Blue smoke on start up

[mrgmhale]

You have already received a lot of great suggestions. If indeed the exhaust smoke is a bluish color it is an oil burning issue. I concur with the opinion that the factory (umbrella) style valve guide seals are not the best solution. I like Perfect Circle style seals that are truly seals, not merely splash deflectors. If it turns out you are having a problem with the valve guide seals, and have Perfect Circle seals installed, I suggest you go the nest step and have the valve guides done in bronze wall guides. They will last far longer than the factory guides.

Now, if there is ANY possibility you are actually getting excess fuel (which I suspect as the problem goes away when the engine warms up) there are a few things that can cause that. On our 73 Mustang with a 2v 2100 (original) carb it was pumping our a lot of dark smoke until the engine warmed up. The cause was a failed choke cap heater (electric). The choke plate would not open as early as it used to with a good electric heater. I changed the cap and the problem was solved. But, I only did that once I verified the electric heater was getting proper voltage (more on that below).

Another problem area for early (pre-1992). Holley carbs is their propensity to have ruptured Power Valves. I mention pre-1992 as the cause of many Power Valve failures is due to an engine backfiring or burping back, which sends a shock of positive pressure from the intake manifold into the vacuum channel that leads to the metering plate and into the cavity where the Power Valve is. Of course, Power Valves can fail for other reasons, but engine burp back and backfiring seems to be a common cause. When a Power Valve fails you end up having the intake manifold vacuum sucking liquid fuel from the front fuel bowl relentlessly. Symptoms include black smoke, fuel fouled spark plugs, inability to lean out the idle mixture screws enough to prevent an overly-rich idle air/fuel mixture. But, usually the condition does not go away when the engine warms up. Still, it is worth considering.

In 1992 Holley began to build their carburetors with a Power Valve Protection feature, which is a spring loaded check ball that lets vacuum pressure reach the Power Valve, but upon a backfire or burp back the positive pressure causes a check ball to seal off access to the vacuum channel leading to the Power Valve chamber. They have a kit folks can use to retro-fit earlier carbs in a similar manner. Well worth getting if you have an older Holley, even if it is not the cause of your current problem. Less than $20. https://www.holley.com/products/tools/carburetor_tools/parts/25-100QFT

Another thing to check for is the voltage to the electric choke (assuming you have an electric choke). Holley requires a 12 volt switched circuit to feed their electric choke. If someone plugged the factory electric choke circuit into the Holley electric choke you will only be getting about 1/2 battery/alternator voltage as the factory circuit (#4) is connected to the alternator's stator circuit, which produces half the voltage of the alternator output terminal, and it is also AC current, not DC (which does not matter to the heater element). There are a few other places to get current from that are viable, and one other that I see folks use that is not as viable.

Another area I see folks tap into for switched power is the "I" (Ignition) terminal on the Starter Relay. When the engine is cranking it produces an output voltage at the battery's cranking voltage (usually 9.5 - 10.5 volts while cranking). When the engine is running it has the resistance wire voltage that is also sent to the ignition coil, often about 10.5 colts or so, but less than battery/alternator voltage when the engine is running. Whether the "I" or stator circuit is being used it is inadequate for the electric choke to open up as soon as it should. There are two better places to tap into for switched full voltage.

One easy to access source of switched power is Circuit #640, which feeds the carburetor's Throttle Position Solenoid (TPS - used on many factory carburetors in 71-73). It is likely the Holley is not using that solenoid, but the wiring harness connector should still be near the front of the carburetor, even if not in use. It is fed using a Red wire with a Yellow hash tracer.

The other easy place to get switched power is Circuit #63, which is the power for the windshield wiper motor. It is easy to tap into that circuit, but I recommend doing it on the wiring at the motor, not the vehicle's main harness just before the connector at the motor.

I have a few videos re: the TPS, and also how I did the rewiring for our Holley electric choke to use Circuit #63 on YouTube, at the following addresses.





I hope that info helps you out.

