Blue smoke on start up

[Superbond]

I have a 72 351c 2v that was rebuilt 3 years ago. 30k over 4 barrel manifold with 600 holley vacuum secondaries. Full ceramic headers. Stock distributor with electronic ignition upgrade. Heads were done by a local machine shop.
When the car sites for awhile and I start it up. It starts but sounds like it has a cold. As is it start to clear it’s self out. The rpm’s start low then up to say 1500 until you kick the carb down. Then the smoke is gone and she runs great. Once warmed up. When turned off for any amount of time there is no smoke. She only smokes if she been sitting for a couple days. I did a compression test last year and all was good. People are saying the heads. I talked to the machine shop that did them and oh course they said the issue isn’t from what they did.
Any ideas?

 

[Sheriff41]

Valve seals, most likely. The machine shop probably used the stock style seals. They are not the best design. It is not uncommon in cars that sit for long periods. If it is just a puff at start up, then not much to worry about. If it is more than just an initial puff at start up then probably need to have it checked out further.

 

[Stanglover]

Probably the same as mine, valve stem seals or guides. If they put in just the ordinary umbrella type, that may be the issue.
In my case ( I posted on this) it is so minimal I'm not going to touch it until it has to be done. If it is bellowing blue smoke, yeah maybe it needs to be looked at. If not just monitor it and go from there.

 

[Stanglover]

Valve seals, most likely. The machine shop probably used the stock style seals. They are not the best design. It is not uncommon in cars that sit for long periods. If it is just a puff at start up, then not much to worry about. If it is more than just an initial puff at start up then probably need to have it checked out further.

That's funny, you must have been typing at the same time, only a bit quicker!

 

[MooseStang]

My 6cyl was blowing smoke since I bought it a few months back. I opened it up last weekend to replace the valve seals, only problem was, THERE WERE NONE!
No seals. After I got finished, no more smoke.

 

[Superbond]

It doesn’t just puff. It will Smoke until the idle come up to what it should be at.

 

[Superbond]

Well
I doesn’t really bother me because it only smokes at home. Lol! When I’m out and about she behaves. I have nothing going on this afternoon, I think I might do an updated compression test and checkout the plugs

 

[Superbond]

Well
I did the compression and 145 except 2 which 1 was 148 and 1 was 140. I think that’s fine

 

[Sheriff41]

Compression numbers are normal. Any fuel smell when it's smoking? Is the smoke white-blue, or black-blue?

 

[Stanglover]

One more thought that was bought up back when I posted about my motor blowing blue smoke on start up.
Check the torque on the manifold bolts. I found all of mine had backed off from the last time they were torqued. You could also be leaking from the valley pan as mine was. Could be why yours seems to smoke until after it warms up.
https://7173mustangs.com/threads/occasional-smoke-on-start-up.40931/Oh, it seems we've visited this before.

 

[Superbond]

It is a light blue and smokes bad. Then clears up and you’d never know
I ran a propane torch (not lit) around the carburetor and vacuum lines. No change in acceleration. Timing is set @6atc and 36 @2500. It start and shuts off perfect. And with that I can’t even get the tires to spin from a dead stop. That’s with a new differential 3.50 from a 2.75. It’s got great take off and pickup but lol won’t spin the tires from a dead stop. Unless I’m turning

 

[Stanglover]

It is a light blue and smokes bad. Then clears up and you’d never know
I ran a propane torch (not lit) around the carburetor and vacuum lines. No change in acceleration. Timing is set @6atc and 36 @2500. It start and shuts off perfect. And with that I can’t even get the tires to spin from a dead stop. That’s with a new differential 3.50 from a 2.75. It’s got great take off and pickup but lol won’t spin the tires from a dead stop. Unless I’m turning

6 degrees ATC? must be a typo, you mean 6 BTDC.
Timing isn't the cause of smoke at start up, or at least, as far as I know.
If by using the propane torch, you were testing for the manifold potential leak, I don't think you'll find it that way as it will be internal. You said the motor was rebuilt 3 years ago, well mine was rebuilt in 2016 and I've had to pull the intake to fix an oil leak on the ends. That was about 4 year ago if I remember and it was torqued to spec then. Recently, I retorqued it and all bolts moved at least a 1/4 turn. It's worth the work to check those bolts. At least you're eliminating one more possibility if it's not the intake.
Are you sure the smoke is blue, not blackish? Rereading your initial post again, it seems more like over rich. Do you smell gas? Gasoline that is!!

