White smoke after mild tune up

[Steffan514]

I have a 69 C10 with a 400 CI SBC that I was told came from a 71 GMC, I was doing a general tune up on it because it barely ran which involved:

Replacing a collapsed fuel line that was pinched off that ran from the frame to the fuel pump

Going through the carb which is a 750 double pumper and replacing the jets from 70 and 80 to 67 and 77

Adjusting the timing from 28° advanced to 4° retarded because that's what the book I have says the motor called for from stock

Replaced the plugs with another set of R44T plugs gapped to .035 like the manual calls for.

Set the idle from 2000 down to 750

On the old plugs some of them were white on the face and others were black but they all had completely dark porcelains which led me to thinking they were fuel washed. The last change I've made was the plugs which led to the truck running rougher and making a thick white smoke out both sides of the exhaust so I'm curious if this is a fuel delivery or ignition issue or if I should look into changing my valve stem seals to make sure I'm not getting oil in the cylinders.

[Dead Parrot]

HEI or points ignition? Based on years, points was OEM but HEI is a common upgrade. If HEI, then your plug gap is .045 otherwise points is .035.

Timing for SBC without worrying about emissions, start at 8* BTC. 28 BTC is normally a bit much for a daily driver. Possible the timing tab doesn't match TC or the balancer ring shifted.

Fresh gas or old?

Did the smoke continue or quit after things warmed up?

[geezer#99]

Besides the 750 dp what other mods?
What intake, cam ,headers and distributor?

[Steffan514]

Originally Posted by Dead Parrot

HEI or points ignition? Based on years, points was OEM but HEI is a common upgrade. If HEI, then your plug gap is .045 otherwise points is .035.

Timing for SBC without worrying about emissions, start at 8* BTC. 28 BTC is normally a bit much for a daily driver. Possible the timing tab doesn't match TC or the balancer ring shifted.

Fresh gas or old?

Did the smoke continue or quit after things warmed up?

The smoke was still going yesterday after warm up and left a white cloud over my front yard and driveway. Today I fired it up to move it out back to my shop and the damn thing barely smoked at all but I’m halfway through swapping the valve seals right now. It does have an HEI on it now so as I pull the plugs I’ll go ahead and gap them out further. All 8 seals from the odd side of the motor look good aside from the cylinder 3 exhaust cylinder was pretty mangled up at the bottom of the “umbrella” portion of it. Other than the distributor the only other upgrades I know of on it are the 750 DP and a bigger coil. Also based off the head casting number of 333882 it’s actually a 74-80 400 if that says anything.
Posted via Mobile Device

[geezer#99]

Good exercise changing seals.
But oil burns blue, not white.
At least you’ll have new seals.

You got some pics of this motor.
That would help a lot.

And you need more timing. My books all show 8 btdc for initial.

[hjewell2]

unhook vac advance set for 16 depending on cam. any 750 DP on a small block 70 front 74 rear maybe 73 rear. with 70 jets in front makes 73 hole size opening and with the jets stated in rear 73 would be 79 thou hole size or 74 jet at 80 thou hole size. cant help ya on white smoke , other than it says water from somewhere.

[Steffan514]

https://imgur.com/a/SMS1kC0

Here’s a few pics I have of the motor and some of the numbers on it.

Once I get the seals swapped and re-gap those plugs I’m gonna spin some more timing into it. It was around 30 or so after TDC before I started and barely wanted to run so at this point it’s doing way better aside from the smoke. These plugs are already completely black after about 30 minutes of total run time.

[geezer#99]

Hopefully you’re plugging off the vacuum to the distributor when you’re setting timing!
I don’t know how it would even start or run with those numbers you gave us.

Doing the seals, what are you using to hold the valves up when you pop the springs off.
Do you know how to set the valve lash when you put the rockers back on?

[WorkinLonghorn]

I've seen clouds of WHITE smoke coming from vehicles with a crack in the transmission modulator diaphragm. Vacuum sucks trans fluid up into the manifold and burns white. But don't listen to me if it shifts ok and the fluid level is normal. -BA

[Boog]

This. ^^^^ You can pull the vacuum line off the trans modulator and see if there is trans fluid in it. Trans fluid burns white and will make a cloud depending how serious the leak is and the plugs in the rear cylinders may be a different color than the front ones due to burning trans fluid. Water in the combustion chamber will make steam which will dissipate quickly out the pipes.