View Full Version : LT1 crossover line?

11-07-2010, 12:37 PM
I recentally bought a 1995 Prostar that needed a little love. I have the engine out right now being rebuilt, but I have a question hopefully someone might be able to help me with. On the LT1, in a Corvette, there is a cooling crossover line between the cylinder heads on the backside. On this boat I just bought, it has been plugged. Was the line omitted by Indmar or has a shadetree mechanic removed this before I bought it? I would appreciate any help.

11-07-2010, 12:46 PM
Early LT1 engines had it there; but, the engine was prone to making steam. If that happened the steam would rise to the front of the engine and there would be an overheat condition near the temperature sensor, and the engine would go into RPM reduction mode.

Since the engine sits at an angle in the boat, with the front higher than the back...the rear crossover line was useless.

The fix was to remove the crossover from the back of the engine and install it on the front. That is where you should put it.

This link details the fix in much more detail. You will have to wade through some doubt about the writer's claims etc. He was involved in working out the original service bulletin, and even came up with a better way to hook up the heaters on these engines. Anyhow, all your questions are answered on that thread:


Good Luck!!!!!!

PS...since your engine is a '95...the crossover probably came installed on the front of the heads from the factory. The early LT-1s came out in the fall of 1993.

11-07-2010, 01:57 PM
I appreciate that link, it answered most most of the questions I had. thank you

11-07-2010, 02:06 PM
as long as you have a steam crossover that hooks into the cooling system you should be good.

On my car, I did away with the metal line and used some bigger an hoses and fittings. Only because the line got fubar'd when I pulled the engine :(

11-07-2010, 02:21 PM
Mine is all missing. The previous owner did some things to this boat, and I got it at a good deal. the ports have been plugged, but thats going to change. The engine is out of the boat right now, and I'm fixing all the "engineering". I you would, give me a little better idea of your system. I got to buy everything anyway, might as well find a better, more cost effective way.

11-07-2010, 02:38 PM
As long as there is a crossover on the front of the heads, dumping into the exhaust manifolds, to eliminate any steam, you will be in good shape.

You can use brass nipples and rubber tubing (with clamps) and it will work just fine.