[Chevy67]

I have a concern that I needs some direction on. I recently rebuilt a mild 350. While breaking in the cam After about 20 minutes of running, the engine suddenly overheated. Warped Edelbrock heads (ouch!) and blown head gasket(s). It appeared that the thermostat was the culprit although it seems odd that it would run that long before overheating. I had the heads cut until flat (.015) and put it back together with a 160 thermostat. The oil and filter didn't show any signs of metal upon visual inspection. The engine now never overheats but seems to blow white smoke out the exhaust at idle and has a somewhat rough idle despite the mild cam (.446/.446, 220 @ .050, 110 LSA). Coolant doesn't appear to be going down and there is no coolant in the oil.
I installed a FAST EZ EFI system and it keeps throwing O2 sensor codes. The techs at work said that antifreeze is the death of O2 sensors so I suspect that the excess moisture blowing out the exhaust (doesn't smell like coolant) might mean coolant leak into the cylinders causing the rough idle and throwing the error codes.
When the engine overheated I did not pull the block and wonder if It may have cracked or if the deck may have some how warped and I still have a leak.

Any ideas before I start turning wrenches?

 

[MrBill66Malibu]

Kevin,

Get it running smooth and also pressure test the cooling system. If you are still getting white smoke and it does smell like antifreeze then it will need to come apart again.

 

[Tom Mobley]

pressure test = good. you might be able to rent a tester at an chain auto parts store. Have you taken it on a ride, like an hour, to burn all the previous stuff out of the exhaust? I sort of think that's what it is, leftover coolant from the first disaster.

 

[z27]

Kevin I wouldn,t be too quick to go taking anything apart just yet. You mentioned the engine was fresh. Did you figure out why it let go thefirst time . Something was not right ,which on a fresh engine ,I find hard to understand. I always checked the surfaces on stuff and the valve seats on new heads and i dont care who they came from my name was going on the engine when it went out the door . I cant tell you how many i had to fix to make them right and this was good stuff from reputable suppliers. That aside i would use a 180 stat .Drive the car around a while to burn out the stuff thats in the exhaust system . Take it on the hyway and let it out a bit to clear out everything and keep checking your coolant and oil. i think you will be o k. If you find that you still have a problem . 1 find yourself a new machine shop . 2 now you really have to check everything with a fine tooth comb and leave no stone unturned. ALEX GOOD LUCK:thumbsup:

 

[Chevy67]

The first time it let go was a bad thermostat. The challenge with taking it for an extended drive is that with the O2 sensor throwing a code it won't go into closed loop operation and goes into FAST's version of limp mode which I assume is to run very rich. Their system doesn't give a whole lot of info to the end user so you are running kind of in the dark. I'll swap the thermostat and take it out when the weather clears up a bit.

Thanks for the help everyone!

 

[johnretired]

Check the vacuum hose for the trans for fluid too.
Tranny fluid can burn white.