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Intermittent puff of blue

I have a lingering issue that is puzzling me, and maybe one you folks have an idea. Its a mystery puff of blue from the exhaust.

On start and warmup there is not evidence of blue in the exhaust. Under normal operation their is no evidence of blue in the exhaust, and the plugs are looking pretty clean - no evidence of oil buildup on the plugs.

When I take the car out for a run after its been sitting for an extended period or idling in the driveway for an extended period (ie tinkering with the carb), at the first stop light after the engine rpms have been up to a city cruise for a few blocks, I get a very distinct cloud of blue. its not a puff, but a noticeable (and embarrassing) cloud.

It happens once and then will not occur again until its next extended period of sitting. It seems to occur that first time you let off the throttle back to an idle.

The car has a PCV but no EGR valve. CompressiIMO..on is good and balance between cylinders is good.

I am baffled - ideas to check?
IMO....
I concur with the valve seals....but..... since you are not picking up any oil ash or residue on the spark plugs, it is likely that one or all of the EXHAUST VALVE seals or guides sre failing. IF you decide to replace the seals, I've had good results with the Perfect Circle Teflon seals with the garter spring....but...they USUALLY require machining of the guide to accommodate the seal and the clearance from the underside of the retainer to stem seal must be checked at maximum valve opening to prevent interference. If the guides are worn, I like aluminum-silicon bronze alloy replacements, but others will have their preferences.
BOB RENTON
 
Oh no, he’s gonna need to “upgrade” his car:
hi volume oil pump
20/50 oil with ZDDP
Pertronix igniter
Blaster II coil
mini starter
amp meter bypass
Optima battery
E3 spark plugs
Dynamat the whole car
LED bulbs throughout
Radial TA’s on 15x8’s
disc brakes conversion
3.55 gears
green axle bearings
Aluminum radiator
Sirius XM radio
classic auto air
Intake gasket(gasket match the heads and intake)
etc, etc!!!

just kidding! valve seals are a likely culprit here.
Now about those green bearings....... :popcorn2:
 
Just really want to avoid removing the heads - that's getting into territory I would really rather avoid unless absolutely necessary.
You can easily replace the valve seals without removing the heads, using either air pressure, or a piece of rope through the spark plug hole.
 
Of course the cylinder your changing the seals on should be at TDC or close to it.
 
Thanks for the article - that is a good one. Pictures are worth a thousand words. Just gathering up the parts list and getting ready to order.

The remaining question I am puzzling with is seal choice. Simple route like the article, is the Felpro OE rubber set - I have them in my cart 'cause I am confident that they will fit. Also been looking at various umbrella seal sets made of viton or other superior materials but am concerned about the length and lower ID specs. I don't know the guide OD (unless it truly is 0.502 like all the replacement guides listed on websites). Is the trick simply to ensure that the umbrella seal ID is greater than 0.502"? Does it matter how much greater than the guide OD so long as it will fit inside the spring?

The engine is totally stock, and will remain so, thus the service certainly isn't severe. Having said that, now that I am going to be doing the seals, might as well make a good choice. I want to be confident that they are pop in replacement and don't require machining of the guides or too long causing interference with the retainer as Bob warned above.
 
Thanks for the article - that is a good one. Pictures are worth a thousand words. Just gathering up the parts list and getting ready to order.

The remaining question I am puzzling with is seal choice. Simple route like the article, is the Felpro OE rubber set - I have them in my cart 'cause I am confident that they will fit. Also been looking at various umbrella seal sets made of viton or other superior materials but am concerned about the length and lower ID specs. I don't know the guide OD (unless it truly is 0.502 like all the replacement guides listed on websites). Is the trick simply to ensure that the umbrella seal ID is greater than 0.502"? Does it matter how much greater than the guide OD so long as it will fit inside the spring?

The engine is totally stock, and will remain so, thus the service certainly isn't severe. Having said that, now that I am going to be doing the seals, might as well make a good choice. I want to be confident that they are pop in replacement and don't require machining of the guides or too long causing interference with the retainer as Bob warned above.
Just use the stock seals you will be fine. Stock has been in there for 48 years. No need to over think or complicate the situation. If you use shop air to hold the valves up do not worry about TDC the air is going to push the piston down. TDC is used when you shove the rope in the hole to hold the valves up. I have several different on car compressors that work ok. This would be a simple and easy to use tool. https://www.ebay.com/itm/2244371677...MIx6mPzbaw8QIVhm5vBB34Jg6wEAQYAyABEgK5Z_D_BwE
 
Just use the stock seals you will be fine. Stock has been in there for 48 years. No need to over think or complicate the situation. If you use shop air to hold the valves up do not worry about TDC the air is going to push the piston down. TDC is used when you shove the rope in the hole to hold the valves up. I have several different on car compressors that work ok. This would be a simple and easy to use tool. https://www.ebay.com/itm/224437167764?_trkparms=ispr=1&amdata=enc:AQAGAAAAkCVIfln+HunUGoh52MqXJJ2Nvjvn7md9GXVZWQvcStV8hkPWz3GqtGmiK/IGLeYJ5zUR32oIr/wt/ecM077LOPUOp73VapERwSe54U4v6lNs7idia3KHyjKgqTPA1IF7MmqQqqedMgjFfFeIPCKfkg3NsN4z78DRE99sIgKLoWzvQibivRMkhvg5wmMaoMuQxg==&chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&itemid=224437167764&targetid=1262906534602&device=c&mktype=pla&googleloc=9058193&poi=&campaignid=12873833206&mkgroupid=123950846602&rlsatarget=pla-1262906534602&abcId=9300536&merchantid=6296724&gclid=EAIaIQobChMIx6mPzbaw8QIVhm5vBB34Jg6wEAQYAyABEgK5Z_D_BwE
 
There is merit in keeping it simple... my plan is to use my air compressor to hold the valves. Tnx for the help...
 
I shove the rope in when the piston is down. Then rotate the crank till it pushes the rope tight doesn't really need to be TDC it's just full of rope and you can't lose a valve.
Note: this is also a great way to torque a balancer bolt.
 
I use cotton rope and Mahle OEM seals.
 
Parts ordered and in transit. Helper lined up (brother). Now just need "refreshments" in the fridge to celebrate success with... Thanks for the help folks. Will post summary when done...
 
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