odd smoking

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yesthatmat

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so i bought a 97 rcsb that didnt run. put a cap and rotor on it and it fired up. 3 days later it turned in to a steam cleaner. so i pulled the heads to find the grand canyon of a crack (or 6) in the heads as expected. now mind you it was blowing steam at this point. so a set of dart vortec heads some felpro gaskets (all rubber intake gasket aswell)
and some arp head bolts later its back together. well now it is still burning coolant but its different. it is burning it. like smoke not steam. still coolant you can smell the chemical smell of propylene glycol. but it is smoke. andddddd it only does it for 20-30 seconds. then stops. if it were residual coolant in the exhaust it would steam until it was gone id assume. ive ran it a good 10 hours solid twice. the coolant is dropping slightly. none in the oil. no skip runs fine (neither of my compression testers seem to work) pressure tester and exhaust gas testers are on the way (mostly because i needed them anyway) . so my question is what am i overlooking. im assuming it has to be something like a crack in the cylinder liner. that is sealing when it gets hot seems like a long shot on a sbc. (this is a l31 btw) so tell me what im missing before this texas speed 427winds up in here
 

Komet

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Leakdown test is a step in the right direction. Could also try pressure testing the coolant system, use a borescope to see which chamber is getting the juice. My other guesses would be warped block surface or an intake coolant passage not sealing but those wouldn't be the first things I consider.
 

Schurkey

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Remove spark plugs, top-off coolant.

Pressurize the cooling system overnight. Pump-up the pressure as needed if it leaks down.

In the morning, have someone crank the engine while you look to see which cylinder(s) are shooting coolant out the plug hole(s).
 

yesthatmat

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ive borescoped all the holes none of them look wet (done at opp temp so that some pressure should be in the cooling system) i suppose it could be an intake gasket. not sure how i would have messed that up tho dumber things have happened
tools should be here tomorrow so maybe taht will help. im going to mess with this for a couple more days then im just going to get ready for the swap that was going to happen eventually anyway
 

yesthatmat

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im going to pump it up tomorrow and see what it does. but i think im going to put this parts shelf to use and just move to stage 2, now to find an 80 to go behind this 7.0
 

Erik the Awful

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One quick check - take the radiator cap off, fire it up, and wait until the thermostat opens. If after a few minutes you see big bubbles like it's trying to burp air out of the system, you have a leak between a combustion chamber and a coolant passage, likely a cracked cylinder.
 

Schurkey

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still coolant you can smell the chemical smell of propylene glycol. but it is smoke. andddddd it only does it for 20-30 seconds. then stops.
ive borescoped all the holes none of them look wet (done at opp temp so that some pressure should be in the cooling system)
You're complaining about steam when cold. Doesn't make sense to test when hot.

Pressure test overnight, so it's sure to be at ambient temp.
 

yesthatmat

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iit isnt steam it is smoke. steam dissipates this does not. it only happens when its been off for a while. i let the truck run for 10 solid hours to make sure it wasnt just residual. the sense it makes to test it when it is hot is that when it is hot the coolant system (the thing im trying to find a leak in) is self pressurized from thermal expansion and as my pressure tester was broken at the time it was the best way i could pressurize it.
 
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