engine break - in - am I paranoid?? Mist from oil tank at idle
 

Just fired up the new 3.6. It is a 964 bottom end, rebuilt with new bearings and rings. The top end is 993 heads (rebuilt w/ 3 angle valve job from AASCO) with back dated cam towers and manual lifter cams. '95 intake and motronic engine management.

The cams are Webcams Supersport and valve train is uprated with heavier springs and titanium locks from AASE.

I followed Wayne's cam break - in and first drive instructions in his rebuild book.

The valve train is very noisy, can't imagine driving for 500 miles like this. I plan a valve adjustment soon. Also, I have pressure in the oil tank, rather than vaccuum like the old 3.2. Looks like oil mist is puffing out of the tank when the cap is off.

I did a leak down test on one cylinder and it was 11%. Didn't have a lot of time to check things out.

Additionally, when driving it, starting it and on decel I see zero smoke. I think that's a good sign. However, on decel the compression braking effect seems to be very low (as if I still had my foot part way on the throttle). My first concern, maybe paranoia, was that the rings weren't holding compression?

Maybe the rings haven't seated?

Could the larger cams relate to lack of low speed vacuum?

Any comments?

How would you test?

Again, it is possible I'm just paranoid.

Thank you,

Doug

You mentioned that you did a leakdown, but I wasn't very clear that you had identified the leakage as going by the rings. Is that the case then? I assume the leakdown was performed hot? What oil did you use at break-in?

Charles,
Thank you for taking the time to respond!

Is oil mist coming from the tank definitive of leaking compression into the case?

To answer your questions:
I could hear leakage into the case, I believe and could hear air exiting the oil tank. However, even if 1/2 of the leakage is via the rings, I would hear air entering the case, right? The noise wasn't so pronounced that made it 100% obvious to where the air was escaping.

I used Pennzoil 20W-50 dyno oil and yes, I did the leak down hot. I didn't have time to do more cylinders, unfortuantely.

Do I risk something if I heat up and test leakdown again? I was thinking that maybe some of the valves could be tight and leaking a bit.

At this stage, do valves usually get tigher or looser - is there a generalization that we can apply?

Can you recommend steps to check things out further?

I was thinking:
plan A
1. adjust valves
2. warm up
3. complete leak down

OR
plan B
1. adjust valves
2. warm up
3. continue driving to see if the rings seat.

Plan C
1. warm up
2. retest leak down

Plan D-
Please propose??

Thank you very much!

Doug

I just checked another cylinder for leak down (cold this time) and ended up at 78 / 100 or 22% leaking. Doesn't seem good. From what I can tell, most of the leakage is into the case - the oil tank actually gets pressurized a bit. When I unscrew the cap, I can hear it coming from the oil fill.

Can anyone offer a recommended approach or testing suggestions?

I'd be glad to collect more information, so you can offer insight.

Doug

I would probably do plan a- if all the cylinders are about even after re-doing the leak down test, I would then continue to drive the engine, then re-check it later. If one cylinder or one bank of cylinders is uneven, then I would look a little deeper.

About the valves, they would be tight rather than loose at this point, so adjusting them wouldn't be a bad thing, especially since you were breaking in a new cam.

I can't be 100% sure on the oil mist- sometimes it can be as simple as windage or excessive crankcase pressures (clogged/pinched breather) or something as sinister as the oil rings not doing their job and forcing the added workload onto the second ring. Watch your oil consumption over say a 1000 miles- that should rule out that problem.

I'll go one step further to ask how were the pistons and cylinders prepped- i'm assuming they re-ringed factory cylinders. I'll also assume that you measured them and they were in-spec? Did you scuff the bores with a green scotch brite pad or grape hone them?

Charles,
Thank you again for your generous advice.

I bought the engine complete from a friend who had hired the tech that rebuilt it. I'm going to ask and find out. I believe they are used, but low-mile factory cylinders and pistons with new rings. Hopefully, he may know the process used to prepare the cylinders / pistons.

Thank you,

Doug

I think your rings just haven't seated yet. Drive it awhile and see if it gets better.

-Andy

That's what I'm leaning towards too, but it doesn't hurt to check :-)

I agree about the ring seat. That said, I leak down test every motor I build before start up (I don't know why, I am just curious I guess! :) ) they average around 15% befor I ever turn the key. Note, I have only built a half dozen so...........

Be aggressive with the break in. once you have some oil temp. Don't drive it like you stole it, but don't baby it either. The motor needs to see lots of vacumm too, accelerate up through the revs then take your foot off the accelerator and let the motor "engine brake" the car. Even better if you can do it down hill. You will probably feel a difference over just a very few minutes. Keep an eye on the oil temp and level.

Good luck, I am sure in a few more miles she will be great and you will be resting easily.

Cheers

I am far from a pro but if the valves are that noise I dont think I would want to drive it like that for 500miles. It should be comparable to your old 3.2 . They could be too tight or by the sounds of it way too loose.
Dont want them slaming your pistons.

