smoke smoke smoke........

degreeoff1 · 01-18-2009, 08:33 AM

hello all,
I thank you for this great forum Wayne.

OK so here is my issue.

The 2.7 I have in my 914-6 smokes....I rebuilt it to the best of my ability and near as I can tell its doing fine, pulls hard runs great etc etc.

It only smokes IF I am sitting at a stop light ( a minute or so ) and I gun it when I leave the line POOF! big cloud of smoke, then only if I leave the car running at idle for a few minutes and I will start to see little puffs coming out of the tail pipe.

Now I have done a compression test (incorrectly AKA cold with the carbs not WOT) but come up with a steady 140psi.

Specs on the engine are 7R case, GE40 cams, Ross P&C 9.8 to one comp, cam timing is set at 4.5mm.

Another item of note is that when putting together I had a rough time getting the thing to start due to my ignition (HPV-1) not firing because of a missing in line resister and the re was a fair amount of gas that got washed down the pipes as it were. I have a AFR on the exhaust and run fairly rich this I know....But when I go from the 60's idles down to 55's I have no joy with low end so.....?

What could it be, valve stem seals, not seated rings? URGH!!!! valve guides?

I have no smoke issues on decel or one up and running at 3-6k rpm. Oh I fogot to mention they are nikasil cylinders and I scotch brited them...

Thank you

Josh

degreeoff1 · 01-18-2009, 08:35 AM

Also I am running PMO carbs......

Aurel · Aurel's Garage

A few suggestions and questions:

- How much oil did you put in it? I think 9.5 quarts is about right, oil overfill will make it smoke.
- Were the P&Cs in spec? Did you put new rings, and did you verify the ring lands and rings gap? Did you make sure you did not line up the ring gaps?
- Were the heads rebuilt?

degreeoff1 · 01-18-2009, 01:21 PM

Well its funny you should ask about the oil level. I have about 14 quarts in there BUT I also have a front mounted oil cooler (GT 914-6) and it still does not register on the dip stick (all OEM stuff) Oil pressure is fine and I have yet to reach 200 degree oil temps.

The Pistons/Cylindrs heads were all from a guy here "thorshammer" and he said they were all from a 1000 mile motor. I have no reason to think he was lying as I believe he has a fair amount of knowledge and experience in these things.

Ring alignment was by the book.

Is it possible that my rings have not seated yet as I only have about 500 miles on it split over spirited driving around the twisty back roads and a couple autoX's?

I will be pulling the motor here in a week or two to do a valve adjust and second torqueing of the head bolts...while out I will also do a leakdown but Jeez....

J P Stein · 01-18-2009, 03:34 PM

What oil did you use for break in?

degreeoff1 · 01-18-2009, 03:38 PM

Hey JP...20w50 castrol.......

J P Stein · 01-18-2009, 04:38 PM

Quote:

Originally Posted by degreeoff1

Hey JP...20w50 castrol.......

Humm.....I always use a non detergent oil like Brad Penn break in oil to get the rings to seat. It's not too late, me thinks.....and worth a shot.

Generally, smoke as you've described is rings. Smoke on decell......or more smoke

is valve guides.

Rusty 356 · 01-19-2009, 06:01 AM

No seals on the intake valves and throttle closed results in a high vacuum may pull oil down intake guide and burn it. Sometimes gobs when you shift, that is throttle closed then shift and when you stand on it a puff of smoke out the exhaust. Make sure all your hoses are hooked up correctly. If you have a hand throttle open the throttle a bit above the idle and check for smoke as well. If you decide to change oil, do it hot, drain the case first and see how much oil comes out prior to the wet oil tank. Seems 14 quarts is too much even for a front cooler, that leave the scavenger mode a little weak. Good luck, do the simple things first.

degreeoff1 · 01-19-2009, 06:32 AM

well so far as hoses go aside from the in out back and forth of my oil tank and mocal its AN 12 to the cooler and the only other is a breather from the case to tank and tank to catch tank to air filters......

How much difference would my not getting up to temp (210+) make in breaking in the rings?

I am inclined to think thats the issue and because she runs like a scat rat I REALLY don't want to pull it apart. But its coming out anyway as I can do all my valves + retorque the heads soooo much easier that way. heck with a scissor lift and my transmission jack 2000 lb its onlt 4 bolts and a few other connections and she be out O there!

Rusty 356 · 01-19-2009, 06:49 AM

Breaking in the rings shouldn't require full temp and load. If you drive it in a gear higher than you normally do to increase the load on the rings should do it. I run in a gear that I normally would cruise in and feed the throttle in and vary the load with the throttle. I'm in Virginia Beach so pretty flat. your area is a little more hilly, so find a few good grades and break the rings in. Good luck

Happy Martin Luther King Day,

69BahamaYellow · 01-20-2009, 05:32 PM

Just built a 2.2 liter T motor and it does the exact same thing. I have about 1000 miles on my motor. Runs strong and idles perfect. No smoke except under conditions you describe. I don't think it's valve guides / seals, or it would smoke when decelerating with closed throttle. Ring gaps and cylinder specs were perfect, when I put it together, but I'm now thinking my honing job was a bit too rough for the stock piston rings I used and caused the ring gaps to open up too much after break in. Compression is a bit lower than I like, which seems to confirm this theory. No way to know, without opening it back up, so I'm curious to learn what you find out on yours.

