thought i blew a head gasket, thick white smoke coming from tailpipe smelled of coolant. pulled heads, coolant in cyls. decided to swap cam and intake while i was at it (to a miniram) and installed new arp headbolts. put it all back together, still white smoke. to make a long story short, i am on my third set of head gaskets (first was felpro 1010, then tried cometic and felpro 1003), tried 2 different intakes (superram and miniram), 3 sets of intake gaskets, sealing the water jackets well with rtv (dont appear to have leaked). have pressure tested the cooling system (pressure drops very very slowly i.e. 1 psi every 10-15 mins or so), have taken the intake and heads to the machine shop to be checked and planed flat. each time it goes back together, the result has been exactly the same - white smoke and coolant blowing out the tailpipe. ive checked all the heater and intake connections, everything is connected properly. coolant appears to be entering the cylinders first, rather than the crankcase oil whereas if it runs only for a short time white smoke appears in the exhaust but no coolant in the oil until it runs for a while, then it starts showing up in the oil. i inspected the cylinder bores very carefully for cracking, no visible signs. cant see signs of coolant in the plenum. i'm at a total loss here, experts please help.

 

crack in head somewhere maybe?...

 

Do both of those intakes use the same throttle body?
If so, try the coolant bypass thing.

 

Or maybe your block has a hairline crack...
Any antifreeze in the oil? Foamy, nasty looking goo on the dipstick?

Tim sends

 

And has the motor been over heated before?

 

throttlebody has been coolant bypassed. engine has never been overheated and was running great up until this.
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like my original post said:

coolant appears to be entering the cylinders first, rather than the crankcase oil whereas if it runs only for a short time white smoke appears in the exhaust but no coolant in the oil until it runs for a while, then it starts showing up in the oil.

 

Which cylinder heads are you using and have they been ported? The machine shop might not think to check the intake and exhaust valve pockets for cracks, just the headgasket surface and valve seats. Usually you can see this problem on the sparkplug of the cylinder in question if it is an intake leak, but not if it is an exhaust port leak. Here's something you might want to try:
Run engine to operating temp.With a pressure tester on to keep pressure on the cooling system, remove spark plugs and let it sit for an hour. Put cardboard on both sides of engine opposite sparkplug holes. Spin the engine with the starter and see if one of the plug holes wets the cardboard. Won't cost anything but time.

 

LPE vette L98's and yes, extensively cnc ported. yeah, i know where youre going with this one. i was hoping the machine shop hadnt done a half-assed job, theyve done right by me lots before, but at this point it seems to be possibly pointing in that direction.


and right on. that's exactly what i had planned for today. i'll let you know how it goes.

 

ok. ran that test. inconclusive. no coolant showed up. the only other thing i can think of is a crack between the water jacket and the exhaust port but last time the headers were off i saw no signs of coolant in any of the exhaust ports. currently there is no coolant in the oil so im doubting a cracked block. at this point im guessing its a cracked head but i really have no conclusive evidence to support that, just have exhausted other possibilities...

 

I thought of one other small, slight possibility. And I do mean it is a stretch. The valve that controls the coolant flow to the heater is a vacuum operated valve. It might be possible that it is leaking coolant into the vacuum hose and into the engine. Like I said, it's a stretch, it would have to be plumbed wrong also. But it is a possibility.

 

good advice but i already checked that. all the vac lines were dry as a bone. thanks much tho

 

well...i guess im about to bite the bullet and pull the heads one more time. theyre gonna get magnafluxed just for my peace of mind but im going with a brand new set of afr 195 comps (which i was contemplating anyway). if that doesnt work, i pull the whole engine and start over. yes, your heartfelt sympathy is most appreciated.