How many miles before I get to freak out about the engine smoking?

[SoCal_Lynch]

I did some research from prior discussions and I think the answer is at least 150 miles but it’s obviously more than slightly concerning to have one of these engines laying down a smoke screen.

I recently installed a 2.4 L out of the 1973 in my 1974 914. I bought the engine from one of the well-known dismantlers and they told me, in a fairly extensive conversation before I bought it, that it had goodly down numbers and did not smoke when it was taken out of the car that was getting a monster 3.6 build.

Due to Covid and work related things the engine sat for 6+ months after it showed up and I only recently got it up and running.

The good news is that it has really good power and pulls more strongly than I would expect and has good oil pressure numbers at idle and underway even once the car is warmed up. The bad news is that it’s smoking noticeably and that’s obviously a bit concerning.

It looks like it’s not uncommon for these engines to smoke a bit after they’ve been sitting especially for multiple years and often times running them for 100+ miles takes care of it but.....

So - thoughts or experience to share gentlemen?

Thanks!

[darrin]

As I understand it, there are several reasons for smoke at startup.

1) most common, oil makes its way into the combustion chamber while the engine sits (past valve guides and/or piston rings) and creates a relatively brief "puff" of smoke at startup. Since you're seeing your smoke continue, doubt this is your issue.

2) less common, oil then makes its way into the exhaust/onto heat exchangers over time while sitting and the observed smoke is coming from the oil burning off the exhaust and not during combustion.

3) easy to determine -- oil was overfilled at oil change and the overfilled oil is finding a place to leak out/burn off --

Did your engine install include the original exhaust? Have you checked oil level (while the engine's fully warmed up and running while on a level surface)? Is oil level midway between the 2 marks on the dipstick?

[SoCal_Lynch]

Thank you for the detailed response Darrin.

1) agree, unfortunately this is not the normal puff at start up

2) it is a used exhaust that I don’t have history with but it sure seems like a lot of smoke for that to be burning off still, but would love that to be the problem!

3) let me double check but I don’t think I overfilled it, but I will own up to it if I did

I think potential cause #4 is the biggie – the rings or belt guides. I don’t think it’s valve guides because it does it when the car is not decelerating so it’s more likely rings.

[MichaelSJackson]

^+1

Don't top off the oil. Aim for the middle. If valve guides are worn, the topped off oil can keep getting past and into the chamber.

Maybe drain a little?

[porsche930dude]

If you suspect the rings are stuck try a bottle of marvel mystery oil in the oil. It freed the rings in my truck. Get it good and hot. It cant hurt.

[Tea Tray]

Regarding the used exhaust, I bought used heat exchangers and noted there was oily guck inside the RH side.
Upon startup and for several hundred miles, the thing smoked badly. For several hundred more miles it would smoke when I let the horses run.
Do/does the tail pipe (s) have residue up inside?

[SoCal_Lynch]

Thanks for all go the responses.

Oil tank is not overly full.

Exhaust exit pipe is pretty gunky but hard to tell how much of that is new vs from prior install. I honestly don’t remember what the inside of the tailpipe looked like before I installed it.

EDIT - I just look at the headers that I took off this engine too install it into the 914 and they are pretty black inside.

It looks like I need to just suck it up and run it and see what happens.

[SoCal_Lynch]

[Larmo63]

I second the Marvel Mystery Oil idea.

I always use it in my old air cooled cars in the gas.

[SoCal_Lynch]

I will definitely give MMO a try, thanks for the suggestion.

When I put my finger on the inside of the exhaust header it had the same oily coating that the exhaust on the car does now, and that sure suggests that this engine was smoking badly when it was removed and sold to me.

[fanaudical]

Did the engine seller provide values for the leak down and compression tests? What were the numbers?

[SoCal_Lynch]

Originally Posted by fanaudical

Did the engine seller provide values for the leak down and compression tests? What were the numbers?

They did. I have to go back and check my documentation on it but the figures I was provided were consistent in the 7+/- range which did not agree at all with the 30+ or minus I got when I had the engine checked once I got it out of the crate.

[Tea Tray]

How many miles did you drive so far?
If you’ve driven enough to get the engine hot, had the throttle opened up, etc, a plug reading may be a good indicator of oiling issues.

[Focker]

Have you pulled any plugs to see their condition?

Since it is from a dismantler, it is possible that they used fogging oil in the cylinders in anticipation of storing the engine until it was sold.

I used to fog both my generator and racing motorcycles and they would smoke badly. Generator for much longer as the bike got flogged pretty hard.

[GH85Carrera]

Check your plugs and see if they look fouled. put in new plugs. Then go for a rural interstate trip of 100 miles from home. After 200 miles of constant driving at 70 MPH, the oil should be pretty much burned out of the exhaust system.

Then check the plugs again. Compare them to the old plugs. If one or more cylinders show a problem you will have an answer.

[SoCal_Lynch]

Thanks Glen, will do exactly that and report back.

[targa72e]

Many years ago I purchased a 72 2.4T project which been sitting for 5+ years while body/Paint work was being done. When I first got it running the rings were stuck in place from sitting and it pumped oil into the exhaust and muffler. It would be fine when first started but as the exhaust heated up it would start to smoke. I took the muffler off and was able to poor oil out of the muffler. I reinstalled the muffler and when It got dark that night I got on the highway and ran up and back many times with the engine at 4000+ RPM and heavy throttle to get the exhaust hot. I created quite a fog. After about 1/2 hour it was cleared up. Car ran fine with minimal oil consumption afterwards.

john

[SoCal_Lynch]

Thanks for that reply John, I’m glad that it was a relatively simple fix for you. I bet actually being able to pour oil out of the muffler was a bit eye-opening.

So I put some MMO into the oil making sure to not over fill the oil tank and then decided to just go for it and get some miles onto the car at highway speeds.

I have to say that I am happily surprised to report that it doesn’t seem to be smoking much if at all at this point. I drove it for a 35 minutes nonstop between 60 and 80 miles an hour with a good number of aggressive throttle use at speed.

Not going to declare victory yet but encouraging turn of events.

[Focker]

Originally Posted by SoCal_Lynch

Thanks for that reply John, I’m glad that it was a relatively simple fix for you. I bet actually being able to pour oil out of the muffler was a bit eye-opening.

So I put some MMO into the oil making sure to not over fill the oil tank and then decided to just go for it and get some miles onto the car at highway speeds.

I have to say that I am happily surprised to report that it doesn’t seem to be smoking much if at all at this point. I drove it for a 35 minutes nonstop between 60 and 80 miles an hour with a good number of aggressive throttle use at speed.

Not going to declare victory yet but encouraging turn of events.

Awesome news.