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Head gasket blown before engine at temperature

Old 01-10-2019, 09:27 PM
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PlasticFantastic92
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Default Head gasket blown before engine at temperature

Hello folks! I swapped a junkyard engine into my 1972 Corvette and have driven it over 2 hours at highway speeds and in stop and go traffic. Today after checking all fluids and seeing everything was perfect, I turned the car on. Both exhaust pipes showed no signs of any problems as the smoke was just the typical condensation you would see. After 2 minutes, before the engine even got warm, the driver's side started a smoke show! It was white smoke so it is likely burning coolant. I'm unsure if this is from the intake gasket or maybe from the head gasket. Can gaskets go bad after sitting in an engine for a long time? The engine is out of a 1995 Silverado with 175k miles and it is still smooth despite the smoke. Of course I turned it off right away to avoid any damage. It ran like a champ after the swap and I drove it for about 2 and a half hours straight on a little road trip. Temperature stayed at 190 the whole time. Maybe my sensor lied to me and it was running hot the whole time? Not sure what to think since it was running so strong. Any opinions before I start taking it apart?
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Old 01-10-2019, 09:37 PM
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PlasticFantastic92
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Just had a thought:

I took the old intake and carb off of the original engine and had to slot the center holes of the intake to make it fit. It all sealed up nicely. I'm now suspicious that this may be the cause of the coolant leak though as the manifold was not meant to mate up to 1987 and newer iron heads.
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Old 01-11-2019, 07:05 AM
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terrys6t8roadster
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Look at Edelbrocks intake manifolds a see if you can any differences between the Vortec and old style intakes other that the center bolt hole differences. T
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Old 01-11-2019, 08:14 AM
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I have done this before and it worked. he has the TBI head, not the vortec. did the engine get the car to the new home? first, pressure test the engine. the first and quickest pressure test. fill radiator with water to top of filler neck. start engine with no radiator cap. does it do the old faithful geyser thing? if so, definite head gasket. pull the heads. if not, get or make a pressure tester. I am thinking vortec heads or stop messing with that 305 now that it got the car to new home.
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Old 01-11-2019, 03:47 PM
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Thought 96 and up was vortec? OP if you pop a valve cover theres an 8 ? digit number cast what is it
If its vortec how would his intake cover the ports?
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Old 01-11-2019, 06:23 PM
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96 & up are vortec.

TBI heads also have center bolt valve covers BUT have a bastard intake bolt angle ... so, pre-TBI intake needs its bolt-holes slotted.

Too bad he didn't get a 96 & up vortec motor ... would've had to buy a vortec intake but it would have been worth it.
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Old 01-12-2019, 01:02 AM
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Hold up.........................you are running a 29 year old engine with 175K miles on it? You ran it for 2 hours and it pooped the bed? Dont waste another minute diagnosing WHAT went wrong and just pull that old, sloppy motor out. I know you are miffed that it ran for 2 hours and then died, but cmon man, you are dealing with an unknown, high mileage junk engine. Toss it and start new.

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Old 01-12-2019, 09:22 AM
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I never realized it was a 175k engine you put in there. You are under serious time pressure to get that car out of the old house. But you did get it out of there, I assume. And Can you replace the engine where you live now? some towns will not permit you to remove an engine from a car in the driveway in a residential zone. if not and you're stuck with this engine for the time being, replace those heads would either vortec or the aluminum heads from the what is it 84-85 Corvette? That's got a 58cc chamber and it's pretty decent head. It's also not real expensive to find.
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Old 01-12-2019, 05:10 PM
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Hello everyone!

I haven't had a chance to dig in yet and may have to wait a few days before pressure testing. I can confirm that the car did get me to my new home which was fantastic! Ran great the whole way and was very smooth.

I believe these are TBI heads but can confirm later on. They have center bolt valve covers. Oil pressure was around 40psi at idle which makes me think the engine isn't in terrible shape for 175k miles. It still idles smoothly since I haven't given anything a chance to get hurt since this leak popped up. The plan was to make this work while I fix the rest of the car and wait for the funds for a crate motor. I don't have the means to swap an engine where I live currently. It's not allowed and if I tried I don't have enough space.

I am VERY suspicious of the intake on the car. After some thinking, I realized that the old engine before this swap was ALSO leaking coolant on the driver's side and it seems the previous owner killed it by driving without fixing the issue. When I took the head off, the gasket was in great shape. That explains the giant gouge on the #3 cylinder wall and the clear coolant leak there. Originally I thought the coolant was leaking through the gouge in the wall but it may have been the intake the whole time. The ONLY thing consistent from the previous engine to this one is the intake and carb. Those were the two things I swapped over from the old engine. Now you see why I am suspicious right?

Derek, I haven't tested in this way before but I have heard of this method. The one issue I am wondering about is that my radiator does not have a cap. It is a closed system and is filled through the reservoir. Would I be able to check through the reservoir instead? I would just look for a consistent stream of bubbles right? Doesn't sound as cool as the "old faithful" thing haha.

What do you all think? I'm guessing my hunch is right but I'm not sure how to check the intake especially since I installed the new intake gaskets like a champ!
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Old 01-12-2019, 06:10 PM
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yes. fill til reservoir is topped up and start it. if cyl pressure is entering cooling system, it will at least bubble a lot if not shoot up like a geyser. they are TBI heads. the intake bolt pattern confirms it. I have also pulled intake and bolted a piece of wood over water openings front and back of head-with gasket of course. then pressure tested heads and block. and this also lets you look for leaks in the intake valley.
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Old 01-12-2019, 06:16 PM
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pull the spark plugs,are any real clean/white?
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Old 01-12-2019, 09:53 PM
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Originally Posted by dmaxx3500 View Post
pull the spark plugs,are any real clean/white?
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Old 01-13-2019, 12:28 AM
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Old 01-13-2019, 10:34 AM
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derekderek
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first pull the dipstick and check color of oil for milkshake. being a boat guy I have found corrosion issues I HOPE people here won't see. like the water passage across the front of the intake rotting through and leaking into the lifter valley. this is an aluminum aftermarket intake, correct? came with car? then you have no idea where it has been.

Last edited by derekderek; 01-13-2019 at 10:34 AM.
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Old 01-13-2019, 10:34 AM
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smoking while at start up in the morning after a good run the day before is symptom of a intake pressure leak or a head gasket leak.
check plugs, pressure check, re-torque head and intake bolts, try a can of stop leak, even a can of black pepper...( what have you got to lose?) see if it clears up after running for 10 minutes..
after it warms up it might just expand and seal up..
pulling a head and eyeballing the gasket will not always show the problem...head or cylinder deck may be warped, or cracked, then try a thicker head gasket..
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Old 01-13-2019, 10:39 AM
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derekderek
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heads have been on this engine for 175k miles. most likely intake problem. intake is the only thing OP changed. and with old radiator and old heater core, stop leak is bad idea. and if heads come off, the 175k valves-seats-springs go straight to the scrap yard. can't justify spending more than new heads cost to recondition these heads.

Last edited by derekderek; 01-13-2019 at 10:44 AM.
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