Blue smoke under hard acceleration

jcode68 · Jul 17, 2011

I have had this problem since I did my engine swap, but thought it was more to do with tuning issue so just continue to tune on the car and not pay much attention to it. But I think I have the motor dialed in really well now and I am still getting blue smoke out the exhaust under hard acceleration. I know black smoke means fuel and blue means oil but I'm not sure what could be causing this. Engine specs in my sig, I have no leaks. Is it possible the pcv valve I am running is allowing blow by into the intake charge under acceleration? I have always wondered if I should even be running a pcv but I installed it since it was on my previous engine I swapped out. I searched the forum, but didn't see anything that put me on the right course. Appreciate any suggestions!

zookeeper · Jul 17, 2011

My first guess is rings not sealing, but check your plugs. If they aren't oil-fouled or heavily carboned, I'd forget about it, assuming it's not too bad. Some 347 motors have oil-control issues, yours might be one depending on pistons. But you do need to keep the pcv setup, either way.

jcode68 · Jul 17, 2011

Motor was built by Coast High Performance and is the Street Fighter and has about 1,000 miles on it, mostly 50 mile weekend joy rides. I will pull my plugs when I get a chance. Is there anything that can be done if it is an oil control problem caused by the rings? Kind of embarrassing when I do a hard launch and leave a cloud from the exhaust pipes

robbz28 · Jul 17, 2011

You might can take your PCV one step further and get a crankcase evacuation system plumbed into your exhaust...in both sides. Just a thought.

Bluepiper · Jul 17, 2011

Check with the engine builder and see if this is normal...might need additional miles on it to make good seal at rings. 1,000 miles is still pretty new. Also, what about the cyl head? Was it redone? What type of valve seals. Could be leaking from valve stems seals.

Rmoore45 · Jul 17, 2011

Did you run break in oil? My local machinist recommends the break in oil with zinc for these old engines.

zookeeper · Jul 17, 2011

While I agree that it may get better with break-in, I honestly wouldn't count on it after 1,000 miles. Hopefully you didn't hold it at steady throttle or lug it during break-in, engines like to be at varied throttle under little load (as in twisties) prior to the first oil change. It also doesn't sound like avalve problem, since that typically only smokes upon start-up, not usually once the car has ran for a few seconds. I would absolutely call the einge builder and see what they recommend, my guess is they'd like to see a leak-down test before they'll make a determination on the cause, and hopefully your engine came with a warranty. I also wouldn't run a pan-evac system on a street car, they tend to suck oil out as well as pressure and really aren't needed for mild street engines. Good luck and keep us posted.

jcode68 · Jul 18, 2011

Thanks for the replies. I will call the engine builder and see what they reccomend. I ran regular oil for the first 2 changes and then used Mobil 1 synthetic on the last oil change. I am wonderring if the builder requires/suggests a specific viscocity oil which could be contributing. Unfortunately, the engine had a 1 year warranty, of which probably chewed 6 months of that time up before even getting it installed in the car due to other projects being done at the same time. Will let you know how things work out for me on this problem.

jcode68 · Jul 19, 2011

I called and spoke with the engine builder tonight about e problem. He asked if my valve covers had baffles? Yes. Asked if my PCV valve was good? Told him wasn't sure, he suggested as a test I put a clear fuel filter inline to see if oil was passing by the PCV. Not sure I will go through the hassle, but will replace the PCV with a new to be sure. I asked what oil they recommend using, and he said 10-40. Told him I did first two oils changes with regular oil, last one with Mobil 1 synthetic. He suggested to not run synthetic until at least 5,000 miles on the engine. Said the synthetic could be causing "wash down", which I took to mean would not cling well to the piston skirts or cylinder walls in turn effecting the seal capability of the rings, but not exactly sure. So I will swap PCV and change oil and see what happens. Definitely started noticing after last oil change, so maybe this is the right path. Comments on this info?

zookeeper · Jul 19, 2011

Certainly sounds reasonable. Most engine builders who've been around have seen it all and know what works best for their combo of pistons, rings and cylinder wall finish. Good luck!

65ShelbyClone · Jul 19, 2011

The part about synthetic oil causing "washdown," whatever the heck that is supposed to mean as it relates to oil type, sounds ridiculous. The rest sounds realistic, though.

How was the engine broken-in? Did it not smoke at all before filling with synthetic? What kind of piston rings?

mycoses · Jul 20, 2011

Sounds like you are sucking oil into the cylinders. plugs will tell which cylinders are sucking oil. Could be a bad intake manifold gasket seal so that the intake port sucks oil from under the intake past the gasket and into the cylinder. Also check the valve seals to see if they are in position and not damaged. If the valve seals look good I would change the intake gasket and take special care to ensure a good seal. I cut 4 short pieces of threaded rod same size as manifold bolts and screw into 4 corners so that when you drop down the manifold it drops over the rod pieces perfectly into position. Remove the rod and replace with bolts one at a time. I use permatex form a gasket sealer #2 around the openings to help seal better. Otherwise you could have a problem with rings not sealing but CHP has a good rep for quality work. The only place you can suck oil into the cylinder is intake, rings , valve seals

PoppyMod · Jul 20, 2011

Hi,

Reading through all of the threads, while all make good points, I'll offer this:
A couple of things come to mind.

