Why are some engines a 2 port and some are a 4 port. My lq9 from `02 is a 2 port, but would like to know more about it. When would you go to a four port?....

 

My 5.3 liter truck motor from 1999 is a four port. GM made the decision that perhaps only two were needed for your engine. I don't believe this choice is up to us end users. It is what it is.

Rick

 

My LS1 came with the rear steam cross over ports plugged and so did all of the LS2's, 3's and 7's. I'm running it the same way with aftermarket LS7 style heads on an LSX block with the factory water pump, radiator, fans, etc. and haven't had any issues. When running a high performance engine on the street its not a good idea to be sitting in stopped traffic during the heat of summer with the air conditioner on for any extended period of time. Of course we can always improve on the cooling system such as electric pumps, larger radiators and fans and yes utilizing the four corner steam crossovers.

 

GM went to 2-port steam vents for building ease as the engines did fine on a PRODUCTION BASIS. The 4-port setup has an advantage for the car hobbyist (that would be "US") in that when filling the cooling system, it does a better job of bleeding all the air out.

 

It's not really about bleeding the air. It's more about getting more coolant out of the rear hotter cylinders.

I did a 4 corner coolant mod to a 8sec turbo ls camaro a few years ago for a guy. He was having head gasket issues and woukd run hot sometimes. I set his up with a surge tank. Ran all 4 corners individually to the tank then plumbed the return to the upper rad hose. Last time i talked to him is was fine and no more blown headgaskets.

 

So if the heads are blocked from the factory how do you open up the coolant passages?

 

The heads aren't blocked, they just have plugs installed instead of a steam pipe.

Not sure about the truck motors, but when GM made the LS6 intake standard on the LS1s in '01, they switched to the 2 port steam vent. I thought it was for clearance issues under the manifold but my memory is getting foggy.

 

I think there are some ribs under the LS6 manifold that need to be ground away (not a big deal) so the steam lines can be run underneath.

 

I drilled mine, no big deal One head just had a block off the other head had the location for the hole but it was never drilled.

 

Some have used truck crossovers on the rear. I plan on running HPDEs with my C5 so I added a factory front crosspver to the rear, if it were a street car I'd likely leave the stock rear block offs and the front crossover.

https://ls1tech.com/forums/generatio...line-help.html
https://www.corvetteforum.com/forums...eads-rear.html

 

Thanks for all your input, good info. I may update to a 4 port. The little added cost is far worth it to me to help, possibly avoid issues.

 

I drilled/tapped my ports to fit 4an adapter fittings directly to the heads and plumbed the whole system in an fittings and braided line.

 

I swapped from a 4 port to a 2 port when I did the LS6 Manifold/PCV setup

 

**** it why not go 8 port! or 16 port?

 

Try it! Let us know how it works out. Oh, and pics please!

 

I'm betting that the coolant temperature at the back of the heads are most likely the same whether your a 2 or a 4 port or whatever.

 

Not sure how true that is.....u hook up a coolant temp to the rear passenger port and it reads cooler than the drivers side up front

 

I said my bet is that the temperature will be no different. May be somebody can chime in and disprove my theory. If you want to add another crossover go ahead but I don't think your doing anything more than added another place for the coolant to go.

 

The argument isn't that you'll see a drop in temp on your coolant gauge. It is that you will prevent steam from building up over the rear cylinders which is where LS motor tend to be more detonation prone.

 

Lamar! Hope your well. How’s that 5.3?