How To LS1 Throttle Body Coolant Bypass

How To LS1 Throttle Body Coolant Bypass


Today will be taking a look at the LS1 throttle body or more specifically the coolant bypass mod that can squeeze a few extra horsepower from your LS1 swap. the LS series of engines unfortunately shares the same throttle body design as many late-model cars.

By routing engine coolant through the throttle body GM is able prevent any icing up of the throttle body or throttle body blades during inclement weather that could further complicate cold start issues. While this may be an issue for Santa Claus, it almost always just an annoying factor for most performance enthusiasts.

Many late model cars have coolant passages incorporated into the throttle body

We understand the functionality and purpose of this device and while it does contribute to less emissions and a lower carbon foot print it is not advantageous for performance. The very same coolant passages that warm your throttle body and prevent it from icing, will also warm up the throttle body unnecessarily raising intake pressure and lowering horsepower.

Parts you will need to make this LS1 Coolant Bypass adapter :

We are moving from a 3/8th size line to a 1/4 sized line and incorporating a 90 degree turn in the middle fitting. We’ll be using Redhorse 3/8th push barb to quarter pipe thread 90, with a 1/4inch push barb to quarter pipe thread fitting.


Most performance enthusiasts who are serious about performance and less about creature comforts, simply bypass the throttle body coolant lines by eliminating or teeing the coolant line. However the LS1 throttle body cannot be bypassed with a single section of hose as the line that enters the throttle body is a smaller diameter than the line that will exit.

We solve this issue by simply replacing the line from your water pump outlet and run the line straight behind and under your throttle body, bypassing the coolant lines in the throttle body itself.


There are many vendors that have their own solution for this modification, but most weekend warrior’s will simply construct their own.

When making your own fitting, secure any and all threads that you may be assembling together with Teflon tape to prevent leaking or any chance of contamination in your coolant.

Here you’ll notice the adapter fitted between the two lines connecting the throttle body passages. The line from the drivers side of the throttle body can be seen here snaking behind the throttle body and clamped the adapter fitting. You will not need to drain the cooling system while performing this mod but you should definitely allow the engine to cool down.

Might also be a good idea to have a few rags ready to catch and clean up the coolant from the lines and throttle body as you begin disconnecting and reconnecting the coolant lines and your adapter fitting.

The finishing touches on this case must route the line safely away all your accessories including use of time felt. Make sure that your coolant bypass lines are unexposed, and out of harms way to prevent any damage to the line and subsequent coolant leakage.

You have now completed your LS1 Coolant Bypass mod, make sure to check out our LS1 How To Swap writeup, along with our LS1 Sensor checklist and our LS1 throttle body mod.

Happy Racing!