Rilmar

I'm generally a novice when It comes to engine repair. I know just enough to get myself into trouble. Having said that; can an intake manifold gasket leak cause the same symptoms as a head gasket leak? I changed my intake out on my 68 455 and a short time after doing so, I noticed white smoke coming out of both tail pipes (no crossover or x pipe). I assumed it was a bad intake manifold seal job on my part, then I started looking into it and notice a brown milky liquid in my radiator overflow. And the coolant in the radiator smells more or less like exhaust.

Is it odd that smoke is coming out of both tailpipes or is it common for both head gaskets to go out at the same time?

Engine does not overheat and at temp the white smoke goes away. I haven't done a compression check yet, but did pick up a tester.

I guess I'm really hoping this is only the intake seal since I've never replaced head gaskets before.

Thanks for any advice.

oldcutlass

Is there milky stuff in your oil? Engines will emit a certain amount of white smoke on startup (condensation) and normally disappears upon warm up. I would do a pressure test of the cooling system to see of you possibly have blown head gaskets to be on the safe side. Getting exhaust gases into the cooling system with a bad intake gasket is not what usually happens, its water in the oil, in a close cylinder, and/or on the ground.

seansolds

Question..you say you changed the intake out, was it for a after market or did you have this same issue prior to removing the intake? What did the engine do before you originally changed out the intake?
Sean

Rilmar

Did a recent oil change after the intake swap and the oil looked 'normal". Checked the dipstick this morning and oil looked fine. I swapped the intake because I wanted a dual plane, it had an offy 360 on it. It didn't seem to have any issues prior to the swap. I did see some coolant on the back side of the engine this morning. It is collecting on the block near the distributor. So, there is a leak and I assume the location of the coolant would suggest there is at least a leak at the intake? Thanks

oldcutlass

I would check the heater hose area first. Then I would retorque all the intake bolts and see if it goes away before taking it apart. If you used a metal turkey tray, you did put RTV on both sides of the gasket prior to installing. Also, did you make sure all the gasket guide nubs were securely in the bolt holes and the gasket laid flat?

Rilmar

I will check all of that. I did not use the tray just gaskets with RTV. I'll hope for the best. Thanks

MartinH

Just wondering why most everyone tosses the rubber end gaskets and uses RTV instead. Seems very messy and likely to put globs inside the engine galley. Do they really not work even with RTV in the corners?

BillK

Martin,
This is a 5 year old thread by the way That being said, the rubber end seals are designed for when everything is brand new and at factory tolerances. In that situation they work fine. As soon as you resurface the heads or deck the block or go to an aftermarket manifold, all bets are off. Thats where rtv does the best job. If you do it correctly it really is not messy at all and looks fine. GM pretty much went to that method somewhere along the line too.

joe_padavano

I'll add that I've taken great care to install the rubber end gaskets, including the trick of punching dimples in the end walls to add friction and even gluing them into place. They ALWAYS work their way out. As Bill points out, any machine work that changes the relative position of the heads and intake on the block (like milling the heads or using an aftermarket intake) will change the fitment of those seals and potentially cause problems. Sorry, but you have to really try to get RTV inside the motor. Anyone who is at all careful has no issue with this. On the production line there wasn't time to let the RTV cure, thus the use of molded rubber gaskets.

Vintage Chief

Unlike you'll find in the vast majority of posts/threads I'm the lone Maverick here. When I purchased my 71 CS convertible (sbo) in 2018 the intake manifold was leaking. I should note as has been mentioned above, my intake manifold is completely stock (55 lbs of iron). It appeared to me no one had milled or decked anything. Therefore, I chose to use the turkey tray gasket - including the rubber end gaskets (front & rear). I used Permatex® Ultra Black® Maximum Oil Resistance RTV Silicone Gasket Maker around all port openings and ensured I used appropriate amounts at the corners and small amounts along the rubber end gaskets. I have no leaks - knock-on-wood.

Schne442

x2 ^^
I however did have my heads milled .025 to make up for replacing the .017 original steel head gaskets, I used the Felpro Gaskets .042, I believe.
Everything lined back up as stock, I installed the rubber end seals with the Turkey tray as described above and two years later , no leaks