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Old 01-13-2025, 04:43 PM
PontiacHO PontiacHO is offline
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Default 350 - First Start - Alarmed

You all have shared advise for my 1968 Firebird cam swap and heads rebuilt. It’s been 15 years since my last engine job and in my mid sixties now so memory and strength has faded some….
Swapped a rough idle performance cam for a stock “066” cam to include Hy-lift Johnson lifters, rebuilt the heads with new valves, springs, and milled .020, using all Felpro gaskets throughout.
Set out today to perform the break in. It fired off amazingly fast and I brought it up to around 2,500 RPMs and held there for several minutes. Immediately there was a lot of smoke from both exhaust pipes.
Initially I’m thinking that’s the oils etc. from the machine shop and-or the coolant that drained into both head pipes when the heads were removed.
I ran it for maybe 3 minutes and the smoke didn’t clear so I aborted the attempt.
I pulled all the spark plugs and they all were dry. No dampness.
Would antifreeze that collected in the head pipes from the head removal create this smoke?
This happened about the time all the kids were home from school and I didn’t want to cause any parental concerns in the neighborhood. The wind unfortunately was blowing directly towards my house and I didn’t want smoke in the eve vents.

Mind spinning…….

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Old 01-13-2025, 05:15 PM
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Antifreeze burning has a very distinct smell and to me really can’t be confused with oil burning.

Oil burning is blueish. Antifreeze is white and smells sweet.

It might take 5 or more minutes of run time to burn out all of the antifreeze that got dumped into the exh system.

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Old 01-13-2025, 06:57 PM
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Thanks Steve. It’s a real quick “downer” to go from an instant startup to puffing smoke-steam. Maybe it wouldn’t have been as shocking if this was warm weather. I kept going over in my head “did I mess up the head gaskets” but I did speak with a Felpro technical person who said “there is no up or down” on the Felpro head gaskets I used. I reckon another attempt tomorrow or Friday. Thanks again.

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Old 01-13-2025, 07:15 PM
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Could be just condensation in the exhaust pipes and mufflers.

It’s probably pretty cold where you are.

Smoke or steam, which is it?

Steam would be normal, with water dripping out of the tailpipes.

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Old 01-13-2025, 07:37 PM
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Tomorrow drain all the coolant out and run it for 30 seconds, no you will not harm anything but if it still smokes then it’s not anything to do with head gaskets.

After doing this just don’t put any coolant back on for 20 minutes.

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And he was not talking about 1/8 or 1/4 mile ETs!

1) 1940s 100% silver 4 cup tea server set.

Two dry rotted 14 x 10 Micky Thompson slicks.

1) un-mailed in gift coupon from a 1972 box of corn flakes.
Two pairs of brown leather flip flops, never seen more then 2 mph.

Education is what your left with once you forget things!
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Old 01-13-2025, 08:16 PM
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When i rebuilt my 389 a lot of coolant had gone into the exhaust. The new engine ran a long time with a lot of smoke coming out the exhaust. I also was worried. I shut it off a couple of times to check everything out. Eventually the smoke/steam disappeared. Don't give up hope yet.

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Old 01-13-2025, 09:43 PM
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While working in a Buick dealership I had occasion to head gasket dozens of 350 Buick engines due to premature deterioration of the fiber head gaskets Buick used.

By the time they were brought in for head gaskets they're had been pouring coolant into the exhaust for awhile. After completing the repairs, they belched steam out of the exhaust for 20-30 minutes. It takes awhile to turn all that coolant to steam. Knowing this I would say by the time you run it for 15 minutes you should see a huge reduction in the amount of steam. If it hasn't abated by 15 minutes of run time, you might be looking at some other problem.

Hope it all works out for you..........

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Old 01-13-2025, 10:56 PM
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How would you still have coolant in the exhaust manifolds? You typically remove the manifolds if the heads were sent to the machine shop for valve and machine work. You will typically get coolant spillage into the cylinders which you should remove with towels or a wet vac. The residual coolant that remains in the ring lands will cause a bit of initial smoke on startup but it clears up immediately.

Check your oil for antifreeze contamination. The obvious culprits are intake or head gasket leaks.

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Old 01-13-2025, 11:33 PM
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'parental concerns" ?? Invite all the kids over and fire that sucker up. it will stop smoking, they would love it.
I might shut a engine down to my own mechanical concerns. But never for some helicopter parent.
And I light mine up with open exhaust.
I am sure there a lots of hot rod engines fired up there in NASCAR country.