Rusty 356 · 01-20-2009, 07:37 PM

Bahama Yellow, with engine hot, drain the oil and take a clean sample to your local CAT dealer. They'll analyze the oil and let you know from the report if there is any foreign material found such as a silica, high iron content, etc. I just rebuilt my 69 2.0 also a bahama yellow car. used a flex hone and then spent about 10 minutes per cylinder cleaning with Tide.
Remove all residue until your white shop towel is clean. The analysis will also give you a sense of the cleanliness of your rebuild. Just a side note. Let us know what your analysis uncovers.

69BahamaYellow · 01-21-2009, 05:01 AM

All good tips, Rusty. I honed and cleaned my cylnders just like you described, and used about 220 grit stones to make a nice crosshatch pattern. I don't have a roughness guage, so I have no idea if this method left a smooth enough surface to keep the ring gaps from opening up too much during break in. The smoking that occurs, leaving a red light after a long idle only started after about 600 miles. Before this, oil consumption and smoke seemed totally normal for a rebuilt motor. Now, oil consumption is less, but I leave the embarrasing smoke cloud at red lights..... Everything is pointing to piston rings that did not seat right during break in, but maybe Degreeoff1 will discover something simple that is causing his motor to do the same thing

degreeoff1 · 01-21-2009, 10:08 AM

Humph! I have noticed nothing is simple with these motors! I have a sinking feeling that my rings have not seated (used nikasil .....), and no easy fix for that.....It'll be a month before I get into this and unless my leakdown numbers are WAY off I will most likly let it eat HOPING for the buggers to seat this summer....

We'll see??

Josh

69BahamaYellow · 01-21-2009, 04:49 PM

I was kind of thinking I would put up with the smoke clouds for a while myself and hope for the best. I drove about 50 miles of backroads today, using 1st gear to 3rd to 5th shifts, or 2nd to 4th whenever I accelerated. I'm thinking the longer periods of heavy throttle between shifts puts more pressure on the rings than normal. After about 100 miles of this I will check to see if compression is rising or falling. For what it's worth, it looked like the smoke clouds were smaller at red lights, after this treatment, but that could be false hope clouding my vision

It's too bad about the smoke after idle, as the motor runs so good in every other respect..... It's also ironic that the motor smoked all the time before the rebuild, but it was never highly visible and never made big plumes leaving red lights (5 of 6 pistons had broken compression rings. Hmmmmmmm.)

69BahamaYellow · 04-06-2009, 05:23 PM

After 2000 miles my rebuilt motor still leaves white smoke clouds at red lights and at startup. It never smokes any other time. Still runs great, but 3 of 6 spark plugs still get oily. At wits end, I decided to try a quart of the miracle monkey juice you can find at any auto parts store to "stop engine smoking". I suppose their all the same and have the viscosity of honey when you pour it in the tank. Well I'm happy to say the stuff actually works. After a 20 minute drive, 90% of the smoke is gone and has stayed that way for the last 200 miles. I can't tell any difference in the way the car runs, so any of the other claims you may find on the bottle is probably rubbish.

Rusty 356 · 04-06-2009, 07:23 PM

Years ago we use to lap the rings to the pistons ring lands. That's where the sneaky oil gets by. Used a jewelers rouge for lapping. Good luck with the smoke. How about oil consumption BahamaY? Have you had to add any back to the system? Short of pulling the egnine down again, not much else you can do. On the big diesels some of the shop gave them a dose of bon ami to help seat the rings.

T77911S · 04-07-2009, 04:38 AM

could it have something to do with the carb setting? too rich at idle maybe?
you didnt put the oil ring gap at the 6 o clock position did ya?
what if you idle it at 1500 or 2k for a few minutes, same thing?

al lkosmal · 04-07-2009, 05:13 AM

I hate to say it, but it sounds like a broken ring(s). (ask me how I know) If I were you i would proceed with a leakdown test to help identify the source of your issue.

regads,

al

PS: verify that 14 qts of oil is not too much...1st.

fast0911 · 04-07-2009, 10:15 AM

Josh,

I have a similar set up on my 911 with PMOs as well. I used to have this similar problem. I thought it was oil being burned at first . However, it was my carbs running rich while at IDLE. There was too much unburned gas being delivered at idle speed at a stop light and as soon as I would pull away it would create a puff of dark smoke. If you can smell the excess gas this may be your problem.

If so I would look at cleaning the PMOs. You can download a simple procedure to do so from the PMO website. Also check that you have all your Carb gaskets in good condition. Just one cylinder could be the culprit if your idle circuit is running too rich to cause this condition.

GM