 

[71ProjectJunk]

Yes, seems like over rich to me too. Like the carb is leaking a bit and when he starts it the engine is all loaded up with fuel, and as soon as the fuel is burned off it all goes back to normal. It may not be fuel, but from the description that it sounds like it has a cold when you start it, it sure seems like it is fuel. Usually if you have just a little oil seeping through the valve seals you will not have an engine with a miss at idle, unless there is a lot of oil going into the combustion chambers. What I would do to double check is just to pull the plugs and look at them. See if you see oil on them, or are they just wet with fuel. Do you have the receipt from the machine shop that did the heads? Did they itemize it? Did they put in new guides, or did they just ream them? Did they put what type of seals they used, or maybe a part number? Maybe you can figure out what seals they used and if they put new guides in the heads or just reamed the guides. Reaming the guides is cheap but will not last long, and you will start consuming oil again pretty fast.

 

[c9zx]

Try adjusting the choke setting, it may be set too rich. Chuck

 

[Cleveland Crush]

I suggest you pull the intake manifold (super easy on your Cleveland) after the car has been sitting a couple days. With a flashlight get a good look into several head intake ports at the valve stem/guide area. If it's oil sogged, problem is guides or seals. If there's fuel puddling (very common) focus on the carb.

 

[Stanglover]

I suggest you pull the intake manifold (super easy on your Cleveland) after the car has been sitting a couple days. With a flashlight get a good look into several head intake ports at the valve stem/guide area. If it's oil sogged, problem is guides or seals. If there's fuel puddling (very common) focus on the carb.

Well, I wouldn't call pulling the intake manifold "super easy", doable with some knowledge, help and tools. It is certainly easier than pulling heads IF the oil is seeping through the valley pan. If that was not installed correctly and with proper sealant used around the ports and gaskets, then a good candidate for the cause.
First things first, eliminate one thing at a time, but as said before, re-reading the first post, eliminate the carb. One thing our friend could do is have a helper literally sniff the exhaust (oil and gas smell differently) and look at the color or do as I did, video the smoke.

 

[RacerX]

Pull a valve cover and look for valve stem seals. Either there are none, umbrella seals of the seals aren't on the guides but rode up the stems.
Shop probably knurled the guides, which is only a temporary, cheap fix. Old school cheap way.

 

[Cleveland Crush]

Well, I wouldn't call pulling the intake manifold "super easy", doable with some knowledge, help and tools. It is certainly easier than pulling heads IF the oil is seeping through the valley pan. If that was not installed correctly and with proper sealant used around the ports and gaskets, then a good candidate for the cause.
First things first, eliminate one thing at a time, but as said before, re-reading the first post, eliminate the carb. One thing our friend could do is have a helper literally sniff the exhaust (oil and gas smell differently) and look at the color or do as I did, video the smoke.

 

[Cleveland Crush]

Needing "Help" to pull a Cleveland intake is about equivalent to needing "Help" to pull a valve cover. Just sayin....

 

[Stanglover]

Needing "Help" to pull a Cleveland intake is about equivalent to needing "Help" to pull a valve cover. Just sayin....

Let's not get personal.
I was referring to "help" for lifting a heavy cast iron manifold in and out stretching over a fender. I suppose if you're a bigger guy with the strength of a crane, I guess not.
Personally, I found it far easier to have "help" especially to install it. Far better than having no help. Besides, it's always better to have a buddy to drink your beer with.
However, going back over the first post, superbond mentions a 4 barrel manifold being added to his original 2V motor, so the manifold is likely aluminum, which would be lighter and therefore doable on one's own.