fire at exhaust manifold upon startup 5.7

[ab59]

first start of new engine went fine but when started later in the day had a fire at the turnback . Rebuilt Holley 4010 , 1 1/4 turns out both sides . Engine starts and runs good otherwise but a little worried about the fire. Floats ?

 

[ab59]

Forgot to say that i'm running a half closed system and had the water running through the manifolds at the time of the fire.

 

[bruceb58]

Forgot to say that i'm running a half closed system and had the water running through the manifolds at the time of the fire.

You had water running through the heat exchanger and out through the risers right?

 

[ab59]

yes water running but not very long at that start. I had started the engine warmed it up set up the timing 3* btdc to burn regular gas , adjusted the Holley 4010 to 1 1/4 turns per side running about 16-18 vacuum earlier with no problems at start. I will say that I did had an unusual black substance floating in the water before this as the engine was running that bothered me a little. We were about to re start and hook up the Tac when I hit the the button and had a fire in one or two revolutions of the engine.

 

[bruceb58]

The black is normal. That's from running slightly rich at startup. All engines do that.