1. What's with the "hard launches"and when did you start with this?

2. Having a good working PCV system on any of our engines is a must, for this reason(s).
a. They reduce crankcase pressures, which inturn reduce tendencies for annoying oil seepage. I would even go so far as to recommend a "closed" system, as they do a better job at reducing these pressures. There is an added benefit, of parasetic HP gains through less piston resistence. Also, not to mention, helping our environment

3. Did the "shop" install low pressure rings? Ask about this.

4. I think you mentioned this is a 347. If so, there are two versions: Long rod and short road.
The "long rod", when running an 8.20 block, places the oil control ring partially within the wrist pin openings and while this may be fine for racing, IMHO, not fine for a street warrior whose owner is looking for longevity in his engine. The "short rod " version, leaves just enough distance to allow that oil control ring to be "wholly" within the piston circumference.
I learned these things when researching and designing my build and is why I chose a 333 (.040 - 331 stroker) for my street warrior. I get plenty of "grunt" with it making 392 RWHP @ 6100 with 400 RWTQ @ 4400 Rs. It does have "low" pressure rings, which only expose their nastier qualities during the dyno runs. But none of thse runs took place until 1500-2000 miles were logged.

So, ask the shop about the last 3 points and keep you "foot out of it" for a little while longer. BTW, ask them if they installed umbrellas or posi-seals?

Happy Motoring!

Hack · Jul 20, 2011

Hopefully it's just running a little rich and isn't a ring problem. If you are burning excessive oil, you should notice some consumption or you might get some detonation. Pulling the spark plugs is good advice, which should help you determine what's happening.

I completely disagree with those that say you should go easy on an engine when it's new. The cam needs a break-in at 2000-2500 rpm for 20 minutes if it's a flat tappet. If you have a roller lifter cam, the best thing to do is get out and beat on it right away. The throttle should either be completely open or completely closed during the first few miles, and as much as possible for the first few hundred miles. No steady light throttle cruising with a new engine.

You should avoid lugging or winding the engine to high rpm during break-in, but don't go easy on the throttle! You want the rings to seat, and high cylinder pressures help the rings seat better.

Edit: oh, and don't worry about long/short rods. Many, many 347s have been built with both the longer and shorter rods available, and with proper machining and break-in they work fine. One version is not "wrong" or a poor design.

jcode68 · Jul 20, 2011

Thanks for the replies and suggestions. Let me see if I can answer some of the questions:

How was the engine broken-in? Did it not smoke at all before filling with synthetic? What kind of piston rings?
- Broke the engine in with normal driving for the first 500 miles, varying RPM's and generally not beating on it at all. I don't recall specifically if it was smoking before I switched to synthetic because I was chasing other tuning problems, mainly jetting and running rich issues.
Could be a bad intake manifold gasket seal so that the intake port sucks oil from under the intake past the gasket and into the cylinder. Also check the valve seals to see if they are in position and not damaged. If the valve seals look good I would change the intake gasket and take special care to ensure a good seal.
- I suppose this could be the issue, but I was very careful when installing the intake and gasket. Will pull the valve covers and look at the valve seals for obvious problems, they are/were new AFR 185's so hope they wouldn't have a problem yet. Will also pull the plugs and have a look as several have suggested.
What's with the "hard launches"and when did you start with this?
1. The engine had at least 500+ miles on it before I put my foot into it at all. I would categorize it as spirited launches and not thrashing the motor.
Having a good working PCV system on any of our engines is a must
- Agreed and I will change the PCV to remove from the possibilities.
Did the "shop" install low pressure rings? Ask about this.
1. Not sure, I will look at the build sheet and see if it specifies.
I think you mentioned this is a 347. If so, there are two versions: Long rod and short road.
- Wll need to check this as well. Seems like opinions vary on this one.

Thanks again everyone, may be a week before I can post back with some info.

mycoses · Jul 20, 2011

So, ask the shop about the last 3 points and keep you "foot out of it" for a little while longer.

I do not understand the reasoning for easy driving a new motor for 1500+ miles. This used to be a common beleif. I have become more skeptical after watching TV auto repair shows where they take a new motor , do a 20 minute break in then perform mutliple dyno runs up to 6000 rpm. What gives?

Oh yeh, if the heads or decks were shaved or milled the intake will not align with the intake ports in the head because the intake would sit up too high. The intake faces would have to be milled the same amount as the heads/deck were milled to get the ports to line up.

MitchGT · Jul 23, 2011

just plug the port that the pcv is hooked to, and test it again. If the problem goes away, then you are sucking oil through the pcv.
If it doesn't go away then worry about the more complicated and/or expensive problems...

Blue smoke under hard acceleration

jcode68

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