Puff of blue smoke at start up

[Root Moose]

Yeah, as the subject says. This is on the work horse.

Not always, but most times at start up. Still passes the stricter e-test sniff test in my jurisdiction so thinking it is a start up only thing (i.e. not rings).

Leaking valve seals? This is an ACH replacement 0331 head I put on the Jeep around 40k kms ago. Other than external bolt-ons all stock otherwise.

What is the best way to diagnose? I picked up a compression tester/leak down tool from a buddy. Would like some hints on what exactly to do, diagnose if all cylinders have the issue.

I have a spare head kicking around... may swap in the short term and do a port/polish/rebuild on this head. Just want to figure out what I'm dealing with in the meantime while I build motivation to fix it.

Thx.

 

[Dr. Dyno]

A puff of blue smoke at start up alone does point to worn valve stem oil seals.
If you do "wet and dry" compression tests on all cylinders, you'll at least find out if there's a problem with the rings.
Inspect the plugs and see if any of them are more oil-stained than the rest.

 

[Root Moose]

I'll have to do a full work up this weekend if I can find the time (on the other side of the country on a business trip - honey do list is growing).

Anyone have good references, web sites, with a guide to work up/ diagnose? Lot of wrong crap out there.

Maybe this will be the excuse to move a stroker build into the foreground, stick that Edelbrock head on it while I'm at it...

 

[joejeep92]

Sounds like valve seals to me

 

[GrimmJeeper]

what he said ^

 

[yossarian19]

xWhatever on valve seals.
No direct way to diagnose that I'm aware of.
All you can do is check leakdown, wet / dry compression, etc and establish that it's not the rings. Blue smoke is oil and by far the most common issue causing blue puff at startup is the valve seals.
I think you should build a stroker & top it off with the Edelbrock, swap it in over a weekend.

 

[Root Moose]

LOL @ the weekend swap idea. It's in the back of my mind already... Just too many balls in the air right now - it's the crazy time of year at my workplace, my wife wants a kitchen reno... etc. Thinking ATK block ready to bolt in, Scat crank, Edelbrock head, look further into cams, etc.

Still haven't diagnosed it at all. Just got out of the Jeep actually... cruising at ~70 mi/h I've got about 50 psi of oil pressure. Crappy OEM gauge so not sure how accurate (actually reads 3.5 bar). At idle it has decent pressure but I don't recall the value.

 

[Talyn]

Probably just the valve seals. If you want you can pull the intake and verify that oil is pooling on the back of the valves after its shut down for a while. You can change the seals with the head on the engine if you want. Or you could just run it as is.

 

[Hypoid]

This is an ACH replacement 0331 head I put on the Jeep around 40k kms ago.

So that is around 25,000 miles? That is disappointing! I'm guessing the valve guides have too much slop, taking out the valve seals.

Just for the sake of red-neck, shade tree diagnostics, take it out at highway speed, down-shift and take your foot off the gas. If the high vacuum operating condition does not produce a cloud of smoke, drive like you stole it!

 

[old_man]

So that is around 25,000 miles? That is disappointing! I'm guessing the valve guides have too much slop, taking out the valve seals.

Just for the sake of red-neck, shade tree diagnostics, take it out at highway speed, down-shift and take your foot off the gas. If the high vacuum operating condition does not produce a cloud of smoke, drive like you stole it!

Sounds like another old shade tree mechanic teaching the computer generation how to really troubleshoot an engine.

There are two options on shot valve guides. There is a company that manufacturers valves that they chrome plate the shafts for long wear. They end up with a shaft that is a couple of thousandths larger. The other method is to have a machine shop ream out the existing head and press fit bronze inserts. NEVER have the guides knurled. They last 10-20k miles then start sucking worse than ever. Sounds like what you got.

 

[Root Moose]

Thanks, Guys.

Yeah, only smoke is at startup - nothing any other time. I haven't tried to force the issue via downshifting and will next time I take the Jeep, but from the driving I've done with it I don't think there are any other issues like that.

Btw, is it possible to inspect the head for knurled guides before installing? Assuming I'd have to pull a spring/valve (excuse to buy a spring compressor)?

I ask because I have another ACH head in the garage on the bench that hasn't been installed yet.

 

[yossarian19]

Sell that head, buy the edelbrock.
...
You can imagine where I'm going here, right?

In all seriousness, I'd just top off the oil as needed & keep driving it. If it's what you want and it's someday practical to do so, sure, put a hot rod I6 in there. Personally I wouldn't tear the head off an engine and have guides / seals done unless it was burning a *lot* of oil and I absolutely could not find a way to spend the extra cash and upgrade while I was at it.
Replacing the seals while the head is on the car, I could maybe see - provided they aren't going out because the guides are bad. Not sure how to diagnose that on-car but maybe one of the other gearheads knows.

 

[Root Moose]

Yeah, that's the kind of things I am mulling over. I need to get it e-tested again in winter 2016 so that is a timeline for doing something with it. Also, "I know a guy" so it might not be a big deal if it's just at start up and I bring it in hot.

I like the idea of a "big engine" in a small truck/Jeep though.

 

[Hypoid]

Btw, is it possible to inspect the head for knurled guides before installing? Assuming I'd have to pull a spring/valve (excuse to buy a spring compressor)?

I ask because I have another ACH head in the garage on the bench that hasn't been installed yet.

Poor workmanship/QA can result in tapered or loose guides in the final product. If a given shop does not have the equipment to measure the valve guides, take your work somewhere else. BTW, my Google-Fu could not find anything on "ACH heads." Do they have a web site?

Here is more information than you ever wanted to know about valve guides: http://www.aa1car.com/library/ar696.htm

 

[Root Moose]

ACH = Alabama Cylinder Head; they used to sell heads through a web site and eBay. I bought via eBay about two years ago, maybe longer.

Looks like they've rebranded themselves as "Promaxx Performance" if it is the same company in Rainbow City, Alabama.

The part I bought is roughly this one: http://www.quadratec.com/products/51108_1002_07.htm (with valvetrain)

At any rate, I rolled the dice on a ~$520 complete head via eBay and it got me through the issue I was having (cracked head). It worked fine for a while and I can't make any assumptions about the skill or quality of work and materials on this particular head without taking it apart. Could be just luck of the draw, sometimes stuff breaks even with good QA and effort.

 

[Dr. Dyno]

I like the idea of a "big engine" in a small truck/Jeep though.

I like the idea of a big powerful engine in any lightweight vehicle. With modern cars becoming porkier with every new model (much like their occupants ) even a 3500lb car looks lightweight these days as "medium" size cars close in on a 4000lb curb weight.

 

[CJR]

Moose,

Gasoline contains lacquers which coat rings, lock the rings up in the piston and also plugs up inadequate sized oil drain back holes in the pistons. On start-up, blue smoke can come from worn valve guides/valve seals and/or oil laying around stuck piston rings. Gasoline is not a solvent for lacquer, but Gumout is. Here's a cheap check and something I do at every tune-up. Pull all the plugs and spray Gumout in each spark plug hole until the can of Gumout is empty. Let the engine set for a couple of hours, or better yet overnight. The Gumout loosens any stuck piston rings, opens up the piston oil drain-back holes and then evaporates.

Replace all the spark plugs and fire it up. Initially you'll get a cloud of smoke and then it'll run fine. See if that stops the smoke on start-up. If it does, periodically add Mystery oil to your oil to keep the rings free and piston drain-back holes (in bottom piston oil control grooves) working properly. If not, replace the valve guide seals which can be done without pulling the head.

Best regards,

CJR