As for the mist. My 72 when I looked in the tank when it was running at a fast idle there was a fine mist just from all the oil flying into the tank I remeber not wanting to breath it heh, heh.

I would really focus on those valve's for a start forget about the mist for now. There is no reason for solid lifters to be noise other than bad instalation or bad adjustment.
Just be sure they are getting oil and that nothing is blocked running them dry would suck.

Is the idle smooth?

One other thing, if you want the rings to seat, get out and drive it. For piece of mind, adjust the valves first. But, whatever you do, don't let a motor with new unbroken in rings warm up by idling any more than you absolutely have to. The rings need to see some pressure on both sides to seat and the earlier in their lives you can do that, the better!.

Cheers

Guys,
Thanks for the thoughtful advice! It runs, so that's a place to start. For peace of mind, I'll adjust the valves and then just drive and cross my fingers. I haven't babied it more than just not revving beyond 4800 to 5k.

I know my exhaust is less restrictive than factory, so I'm thinking it may run too lean. Does a '95 go into open loop under full throttle (like earlier Motronic systems?). For that reason, I didn't want to hammer it either. I haven't been shy about giving it 3/4 throttle, though.

The idle doesn't seem perfect, but could be due to valve lash and the larger cams. I started looking for a vacuum leak, but didn't want to idle it very long. I had a vacuum diagram out and double checked the idle ports, which all seem to be blocked.

Doug

Jeff,
How long did it take your rings to seat? A few people with whom I've spoken have said they seat virtually immediately.

Thanks again,

Doug

They do seat pretty darn fast. I would say that within a few miles is a fair acount of it. That is the catch with breaking in a new motor. The advice is conflicting, letting it run at a high idle (2k) for 20mins to break the cams in right away also doesn't help the rings seat!

I would think though that rings continue to wear in over the first few hundred miles.

I read your first post now more carefully and see that you do have some miles on it now. Also, it appears from your above post that you have been giving it some load, so that is all good!!


Cheers

Yep, I've got a total of 10 to 15 miles and did get on the gas, but only to 4800 or 5k rpms.

I adjusted 1/4 of the valves today (just 3 under one valve cover). They were loose, rather than tight. Not sure why?

I'll finish the other 3 banks, start up and try again.

Thanks!
Any other comments are welcome!

Doug

fwiw.. only what I did on a complete rebuild. I'm no pro.

Straight 30w non-detergent. my engine needs 10mi to warm up so I only did 50-75mi rides on only hy for 500mi. I rode 4th gear and continually floored the pedal to increase revs about 500-800. Then I took foot off pedal to lower the revs. I never held a constant rpm. Boring as hell.

Results are it's tighter than a crabs ass and that's water tight.

be careful pulling spark plugs from a hot engine as the head threads are delicate imo.

I have been there done that a few times. is it possible that either the cam timing is off or the cams are ground wrong causing for the valaves to have some interesting overlap??????????;) Again not a pro but dealing with hundred of aircraft engines in another life we saw that a few times and hey once in my 2.7 in the 914-6 don't laugh at me PLEASE. Doug give me a call happy to help if you like

Guys,
Here's a quick summary. Not looking good. I have to say, I don't think it is cam timing since the oil tank (via crankcase) is being pressurized.

After following the cam break-in procedure and then driving about 15 miles a few days ago, I did a valve adjustment this AM and then put 30 wt. non-detergent oil in it as some suggested for break in. First batch of oil was 20w-50. The valves were univerally loose, but not terribly. Enough to make noise, though.

I ran about 15 more miles today. Full on the gas, full off the gas 3k to 5k rpm, once to 5500. Decel still sucks. Acceleration is weak. My old 3.2 would blow the doors off of this. The pressure in the oil tank blew one of the vacuum caps off of the tank and puked oil out. Not good. As you know, with a dry sump, the scavenge pump causes vacuum in the crank case and oil tank of a solid engine (at least bottom end, pistons / rings sealing properly). The massive blow by is pressurizing the oil tank.

When it was hot, I took it home and immediately did a leak down test.

Where results for a perfect motor would read 98/100 and good 92+ / 100. Mine is:
1 – 80/100
2 – 73/100
3 – 56/100
4 – 46/100
5 – 61/100
6 – 64/100

I’m confident that the valves are not leaking, since I heard no leaks either in the exhaust or the intake manifold. The oil cap would actually float from the pressure as it was unscrewed.

Geez Doug, not what I was expecting to hear. What is the story on the P/C set? Have you got the story yet? Sounds to me like you did your part in attempting to get the rings to seat. I would like to hear what the "tech" did to prepare the cylinders. Were the rings actually new? Was the P/C set measured and in spec? ''

I hope there is a good outcome here, keep us posted.

Love your car by the way, just stunning.

Cheers