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Old 01-14-2025, 03:55 AM
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You're right to be wary, but I'd say it'll take considerably more than 3 minutes to cook all the condensation out of an exhaust system. And that's with a daily driver. Wouldn't a cold muffler act as a moisture trap until it's good and hot? If some folks in the neighborhood are going to wrinkle their noses, you can always run it after dark. Internet says sundown in NC is 5:26.

Life's too short to worry about what everyone else might be thinking. Heard a neighbor doing a compression test in the evening once, went over and offered a hand 'cause I though he had a no-start. He was concerned about the neighbors too. Told him the "noise" wasn't an issue and anyone that would call the cops need their head examined.

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Originally Posted by NeighborsComplaint View Post
How would you still have coolant in the exhaust manifolds?
Head. Pipes. It's right there in the original post.

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Old 01-14-2025, 09:02 AM
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Yes I know I worry too much about what the neighbors think. Me and my wife are the “elderly couple” on our cul-de-sac. All the other households have school aged kids. There’s 13 kids out of the 8 houses on our street. I’ll fire it off today and see what happens. I tried again late yesterday and lost my spark. I may be replacing coil, module, etc. in this GM HEI. Looking for a step by step test scenario now….

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Old 01-14-2025, 09:24 AM
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Just for reference you should never crank over a powered up HEI if you have the plugs not hooked up.

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And he was not talking about 1/8 or 1/4 mile ETs!

1) 1940s 100% silver 4 cup tea server set.

Two dry rotted 14 x 10 Micky Thompson slicks.

1) un-mailed in gift coupon from a 1972 box of corn flakes.
Two pairs of brown leather flip flops, never seen more then 2 mph.

Education is what your left with once you forget things!
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Old 01-14-2025, 09:32 AM
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“Check your oil for antifreeze contamination. The obvious culprits are intake or head gasket leaks.”

No way for an intake manifold gasket to cause this issue on a Pontiac.

I cannot see coolant going into the chamber, more so the situation would be combustion pressure to the cooling system.

It’s most likely Residual coolant, oil on guides from install, the anti corrosion spay from the machine shop, and the normal moisture condensating from the exhaust…amplified visibility on a cold day. Keep an eye on the cooling system….and

Run It!
✌🏼

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Old 01-14-2025, 09:38 AM
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Drop the pipes off the manifolds and start it for a minute see if it’s still huffing smoke.

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Old 01-14-2025, 09:56 AM
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Ok guys. I’ll report back later today. I’m too old to cry but if I have to take this apart all over again I just might….

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Old 01-14-2025, 11:02 AM
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After it sits a bit, and before you continue, it would also be a good idea to pull the drain plug out of the oil pan for a bit and make sure no coolant in the crankcase.

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Old 01-14-2025, 12:37 PM
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I think I would do pressure test on the coolant system. I think you can get the pressure tester from O'reilly's. Could rule out a gasket leak pretty quik.
Also pull the dipstick and make sure you only see oil on it.

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Old 01-14-2025, 03:57 PM
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I have had engines take 1/2 hour, sometimes a little more, to stop "smoking/steaming" after an engine change or fresh rebuild. Depends mostly on what was in the exhaust system when the engine failed and removed. Also, how long the car has been sitting. I would monitor the engine temp, make sure there isn't excessive pressure in the cooling system, and check the color and smell of what's coming out of the tailpipes. Regular water, steam, out the exhaust will leave the tailpipe, (s), and rise up and over the back of the car and dissipate into the atmosphere. Coolant in the exhaust will leave the tailpipe, (s) and stay low, gathering a cloud near the ground and engulfing the rear of the car. It generally has a slight gray color to it and the sweet syrup smell others have mentioned. I would run it and observe much longer before pushing the panic button.

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Old 01-14-2025, 04:20 PM
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Didn’t notice anyone make this suggestion but it would be the first thing I’d do is check the coolant level and see if it’s gone down any. If your down coolant your probably burning it

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Old 01-14-2025, 05:32 PM
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Quote:
Originally Posted by rohrt View Post
I think I would do pressure test on the coolant system. I think you can get the pressure tester from O'reilly's. Could rule out a gasket leak pretty quik.
Also pull the dipstick and make sure you only see oil on it.
My old 48 year old coolant pressure tester is now junk. I’ve ordered a new one through Amazon that’s supposed to be here in the morning. That will tell the story. My stinking heater core is leaking so I’ll by pass that for now until the break in.

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