 

[Superbond]

to clear up a couple things.
Yes it was a typo. It was supposed to say 6 degrees btdc
And yes it’s a aluminum manifold.
Next time I start it up I’ll film it.
Maybe at winter I’ll tear it apart to take my heads in to someone else and hat the valve guides looked at

 

[Superbond]

So
To correct a few things. 1. Yes I Made a mistake it is 6 degrees btdc.
2. The blue smoke is a light blue and a lot out of both exhaust pipes which does not have an H pipe.
I do see some oil by my distributor which I’m assuming is from my manifold.
So maybe you right! The intake could have loosened off

 

[Superbond]

I do have an electric chock and it is being fed by the tp. All 8 plugs that were pulled when I did my compression test yesterday were a nice light brown.

 

[Superbond]

I must say I do like your test light with the digital read out! Where do you purchase that if you don’t mind me asking

 

[Cleveland Crush]

++ on the digital test probe.

 

[71ProjectJunk]

Plugs look nice and clean. I would not doubt that the issue is with the intake manifold gasket and oil leaking in that way.

 

[Stanglover]

So
To correct a few things. 1. Yes I Made a mistake it is 6 degrees btdc.
2. The blue smoke is a light blue and a lot out of both exhaust pipes which does not have an H pipe.
I do see some oil by my distributor which I’m assuming is from my manifold.
So maybe you right! The intake could have loosened off

Definitely worth checking the manifold bolts and re-torque them to manufacturers spec. Aluminum and steel expand/contract at different rates as you know.
Obviously there won't be a valley pan, my bad, I forgot you said 4v manifold on a 2V motor which would have to be aftermarket. If necessary, maybe pull the intake and replace and seal the gaskets. At the ends, I like to use "The Right Stuff" from Permatex instead of rubber end seals. Oil leaking from the rubber ends on my stock manifold was the reason for me pulling the intake as mentioned before. The Right Stuff fixed the problem. Wonderful stuff, but EXPENSIVE!! I've seen this in smaller tubes in the US, but only in small caulking gun size here. Regardless, still worth it.
Good luck, you'll sort it out soon.

 

[Hemikiller]

Agree with Stanglover, check the intake bolts first. They will loosen up over time. Your plugs look clean, I don't see any oil on them, so that's good. Factory type valve seals will last ten years at best before they start to harden and fall apart. Pull a valve cover and look for the broken bits in the valley, and inside the valve springs.

 

[c9zx]

Unrelated to the blue smoke problem, I'd suggest switching back to a copper core plug. Copper is a better conductor (less resistance), they can be gapped, and dissipates heat better. Please let us know when you find the source of the smoke. Chuck

 

[Superbond]

I now this may sound silly but. When I put the valley pan gasket in. Was I supposed to put the traditional felt gasket before the valley pan?
And I will check the bolts. If that is not the issue,I’ll wait for winter to dive into the top end. Just going to enjoy the rest of the summer.

 

[Superbond]

I checked the manifold bolts and their good and tight

 

[Hemikiller]

The Felpro valley pan comes with a pair of paper gaskets that get glued to the cylinder head, then the pan is laid over them.

IMO, use a small bead of Ultra Black RTV around each port on both sides of the valley pan. I've re-used them many times this way.

 

[Stanglover]

The Felpro valley pan comes with a pair of paper gaskets that get glued to the cylinder head, then the pan is laid over them.

IMO, use a small bead of Ultra Black RTV around each port on both sides of the valley pan. I've re-used them many times this way.

Would they use a valley pan under an aftermarket aluminum intake? I thought that was only on factory cast iron intakes, but.............

 

[Superbond]

Oh brother
I did not put a felt gasket on the heads. Just the valley pan. And I was with a couple die hard Cleveland guys. I didn’t have them when I took off the original intake manifold

 

[c9zx]

If you change the gasket again I'd suggest using a quality regular gasket (NOT Fel-Pro Print-O-Seal) and a bead of oil resistant RTV for the end seals. But, then again I am still into risk mitigation. Chuck

 

[Cleveland Crush]

Oh brother
I did not put a felt gasket on the heads. Just the valley pan. And I was with a couple die hard Cleveland guys. I didn’t have them when I took off the original intake manifold

Consider Mr. Gasket Ultra Seal intakes next time. They have a silicone bead.