Temp differential on 5.7L intake manifold

bj2455

Seaman Apprentice
Joined
Jul 20, 2009
Messages
38
Im new to the forum so I hope you'll bear with me on this. I have a 1989 5.7L 260hp Alpha One in a 23' SeaRay Cuddy. A few weeks ago we got grounded on a sandbar and pluged the drive and engine with a lot of fine sand. Ive replaced the outdrive impeller, pulled and flushed all the lines, backflushed the block and changed the thermostat. I've purged sand out of everything I can find without actually disassembleing the engine. The temp gauge tells me the engine temp is fine but I have a infared thermometer that shows the temps on the outer intake manifold ports to be around the 150? mark but the center ports (closest to carb) running much hotter around 200-210?. I see the paint on the manifold discolored on the center port areas. Could I have a plugged water line in the intake manifold causing the temerature differential? Anyone else seem to show similar temp variations?
The engine seems to run fine and I have plenty of water flow on the muffs.The intake manifold is the only area I see such a drastic temperature change. Any thoughts would be greatly appreciated.
 

studdy05

Petty Officer 3rd Class
Joined
Mar 27, 2008
Messages
81
Re: Temp differential on 5.7L intake manifold

Right under the carb there is an exhaust port that heats up the carb...took mine in to the head shop - an 84 5.7L - because mine shot the same temp as yours and was discolored...thats what they told me...I've accepted it as true, but would like more info on it if someone has it...
 

Maclin

Admiral
Joined
May 27, 2007
Messages
6,761
Re: Temp differential on 5.7L intake manifold

Heat, even enough to discolor paint, where you describe is normal. The intake manifold has exhaust cross over passages that heat the plenum chamber to keep the mix vaoprized.
 

bj2455

Seaman Apprentice
Joined
Jul 20, 2009
Messages
38
Re: Temp differential on 5.7L intake manifold

This forum is the best! Thanks to all for the feedback.
 
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