thermostat has three passages that it controls. Hot-side from the engine, outlet to the engine, and cold-side radiator. The thermostat opens to allow cold water from the radiator to mix with the already circulating warm water. At a certain temperature, the thermostat is fully-open, and the bypass port is fully closed. The disc that covers the bypass port is spring-loaded and will open at higher engine RPM where cooling system pressure would be detrimental to plastic tank aluminum core radiators. The LT5 in the ZR-1 has the same cold-side thermostat configuration. In the LT5 the flow to the radiator is about 40% at redline RPM which is more than adequate. The remainder of flow remains in the engine where the pressure reduces cavitation and precipitous boiling in the heads around the exhaust ports.
The hi-fill tank on the LT1 is where air and vapor in the cooling system is exhausted to atmosphere. The steam and air-bleeds also vent to the hi-fill tank. You want to maintain flow through the hi-fill tank.
To by-pass the heater core, find a 3/4 to 5/8 inch hose adapter and connect the 3/4 fitting on the tank (that is currently the U-hose to the core) directly to the 5/8 hose that is currently on the core. The cooling system and thermostat operation (including flow through the engine itself) won't be affected at all by bypassing the heater core.
In the pic below, the "U" hose is removed, and the existing 5/8" hose to the heater core (not visible in the pic) is routed to the upper 3/4" nipple on the hi-fill tank. The lower hose on the hi-fill tank in the pic remains as-is.Comment
-
Dave Perry- Thank you for the detailed response and image. Very helpful. Another example of why the NCRS membership fee is the best investment a Corvette owner can make.
Cheers!Comment
-
There is another consideration regarding bypasses and heater core flow that neither Duke or I addressed. There must be some flow in the engine and past the thermostat's pellet or the thermostat isn't exposed to, nor can it react to engine coolant temperature. This is true for any engine, in this case both the SBC and the LT1/4.
In the LT1, the return flow from the heater core exits into the "pellet chamber" of the three-chambers the thermostat controls. In the SBC both the heater core and the internal passage on the right bank pulls flow across the intake manifold past the thermostat's pellet.
Like Duke, I also owned a Cosworth Vega but having sold it almost 30 years ago I don't recall any details about it's cooling system. I find it interesting that his concern is water pump cavitation stuff. What's seems more important to me is that there is some circulation with the thermostat closed to avoid hot spots in the heads, and again, there must be flow past the thermostat pellet or the thermostat won't open until convection through the coolant reaches thermostat opening temperature which by the time it does the engine could be at a higher temperature. One work-around is to drill an 1/8" hole in the thermostat to allow flow past the pellet. << It is common practice to drill the hole to facilitate filling the cooling system when the thermostat is closed, but the hole will also promote more linear thermostat operation in the absence of "heater core" flow.
Thank you for the accolades.
Comment
Comment